Opt out nnbd in packages/flutter (#59186)

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

packages/flutter/analysis_options.yaml

diff --git a/packages/flutter/analysis_options.yaml b/packages/flutter/analysis_options.yaml
new file mode 100644
index 0000000..8caedca
--- /dev/null
+++ b/packages/flutter/analysis_options.yaml
@@ -0,0 +1,7 @@
+# Use the parent analysis options settings and enable null-experiment.
+
+include: ../analysis_options.yaml
+
+analyzer:
+  enable-experiment:
+    - non-nullable

packages/flutter/lib/animation.dart

diff --git a/packages/flutter/lib/animation.dart b/packages/flutter/lib/animation.dart
index 88bec71..360c1b3 100644
--- a/packages/flutter/lib/animation.dart
+++ b/packages/flutter/lib/animation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter animation system.
 ///
 /// To use, import `package:flutter/animation.dart`.

packages/flutter/lib/cupertino.dart

diff --git a/packages/flutter/lib/cupertino.dart b/packages/flutter/lib/cupertino.dart
index b097482..d93282d 100644
--- a/packages/flutter/lib/cupertino.dart
+++ b/packages/flutter/lib/cupertino.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Flutter widgets implementing the current iOS design language.
 ///
 /// To use, import `package:flutter/cupertino.dart`.

packages/flutter/lib/foundation.dart

diff --git a/packages/flutter/lib/foundation.dart b/packages/flutter/lib/foundation.dart
index 0ace04d..e519f48 100644
--- a/packages/flutter/lib/foundation.dart
+++ b/packages/flutter/lib/foundation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Core Flutter framework primitives.
 ///
 /// The features defined in this library are the lowest-level utility

packages/flutter/lib/gestures.dart

diff --git a/packages/flutter/lib/gestures.dart b/packages/flutter/lib/gestures.dart
index 3d1cdc6..dffd139 100644
--- a/packages/flutter/lib/gestures.dart
+++ b/packages/flutter/lib/gestures.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter gesture recognizers.
 ///
 /// To use, import `package:flutter/gestures.dart`.

packages/flutter/lib/material.dart

diff --git a/packages/flutter/lib/material.dart b/packages/flutter/lib/material.dart
index 6b2d218..ac012ec 100644
--- a/packages/flutter/lib/material.dart
+++ b/packages/flutter/lib/material.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Flutter widgets implementing Material Design.
 ///
 /// To use, import `package:flutter/material.dart`.

packages/flutter/lib/painting.dart

diff --git a/packages/flutter/lib/painting.dart b/packages/flutter/lib/painting.dart
index 1788092..02bb456 100644
--- a/packages/flutter/lib/painting.dart
+++ b/packages/flutter/lib/painting.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter painting library.
 ///
 /// To use, import `package:flutter/painting.dart`.

packages/flutter/lib/physics.dart

diff --git a/packages/flutter/lib/physics.dart b/packages/flutter/lib/physics.dart
index 2475523..fd5284e 100644
--- a/packages/flutter/lib/physics.dart
+++ b/packages/flutter/lib/physics.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Simple one-dimensional physics simulations, such as springs, friction, and
 /// gravity, for use in user interface animations.
 ///

packages/flutter/lib/rendering.dart

diff --git a/packages/flutter/lib/rendering.dart b/packages/flutter/lib/rendering.dart
index ea4c648..51068bf 100644
--- a/packages/flutter/lib/rendering.dart
+++ b/packages/flutter/lib/rendering.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter rendering tree.
 ///
 /// To use, import `package:flutter/rendering.dart`.

packages/flutter/lib/scheduler.dart

diff --git a/packages/flutter/lib/scheduler.dart b/packages/flutter/lib/scheduler.dart
index f1cbdc2..2652ea3 100644
--- a/packages/flutter/lib/scheduler.dart
+++ b/packages/flutter/lib/scheduler.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter Scheduler library.
 ///
 /// To use, import `package:flutter/scheduler.dart`.

packages/flutter/lib/semantics.dart

diff --git a/packages/flutter/lib/semantics.dart b/packages/flutter/lib/semantics.dart
index f838d2a..8eeb8af 100644
--- a/packages/flutter/lib/semantics.dart
+++ b/packages/flutter/lib/semantics.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter semantics package.
 ///
 /// To use, import `package:flutter/semantics.dart`.

packages/flutter/lib/services.dart

diff --git a/packages/flutter/lib/services.dart b/packages/flutter/lib/services.dart
index 8199457..ff5422e 100644
--- a/packages/flutter/lib/services.dart
+++ b/packages/flutter/lib/services.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Platform services exposed to Flutter apps.
 ///
 /// To use, import `package:flutter/services.dart`.

packages/flutter/lib/src/animation/animation.dart

diff --git a/packages/flutter/lib/src/animation/animation.dart b/packages/flutter/lib/src/animation/animation.dart
index b1cfaa3..65d7d35 100644
--- a/packages/flutter/lib/src/animation/animation.dart
+++ b/packages/flutter/lib/src/animation/animation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 
 import 'package:flutter/foundation.dart';
 

packages/flutter/lib/src/animation/animation_controller.dart

diff --git a/packages/flutter/lib/src/animation/animation_controller.dart b/packages/flutter/lib/src/animation/animation_controller.dart
index c8adf11..2d5375b 100644
--- a/packages/flutter/lib/src/animation/animation_controller.dart
+++ b/packages/flutter/lib/src/animation/animation_controller.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui show lerpDouble;
 

packages/flutter/lib/src/animation/animations.dart

diff --git a/packages/flutter/lib/src/animation/animations.dart b/packages/flutter/lib/src/animation/animations.dart
index 852f42a..28d8a58 100644
--- a/packages/flutter/lib/src/animation/animations.dart
+++ b/packages/flutter/lib/src/animation/animations.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/animation/curves.dart

diff --git a/packages/flutter/lib/src/animation/curves.dart b/packages/flutter/lib/src/animation/curves.dart
index 96264d2..af3c18c 100644
--- a/packages/flutter/lib/src/animation/curves.dart
+++ b/packages/flutter/lib/src/animation/curves.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui';
 

packages/flutter/lib/src/animation/listener_helpers.dart

diff --git a/packages/flutter/lib/src/animation/listener_helpers.dart b/packages/flutter/lib/src/animation/listener_helpers.dart
index ce4b2af..6b2d3f2 100644
--- a/packages/flutter/lib/src/animation/listener_helpers.dart
+++ b/packages/flutter/lib/src/animation/listener_helpers.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'animation.dart';

packages/flutter/lib/src/animation/tween.dart

diff --git a/packages/flutter/lib/src/animation/tween.dart b/packages/flutter/lib/src/animation/tween.dart
index 148e4b7..dc78aec 100644
--- a/packages/flutter/lib/src/animation/tween.dart
+++ b/packages/flutter/lib/src/animation/tween.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color, Size, Rect;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/animation/tween_sequence.dart

diff --git a/packages/flutter/lib/src/animation/tween_sequence.dart b/packages/flutter/lib/src/animation/tween_sequence.dart
index 30b81b0..fa5050e 100644
--- a/packages/flutter/lib/src/animation/tween_sequence.dart
+++ b/packages/flutter/lib/src/animation/tween_sequence.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'animation.dart';

packages/flutter/lib/src/cupertino/action_sheet.dart

diff --git a/packages/flutter/lib/src/cupertino/action_sheet.dart b/packages/flutter/lib/src/cupertino/action_sheet.dart
index c025812..d2bc5b3 100644
--- a/packages/flutter/lib/src/cupertino/action_sheet.dart
+++ b/packages/flutter/lib/src/cupertino/action_sheet.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show ImageFilter;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/cupertino/activity_indicator.dart

diff --git a/packages/flutter/lib/src/cupertino/activity_indicator.dart b/packages/flutter/lib/src/cupertino/activity_indicator.dart
index 16c323e..de52d2a 100644
--- a/packages/flutter/lib/src/cupertino/activity_indicator.dart
+++ b/packages/flutter/lib/src/cupertino/activity_indicator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/cupertino/app.dart

diff --git a/packages/flutter/lib/src/cupertino/app.dart b/packages/flutter/lib/src/cupertino/app.dart
index 20286e0..a51d61d 100644
--- a/packages/flutter/lib/src/cupertino/app.dart
+++ b/packages/flutter/lib/src/cupertino/app.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/cupertino/bottom_tab_bar.dart

diff --git a/packages/flutter/lib/src/cupertino/bottom_tab_bar.dart b/packages/flutter/lib/src/cupertino/bottom_tab_bar.dart
index a53d22c..7502767 100644
--- a/packages/flutter/lib/src/cupertino/bottom_tab_bar.dart
+++ b/packages/flutter/lib/src/cupertino/bottom_tab_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show ImageFilter;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/cupertino/button.dart

diff --git a/packages/flutter/lib/src/cupertino/button.dart b/packages/flutter/lib/src/cupertino/button.dart
index e44257b..58db983 100644
--- a/packages/flutter/lib/src/cupertino/button.dart
+++ b/packages/flutter/lib/src/cupertino/button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/cupertino/colors.dart

diff --git a/packages/flutter/lib/src/cupertino/colors.dart b/packages/flutter/lib/src/cupertino/colors.dart
index 5c8ed9e..e73485d 100644
--- a/packages/flutter/lib/src/cupertino/colors.dart
+++ b/packages/flutter/lib/src/cupertino/colors.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color, Brightness;
 
 import '../../foundation.dart';

packages/flutter/lib/src/cupertino/constants.dart

diff --git a/packages/flutter/lib/src/cupertino/constants.dart b/packages/flutter/lib/src/cupertino/constants.dart
index 2831c50..5fbbf04 100644
--- a/packages/flutter/lib/src/cupertino/constants.dart
+++ b/packages/flutter/lib/src/cupertino/constants.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The minimum dimension of any interactive region according to the iOS Human
 /// Interface Guidelines.
 ///

packages/flutter/lib/src/cupertino/context_menu.dart

diff --git a/packages/flutter/lib/src/cupertino/context_menu.dart b/packages/flutter/lib/src/cupertino/context_menu.dart
index 14008b3..0800a2a 100644
--- a/packages/flutter/lib/src/cupertino/context_menu.dart
+++ b/packages/flutter/lib/src/cupertino/context_menu.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui;
 import 'package:flutter/gestures.dart' show kMinFlingVelocity, kLongPressTimeout;

packages/flutter/lib/src/cupertino/context_menu_action.dart

diff --git a/packages/flutter/lib/src/cupertino/context_menu_action.dart b/packages/flutter/lib/src/cupertino/context_menu_action.dart
index 5663169..3b319a3 100644
--- a/packages/flutter/lib/src/cupertino/context_menu_action.dart
+++ b/packages/flutter/lib/src/cupertino/context_menu_action.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'colors.dart';

packages/flutter/lib/src/cupertino/date_picker.dart

diff --git a/packages/flutter/lib/src/cupertino/date_picker.dart b/packages/flutter/lib/src/cupertino/date_picker.dart
index 71a75f6..10aed4d 100644
--- a/packages/flutter/lib/src/cupertino/date_picker.dart
+++ b/packages/flutter/lib/src/cupertino/date_picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/scheduler.dart';

packages/flutter/lib/src/cupertino/dialog.dart

diff --git a/packages/flutter/lib/src/cupertino/dialog.dart b/packages/flutter/lib/src/cupertino/dialog.dart
index 1585460..f8c5361 100644
--- a/packages/flutter/lib/src/cupertino/dialog.dart
+++ b/packages/flutter/lib/src/cupertino/dialog.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show ImageFilter;
 

packages/flutter/lib/src/cupertino/icon_theme_data.dart

diff --git a/packages/flutter/lib/src/cupertino/icon_theme_data.dart b/packages/flutter/lib/src/cupertino/icon_theme_data.dart
index 4c6f32b..85dbde0 100644
--- a/packages/flutter/lib/src/cupertino/icon_theme_data.dart
+++ b/packages/flutter/lib/src/cupertino/icon_theme_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'colors.dart';

packages/flutter/lib/src/cupertino/icons.dart

diff --git a/packages/flutter/lib/src/cupertino/icons.dart b/packages/flutter/lib/src/cupertino/icons.dart
index aa09e9a..cbb18d6 100644
--- a/packages/flutter/lib/src/cupertino/icons.dart
+++ b/packages/flutter/lib/src/cupertino/icons.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 /// Identifiers for the supported Cupertino icons.

packages/flutter/lib/src/cupertino/interface_level.dart

diff --git a/packages/flutter/lib/src/cupertino/interface_level.dart b/packages/flutter/lib/src/cupertino/interface_level.dart
index 2a1faa8..328c08b 100644
--- a/packages/flutter/lib/src/cupertino/interface_level.dart
+++ b/packages/flutter/lib/src/cupertino/interface_level.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import '../widgets/framework.dart';

packages/flutter/lib/src/cupertino/localizations.dart

diff --git a/packages/flutter/lib/src/cupertino/localizations.dart b/packages/flutter/lib/src/cupertino/localizations.dart
index 7261bab..6f81fc7 100644
--- a/packages/flutter/lib/src/cupertino/localizations.dart
+++ b/packages/flutter/lib/src/cupertino/localizations.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/cupertino/nav_bar.dart

diff --git a/packages/flutter/lib/src/cupertino/nav_bar.dart b/packages/flutter/lib/src/cupertino/nav_bar.dart
index 504d547..b6c5a4e 100644
--- a/packages/flutter/lib/src/cupertino/nav_bar.dart
+++ b/packages/flutter/lib/src/cupertino/nav_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show ImageFilter;
 

packages/flutter/lib/src/cupertino/page_scaffold.dart

diff --git a/packages/flutter/lib/src/cupertino/page_scaffold.dart b/packages/flutter/lib/src/cupertino/page_scaffold.dart
index 82380f2..717d493 100644
--- a/packages/flutter/lib/src/cupertino/page_scaffold.dart
+++ b/packages/flutter/lib/src/cupertino/page_scaffold.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';

packages/flutter/lib/src/cupertino/picker.dart

diff --git a/packages/flutter/lib/src/cupertino/picker.dart b/packages/flutter/lib/src/cupertino/picker.dart
index e379e7e..805a057 100644
--- a/packages/flutter/lib/src/cupertino/picker.dart
+++ b/packages/flutter/lib/src/cupertino/picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/lib/src/cupertino/refresh.dart

diff --git a/packages/flutter/lib/src/cupertino/refresh.dart b/packages/flutter/lib/src/cupertino/refresh.dart
index 342d25e..baecd38 100644
--- a/packages/flutter/lib/src/cupertino/refresh.dart
+++ b/packages/flutter/lib/src/cupertino/refresh.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math';
 

packages/flutter/lib/src/cupertino/route.dart

diff --git a/packages/flutter/lib/src/cupertino/route.dart b/packages/flutter/lib/src/cupertino/route.dart
index 5e68a9e..907e6d7 100644
--- a/packages/flutter/lib/src/cupertino/route.dart
+++ b/packages/flutter/lib/src/cupertino/route.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math';
 import 'dart:ui' show lerpDouble, ImageFilter;

packages/flutter/lib/src/cupertino/scrollbar.dart

diff --git a/packages/flutter/lib/src/cupertino/scrollbar.dart b/packages/flutter/lib/src/cupertino/scrollbar.dart
index a79f7d9..bc2f02e 100644
--- a/packages/flutter/lib/src/cupertino/scrollbar.dart
+++ b/packages/flutter/lib/src/cupertino/scrollbar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/cupertino/segmented_control.dart

diff --git a/packages/flutter/lib/src/cupertino/segmented_control.dart b/packages/flutter/lib/src/cupertino/segmented_control.dart
index 467087b..5f1ab53 100644
--- a/packages/flutter/lib/src/cupertino/segmented_control.dart
+++ b/packages/flutter/lib/src/cupertino/segmented_control.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:math' as math;
 

packages/flutter/lib/src/cupertino/slider.dart

diff --git a/packages/flutter/lib/src/cupertino/slider.dart b/packages/flutter/lib/src/cupertino/slider.dart
index e1327a9..4c5f665 100644
--- a/packages/flutter/lib/src/cupertino/slider.dart
+++ b/packages/flutter/lib/src/cupertino/slider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show lerpDouble;
 

packages/flutter/lib/src/cupertino/sliding_segmented_control.dart

diff --git a/packages/flutter/lib/src/cupertino/sliding_segmented_control.dart b/packages/flutter/lib/src/cupertino/sliding_segmented_control.dart
index 4aba837..f1bcd9e 100644
--- a/packages/flutter/lib/src/cupertino/sliding_segmented_control.dart
+++ b/packages/flutter/lib/src/cupertino/sliding_segmented_control.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/cupertino/switch.dart

diff --git a/packages/flutter/lib/src/cupertino/switch.dart b/packages/flutter/lib/src/cupertino/switch.dart
index 0988de1..bf03351 100644
--- a/packages/flutter/lib/src/cupertino/switch.dart
+++ b/packages/flutter/lib/src/cupertino/switch.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/cupertino/tab_scaffold.dart

diff --git a/packages/flutter/lib/src/cupertino/tab_scaffold.dart b/packages/flutter/lib/src/cupertino/tab_scaffold.dart
index 5b9e0d6..d81f404 100644
--- a/packages/flutter/lib/src/cupertino/tab_scaffold.dart
+++ b/packages/flutter/lib/src/cupertino/tab_scaffold.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'bottom_tab_bar.dart';

packages/flutter/lib/src/cupertino/tab_view.dart

diff --git a/packages/flutter/lib/src/cupertino/tab_view.dart b/packages/flutter/lib/src/cupertino/tab_view.dart
index 65b8433..29167c7 100644
--- a/packages/flutter/lib/src/cupertino/tab_view.dart
+++ b/packages/flutter/lib/src/cupertino/tab_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'app.dart' show CupertinoApp;

packages/flutter/lib/src/cupertino/text_field.dart

diff --git a/packages/flutter/lib/src/cupertino/text_field.dart b/packages/flutter/lib/src/cupertino/text_field.dart
index e52b44c..f713296 100644
--- a/packages/flutter/lib/src/cupertino/text_field.dart
+++ b/packages/flutter/lib/src/cupertino/text_field.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show BoxHeightStyle, BoxWidthStyle;
 
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/cupertino/text_selection.dart

diff --git a/packages/flutter/lib/src/cupertino/text_selection.dart b/packages/flutter/lib/src/cupertino/text_selection.dart
index 1a90c61..d3bd9e0 100644
--- a/packages/flutter/lib/src/cupertino/text_selection.dart
+++ b/packages/flutter/lib/src/cupertino/text_selection.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:math' as math;
 import 'dart:ui' as ui;

packages/flutter/lib/src/cupertino/text_theme.dart

diff --git a/packages/flutter/lib/src/cupertino/text_theme.dart b/packages/flutter/lib/src/cupertino/text_theme.dart
index 21f5f87..0cf125c 100644
--- a/packages/flutter/lib/src/cupertino/text_theme.dart
+++ b/packages/flutter/lib/src/cupertino/text_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart' show Brightness;
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/cupertino/theme.dart

diff --git a/packages/flutter/lib/src/cupertino/theme.dart b/packages/flutter/lib/src/cupertino/theme.dart
index d75df0f..c2f450c 100644
--- a/packages/flutter/lib/src/cupertino/theme.dart
+++ b/packages/flutter/lib/src/cupertino/theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/cupertino/thumb_painter.dart

diff --git a/packages/flutter/lib/src/cupertino/thumb_painter.dart b/packages/flutter/lib/src/cupertino/thumb_painter.dart
index c5a56c1..7f3bd49 100644
--- a/packages/flutter/lib/src/cupertino/thumb_painter.dart
+++ b/packages/flutter/lib/src/cupertino/thumb_painter.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 
 import 'colors.dart';

packages/flutter/lib/src/foundation/_bitfield_io.dart

diff --git a/packages/flutter/lib/src/foundation/_bitfield_io.dart b/packages/flutter/lib/src/foundation/_bitfield_io.dart
index a4f3bac..c71676c 100644
--- a/packages/flutter/lib/src/foundation/_bitfield_io.dart
+++ b/packages/flutter/lib/src/foundation/_bitfield_io.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'bitfield.dart' as bitfield;
 
 /// The dart:io implementation of [bitfield.kMaxUnsignedSMI].

packages/flutter/lib/src/foundation/_bitfield_web.dart

diff --git a/packages/flutter/lib/src/foundation/_bitfield_web.dart b/packages/flutter/lib/src/foundation/_bitfield_web.dart
index e1f74cc..698e3ec 100644
--- a/packages/flutter/lib/src/foundation/_bitfield_web.dart
+++ b/packages/flutter/lib/src/foundation/_bitfield_web.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'bitfield.dart' as bitfield;
 
 /// The dart:html implementation of [bitfield.kMaxUnsignedSMI].

packages/flutter/lib/src/foundation/_isolates_io.dart

diff --git a/packages/flutter/lib/src/foundation/_isolates_io.dart b/packages/flutter/lib/src/foundation/_isolates_io.dart
index f114bb1..104b25a 100644
--- a/packages/flutter/lib/src/foundation/_isolates_io.dart
+++ b/packages/flutter/lib/src/foundation/_isolates_io.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:developer';
 import 'dart:isolate';

packages/flutter/lib/src/foundation/_isolates_web.dart

diff --git a/packages/flutter/lib/src/foundation/_isolates_web.dart b/packages/flutter/lib/src/foundation/_isolates_web.dart
index e7a2054..4af328e 100644
--- a/packages/flutter/lib/src/foundation/_isolates_web.dart
+++ b/packages/flutter/lib/src/foundation/_isolates_web.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'isolates.dart' as isolates;
 
 /// The dart:html implementation of [isolate.compute].

packages/flutter/lib/src/foundation/_platform_io.dart

diff --git a/packages/flutter/lib/src/foundation/_platform_io.dart b/packages/flutter/lib/src/foundation/_platform_io.dart
index a8e0005..cc005e7 100644
--- a/packages/flutter/lib/src/foundation/_platform_io.dart
+++ b/packages/flutter/lib/src/foundation/_platform_io.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:io';
 import 'assertions.dart';
 import 'platform.dart' as platform;

packages/flutter/lib/src/foundation/_platform_web.dart

diff --git a/packages/flutter/lib/src/foundation/_platform_web.dart b/packages/flutter/lib/src/foundation/_platform_web.dart
index a21b91a..0bc21bb 100644
--- a/packages/flutter/lib/src/foundation/_platform_web.dart
+++ b/packages/flutter/lib/src/foundation/_platform_web.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:html' as html;
 import 'platform.dart' as platform;
 

packages/flutter/lib/src/foundation/annotations.dart

diff --git a/packages/flutter/lib/src/foundation/annotations.dart b/packages/flutter/lib/src/foundation/annotations.dart
index b57bfac..076e2dc 100644
--- a/packages/flutter/lib/src/foundation/annotations.dart
+++ b/packages/flutter/lib/src/foundation/annotations.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // Examples can assume:
 // class Cat { }
 

packages/flutter/lib/src/foundation/assertions.dart

diff --git a/packages/flutter/lib/src/foundation/assertions.dart b/packages/flutter/lib/src/foundation/assertions.dart
index dfbb2e4..ea3db59 100644
--- a/packages/flutter/lib/src/foundation/assertions.dart
+++ b/packages/flutter/lib/src/foundation/assertions.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:meta/meta.dart';
 
 import 'basic_types.dart';

packages/flutter/lib/src/foundation/basic_types.dart

diff --git a/packages/flutter/lib/src/foundation/basic_types.dart b/packages/flutter/lib/src/foundation/basic_types.dart
index d13984f..ade3d70 100644
--- a/packages/flutter/lib/src/foundation/basic_types.dart
+++ b/packages/flutter/lib/src/foundation/basic_types.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 

packages/flutter/lib/src/foundation/binding.dart

diff --git a/packages/flutter/lib/src/foundation/binding.dart b/packages/flutter/lib/src/foundation/binding.dart
index 957f859..185a34c 100644
--- a/packages/flutter/lib/src/foundation/binding.dart
+++ b/packages/flutter/lib/src/foundation/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert' show json;
 import 'dart:developer' as developer;

packages/flutter/lib/src/foundation/bitfield.dart

diff --git a/packages/flutter/lib/src/foundation/bitfield.dart b/packages/flutter/lib/src/foundation/bitfield.dart
index e0b07a8..ba70eef 100644
--- a/packages/flutter/lib/src/foundation/bitfield.dart
+++ b/packages/flutter/lib/src/foundation/bitfield.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import '_bitfield_io.dart'
   if (dart.library.html) '_bitfield_web.dart' as _bitfield;
 

packages/flutter/lib/src/foundation/change_notifier.dart

diff --git a/packages/flutter/lib/src/foundation/change_notifier.dart b/packages/flutter/lib/src/foundation/change_notifier.dart
index 0e92bce..ecdf8fc 100644
--- a/packages/flutter/lib/src/foundation/change_notifier.dart
+++ b/packages/flutter/lib/src/foundation/change_notifier.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:meta/meta.dart';
 
 import 'assertions.dart';

packages/flutter/lib/src/foundation/collections.dart

diff --git a/packages/flutter/lib/src/foundation/collections.dart b/packages/flutter/lib/src/foundation/collections.dart
index 9caeb50..09b5f4f 100644
--- a/packages/flutter/lib/src/foundation/collections.dart
+++ b/packages/flutter/lib/src/foundation/collections.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // TODO(ianh): These should be on the Set and List classes themselves.
 
 /// Compares two sets for deep equality.

packages/flutter/lib/src/foundation/consolidate_response.dart

diff --git a/packages/flutter/lib/src/foundation/consolidate_response.dart b/packages/flutter/lib/src/foundation/consolidate_response.dart
index a41d84a..0a47828 100644
--- a/packages/flutter/lib/src/foundation/consolidate_response.dart
+++ b/packages/flutter/lib/src/foundation/consolidate_response.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';

packages/flutter/lib/src/foundation/constants.dart

diff --git a/packages/flutter/lib/src/foundation/constants.dart b/packages/flutter/lib/src/foundation/constants.dart
index 5accce0..f93f341 100644
--- a/packages/flutter/lib/src/foundation/constants.dart
+++ b/packages/flutter/lib/src/foundation/constants.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// A constant that is true if the application was compiled in release mode.
 ///
 /// More specifically, this is a constant that is true if the application was

packages/flutter/lib/src/foundation/debug.dart

diff --git a/packages/flutter/lib/src/foundation/debug.dart b/packages/flutter/lib/src/foundation/debug.dart
index 77a07d0..c38a7e4 100644
--- a/packages/flutter/lib/src/foundation/debug.dart
+++ b/packages/flutter/lib/src/foundation/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'assertions.dart';

packages/flutter/lib/src/foundation/diagnostics.dart

diff --git a/packages/flutter/lib/src/foundation/diagnostics.dart b/packages/flutter/lib/src/foundation/diagnostics.dart
index 0bbd73d..a8c753b 100644
--- a/packages/flutter/lib/src/foundation/diagnostics.dart
+++ b/packages/flutter/lib/src/foundation/diagnostics.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:meta/meta.dart';

packages/flutter/lib/src/foundation/isolates.dart

diff --git a/packages/flutter/lib/src/foundation/isolates.dart b/packages/flutter/lib/src/foundation/isolates.dart
index 8fb0808..87fb6cb 100644
--- a/packages/flutter/lib/src/foundation/isolates.dart
+++ b/packages/flutter/lib/src/foundation/isolates.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import '_isolates_io.dart'

packages/flutter/lib/src/foundation/key.dart

diff --git a/packages/flutter/lib/src/foundation/key.dart b/packages/flutter/lib/src/foundation/key.dart
index 6b7ebc2..6622ff5 100644
--- a/packages/flutter/lib/src/foundation/key.dart
+++ b/packages/flutter/lib/src/foundation/key.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show hashValues;
 
 import 'package:meta/meta.dart';

packages/flutter/lib/src/foundation/licenses.dart

diff --git a/packages/flutter/lib/src/foundation/licenses.dart b/packages/flutter/lib/src/foundation/licenses.dart
index 004d6e0..20a24e8 100644
--- a/packages/flutter/lib/src/foundation/licenses.dart
+++ b/packages/flutter/lib/src/foundation/licenses.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:meta/meta.dart' show visibleForTesting;

packages/flutter/lib/src/foundation/node.dart

diff --git a/packages/flutter/lib/src/foundation/node.dart b/packages/flutter/lib/src/foundation/node.dart
index b557104..ac665f2 100644
--- a/packages/flutter/lib/src/foundation/node.dart
+++ b/packages/flutter/lib/src/foundation/node.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:meta/meta.dart';
 
 // This file gets mutated by //dev/devicelab/bin/tasks/flutter_test_performance.dart

packages/flutter/lib/src/foundation/object.dart

diff --git a/packages/flutter/lib/src/foundation/object.dart b/packages/flutter/lib/src/foundation/object.dart
index 2b92413..e580c962 100644
--- a/packages/flutter/lib/src/foundation/object.dart
+++ b/packages/flutter/lib/src/foundation/object.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Framework code should use this method in favor of calling `toString` on
 /// [Object.runtimeType].
 ///

packages/flutter/lib/src/foundation/observer_list.dart

diff --git a/packages/flutter/lib/src/foundation/observer_list.dart b/packages/flutter/lib/src/foundation/observer_list.dart
index 3bd2aa8..15e7940 100644
--- a/packages/flutter/lib/src/foundation/observer_list.dart
+++ b/packages/flutter/lib/src/foundation/observer_list.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 /// A list optimized for the observer pattern when there are small numbers of

packages/flutter/lib/src/foundation/platform.dart

diff --git a/packages/flutter/lib/src/foundation/platform.dart b/packages/flutter/lib/src/foundation/platform.dart
index 4de7a57..eea01f0 100644
--- a/packages/flutter/lib/src/foundation/platform.dart
+++ b/packages/flutter/lib/src/foundation/platform.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import '_platform_io.dart'
   if (dart.library.html) '_platform_web.dart' as _platform;
 

packages/flutter/lib/src/foundation/print.dart

diff --git a/packages/flutter/lib/src/foundation/print.dart b/packages/flutter/lib/src/foundation/print.dart
index 5974dbc..06fb0f5 100644
--- a/packages/flutter/lib/src/foundation/print.dart
+++ b/packages/flutter/lib/src/foundation/print.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 

packages/flutter/lib/src/foundation/serialization.dart

diff --git a/packages/flutter/lib/src/foundation/serialization.dart b/packages/flutter/lib/src/foundation/serialization.dart
index fc0439b..6bb7816 100644
--- a/packages/flutter/lib/src/foundation/serialization.dart
+++ b/packages/flutter/lib/src/foundation/serialization.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:typed_data/typed_buffers.dart' show Uint8Buffer;

packages/flutter/lib/src/foundation/stack_frame.dart

diff --git a/packages/flutter/lib/src/foundation/stack_frame.dart b/packages/flutter/lib/src/foundation/stack_frame.dart
index 120309c..ee039e0 100644
--- a/packages/flutter/lib/src/foundation/stack_frame.dart
+++ b/packages/flutter/lib/src/foundation/stack_frame.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show hashValues;
 
 import 'package:meta/meta.dart';

packages/flutter/lib/src/foundation/synchronous_future.dart

diff --git a/packages/flutter/lib/src/foundation/synchronous_future.dart b/packages/flutter/lib/src/foundation/synchronous_future.dart
index cba9d74..b1d235f 100644
--- a/packages/flutter/lib/src/foundation/synchronous_future.dart
+++ b/packages/flutter/lib/src/foundation/synchronous_future.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 /// A [Future] whose [then] implementation calls the callback immediately.

packages/flutter/lib/src/foundation/unicode.dart

diff --git a/packages/flutter/lib/src/foundation/unicode.dart b/packages/flutter/lib/src/foundation/unicode.dart
index 618c9cb..3419843 100644
--- a/packages/flutter/lib/src/foundation/unicode.dart
+++ b/packages/flutter/lib/src/foundation/unicode.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Constants for useful Unicode characters.
 ///
 /// Currently, these characters are all related to bidirectional text.

packages/flutter/lib/src/gestures/arena.dart

diff --git a/packages/flutter/lib/src/gestures/arena.dart b/packages/flutter/lib/src/gestures/arena.dart
index d59ab63..b2bf9fc 100644
--- a/packages/flutter/lib/src/gestures/arena.dart
+++ b/packages/flutter/lib/src/gestures/arena.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/gestures/binding.dart

diff --git a/packages/flutter/lib/src/gestures/binding.dart b/packages/flutter/lib/src/gestures/binding.dart
index 55e7174..ae1d512 100644
--- a/packages/flutter/lib/src/gestures/binding.dart
+++ b/packages/flutter/lib/src/gestures/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:ui' as ui show PointerDataPacket;

packages/flutter/lib/src/gestures/constants.dart

diff --git a/packages/flutter/lib/src/gestures/constants.dart b/packages/flutter/lib/src/gestures/constants.dart
index 9db80a0..fb4efd0 100644
--- a/packages/flutter/lib/src/gestures/constants.dart
+++ b/packages/flutter/lib/src/gestures/constants.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // Modeled after Android's ViewConfiguration:
 // https://github.com/android/platform_frameworks_base/blob/master/core/java/android/view/ViewConfiguration.java
 

packages/flutter/lib/src/gestures/converter.dart

diff --git a/packages/flutter/lib/src/gestures/converter.dart b/packages/flutter/lib/src/gestures/converter.dart
index 8627419..481e660 100644
--- a/packages/flutter/lib/src/gestures/converter.dart
+++ b/packages/flutter/lib/src/gestures/converter.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show PointerData, PointerChange, PointerSignalKind;
 
 import 'events.dart';

packages/flutter/lib/src/gestures/debug.dart

diff --git a/packages/flutter/lib/src/gestures/debug.dart b/packages/flutter/lib/src/gestures/debug.dart
index 90f4c6b..14961cd 100644
--- a/packages/flutter/lib/src/gestures/debug.dart
+++ b/packages/flutter/lib/src/gestures/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 // Any changes to this file should be reflected in the debugAssertAllGesturesVarsUnset()

packages/flutter/lib/src/gestures/drag.dart

diff --git a/packages/flutter/lib/src/gestures/drag.dart b/packages/flutter/lib/src/gestures/drag.dart
index 2b255a5..401be2f 100644
--- a/packages/flutter/lib/src/gestures/drag.dart
+++ b/packages/flutter/lib/src/gestures/drag.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'drag_details.dart';
 
 /// Interface for objects that receive updates about drags.

packages/flutter/lib/src/gestures/drag_details.dart

diff --git a/packages/flutter/lib/src/gestures/drag_details.dart b/packages/flutter/lib/src/gestures/drag_details.dart
index f8b310c..d35190f 100644
--- a/packages/flutter/lib/src/gestures/drag_details.dart
+++ b/packages/flutter/lib/src/gestures/drag_details.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Offset;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/gestures/eager.dart

diff --git a/packages/flutter/lib/src/gestures/eager.dart b/packages/flutter/lib/src/gestures/eager.dart
index 02b82bb..645d8ea 100644
--- a/packages/flutter/lib/src/gestures/eager.dart
+++ b/packages/flutter/lib/src/gestures/eager.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'arena.dart';
 import 'events.dart';
 import 'recognizer.dart';

packages/flutter/lib/src/gestures/events.dart

diff --git a/packages/flutter/lib/src/gestures/events.dart b/packages/flutter/lib/src/gestures/events.dart
index b67e4de..b2ec8fd 100644
--- a/packages/flutter/lib/src/gestures/events.dart
+++ b/packages/flutter/lib/src/gestures/events.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Offset, PointerDeviceKind;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/gestures/force_press.dart

diff --git a/packages/flutter/lib/src/gestures/force_press.dart b/packages/flutter/lib/src/gestures/force_press.dart
index 98c4de4..486b292 100644
--- a/packages/flutter/lib/src/gestures/force_press.dart
+++ b/packages/flutter/lib/src/gestures/force_press.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Offset;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/gestures/hit_test.dart

diff --git a/packages/flutter/lib/src/gestures/hit_test.dart b/packages/flutter/lib/src/gestures/hit_test.dart
index ff1e72e..d4b9832 100644
--- a/packages/flutter/lib/src/gestures/hit_test.dart
+++ b/packages/flutter/lib/src/gestures/hit_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/gestures/long_press.dart

diff --git a/packages/flutter/lib/src/gestures/long_press.dart b/packages/flutter/lib/src/gestures/long_press.dart
index ec41712..23e7f72 100644
--- a/packages/flutter/lib/src/gestures/long_press.dart
+++ b/packages/flutter/lib/src/gestures/long_press.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'arena.dart';
 import 'constants.dart';
 import 'events.dart';

packages/flutter/lib/src/gestures/lsq_solver.dart

diff --git a/packages/flutter/lib/src/gestures/lsq_solver.dart b/packages/flutter/lib/src/gestures/lsq_solver.dart
index eb5b2fd..1f13d09 100644
--- a/packages/flutter/lib/src/gestures/lsq_solver.dart
+++ b/packages/flutter/lib/src/gestures/lsq_solver.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:typed_data';
 

packages/flutter/lib/src/gestures/monodrag.dart

diff --git a/packages/flutter/lib/src/gestures/monodrag.dart b/packages/flutter/lib/src/gestures/monodrag.dart
index 3fa0e2a..59a7454 100644
--- a/packages/flutter/lib/src/gestures/monodrag.dart
+++ b/packages/flutter/lib/src/gestures/monodrag.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:vector_math/vector_math_64.dart';
 

packages/flutter/lib/src/gestures/multidrag.dart

diff --git a/packages/flutter/lib/src/gestures/multidrag.dart b/packages/flutter/lib/src/gestures/multidrag.dart
index a60a8d7..cc8b682 100644
--- a/packages/flutter/lib/src/gestures/multidrag.dart
+++ b/packages/flutter/lib/src/gestures/multidrag.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show Offset;
 

packages/flutter/lib/src/gestures/multitap.dart

diff --git a/packages/flutter/lib/src/gestures/multitap.dart b/packages/flutter/lib/src/gestures/multitap.dart
index ed31657..8e29287 100644
--- a/packages/flutter/lib/src/gestures/multitap.dart
+++ b/packages/flutter/lib/src/gestures/multitap.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show Offset;
 import 'package:flutter/foundation.dart' show required;

packages/flutter/lib/src/gestures/pointer_router.dart

diff --git a/packages/flutter/lib/src/gestures/pointer_router.dart b/packages/flutter/lib/src/gestures/pointer_router.dart
index 9dfdb7d..a832609 100644
--- a/packages/flutter/lib/src/gestures/pointer_router.dart
+++ b/packages/flutter/lib/src/gestures/pointer_router.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:vector_math/vector_math_64.dart';
 

packages/flutter/lib/src/gestures/pointer_signal_resolver.dart

diff --git a/packages/flutter/lib/src/gestures/pointer_signal_resolver.dart b/packages/flutter/lib/src/gestures/pointer_signal_resolver.dart
index 6636f07..ccd49ff 100644
--- a/packages/flutter/lib/src/gestures/pointer_signal_resolver.dart
+++ b/packages/flutter/lib/src/gestures/pointer_signal_resolver.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'events.dart';

packages/flutter/lib/src/gestures/recognizer.dart

diff --git a/packages/flutter/lib/src/gestures/recognizer.dart b/packages/flutter/lib/src/gestures/recognizer.dart
index 42ab301..a9721eb8 100644
--- a/packages/flutter/lib/src/gestures/recognizer.dart
+++ b/packages/flutter/lib/src/gestures/recognizer.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:ui' show Offset;

packages/flutter/lib/src/gestures/scale.dart

diff --git a/packages/flutter/lib/src/gestures/scale.dart b/packages/flutter/lib/src/gestures/scale.dart
index bf5d959..7fb6453 100644
--- a/packages/flutter/lib/src/gestures/scale.dart
+++ b/packages/flutter/lib/src/gestures/scale.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:vector_math/vector_math_64.dart';

packages/flutter/lib/src/gestures/tap.dart

diff --git a/packages/flutter/lib/src/gestures/tap.dart b/packages/flutter/lib/src/gestures/tap.dart
index 2737e5a..a0e99ea 100644
--- a/packages/flutter/lib/src/gestures/tap.dart
+++ b/packages/flutter/lib/src/gestures/tap.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:vector_math/vector_math_64.dart' show Matrix4;
 import 'package:flutter/foundation.dart';
 

packages/flutter/lib/src/gestures/team.dart

diff --git a/packages/flutter/lib/src/gestures/team.dart b/packages/flutter/lib/src/gestures/team.dart
index 128a323..b5eceae 100644
--- a/packages/flutter/lib/src/gestures/team.dart
+++ b/packages/flutter/lib/src/gestures/team.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'arena.dart';
 import 'binding.dart';
 

packages/flutter/lib/src/gestures/velocity_tracker.dart

diff --git a/packages/flutter/lib/src/gestures/velocity_tracker.dart b/packages/flutter/lib/src/gestures/velocity_tracker.dart
index a1ae2d2..89b728b 100644
--- a/packages/flutter/lib/src/gestures/velocity_tracker.dart
+++ b/packages/flutter/lib/src/gestures/velocity_tracker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Offset;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/about.dart

diff --git a/packages/flutter/lib/src/material/about.dart b/packages/flutter/lib/src/material/about.dart
index f4a8291..b7c7e3a 100644
--- a/packages/flutter/lib/src/material/about.dart
+++ b/packages/flutter/lib/src/material/about.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:developer' show Timeline, Flow;
 import 'dart:io' show Platform;

packages/flutter/lib/src/material/animated_icons.dart

diff --git a/packages/flutter/lib/src/material/animated_icons.dart b/packages/flutter/lib/src/material/animated_icons.dart
index 32b3d3d..c6631b2 100644
--- a/packages/flutter/lib/src/material/animated_icons.dart
+++ b/packages/flutter/lib/src/material/animated_icons.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Flutter widgets implementing Material Design animated icons.
 library material_animated_icons;
 

packages/flutter/lib/src/material/animated_icons/animated_icons.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/animated_icons.dart b/packages/flutter/lib/src/material/animated_icons/animated_icons.dart
index cf2d666..a84b595 100644
--- a/packages/flutter/lib/src/material/animated_icons/animated_icons.dart
+++ b/packages/flutter/lib/src/material/animated_icons/animated_icons.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 part of material_animated_icons;
 
 // The code for drawing animated icons is kept in a private API, as we are not

packages/flutter/lib/src/material/animated_icons/animated_icons_data.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/animated_icons_data.dart b/packages/flutter/lib/src/material/animated_icons/animated_icons_data.dart
index f6de42b..a446c1b 100644
--- a/packages/flutter/lib/src/material/animated_icons/animated_icons_data.dart
+++ b/packages/flutter/lib/src/material/animated_icons/animated_icons_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This file serves as the interface between the public and private APIs for
 // animated icons.
 // The AnimatedIcons class is public and is used to specify available icons,

packages/flutter/lib/src/material/animated_icons/data/add_event.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/add_event.g.dart b/packages/flutter/lib/src/material/animated_icons/data/add_event.g.dart
index 27305b8..19394db 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/add_event.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/add_event.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/arrow_menu.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/arrow_menu.g.dart b/packages/flutter/lib/src/material/animated_icons/data/arrow_menu.g.dart
index 2649d8c..3f2a822 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/arrow_menu.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/arrow_menu.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/close_menu.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/close_menu.g.dart b/packages/flutter/lib/src/material/animated_icons/data/close_menu.g.dart
index a0b86c0..4eee804 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/close_menu.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/close_menu.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/ellipsis_search.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/ellipsis_search.g.dart b/packages/flutter/lib/src/material/animated_icons/data/ellipsis_search.g.dart
index ef8802d..8d8c65e 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/ellipsis_search.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/ellipsis_search.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/event_add.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/event_add.g.dart b/packages/flutter/lib/src/material/animated_icons/data/event_add.g.dart
index 8a012f2..cbdbc48 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/event_add.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/event_add.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/home_menu.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/home_menu.g.dart b/packages/flutter/lib/src/material/animated_icons/data/home_menu.g.dart
index 447a370..6f8eda7 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/home_menu.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/home_menu.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/list_view.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/list_view.g.dart b/packages/flutter/lib/src/material/animated_icons/data/list_view.g.dart
index 35814a0..89f5c34 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/list_view.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/list_view.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/menu_arrow.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/menu_arrow.g.dart b/packages/flutter/lib/src/material/animated_icons/data/menu_arrow.g.dart
index 78613e3..3d10006 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/menu_arrow.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/menu_arrow.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/menu_close.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/menu_close.g.dart b/packages/flutter/lib/src/material/animated_icons/data/menu_close.g.dart
index 43e194f..d78b778 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/menu_close.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/menu_close.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/menu_home.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/menu_home.g.dart b/packages/flutter/lib/src/material/animated_icons/data/menu_home.g.dart
index dfdcc79..5f090b8 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/menu_home.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/menu_home.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/pause_play.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/pause_play.g.dart b/packages/flutter/lib/src/material/animated_icons/data/pause_play.g.dart
index b9d117e..d31bf30 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/pause_play.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/pause_play.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/play_pause.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/play_pause.g.dart b/packages/flutter/lib/src/material/animated_icons/data/play_pause.g.dart
index a850aa3..450cb49 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/play_pause.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/play_pause.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/search_ellipsis.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/search_ellipsis.g.dart b/packages/flutter/lib/src/material/animated_icons/data/search_ellipsis.g.dart
index 93ae867..d047668 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/search_ellipsis.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/search_ellipsis.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/view_list.g.dart

diff --git a/packages/flutter/lib/src/material/animated_icons/data/view_list.g.dart b/packages/flutter/lib/src/material/animated_icons/data/view_list.g.dart
index af9606b..aa30c95 100644
--- a/packages/flutter/lib/src/material/animated_icons/data/view_list.g.dart
+++ b/packages/flutter/lib/src/material/animated_icons/data/view_list.g.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/app.dart

diff --git a/packages/flutter/lib/src/material/app.dart b/packages/flutter/lib/src/material/app.dart
index 0e02df1..205a7f3 100644
--- a/packages/flutter/lib/src/material/app.dart
+++ b/packages/flutter/lib/src/material/app.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/cupertino.dart';

packages/flutter/lib/src/material/app_bar.dart

diff --git a/packages/flutter/lib/src/material/app_bar.dart b/packages/flutter/lib/src/material/app_bar.dart
index f62bddd..fb36c0e 100644
--- a/packages/flutter/lib/src/material/app_bar.dart
+++ b/packages/flutter/lib/src/material/app_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/app_bar_theme.dart

diff --git a/packages/flutter/lib/src/material/app_bar_theme.dart b/packages/flutter/lib/src/material/app_bar_theme.dart
index 5bda6e1..6cde6e1 100644
--- a/packages/flutter/lib/src/material/app_bar_theme.dart
+++ b/packages/flutter/lib/src/material/app_bar_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/arc.dart

diff --git a/packages/flutter/lib/src/material/arc.dart b/packages/flutter/lib/src/material/arc.dart
index 97867ef..c018692 100644
--- a/packages/flutter/lib/src/material/arc.dart
+++ b/packages/flutter/lib/src/material/arc.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show lerpDouble;
 

packages/flutter/lib/src/material/back_button.dart

diff --git a/packages/flutter/lib/src/material/back_button.dart b/packages/flutter/lib/src/material/back_button.dart
index e2867a1..20f944e 100644
--- a/packages/flutter/lib/src/material/back_button.dart
+++ b/packages/flutter/lib/src/material/back_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'debug.dart';

packages/flutter/lib/src/material/banner.dart

diff --git a/packages/flutter/lib/src/material/banner.dart b/packages/flutter/lib/src/material/banner.dart
index 25e5879..ceea095 100644
--- a/packages/flutter/lib/src/material/banner.dart
+++ b/packages/flutter/lib/src/material/banner.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'banner_theme.dart';

packages/flutter/lib/src/material/banner_theme.dart

diff --git a/packages/flutter/lib/src/material/banner_theme.dart b/packages/flutter/lib/src/material/banner_theme.dart
index 798e7e3..7911621 100644
--- a/packages/flutter/lib/src/material/banner_theme.dart
+++ b/packages/flutter/lib/src/material/banner_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/bottom_app_bar.dart

diff --git a/packages/flutter/lib/src/material/bottom_app_bar.dart b/packages/flutter/lib/src/material/bottom_app_bar.dart
index 249a312..2628394 100644
--- a/packages/flutter/lib/src/material/bottom_app_bar.dart
+++ b/packages/flutter/lib/src/material/bottom_app_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/bottom_app_bar_theme.dart

diff --git a/packages/flutter/lib/src/material/bottom_app_bar_theme.dart b/packages/flutter/lib/src/material/bottom_app_bar_theme.dart
index 3e2b310..ff8e0d6 100644
--- a/packages/flutter/lib/src/material/bottom_app_bar_theme.dart
+++ b/packages/flutter/lib/src/material/bottom_app_bar_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/bottom_navigation_bar.dart

diff --git a/packages/flutter/lib/src/material/bottom_navigation_bar.dart b/packages/flutter/lib/src/material/bottom_navigation_bar.dart
index 6700a3a..1e52b17 100644
--- a/packages/flutter/lib/src/material/bottom_navigation_bar.dart
+++ b/packages/flutter/lib/src/material/bottom_navigation_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection' show Queue;
 import 'dart:math' as math;
 

packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart

diff --git a/packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart b/packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart
index 196552e..23f9536 100644
--- a/packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart
+++ b/packages/flutter/lib/src/material/bottom_navigation_bar_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/bottom_sheet.dart

diff --git a/packages/flutter/lib/src/material/bottom_sheet.dart b/packages/flutter/lib/src/material/bottom_sheet.dart
index d1b9aa3..5252f51 100644
--- a/packages/flutter/lib/src/material/bottom_sheet.dart
+++ b/packages/flutter/lib/src/material/bottom_sheet.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show lerpDouble;
 

packages/flutter/lib/src/material/bottom_sheet_theme.dart

diff --git a/packages/flutter/lib/src/material/bottom_sheet_theme.dart b/packages/flutter/lib/src/material/bottom_sheet_theme.dart
index 44ffee1..e85433b 100644
--- a/packages/flutter/lib/src/material/bottom_sheet_theme.dart
+++ b/packages/flutter/lib/src/material/bottom_sheet_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/button.dart

diff --git a/packages/flutter/lib/src/material/button.dart b/packages/flutter/lib/src/material/button.dart
index f052074..8c9554a 100644
--- a/packages/flutter/lib/src/material/button.dart
+++ b/packages/flutter/lib/src/material/button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/button_bar.dart

diff --git a/packages/flutter/lib/src/material/button_bar.dart b/packages/flutter/lib/src/material/button_bar.dart
index c701483..0843c83 100644
--- a/packages/flutter/lib/src/material/button_bar.dart
+++ b/packages/flutter/lib/src/material/button_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/material/button_bar_theme.dart

diff --git a/packages/flutter/lib/src/material/button_bar_theme.dart b/packages/flutter/lib/src/material/button_bar_theme.dart
index 86f7394..f9e7995 100644
--- a/packages/flutter/lib/src/material/button_bar_theme.dart
+++ b/packages/flutter/lib/src/material/button_bar_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/button_theme.dart

diff --git a/packages/flutter/lib/src/material/button_theme.dart b/packages/flutter/lib/src/material/button_theme.dart
index 4a8f7bb..594e099 100644
--- a/packages/flutter/lib/src/material/button_theme.dart
+++ b/packages/flutter/lib/src/material/button_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/card.dart

diff --git a/packages/flutter/lib/src/material/card.dart b/packages/flutter/lib/src/material/card.dart
index c971933..559c448 100644
--- a/packages/flutter/lib/src/material/card.dart
+++ b/packages/flutter/lib/src/material/card.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'card_theme.dart';

packages/flutter/lib/src/material/card_theme.dart

diff --git a/packages/flutter/lib/src/material/card_theme.dart b/packages/flutter/lib/src/material/card_theme.dart
index 0ab3827..57b7d7d 100644
--- a/packages/flutter/lib/src/material/card_theme.dart
+++ b/packages/flutter/lib/src/material/card_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/checkbox.dart

diff --git a/packages/flutter/lib/src/material/checkbox.dart b/packages/flutter/lib/src/material/checkbox.dart
index 286ac8f..a02c5aa 100644
--- a/packages/flutter/lib/src/material/checkbox.dart
+++ b/packages/flutter/lib/src/material/checkbox.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/checkbox_list_tile.dart

diff --git a/packages/flutter/lib/src/material/checkbox_list_tile.dart b/packages/flutter/lib/src/material/checkbox_list_tile.dart
index 8dc7c99..6146663 100644
--- a/packages/flutter/lib/src/material/checkbox_list_tile.dart
+++ b/packages/flutter/lib/src/material/checkbox_list_tile.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'checkbox.dart';

packages/flutter/lib/src/material/chip.dart

diff --git a/packages/flutter/lib/src/material/chip.dart b/packages/flutter/lib/src/material/chip.dart
index 05bcabe..5ee3654 100644
--- a/packages/flutter/lib/src/material/chip.dart
+++ b/packages/flutter/lib/src/material/chip.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/material/chip_theme.dart

diff --git a/packages/flutter/lib/src/material/chip_theme.dart b/packages/flutter/lib/src/material/chip_theme.dart
index 7501366..73bb484 100644
--- a/packages/flutter/lib/src/material/chip_theme.dart
+++ b/packages/flutter/lib/src/material/chip_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/circle_avatar.dart

diff --git a/packages/flutter/lib/src/material/circle_avatar.dart b/packages/flutter/lib/src/material/circle_avatar.dart
index ff06621..5ea3c82 100644
--- a/packages/flutter/lib/src/material/circle_avatar.dart
+++ b/packages/flutter/lib/src/material/circle_avatar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'constants.dart';

packages/flutter/lib/src/material/color_scheme.dart

diff --git a/packages/flutter/lib/src/material/color_scheme.dart b/packages/flutter/lib/src/material/color_scheme.dart
index a0cf874..3839284 100644
--- a/packages/flutter/lib/src/material/color_scheme.dart
+++ b/packages/flutter/lib/src/material/color_scheme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart' show Brightness;
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/colors.dart

diff --git a/packages/flutter/lib/src/material/colors.dart b/packages/flutter/lib/src/material/colors.dart
index a4f2f8c..ec11c7a 100644
--- a/packages/flutter/lib/src/material/colors.dart
+++ b/packages/flutter/lib/src/material/colors.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color;
 
 import 'package:flutter/painting.dart';

packages/flutter/lib/src/material/constants.dart

diff --git a/packages/flutter/lib/src/material/constants.dart b/packages/flutter/lib/src/material/constants.dart
index 2a981a0..6bc9f90 100644
--- a/packages/flutter/lib/src/material/constants.dart
+++ b/packages/flutter/lib/src/material/constants.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 
 /// The minimum dimension of any interactive region according to Material

packages/flutter/lib/src/material/curves.dart

diff --git a/packages/flutter/lib/src/material/curves.dart b/packages/flutter/lib/src/material/curves.dart
index eb57621..a1cf342 100644
--- a/packages/flutter/lib/src/material/curves.dart
+++ b/packages/flutter/lib/src/material/curves.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 
 // The easing curves of the Material Library

packages/flutter/lib/src/material/data_table.dart

diff --git a/packages/flutter/lib/src/material/data_table.dart b/packages/flutter/lib/src/material/data_table.dart
index aa2028e..e86d0ec 100644
--- a/packages/flutter/lib/src/material/data_table.dart
+++ b/packages/flutter/lib/src/material/data_table.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/data_table_source.dart

diff --git a/packages/flutter/lib/src/material/data_table_source.dart b/packages/flutter/lib/src/material/data_table_source.dart
index ccb8fe7..e47ca02 100644
--- a/packages/flutter/lib/src/material/data_table_source.dart
+++ b/packages/flutter/lib/src/material/data_table_source.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'data_table.dart';
 

packages/flutter/lib/src/material/debug.dart

diff --git a/packages/flutter/lib/src/material/debug.dart b/packages/flutter/lib/src/material/debug.dart
index c7bbe8c..dfc7837 100644
--- a/packages/flutter/lib/src/material/debug.dart
+++ b/packages/flutter/lib/src/material/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/dialog.dart

diff --git a/packages/flutter/lib/src/material/dialog.dart b/packages/flutter/lib/src/material/dialog.dart
index 426ade2..2d02097 100644
--- a/packages/flutter/lib/src/material/dialog.dart
+++ b/packages/flutter/lib/src/material/dialog.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // TODO(shihaohong): remove ignoring deprecated member use analysis
 // when AlertDialog.scrollable parameter is removed. See
 // https://flutter.dev/go/scrollable-alert-dialog for more details.

packages/flutter/lib/src/material/dialog_theme.dart

diff --git a/packages/flutter/lib/src/material/dialog_theme.dart b/packages/flutter/lib/src/material/dialog_theme.dart
index 72d10bc..77b6d4b 100644
--- a/packages/flutter/lib/src/material/dialog_theme.dart
+++ b/packages/flutter/lib/src/material/dialog_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/divider.dart

diff --git a/packages/flutter/lib/src/material/divider.dart b/packages/flutter/lib/src/material/divider.dart
index edfb566..f3b42da 100644
--- a/packages/flutter/lib/src/material/divider.dart
+++ b/packages/flutter/lib/src/material/divider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/lib/src/material/divider_theme.dart

diff --git a/packages/flutter/lib/src/material/divider_theme.dart b/packages/flutter/lib/src/material/divider_theme.dart
index a99f526..c5e522a 100644
--- a/packages/flutter/lib/src/material/divider_theme.dart
+++ b/packages/flutter/lib/src/material/divider_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/drawer.dart

diff --git a/packages/flutter/lib/src/material/drawer.dart b/packages/flutter/lib/src/material/drawer.dart
index 42536f3..c8a0ec6 100644
--- a/packages/flutter/lib/src/material/drawer.dart
+++ b/packages/flutter/lib/src/material/drawer.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/lib/src/material/drawer_header.dart

diff --git a/packages/flutter/lib/src/material/drawer_header.dart b/packages/flutter/lib/src/material/drawer_header.dart
index 62ff66a..9383cf7 100644
--- a/packages/flutter/lib/src/material/drawer_header.dart
+++ b/packages/flutter/lib/src/material/drawer_header.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'debug.dart';

packages/flutter/lib/src/material/dropdown.dart

diff --git a/packages/flutter/lib/src/material/dropdown.dart b/packages/flutter/lib/src/material/dropdown.dart
index 06981ee..5b76f8c 100644
--- a/packages/flutter/lib/src/material/dropdown.dart
+++ b/packages/flutter/lib/src/material/dropdown.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show window;
 

packages/flutter/lib/src/material/elevation_overlay.dart

diff --git a/packages/flutter/lib/src/material/elevation_overlay.dart b/packages/flutter/lib/src/material/elevation_overlay.dart
index 92c0764..4cf11fa 100644
--- a/packages/flutter/lib/src/material/elevation_overlay.dart
+++ b/packages/flutter/lib/src/material/elevation_overlay.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/expand_icon.dart

diff --git a/packages/flutter/lib/src/material/expand_icon.dart b/packages/flutter/lib/src/material/expand_icon.dart
index cc3fc51..f7e0a8c 100644
--- a/packages/flutter/lib/src/material/expand_icon.dart
+++ b/packages/flutter/lib/src/material/expand_icon.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/expansion_panel.dart

diff --git a/packages/flutter/lib/src/material/expansion_panel.dart b/packages/flutter/lib/src/material/expansion_panel.dart
index 23714df..c955cbc 100644
--- a/packages/flutter/lib/src/material/expansion_panel.dart
+++ b/packages/flutter/lib/src/material/expansion_panel.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/expansion_tile.dart

diff --git a/packages/flutter/lib/src/material/expansion_tile.dart b/packages/flutter/lib/src/material/expansion_tile.dart
index e166d88..166eb04 100644
--- a/packages/flutter/lib/src/material/expansion_tile.dart
+++ b/packages/flutter/lib/src/material/expansion_tile.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';

packages/flutter/lib/src/material/feedback.dart

diff --git a/packages/flutter/lib/src/material/feedback.dart b/packages/flutter/lib/src/material/feedback.dart
index a36e93c..b2589a0 100644
--- a/packages/flutter/lib/src/material/feedback.dart
+++ b/packages/flutter/lib/src/material/feedback.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/flat_button.dart

diff --git a/packages/flutter/lib/src/material/flat_button.dart b/packages/flutter/lib/src/material/flat_button.dart
index da56989..b86eb6f 100644
--- a/packages/flutter/lib/src/material/flat_button.dart
+++ b/packages/flutter/lib/src/material/flat_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/flexible_space_bar.dart

diff --git a/packages/flutter/lib/src/material/flexible_space_bar.dart b/packages/flutter/lib/src/material/flexible_space_bar.dart
index 82a484c..97593989 100644
--- a/packages/flutter/lib/src/material/flexible_space_bar.dart
+++ b/packages/flutter/lib/src/material/flexible_space_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui;
 

packages/flutter/lib/src/material/floating_action_button.dart

diff --git a/packages/flutter/lib/src/material/floating_action_button.dart b/packages/flutter/lib/src/material/floating_action_button.dart
index cc3211c..3b21fec 100644
--- a/packages/flutter/lib/src/material/floating_action_button.dart
+++ b/packages/flutter/lib/src/material/floating_action_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/floating_action_button_location.dart

diff --git a/packages/flutter/lib/src/material/floating_action_button_location.dart b/packages/flutter/lib/src/material/floating_action_button_location.dart
index 1972103..50052b1 100644
--- a/packages/flutter/lib/src/material/floating_action_button_location.dart
+++ b/packages/flutter/lib/src/material/floating_action_button_location.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/floating_action_button_theme.dart

diff --git a/packages/flutter/lib/src/material/floating_action_button_theme.dart b/packages/flutter/lib/src/material/floating_action_button_theme.dart
index 0361af7..038d2fe 100644
--- a/packages/flutter/lib/src/material/floating_action_button_theme.dart
+++ b/packages/flutter/lib/src/material/floating_action_button_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/flutter_logo.dart

diff --git a/packages/flutter/lib/src/material/flutter_logo.dart b/packages/flutter/lib/src/material/flutter_logo.dart
index 71f9810..b7f5d03 100644
--- a/packages/flutter/lib/src/material/flutter_logo.dart
+++ b/packages/flutter/lib/src/material/flutter_logo.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';

packages/flutter/lib/src/material/grid_tile.dart

diff --git a/packages/flutter/lib/src/material/grid_tile.dart b/packages/flutter/lib/src/material/grid_tile.dart
index 2ca65a5..fa20fed 100644
--- a/packages/flutter/lib/src/material/grid_tile.dart
+++ b/packages/flutter/lib/src/material/grid_tile.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 /// A tile in a material design grid list.

packages/flutter/lib/src/material/grid_tile_bar.dart

diff --git a/packages/flutter/lib/src/material/grid_tile_bar.dart b/packages/flutter/lib/src/material/grid_tile_bar.dart
index 33ea129..24848ad 100644
--- a/packages/flutter/lib/src/material/grid_tile_bar.dart
+++ b/packages/flutter/lib/src/material/grid_tile_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';

packages/flutter/lib/src/material/icon_button.dart

diff --git a/packages/flutter/lib/src/material/icon_button.dart b/packages/flutter/lib/src/material/icon_button.dart
index c30869e..94babb3 100644
--- a/packages/flutter/lib/src/material/icon_button.dart
+++ b/packages/flutter/lib/src/material/icon_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/icons.dart

diff --git a/packages/flutter/lib/src/material/icons.dart b/packages/flutter/lib/src/material/icons.dart
index 87a4bde..96c638e 100644
--- a/packages/flutter/lib/src/material/icons.dart
+++ b/packages/flutter/lib/src/material/icons.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 /// Identifiers for the supported material design icons.

packages/flutter/lib/src/material/ink_decoration.dart

diff --git a/packages/flutter/lib/src/material/ink_decoration.dart b/packages/flutter/lib/src/material/ink_decoration.dart
index 5365797..2085cdc 100644
--- a/packages/flutter/lib/src/material/ink_decoration.dart
+++ b/packages/flutter/lib/src/material/ink_decoration.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/ink_highlight.dart

diff --git a/packages/flutter/lib/src/material/ink_highlight.dart b/packages/flutter/lib/src/material/ink_highlight.dart
index 4775c4f..8b05ef5 100644
--- a/packages/flutter/lib/src/material/ink_highlight.dart
+++ b/packages/flutter/lib/src/material/ink_highlight.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/ink_ripple.dart

diff --git a/packages/flutter/lib/src/material/ink_ripple.dart b/packages/flutter/lib/src/material/ink_ripple.dart
index b2ed186..bd3df65 100644
--- a/packages/flutter/lib/src/material/ink_ripple.dart
+++ b/packages/flutter/lib/src/material/ink_ripple.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/ink_splash.dart

diff --git a/packages/flutter/lib/src/material/ink_splash.dart b/packages/flutter/lib/src/material/ink_splash.dart
index 68ad70e..6ed64ae 100644
--- a/packages/flutter/lib/src/material/ink_splash.dart
+++ b/packages/flutter/lib/src/material/ink_splash.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/ink_well.dart

diff --git a/packages/flutter/lib/src/material/ink_well.dart b/packages/flutter/lib/src/material/ink_well.dart
index db5e8b6..0ab48b1 100644
--- a/packages/flutter/lib/src/material/ink_well.dart
+++ b/packages/flutter/lib/src/material/ink_well.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/input_border.dart

diff --git a/packages/flutter/lib/src/material/input_border.dart b/packages/flutter/lib/src/material/input_border.dart
index 3371a8f..aa1675d 100644
--- a/packages/flutter/lib/src/material/input_border.dart
+++ b/packages/flutter/lib/src/material/input_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show lerpDouble;
 

packages/flutter/lib/src/material/input_decorator.dart

diff --git a/packages/flutter/lib/src/material/input_decorator.dart b/packages/flutter/lib/src/material/input_decorator.dart
index b8e275a..4c68770 100644
--- a/packages/flutter/lib/src/material/input_decorator.dart
+++ b/packages/flutter/lib/src/material/input_decorator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show lerpDouble;
 

packages/flutter/lib/src/material/list_tile.dart

diff --git a/packages/flutter/lib/src/material/list_tile.dart b/packages/flutter/lib/src/material/list_tile.dart
index 7a0fdd6..990c660 100644
--- a/packages/flutter/lib/src/material/list_tile.dart
+++ b/packages/flutter/lib/src/material/list_tile.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/material.dart

diff --git a/packages/flutter/lib/src/material/material.dart b/packages/flutter/lib/src/material/material.dart
index fb758d1..38059e3 100644
--- a/packages/flutter/lib/src/material/material.dart
+++ b/packages/flutter/lib/src/material/material.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/material_button.dart

diff --git a/packages/flutter/lib/src/material/material_button.dart b/packages/flutter/lib/src/material/material_button.dart
index 0f78c0e..7adbf6d 100644
--- a/packages/flutter/lib/src/material/material_button.dart
+++ b/packages/flutter/lib/src/material/material_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/material_localizations.dart

diff --git a/packages/flutter/lib/src/material/material_localizations.dart b/packages/flutter/lib/src/material/material_localizations.dart
index be8ca9d..fa7d392 100644
--- a/packages/flutter/lib/src/material/material_localizations.dart
+++ b/packages/flutter/lib/src/material/material_localizations.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/material_state.dart

diff --git a/packages/flutter/lib/src/material/material_state.dart b/packages/flutter/lib/src/material/material_state.dart
index 5d64c89..32ce53f 100644
--- a/packages/flutter/lib/src/material/material_state.dart
+++ b/packages/flutter/lib/src/material/material_state.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/mergeable_material.dart

diff --git a/packages/flutter/lib/src/material/mergeable_material.dart b/packages/flutter/lib/src/material/mergeable_material.dart
index 8cb5532..b7a7776 100644
--- a/packages/flutter/lib/src/material/mergeable_material.dart
+++ b/packages/flutter/lib/src/material/mergeable_material.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/navigation_rail.dart

diff --git a/packages/flutter/lib/src/material/navigation_rail.dart b/packages/flutter/lib/src/material/navigation_rail.dart
index adbc320..99846ef 100644
--- a/packages/flutter/lib/src/material/navigation_rail.dart
+++ b/packages/flutter/lib/src/material/navigation_rail.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/navigation_rail_theme.dart

diff --git a/packages/flutter/lib/src/material/navigation_rail_theme.dart b/packages/flutter/lib/src/material/navigation_rail_theme.dart
index 470c8d7..fe22a01 100644
--- a/packages/flutter/lib/src/material/navigation_rail_theme.dart
+++ b/packages/flutter/lib/src/material/navigation_rail_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/outline_button.dart

diff --git a/packages/flutter/lib/src/material/outline_button.dart b/packages/flutter/lib/src/material/outline_button.dart
index 95de4af..524ad6b 100644
--- a/packages/flutter/lib/src/material/outline_button.dart
+++ b/packages/flutter/lib/src/material/outline_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/page.dart

diff --git a/packages/flutter/lib/src/material/page.dart b/packages/flutter/lib/src/material/page.dart
index b631439..af0e94f 100644
--- a/packages/flutter/lib/src/material/page.dart
+++ b/packages/flutter/lib/src/material/page.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/page_transitions_theme.dart

diff --git a/packages/flutter/lib/src/material/page_transitions_theme.dart b/packages/flutter/lib/src/material/page_transitions_theme.dart
index 80c3a3a..2b2c523 100644
--- a/packages/flutter/lib/src/material/page_transitions_theme.dart
+++ b/packages/flutter/lib/src/material/page_transitions_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/paginated_data_table.dart

diff --git a/packages/flutter/lib/src/material/paginated_data_table.dart b/packages/flutter/lib/src/material/paginated_data_table.dart
index 941a2ca..a0e9937 100644
--- a/packages/flutter/lib/src/material/paginated_data_table.dart
+++ b/packages/flutter/lib/src/material/paginated_data_table.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/pickers/calendar_date_picker.dart

diff --git a/packages/flutter/lib/src/material/pickers/calendar_date_picker.dart b/packages/flutter/lib/src/material/pickers/calendar_date_picker.dart
index 21591bb..d1214bc 100644
--- a/packages/flutter/lib/src/material/pickers/calendar_date_picker.dart
+++ b/packages/flutter/lib/src/material/pickers/calendar_date_picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/pickers/calendar_date_range_picker.dart

diff --git a/packages/flutter/lib/src/material/pickers/calendar_date_range_picker.dart b/packages/flutter/lib/src/material/pickers/calendar_date_range_picker.dart
index 34d9494..01ef1aa 100644
--- a/packages/flutter/lib/src/material/pickers/calendar_date_range_picker.dart
+++ b/packages/flutter/lib/src/material/pickers/calendar_date_range_picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/lib/src/material/pickers/date_picker_common.dart

diff --git a/packages/flutter/lib/src/material/pickers/date_picker_common.dart b/packages/flutter/lib/src/material/pickers/date_picker_common.dart
index d629955..d13b725 100644
--- a/packages/flutter/lib/src/material/pickers/date_picker_common.dart
+++ b/packages/flutter/lib/src/material/pickers/date_picker_common.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show hashValues;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/pickers/date_picker_deprecated.dart

diff --git a/packages/flutter/lib/src/material/pickers/date_picker_deprecated.dart b/packages/flutter/lib/src/material/pickers/date_picker_deprecated.dart
index 901ac22..e7831a0 100644
--- a/packages/flutter/lib/src/material/pickers/date_picker_deprecated.dart
+++ b/packages/flutter/lib/src/material/pickers/date_picker_deprecated.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/material/pickers/date_picker_dialog.dart

diff --git a/packages/flutter/lib/src/material/pickers/date_picker_dialog.dart b/packages/flutter/lib/src/material/pickers/date_picker_dialog.dart
index 37f01ef..0cd2e88 100644
--- a/packages/flutter/lib/src/material/pickers/date_picker_dialog.dart
+++ b/packages/flutter/lib/src/material/pickers/date_picker_dialog.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/pickers/date_picker_header.dart

diff --git a/packages/flutter/lib/src/material/pickers/date_picker_header.dart b/packages/flutter/lib/src/material/pickers/date_picker_header.dart
index f3f85d0..c8b6ebc 100644
--- a/packages/flutter/lib/src/material/pickers/date_picker_header.dart
+++ b/packages/flutter/lib/src/material/pickers/date_picker_header.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import '../color_scheme.dart';

packages/flutter/lib/src/material/pickers/date_range_picker_dialog.dart

diff --git a/packages/flutter/lib/src/material/pickers/date_range_picker_dialog.dart b/packages/flutter/lib/src/material/pickers/date_range_picker_dialog.dart
index aa1b8c7..ca7c511 100644
--- a/packages/flutter/lib/src/material/pickers/date_range_picker_dialog.dart
+++ b/packages/flutter/lib/src/material/pickers/date_range_picker_dialog.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/pickers/date_utils.dart

diff --git a/packages/flutter/lib/src/material/pickers/date_utils.dart b/packages/flutter/lib/src/material/pickers/date_utils.dart
index 27d67c2..eb2447b 100644
--- a/packages/flutter/lib/src/material/pickers/date_utils.dart
+++ b/packages/flutter/lib/src/material/pickers/date_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 
 // Common date utility functions used by the date picker implementation
 

packages/flutter/lib/src/material/pickers/input_date_picker.dart

diff --git a/packages/flutter/lib/src/material/pickers/input_date_picker.dart b/packages/flutter/lib/src/material/pickers/input_date_picker.dart
index 2c03e0d..ce93683 100644
--- a/packages/flutter/lib/src/material/pickers/input_date_picker.dart
+++ b/packages/flutter/lib/src/material/pickers/input_date_picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/pickers/input_date_range_picker.dart

diff --git a/packages/flutter/lib/src/material/pickers/input_date_range_picker.dart b/packages/flutter/lib/src/material/pickers/input_date_range_picker.dart
index 4661c92..abfa7fa 100644
--- a/packages/flutter/lib/src/material/pickers/input_date_range_picker.dart
+++ b/packages/flutter/lib/src/material/pickers/input_date_range_picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/pickers/pickers.dart

diff --git a/packages/flutter/lib/src/material/pickers/pickers.dart b/packages/flutter/lib/src/material/pickers/pickers.dart
index c68272c..7dca95f 100644
--- a/packages/flutter/lib/src/material/pickers/pickers.dart
+++ b/packages/flutter/lib/src/material/pickers/pickers.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // Date Picker public API
 export 'calendar_date_picker.dart' show CalendarDatePicker;
 export 'date_picker_common.dart' show

packages/flutter/lib/src/material/popup_menu.dart

diff --git a/packages/flutter/lib/src/material/popup_menu.dart b/packages/flutter/lib/src/material/popup_menu.dart
index 56ba76c..edc1166 100644
--- a/packages/flutter/lib/src/material/popup_menu.dart
+++ b/packages/flutter/lib/src/material/popup_menu.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/popup_menu_theme.dart

diff --git a/packages/flutter/lib/src/material/popup_menu_theme.dart b/packages/flutter/lib/src/material/popup_menu_theme.dart
index 875532e..fdf4b3c 100644
--- a/packages/flutter/lib/src/material/popup_menu_theme.dart
+++ b/packages/flutter/lib/src/material/popup_menu_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/progress_indicator.dart

diff --git a/packages/flutter/lib/src/material/progress_indicator.dart b/packages/flutter/lib/src/material/progress_indicator.dart
index c776d11..e9bca15 100644
--- a/packages/flutter/lib/src/material/progress_indicator.dart
+++ b/packages/flutter/lib/src/material/progress_indicator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/radio.dart

diff --git a/packages/flutter/lib/src/material/radio.dart b/packages/flutter/lib/src/material/radio.dart
index 42ec911..be67957 100644
--- a/packages/flutter/lib/src/material/radio.dart
+++ b/packages/flutter/lib/src/material/radio.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/radio_list_tile.dart

diff --git a/packages/flutter/lib/src/material/radio_list_tile.dart b/packages/flutter/lib/src/material/radio_list_tile.dart
index 50274f6..7f71e35 100644
--- a/packages/flutter/lib/src/material/radio_list_tile.dart
+++ b/packages/flutter/lib/src/material/radio_list_tile.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'list_tile.dart';

packages/flutter/lib/src/material/raised_button.dart

diff --git a/packages/flutter/lib/src/material/raised_button.dart b/packages/flutter/lib/src/material/raised_button.dart
index 6373b72..64f6e80 100644
--- a/packages/flutter/lib/src/material/raised_button.dart
+++ b/packages/flutter/lib/src/material/raised_button.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/range_slider.dart

diff --git a/packages/flutter/lib/src/material/range_slider.dart b/packages/flutter/lib/src/material/range_slider.dart
index c394cce..6755745 100644
--- a/packages/flutter/lib/src/material/range_slider.dart
+++ b/packages/flutter/lib/src/material/range_slider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:ui' as ui;

packages/flutter/lib/src/material/refresh_indicator.dart

diff --git a/packages/flutter/lib/src/material/refresh_indicator.dart b/packages/flutter/lib/src/material/refresh_indicator.dart
index 2f2ae8e..88fda30 100644
--- a/packages/flutter/lib/src/material/refresh_indicator.dart
+++ b/packages/flutter/lib/src/material/refresh_indicator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/material/reorderable_list.dart

diff --git a/packages/flutter/lib/src/material/reorderable_list.dart b/packages/flutter/lib/src/material/reorderable_list.dart
index e11ca12..c12d4cf 100644
--- a/packages/flutter/lib/src/material/reorderable_list.dart
+++ b/packages/flutter/lib/src/material/reorderable_list.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math';
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/scaffold.dart

diff --git a/packages/flutter/lib/src/material/scaffold.dart b/packages/flutter/lib/src/material/scaffold.dart
index 41cfb55..2d0c7f3 100644
--- a/packages/flutter/lib/src/material/scaffold.dart
+++ b/packages/flutter/lib/src/material/scaffold.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' as math;

packages/flutter/lib/src/material/scrollbar.dart

diff --git a/packages/flutter/lib/src/material/scrollbar.dart b/packages/flutter/lib/src/material/scrollbar.dart
index 4e89bb8..9283462 100644
--- a/packages/flutter/lib/src/material/scrollbar.dart
+++ b/packages/flutter/lib/src/material/scrollbar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/lib/src/material/search.dart

diff --git a/packages/flutter/lib/src/material/search.dart b/packages/flutter/lib/src/material/search.dart
index 06a822f..8e67097 100644
--- a/packages/flutter/lib/src/material/search.dart
+++ b/packages/flutter/lib/src/material/search.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/selectable_text.dart

diff --git a/packages/flutter/lib/src/material/selectable_text.dart b/packages/flutter/lib/src/material/selectable_text.dart
index ddda220..a4bae6a 100644
--- a/packages/flutter/lib/src/material/selectable_text.dart
+++ b/packages/flutter/lib/src/material/selectable_text.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/lib/src/material/shadows.dart

diff --git a/packages/flutter/lib/src/material/shadows.dart b/packages/flutter/lib/src/material/shadows.dart
index 8c8760c..8570da7 100644
--- a/packages/flutter/lib/src/material/shadows.dart
+++ b/packages/flutter/lib/src/material/shadows.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color, Offset;
 
 import 'package:flutter/painting.dart';

packages/flutter/lib/src/material/slider.dart

diff --git a/packages/flutter/lib/src/material/slider.dart b/packages/flutter/lib/src/material/slider.dart
index e93434b..88690d1 100644
--- a/packages/flutter/lib/src/material/slider.dart
+++ b/packages/flutter/lib/src/material/slider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:math';

packages/flutter/lib/src/material/slider_theme.dart

diff --git a/packages/flutter/lib/src/material/slider_theme.dart b/packages/flutter/lib/src/material/slider_theme.dart
index 5de9d4f..1009f85 100644
--- a/packages/flutter/lib/src/material/slider_theme.dart
+++ b/packages/flutter/lib/src/material/slider_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show Path, lerpDouble;
 

packages/flutter/lib/src/material/snack_bar.dart

diff --git a/packages/flutter/lib/src/material/snack_bar.dart b/packages/flutter/lib/src/material/snack_bar.dart
index fb64414..cd114c5 100644
--- a/packages/flutter/lib/src/material/snack_bar.dart
+++ b/packages/flutter/lib/src/material/snack_bar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/snack_bar_theme.dart

diff --git a/packages/flutter/lib/src/material/snack_bar_theme.dart b/packages/flutter/lib/src/material/snack_bar_theme.dart
index a771254..ef9d15f 100644
--- a/packages/flutter/lib/src/material/snack_bar_theme.dart
+++ b/packages/flutter/lib/src/material/snack_bar_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/stepper.dart

diff --git a/packages/flutter/lib/src/material/stepper.dart b/packages/flutter/lib/src/material/stepper.dart
index 1194b90..01dc682 100644
--- a/packages/flutter/lib/src/material/stepper.dart
+++ b/packages/flutter/lib/src/material/stepper.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'button_theme.dart';

packages/flutter/lib/src/material/switch.dart

diff --git a/packages/flutter/lib/src/material/switch.dart b/packages/flutter/lib/src/material/switch.dart
index 1bf29a8..5404320 100644
--- a/packages/flutter/lib/src/material/switch.dart
+++ b/packages/flutter/lib/src/material/switch.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/material/switch_list_tile.dart

diff --git a/packages/flutter/lib/src/material/switch_list_tile.dart b/packages/flutter/lib/src/material/switch_list_tile.dart
index cf14d89..c860910 100644
--- a/packages/flutter/lib/src/material/switch_list_tile.dart
+++ b/packages/flutter/lib/src/material/switch_list_tile.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'list_tile.dart';

packages/flutter/lib/src/material/tab_bar_theme.dart

diff --git a/packages/flutter/lib/src/material/tab_bar_theme.dart b/packages/flutter/lib/src/material/tab_bar_theme.dart
index e50f6c8..7d94fe0 100644
--- a/packages/flutter/lib/src/material/tab_bar_theme.dart
+++ b/packages/flutter/lib/src/material/tab_bar_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/tab_controller.dart

diff --git a/packages/flutter/lib/src/material/tab_controller.dart b/packages/flutter/lib/src/material/tab_controller.dart
index 23ec1b4..4b7ca51 100644
--- a/packages/flutter/lib/src/material/tab_controller.dart
+++ b/packages/flutter/lib/src/material/tab_controller.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/tab_indicator.dart

diff --git a/packages/flutter/lib/src/material/tab_indicator.dart b/packages/flutter/lib/src/material/tab_indicator.dart
index fb27f2e..5132746 100644
--- a/packages/flutter/lib/src/material/tab_indicator.dart
+++ b/packages/flutter/lib/src/material/tab_indicator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 
 import 'colors.dart';

packages/flutter/lib/src/material/tabs.dart

diff --git a/packages/flutter/lib/src/material/tabs.dart b/packages/flutter/lib/src/material/tabs.dart
index 39773d2..b80fc727 100644
--- a/packages/flutter/lib/src/material/tabs.dart
+++ b/packages/flutter/lib/src/material/tabs.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show lerpDouble;
 

packages/flutter/lib/src/material/text_field.dart

diff --git a/packages/flutter/lib/src/material/text_field.dart b/packages/flutter/lib/src/material/text_field.dart
index fff7fee..46a92df 100644
--- a/packages/flutter/lib/src/material/text_field.dart
+++ b/packages/flutter/lib/src/material/text_field.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // TODO(Piinks): Remove ignoring deprecated member use analysis
 // when TextField.canAssertMaterialLocalizations parameter is removed.
 // ignore_for_file: deprecated_member_use_from_same_package

packages/flutter/lib/src/material/text_form_field.dart

diff --git a/packages/flutter/lib/src/material/text_form_field.dart b/packages/flutter/lib/src/material/text_form_field.dart
index 70bd990..ab58455 100644
--- a/packages/flutter/lib/src/material/text_form_field.dart
+++ b/packages/flutter/lib/src/material/text_form_field.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/lib/src/material/text_selection.dart

diff --git a/packages/flutter/lib/src/material/text_selection.dart b/packages/flutter/lib/src/material/text_selection.dart
index f590ea6..1a441ae 100644
--- a/packages/flutter/lib/src/material/text_selection.dart
+++ b/packages/flutter/lib/src/material/text_selection.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/material/text_theme.dart

diff --git a/packages/flutter/lib/src/material/text_theme.dart b/packages/flutter/lib/src/material/text_theme.dart
index 98588c7..37b104c 100644
--- a/packages/flutter/lib/src/material/text_theme.dart
+++ b/packages/flutter/lib/src/material/text_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/lib/src/material/theme.dart

diff --git a/packages/flutter/lib/src/material/theme.dart b/packages/flutter/lib/src/material/theme.dart
index 7a32098..0c67a4a 100644
--- a/packages/flutter/lib/src/material/theme.dart
+++ b/packages/flutter/lib/src/material/theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/theme_data.dart

diff --git a/packages/flutter/lib/src/material/theme_data.dart b/packages/flutter/lib/src/material/theme_data.dart
index e9bded5..92edc65 100644
--- a/packages/flutter/lib/src/material/theme_data.dart
+++ b/packages/flutter/lib/src/material/theme_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color, hashList, lerpDouble;
 
 import 'package:flutter/cupertino.dart';

packages/flutter/lib/src/material/time.dart

diff --git a/packages/flutter/lib/src/material/time.dart b/packages/flutter/lib/src/material/time.dart
index 2d93b89..33e85b9 100644
--- a/packages/flutter/lib/src/material/time.dart
+++ b/packages/flutter/lib/src/material/time.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show hashValues;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/material/time_picker.dart

diff --git a/packages/flutter/lib/src/material/time_picker.dart b/packages/flutter/lib/src/material/time_picker.dart
index 066a143..d432664 100644
--- a/packages/flutter/lib/src/material/time_picker.dart
+++ b/packages/flutter/lib/src/material/time_picker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/material/toggle_buttons.dart

diff --git a/packages/flutter/lib/src/material/toggle_buttons.dart b/packages/flutter/lib/src/material/toggle_buttons.dart
index 4d3f0a2..0306385 100644
--- a/packages/flutter/lib/src/material/toggle_buttons.dart
+++ b/packages/flutter/lib/src/material/toggle_buttons.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/toggle_buttons_theme.dart

diff --git a/packages/flutter/lib/src/material/toggle_buttons_theme.dart b/packages/flutter/lib/src/material/toggle_buttons_theme.dart
index bbb62e1..17aeccc 100644
--- a/packages/flutter/lib/src/material/toggle_buttons_theme.dart
+++ b/packages/flutter/lib/src/material/toggle_buttons_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/toggleable.dart

diff --git a/packages/flutter/lib/src/material/toggleable.dart b/packages/flutter/lib/src/material/toggleable.dart
index 17898dd..5186e23 100644
--- a/packages/flutter/lib/src/material/toggleable.dart
+++ b/packages/flutter/lib/src/material/toggleable.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/material/tooltip.dart

diff --git a/packages/flutter/lib/src/material/tooltip.dart b/packages/flutter/lib/src/material/tooltip.dart
index abc9ec3..2d8bea0 100644
--- a/packages/flutter/lib/src/material/tooltip.dart
+++ b/packages/flutter/lib/src/material/tooltip.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/material/tooltip_theme.dart

diff --git a/packages/flutter/lib/src/material/tooltip_theme.dart b/packages/flutter/lib/src/material/tooltip_theme.dart
index 1846287..c1831a4 100644
--- a/packages/flutter/lib/src/material/tooltip_theme.dart
+++ b/packages/flutter/lib/src/material/tooltip_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/material/typography.dart

diff --git a/packages/flutter/lib/src/material/typography.dart b/packages/flutter/lib/src/material/typography.dart
index 157165c..af834d7 100644
--- a/packages/flutter/lib/src/material/typography.dart
+++ b/packages/flutter/lib/src/material/typography.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/lib/src/material/user_accounts_drawer_header.dart

diff --git a/packages/flutter/lib/src/material/user_accounts_drawer_header.dart b/packages/flutter/lib/src/material/user_accounts_drawer_header.dart
index 157a8c0..4121d46 100644
--- a/packages/flutter/lib/src/material/user_accounts_drawer_header.dart
+++ b/packages/flutter/lib/src/material/user_accounts_drawer_header.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/lib/src/painting/_network_image_io.dart

diff --git a/packages/flutter/lib/src/painting/_network_image_io.dart b/packages/flutter/lib/src/painting/_network_image_io.dart
index 9a13991..b336844 100644
--- a/packages/flutter/lib/src/painting/_network_image_io.dart
+++ b/packages/flutter/lib/src/painting/_network_image_io.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io';
 import 'dart:typed_data';

packages/flutter/lib/src/painting/_network_image_web.dart

diff --git a/packages/flutter/lib/src/painting/_network_image_web.dart b/packages/flutter/lib/src/painting/_network_image_web.dart
index 99fe45a..7a2845c 100644
--- a/packages/flutter/lib/src/painting/_network_image_web.dart
+++ b/packages/flutter/lib/src/painting/_network_image_web.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui;
 

packages/flutter/lib/src/painting/alignment.dart

diff --git a/packages/flutter/lib/src/painting/alignment.dart b/packages/flutter/lib/src/painting/alignment.dart
index b5d6bc3..79ac7e9 100644
--- a/packages/flutter/lib/src/painting/alignment.dart
+++ b/packages/flutter/lib/src/painting/alignment.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/basic_types.dart

diff --git a/packages/flutter/lib/src/painting/basic_types.dart b/packages/flutter/lib/src/painting/basic_types.dart
index f1ced61..47c7768 100644
--- a/packages/flutter/lib/src/painting/basic_types.dart
+++ b/packages/flutter/lib/src/painting/basic_types.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show TextDirection;
 
 export 'dart:ui' show

packages/flutter/lib/src/painting/beveled_rectangle_border.dart

diff --git a/packages/flutter/lib/src/painting/beveled_rectangle_border.dart b/packages/flutter/lib/src/painting/beveled_rectangle_border.dart
index 9758ee8..f83929c 100644
--- a/packages/flutter/lib/src/painting/beveled_rectangle_border.dart
+++ b/packages/flutter/lib/src/painting/beveled_rectangle_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/binding.dart

diff --git a/packages/flutter/lib/src/painting/binding.dart b/packages/flutter/lib/src/painting/binding.dart
index 884e68f..47c968c 100644
--- a/packages/flutter/lib/src/painting/binding.dart
+++ b/packages/flutter/lib/src/painting/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data' show Uint8List;
 import 'dart:ui' as ui show instantiateImageCodec, Codec;
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/border_radius.dart

diff --git a/packages/flutter/lib/src/painting/border_radius.dart b/packages/flutter/lib/src/painting/border_radius.dart
index fa1b5de..b6aa2d6 100644
--- a/packages/flutter/lib/src/painting/border_radius.dart
+++ b/packages/flutter/lib/src/painting/border_radius.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/borders.dart

diff --git a/packages/flutter/lib/src/painting/borders.dart b/packages/flutter/lib/src/painting/borders.dart
index 9e1fb84..388ccc9 100644
--- a/packages/flutter/lib/src/painting/borders.dart
+++ b/packages/flutter/lib/src/painting/borders.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui show lerpDouble;
 

packages/flutter/lib/src/painting/box_border.dart

diff --git a/packages/flutter/lib/src/painting/box_border.dart b/packages/flutter/lib/src/painting/box_border.dart
index b7d4eca..f3e43fa 100644
--- a/packages/flutter/lib/src/painting/box_border.dart
+++ b/packages/flutter/lib/src/painting/box_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/box_decoration.dart

diff --git a/packages/flutter/lib/src/painting/box_decoration.dart b/packages/flutter/lib/src/painting/box_decoration.dart
index 7a5dc25..d5c647f 100644
--- a/packages/flutter/lib/src/painting/box_decoration.dart
+++ b/packages/flutter/lib/src/painting/box_decoration.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/box_fit.dart

diff --git a/packages/flutter/lib/src/painting/box_fit.dart b/packages/flutter/lib/src/painting/box_fit.dart
index 05035e8..2b71338 100644
--- a/packages/flutter/lib/src/painting/box_fit.dart
+++ b/packages/flutter/lib/src/painting/box_fit.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/box_shadow.dart

diff --git a/packages/flutter/lib/src/painting/box_shadow.dart b/packages/flutter/lib/src/painting/box_shadow.dart
index 947b9b0..58f415a 100644
--- a/packages/flutter/lib/src/painting/box_shadow.dart
+++ b/packages/flutter/lib/src/painting/box_shadow.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui show Shadow, lerpDouble;
 

packages/flutter/lib/src/painting/circle_border.dart

diff --git a/packages/flutter/lib/src/painting/circle_border.dart b/packages/flutter/lib/src/painting/circle_border.dart
index 323d111..dddfc9f 100644
--- a/packages/flutter/lib/src/painting/circle_border.dart
+++ b/packages/flutter/lib/src/painting/circle_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/clip.dart

diff --git a/packages/flutter/lib/src/painting/clip.dart b/packages/flutter/lib/src/painting/clip.dart
index efce339..ced537f 100644
--- a/packages/flutter/lib/src/painting/clip.dart
+++ b/packages/flutter/lib/src/painting/clip.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Canvas, Clip, Path, Paint, Rect, RRect;
 
 /// Clip utilities used by [PaintingContext] and [TestRecordingPaintingContext].

packages/flutter/lib/src/painting/colors.dart

diff --git a/packages/flutter/lib/src/painting/colors.dart b/packages/flutter/lib/src/painting/colors.dart
index 08d75ad..02320d3 100644
--- a/packages/flutter/lib/src/painting/colors.dart
+++ b/packages/flutter/lib/src/painting/colors.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show Color, lerpDouble, hashValues;
 

packages/flutter/lib/src/painting/continuous_rectangle_border.dart

diff --git a/packages/flutter/lib/src/painting/continuous_rectangle_border.dart b/packages/flutter/lib/src/painting/continuous_rectangle_border.dart
index eb730ad..fa53083 100644
--- a/packages/flutter/lib/src/painting/continuous_rectangle_border.dart
+++ b/packages/flutter/lib/src/painting/continuous_rectangle_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/debug.dart

diff --git a/packages/flutter/lib/src/painting/debug.dart b/packages/flutter/lib/src/painting/debug.dart
index 9095db4..cd00303 100644
--- a/packages/flutter/lib/src/painting/debug.dart
+++ b/packages/flutter/lib/src/painting/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:io';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/decoration.dart

diff --git a/packages/flutter/lib/src/painting/decoration.dart b/packages/flutter/lib/src/painting/decoration.dart
index ae2ae4e..07d6f3c 100644
--- a/packages/flutter/lib/src/painting/decoration.dart
+++ b/packages/flutter/lib/src/painting/decoration.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/decoration_image.dart

diff --git a/packages/flutter/lib/src/painting/decoration_image.dart b/packages/flutter/lib/src/painting/decoration_image.dart
index 65a5647..1fae68b 100644
--- a/packages/flutter/lib/src/painting/decoration_image.dart
+++ b/packages/flutter/lib/src/painting/decoration_image.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Image;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/edge_insets.dart

diff --git a/packages/flutter/lib/src/painting/edge_insets.dart b/packages/flutter/lib/src/painting/edge_insets.dart
index c1ec757..985070c 100644
--- a/packages/flutter/lib/src/painting/edge_insets.dart
+++ b/packages/flutter/lib/src/painting/edge_insets.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show lerpDouble, WindowPadding;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/flutter_logo.dart

diff --git a/packages/flutter/lib/src/painting/flutter_logo.dart b/packages/flutter/lib/src/painting/flutter_logo.dart
index bc783fb..da111d3 100644
--- a/packages/flutter/lib/src/painting/flutter_logo.dart
+++ b/packages/flutter/lib/src/painting/flutter_logo.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:typed_data';
 import 'dart:ui' as ui show Gradient, TextBox, lerpDouble;

packages/flutter/lib/src/painting/fractional_offset.dart

diff --git a/packages/flutter/lib/src/painting/fractional_offset.dart b/packages/flutter/lib/src/painting/fractional_offset.dart
index ef44361..e762b10 100644
--- a/packages/flutter/lib/src/painting/fractional_offset.dart
+++ b/packages/flutter/lib/src/painting/fractional_offset.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/geometry.dart

diff --git a/packages/flutter/lib/src/painting/geometry.dart b/packages/flutter/lib/src/painting/geometry.dart
index 2b1d665..856b88e 100644
--- a/packages/flutter/lib/src/painting/geometry.dart
+++ b/packages/flutter/lib/src/painting/geometry.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/gradient.dart

diff --git a/packages/flutter/lib/src/painting/gradient.dart b/packages/flutter/lib/src/painting/gradient.dart
index 7f57e8c..1dde54c 100644
--- a/packages/flutter/lib/src/painting/gradient.dart
+++ b/packages/flutter/lib/src/painting/gradient.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:math' as math;
 import 'dart:typed_data';

packages/flutter/lib/src/painting/image_cache.dart

diff --git a/packages/flutter/lib/src/painting/image_cache.dart b/packages/flutter/lib/src/painting/image_cache.dart
index 777a888..159478f 100644
--- a/packages/flutter/lib/src/painting/image_cache.dart
+++ b/packages/flutter/lib/src/painting/image_cache.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:developer';
 import 'dart:ui' show hashValues;
 

packages/flutter/lib/src/painting/image_decoder.dart

diff --git a/packages/flutter/lib/src/painting/image_decoder.dart b/packages/flutter/lib/src/painting/image_decoder.dart
index 7bbb297..c2e5313 100644
--- a/packages/flutter/lib/src/painting/image_decoder.dart
+++ b/packages/flutter/lib/src/painting/image_decoder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui show Codec, FrameInfo, Image;

packages/flutter/lib/src/painting/image_provider.dart

diff --git a/packages/flutter/lib/src/painting/image_provider.dart b/packages/flutter/lib/src/painting/image_provider.dart
index c6ffb7f..370f854 100644
--- a/packages/flutter/lib/src/painting/image_provider.dart
+++ b/packages/flutter/lib/src/painting/image_provider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io';
 import 'dart:typed_data';

packages/flutter/lib/src/painting/image_resolution.dart

diff --git a/packages/flutter/lib/src/painting/image_resolution.dart b/packages/flutter/lib/src/painting/image_resolution.dart
index 172d635..f06e635 100644
--- a/packages/flutter/lib/src/painting/image_resolution.dart
+++ b/packages/flutter/lib/src/painting/image_resolution.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';

packages/flutter/lib/src/painting/image_stream.dart

diff --git a/packages/flutter/lib/src/painting/image_stream.dart b/packages/flutter/lib/src/painting/image_stream.dart
index 49e4328..abf9b29 100644
--- a/packages/flutter/lib/src/painting/image_stream.dart
+++ b/packages/flutter/lib/src/painting/image_stream.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui show Image, Codec, FrameInfo;
 import 'dart:ui' show hashValues;

packages/flutter/lib/src/painting/inline_span.dart

diff --git a/packages/flutter/lib/src/painting/inline_span.dart b/packages/flutter/lib/src/painting/inline_span.dart
index dea7e63..412e6d2 100644
--- a/packages/flutter/lib/src/painting/inline_span.dart
+++ b/packages/flutter/lib/src/painting/inline_span.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show ParagraphBuilder;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/matrix_utils.dart

diff --git a/packages/flutter/lib/src/painting/matrix_utils.dart b/packages/flutter/lib/src/painting/matrix_utils.dart
index ef9f791..56695ce 100644
--- a/packages/flutter/lib/src/painting/matrix_utils.dart
+++ b/packages/flutter/lib/src/painting/matrix_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/notched_shapes.dart

diff --git a/packages/flutter/lib/src/painting/notched_shapes.dart b/packages/flutter/lib/src/painting/notched_shapes.dart
index 4e79410..9c6b9a1 100644
--- a/packages/flutter/lib/src/painting/notched_shapes.dart
+++ b/packages/flutter/lib/src/painting/notched_shapes.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/paint_utilities.dart

diff --git a/packages/flutter/lib/src/painting/paint_utilities.dart b/packages/flutter/lib/src/painting/paint_utilities.dart
index 54629b9..339daa6 100644
--- a/packages/flutter/lib/src/painting/paint_utilities.dart
+++ b/packages/flutter/lib/src/painting/paint_utilities.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/placeholder_span.dart

diff --git a/packages/flutter/lib/src/painting/placeholder_span.dart b/packages/flutter/lib/src/painting/placeholder_span.dart
index bf87624..1eb22d4 100644
--- a/packages/flutter/lib/src/painting/placeholder_span.dart
+++ b/packages/flutter/lib/src/painting/placeholder_span.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show PlaceholderAlignment;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/rounded_rectangle_border.dart

diff --git a/packages/flutter/lib/src/painting/rounded_rectangle_border.dart b/packages/flutter/lib/src/painting/rounded_rectangle_border.dart
index 0dd817a..4cd14db 100644
--- a/packages/flutter/lib/src/painting/rounded_rectangle_border.dart
+++ b/packages/flutter/lib/src/painting/rounded_rectangle_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/shader_warm_up.dart

diff --git a/packages/flutter/lib/src/painting/shader_warm_up.dart b/packages/flutter/lib/src/painting/shader_warm_up.dart
index d2694b9..7a31cd4 100644
--- a/packages/flutter/lib/src/painting/shader_warm_up.dart
+++ b/packages/flutter/lib/src/painting/shader_warm_up.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:developer';
 import 'dart:ui' as ui;

packages/flutter/lib/src/painting/shape_decoration.dart

diff --git a/packages/flutter/lib/src/painting/shape_decoration.dart b/packages/flutter/lib/src/painting/shape_decoration.dart
index 6237e46..e4e5b1f 100644
--- a/packages/flutter/lib/src/painting/shape_decoration.dart
+++ b/packages/flutter/lib/src/painting/shape_decoration.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/stadium_border.dart

diff --git a/packages/flutter/lib/src/painting/stadium_border.dart b/packages/flutter/lib/src/painting/stadium_border.dart
index 159c9f6..d19dca7 100644
--- a/packages/flutter/lib/src/painting/stadium_border.dart
+++ b/packages/flutter/lib/src/painting/stadium_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show lerpDouble;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/strut_style.dart

diff --git a/packages/flutter/lib/src/painting/strut_style.dart b/packages/flutter/lib/src/painting/strut_style.dart
index f405e5e..24f63a5 100644
--- a/packages/flutter/lib/src/painting/strut_style.dart
+++ b/packages/flutter/lib/src/painting/strut_style.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic_types.dart';

packages/flutter/lib/src/painting/text_painter.dart

diff --git a/packages/flutter/lib/src/painting/text_painter.dart b/packages/flutter/lib/src/painting/text_painter.dart
index 0b3b9c9..ed50f6b 100644
--- a/packages/flutter/lib/src/painting/text_painter.dart
+++ b/packages/flutter/lib/src/painting/text_painter.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' show min, max;
 import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, PlaceholderAlignment, LineMetrics, TextHeightBehavior, BoxHeightStyle, BoxWidthStyle;
 

packages/flutter/lib/src/painting/text_span.dart

diff --git a/packages/flutter/lib/src/painting/text_span.dart b/packages/flutter/lib/src/painting/text_span.dart
index 2387294..7373712 100644
--- a/packages/flutter/lib/src/painting/text_span.dart
+++ b/packages/flutter/lib/src/painting/text_span.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show ParagraphBuilder;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/painting/text_style.dart

diff --git a/packages/flutter/lib/src/painting/text_style.dart b/packages/flutter/lib/src/painting/text_style.dart
index 24b59b2..cba43ca 100644
--- a/packages/flutter/lib/src/painting/text_style.dart
+++ b/packages/flutter/lib/src/painting/text_style.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show ParagraphStyle, TextStyle, StrutStyle, lerpDouble, Shadow, FontFeature, TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/physics/clamped_simulation.dart

diff --git a/packages/flutter/lib/src/physics/clamped_simulation.dart b/packages/flutter/lib/src/physics/clamped_simulation.dart
index d5fa6e2..0b21c36 100644
--- a/packages/flutter/lib/src/physics/clamped_simulation.dart
+++ b/packages/flutter/lib/src/physics/clamped_simulation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'simulation.dart';
 
 /// A simulation that applies limits to another simulation.

packages/flutter/lib/src/physics/friction_simulation.dart

diff --git a/packages/flutter/lib/src/physics/friction_simulation.dart b/packages/flutter/lib/src/physics/friction_simulation.dart
index a416c78..efa89c6 100644
--- a/packages/flutter/lib/src/physics/friction_simulation.dart
+++ b/packages/flutter/lib/src/physics/friction_simulation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'simulation.dart';

packages/flutter/lib/src/physics/gravity_simulation.dart

diff --git a/packages/flutter/lib/src/physics/gravity_simulation.dart b/packages/flutter/lib/src/physics/gravity_simulation.dart
index 4f3bdf2..df76856 100644
--- a/packages/flutter/lib/src/physics/gravity_simulation.dart
+++ b/packages/flutter/lib/src/physics/gravity_simulation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'simulation.dart';
 
 // Examples can assume:

packages/flutter/lib/src/physics/simulation.dart

diff --git a/packages/flutter/lib/src/physics/simulation.dart b/packages/flutter/lib/src/physics/simulation.dart
index fc67321..0575e8c 100644
--- a/packages/flutter/lib/src/physics/simulation.dart
+++ b/packages/flutter/lib/src/physics/simulation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'tolerance.dart';

packages/flutter/lib/src/physics/spring_simulation.dart

diff --git a/packages/flutter/lib/src/physics/spring_simulation.dart b/packages/flutter/lib/src/physics/spring_simulation.dart
index cf72ada..0085c25 100644
--- a/packages/flutter/lib/src/physics/spring_simulation.dart
+++ b/packages/flutter/lib/src/physics/spring_simulation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/physics/tolerance.dart

diff --git a/packages/flutter/lib/src/physics/tolerance.dart b/packages/flutter/lib/src/physics/tolerance.dart
index 6351a2d..58d7235 100644
--- a/packages/flutter/lib/src/physics/tolerance.dart
+++ b/packages/flutter/lib/src/physics/tolerance.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Structure that specifies maximum allowable magnitudes for distances,
 /// durations, and velocity differences to be considered equal.
 class Tolerance {

packages/flutter/lib/src/physics/utils.dart

diff --git a/packages/flutter/lib/src/physics/utils.dart b/packages/flutter/lib/src/physics/utils.dart
index 8bfef96..9d760a3 100644
--- a/packages/flutter/lib/src/physics/utils.dart
+++ b/packages/flutter/lib/src/physics/utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Whether two doubles are within a given distance of each other.
 ///
 /// The `epsilon` argument must be positive and not null.

packages/flutter/lib/src/rendering/animated_size.dart

diff --git a/packages/flutter/lib/src/rendering/animated_size.dart b/packages/flutter/lib/src/rendering/animated_size.dart
index 4b02cbf..689e6bf 100644
--- a/packages/flutter/lib/src/rendering/animated_size.dart
+++ b/packages/flutter/lib/src/rendering/animated_size.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';

packages/flutter/lib/src/rendering/binding.dart

diff --git a/packages/flutter/lib/src/rendering/binding.dart b/packages/flutter/lib/src/rendering/binding.dart
index 49ea361..5f78c21 100644
--- a/packages/flutter/lib/src/rendering/binding.dart
+++ b/packages/flutter/lib/src/rendering/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:developer';
 import 'dart:typed_data';

packages/flutter/lib/src/rendering/box.dart

diff --git a/packages/flutter/lib/src/rendering/box.dart b/packages/flutter/lib/src/rendering/box.dart
index 4e49ab8..cae042f 100644
--- a/packages/flutter/lib/src/rendering/box.dart
+++ b/packages/flutter/lib/src/rendering/box.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui show lerpDouble;
 

packages/flutter/lib/src/rendering/custom_layout.dart

diff --git a/packages/flutter/lib/src/rendering/custom_layout.dart b/packages/flutter/lib/src/rendering/custom_layout.dart
index ebb1075..b650b63 100644
--- a/packages/flutter/lib/src/rendering/custom_layout.dart
+++ b/packages/flutter/lib/src/rendering/custom_layout.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'box.dart';

packages/flutter/lib/src/rendering/custom_paint.dart

diff --git a/packages/flutter/lib/src/rendering/custom_paint.dart b/packages/flutter/lib/src/rendering/custom_paint.dart
index 4ba6dd5..f6b8d0e 100644
--- a/packages/flutter/lib/src/rendering/custom_paint.dart
+++ b/packages/flutter/lib/src/rendering/custom_paint.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/debug.dart

diff --git a/packages/flutter/lib/src/rendering/debug.dart b/packages/flutter/lib/src/rendering/debug.dart
index 7530c85..bc4ab42 100644
--- a/packages/flutter/lib/src/rendering/debug.dart
+++ b/packages/flutter/lib/src/rendering/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/lib/src/rendering/debug_overflow_indicator.dart

diff --git a/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart b/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart
index c013347..1acd095 100644
--- a/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart
+++ b/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui;
 

packages/flutter/lib/src/rendering/editable.dart

diff --git a/packages/flutter/lib/src/rendering/editable.dart b/packages/flutter/lib/src/rendering/editable.dart
index 9fd74ca..1e2e776 100644
--- a/packages/flutter/lib/src/rendering/editable.dart
+++ b/packages/flutter/lib/src/rendering/editable.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui show TextBox, lerpDouble, BoxHeightStyle, BoxWidthStyle;
 

packages/flutter/lib/src/rendering/error.dart

diff --git a/packages/flutter/lib/src/rendering/error.dart b/packages/flutter/lib/src/rendering/error.dart
index 31777a5..cc02bf6 100644
--- a/packages/flutter/lib/src/rendering/error.dart
+++ b/packages/flutter/lib/src/rendering/error.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Paragraph, ParagraphBuilder, ParagraphConstraints, ParagraphStyle, TextStyle;
 
 import 'box.dart';

packages/flutter/lib/src/rendering/flex.dart

diff --git a/packages/flutter/lib/src/rendering/flex.dart b/packages/flutter/lib/src/rendering/flex.dart
index 45cdc72..2086674 100644
--- a/packages/flutter/lib/src/rendering/flex.dart
+++ b/packages/flutter/lib/src/rendering/flex.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/flow.dart

diff --git a/packages/flutter/lib/src/rendering/flow.dart b/packages/flutter/lib/src/rendering/flow.dart
index 1ec9ef6..49ab2ba 100644
--- a/packages/flutter/lib/src/rendering/flow.dart
+++ b/packages/flutter/lib/src/rendering/flow.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Color;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/image.dart

diff --git a/packages/flutter/lib/src/rendering/image.dart b/packages/flutter/lib/src/rendering/image.dart
index ffd8864..bc354c3 100644
--- a/packages/flutter/lib/src/rendering/image.dart
+++ b/packages/flutter/lib/src/rendering/image.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Image;
 
 import 'box.dart';

packages/flutter/lib/src/rendering/layer.dart

diff --git a/packages/flutter/lib/src/rendering/layer.dart b/packages/flutter/lib/src/rendering/layer.dart
index 8d76ee2..17f3cd1 100644
--- a/packages/flutter/lib/src/rendering/layer.dart
+++ b/packages/flutter/lib/src/rendering/layer.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:ui' as ui;

packages/flutter/lib/src/rendering/list_body.dart

diff --git a/packages/flutter/lib/src/rendering/list_body.dart b/packages/flutter/lib/src/rendering/list_body.dart
index 00e5251..3ace7da 100644
--- a/packages/flutter/lib/src/rendering/list_body.dart
+++ b/packages/flutter/lib/src/rendering/list_body.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'box.dart';

packages/flutter/lib/src/rendering/list_wheel_viewport.dart

diff --git a/packages/flutter/lib/src/rendering/list_wheel_viewport.dart b/packages/flutter/lib/src/rendering/list_wheel_viewport.dart
index 7ae0aab..c324fae 100644
--- a/packages/flutter/lib/src/rendering/list_wheel_viewport.dart
+++ b/packages/flutter/lib/src/rendering/list_wheel_viewport.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/rendering/mouse_cursor.dart

diff --git a/packages/flutter/lib/src/rendering/mouse_cursor.dart b/packages/flutter/lib/src/rendering/mouse_cursor.dart
index d8c9efc..eafd597 100644
--- a/packages/flutter/lib/src/rendering/mouse_cursor.dart
+++ b/packages/flutter/lib/src/rendering/mouse_cursor.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection' show LinkedHashSet;
 

packages/flutter/lib/src/rendering/mouse_tracking.dart

diff --git a/packages/flutter/lib/src/rendering/mouse_tracking.dart b/packages/flutter/lib/src/rendering/mouse_tracking.dart
index a1fccb8..2d06a08 100644
--- a/packages/flutter/lib/src/rendering/mouse_tracking.dart
+++ b/packages/flutter/lib/src/rendering/mouse_tracking.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection' show LinkedHashSet;
 import 'dart:ui';
 

packages/flutter/lib/src/rendering/object.dart

diff --git a/packages/flutter/lib/src/rendering/object.dart b/packages/flutter/lib/src/rendering/object.dart
index a6abe70..044a9f4 100644
--- a/packages/flutter/lib/src/rendering/object.dart
+++ b/packages/flutter/lib/src/rendering/object.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:developer';
 import 'dart:ui' as ui show PictureRecorder;
 

packages/flutter/lib/src/rendering/paragraph.dart

diff --git a/packages/flutter/lib/src/rendering/paragraph.dart b/packages/flutter/lib/src/rendering/paragraph.dart
index e68b69d..1c60f72 100644
--- a/packages/flutter/lib/src/rendering/paragraph.dart
+++ b/packages/flutter/lib/src/rendering/paragraph.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:math' as math;
 import 'dart:ui' as ui show Gradient, Shader, TextBox, PlaceholderAlignment, TextHeightBehavior;

packages/flutter/lib/src/rendering/performance_overlay.dart

diff --git a/packages/flutter/lib/src/rendering/performance_overlay.dart b/packages/flutter/lib/src/rendering/performance_overlay.dart
index 9ec2952..56d061e 100644
--- a/packages/flutter/lib/src/rendering/performance_overlay.dart
+++ b/packages/flutter/lib/src/rendering/performance_overlay.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'box.dart';
 import 'layer.dart';
 import 'object.dart';

packages/flutter/lib/src/rendering/platform_view.dart

diff --git a/packages/flutter/lib/src/rendering/platform_view.dart b/packages/flutter/lib/src/rendering/platform_view.dart
index 52d5211..3ce6124 100644
--- a/packages/flutter/lib/src/rendering/platform_view.dart
+++ b/packages/flutter/lib/src/rendering/platform_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui';
 

packages/flutter/lib/src/rendering/proxy_box.dart

diff --git a/packages/flutter/lib/src/rendering/proxy_box.dart b/packages/flutter/lib/src/rendering/proxy_box.dart
index 0d85ea2..eb252ae 100644
--- a/packages/flutter/lib/src/rendering/proxy_box.dart
+++ b/packages/flutter/lib/src/rendering/proxy_box.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'dart:ui' as ui show ImageFilter, Gradient, Image, Color;

packages/flutter/lib/src/rendering/proxy_sliver.dart

diff --git a/packages/flutter/lib/src/rendering/proxy_sliver.dart b/packages/flutter/lib/src/rendering/proxy_sliver.dart
index c8ef508..eeb287d 100644
--- a/packages/flutter/lib/src/rendering/proxy_sliver.dart
+++ b/packages/flutter/lib/src/rendering/proxy_sliver.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Color;
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/rendering/rotated_box.dart

diff --git a/packages/flutter/lib/src/rendering/rotated_box.dart b/packages/flutter/lib/src/rendering/rotated_box.dart
index 3470537..ba91d68 100644
--- a/packages/flutter/lib/src/rendering/rotated_box.dart
+++ b/packages/flutter/lib/src/rendering/rotated_box.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/shifted_box.dart

diff --git a/packages/flutter/lib/src/rendering/shifted_box.dart b/packages/flutter/lib/src/rendering/shifted_box.dart
index 832359c..b5f0537 100644
--- a/packages/flutter/lib/src/rendering/shifted_box.dart
+++ b/packages/flutter/lib/src/rendering/shifted_box.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/sliver.dart

diff --git a/packages/flutter/lib/src/rendering/sliver.dart b/packages/flutter/lib/src/rendering/sliver.dart
index 48e0ba9..c93b6cd 100644
--- a/packages/flutter/lib/src/rendering/sliver.dart
+++ b/packages/flutter/lib/src/rendering/sliver.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/sliver_fill.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_fill.dart b/packages/flutter/lib/src/rendering/sliver_fill.dart
index fc51eb6..92448d4 100644
--- a/packages/flutter/lib/src/rendering/sliver_fill.dart
+++ b/packages/flutter/lib/src/rendering/sliver_fill.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart b/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart
index 7884578..97ec874 100644
--- a/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart
+++ b/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/sliver_grid.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_grid.dart b/packages/flutter/lib/src/rendering/sliver_grid.dart
index 34be07f..a29fe11 100644
--- a/packages/flutter/lib/src/rendering/sliver_grid.dart
+++ b/packages/flutter/lib/src/rendering/sliver_grid.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/sliver_list.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_list.dart b/packages/flutter/lib/src/rendering/sliver_list.dart
index cdc9c1a..458a32e 100644
--- a/packages/flutter/lib/src/rendering/sliver_list.dart
+++ b/packages/flutter/lib/src/rendering/sliver_list.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'box.dart';

packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart b/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
index 95fbc41..244e7e0 100644
--- a/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
+++ b/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:vector_math/vector_math_64.dart';

packages/flutter/lib/src/rendering/sliver_padding.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_padding.dart b/packages/flutter/lib/src/rendering/sliver_padding.dart
index c923fa9..5f4e3bf 100644
--- a/packages/flutter/lib/src/rendering/sliver_padding.dart
+++ b/packages/flutter/lib/src/rendering/sliver_padding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/rendering/sliver_persistent_header.dart

diff --git a/packages/flutter/lib/src/rendering/sliver_persistent_header.dart b/packages/flutter/lib/src/rendering/sliver_persistent_header.dart
index 2bf1fd3..11853de 100644
--- a/packages/flutter/lib/src/rendering/sliver_persistent_header.dart
+++ b/packages/flutter/lib/src/rendering/sliver_persistent_header.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/rendering/stack.dart

diff --git a/packages/flutter/lib/src/rendering/stack.dart b/packages/flutter/lib/src/rendering/stack.dart
index 5eacb7b..d729e08 100644
--- a/packages/flutter/lib/src/rendering/stack.dart
+++ b/packages/flutter/lib/src/rendering/stack.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show lerpDouble, hashValues;
 

packages/flutter/lib/src/rendering/table.dart

diff --git a/packages/flutter/lib/src/rendering/table.dart b/packages/flutter/lib/src/rendering/table.dart
index df14823..79b06e8 100644
--- a/packages/flutter/lib/src/rendering/table.dart
+++ b/packages/flutter/lib/src/rendering/table.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:math' as math;
 

packages/flutter/lib/src/rendering/table_border.dart

diff --git a/packages/flutter/lib/src/rendering/table_border.dart b/packages/flutter/lib/src/rendering/table_border.dart
index bb1ec1f..1a5a99a 100644
--- a/packages/flutter/lib/src/rendering/table_border.dart
+++ b/packages/flutter/lib/src/rendering/table_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart' hide Border;
 

packages/flutter/lib/src/rendering/texture.dart

diff --git a/packages/flutter/lib/src/rendering/texture.dart b/packages/flutter/lib/src/rendering/texture.dart
index 92b84b9..6e5817c 100644
--- a/packages/flutter/lib/src/rendering/texture.dart
+++ b/packages/flutter/lib/src/rendering/texture.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'box.dart';
 import 'layer.dart';

packages/flutter/lib/src/rendering/tweens.dart

diff --git a/packages/flutter/lib/src/rendering/tweens.dart b/packages/flutter/lib/src/rendering/tweens.dart
index fc76110..0f010f2 100644
--- a/packages/flutter/lib/src/rendering/tweens.dart
+++ b/packages/flutter/lib/src/rendering/tweens.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/lib/src/rendering/view.dart

diff --git a/packages/flutter/lib/src/rendering/view.dart b/packages/flutter/lib/src/rendering/view.dart
index 464e4b5..101ba11 100644
--- a/packages/flutter/lib/src/rendering/view.dart
+++ b/packages/flutter/lib/src/rendering/view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:developer';
 import 'dart:io' show Platform;
 import 'dart:ui' as ui show Scene, SceneBuilder, Window;

packages/flutter/lib/src/rendering/viewport.dart

diff --git a/packages/flutter/lib/src/rendering/viewport.dart b/packages/flutter/lib/src/rendering/viewport.dart
index e160af8..ab87647 100644
--- a/packages/flutter/lib/src/rendering/viewport.dart
+++ b/packages/flutter/lib/src/rendering/viewport.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/rendering/viewport_offset.dart

diff --git a/packages/flutter/lib/src/rendering/viewport_offset.dart b/packages/flutter/lib/src/rendering/viewport_offset.dart
index 00164cb..0f82d62 100644
--- a/packages/flutter/lib/src/rendering/viewport_offset.dart
+++ b/packages/flutter/lib/src/rendering/viewport_offset.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/rendering/wrap.dart

diff --git a/packages/flutter/lib/src/rendering/wrap.dart b/packages/flutter/lib/src/rendering/wrap.dart
index c1bb0d7..0e42289 100644
--- a/packages/flutter/lib/src/rendering/wrap.dart
+++ b/packages/flutter/lib/src/rendering/wrap.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'box.dart';

packages/flutter/lib/src/scheduler/binding.dart

diff --git a/packages/flutter/lib/src/scheduler/binding.dart b/packages/flutter/lib/src/scheduler/binding.dart
index f4daa75..df2243b 100644
--- a/packages/flutter/lib/src/scheduler/binding.dart
+++ b/packages/flutter/lib/src/scheduler/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:developer' show Flow, Timeline;

packages/flutter/lib/src/scheduler/debug.dart

diff --git a/packages/flutter/lib/src/scheduler/debug.dart b/packages/flutter/lib/src/scheduler/debug.dart
index 82af69f..dc21d03 100644
--- a/packages/flutter/lib/src/scheduler/debug.dart
+++ b/packages/flutter/lib/src/scheduler/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 // Any changes to this file should be reflected in the debugAssertAllSchedulerVarsUnset()

packages/flutter/lib/src/scheduler/priority.dart

diff --git a/packages/flutter/lib/src/scheduler/priority.dart b/packages/flutter/lib/src/scheduler/priority.dart
index 12cecc9..8b108d6 100644
--- a/packages/flutter/lib/src/scheduler/priority.dart
+++ b/packages/flutter/lib/src/scheduler/priority.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 /// A task priority, as passed to [SchedulerBinding.scheduleTask].

packages/flutter/lib/src/scheduler/ticker.dart

diff --git a/packages/flutter/lib/src/scheduler/ticker.dart b/packages/flutter/lib/src/scheduler/ticker.dart
index d7dc2c6..c686d4f 100644
--- a/packages/flutter/lib/src/scheduler/ticker.dart
+++ b/packages/flutter/lib/src/scheduler/ticker.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/semantics/binding.dart

diff --git a/packages/flutter/lib/src/semantics/binding.dart b/packages/flutter/lib/src/semantics/binding.dart
index 9370bf7..0ed6c51 100644
--- a/packages/flutter/lib/src/semantics/binding.dart
+++ b/packages/flutter/lib/src/semantics/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show AccessibilityFeatures;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/semantics/debug.dart

diff --git a/packages/flutter/lib/src/semantics/debug.dart b/packages/flutter/lib/src/semantics/debug.dart
index 4236f84..ef89879 100644
--- a/packages/flutter/lib/src/semantics/debug.dart
+++ b/packages/flutter/lib/src/semantics/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Overrides the setting of [SemanticsBinding.disableAnimations] for debugging
 /// and testing.
 ///

packages/flutter/lib/src/semantics/semantics.dart

diff --git a/packages/flutter/lib/src/semantics/semantics.dart b/packages/flutter/lib/src/semantics/semantics.dart
index 4f58c1f..3baf444 100644
--- a/packages/flutter/lib/src/semantics/semantics.dart
+++ b/packages/flutter/lib/src/semantics/semantics.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/lib/src/semantics/semantics_event.dart

diff --git a/packages/flutter/lib/src/semantics/semantics_event.dart b/packages/flutter/lib/src/semantics/semantics_event.dart
index c15ad26..945c836 100644
--- a/packages/flutter/lib/src/semantics/semantics_event.dart
+++ b/packages/flutter/lib/src/semantics/semantics_event.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/lib/src/semantics/semantics_service.dart

diff --git a/packages/flutter/lib/src/semantics/semantics_service.dart b/packages/flutter/lib/src/semantics/semantics_service.dart
index 6417e52..0a212de 100644
--- a/packages/flutter/lib/src/semantics/semantics_service.dart
+++ b/packages/flutter/lib/src/semantics/semantics_service.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show TextDirection;
 

packages/flutter/lib/src/services/asset_bundle.dart

diff --git a/packages/flutter/lib/src/services/asset_bundle.dart b/packages/flutter/lib/src/services/asset_bundle.dart
index ca65bbe..5242445146 100644
--- a/packages/flutter/lib/src/services/asset_bundle.dart
+++ b/packages/flutter/lib/src/services/asset_bundle.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';

packages/flutter/lib/src/services/autofill.dart

diff --git a/packages/flutter/lib/src/services/autofill.dart b/packages/flutter/lib/src/services/autofill.dart
index 96b058d..61a54d5 100644
--- a/packages/flutter/lib/src/services/autofill.dart
+++ b/packages/flutter/lib/src/services/autofill.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'text_input.dart';
 

packages/flutter/lib/src/services/binary_messenger.dart

diff --git a/packages/flutter/lib/src/services/binary_messenger.dart b/packages/flutter/lib/src/services/binary_messenger.dart
index 7e04216..789f586 100644
--- a/packages/flutter/lib/src/services/binary_messenger.dart
+++ b/packages/flutter/lib/src/services/binary_messenger.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/lib/src/services/binding.dart

diff --git a/packages/flutter/lib/src/services/binding.dart b/packages/flutter/lib/src/services/binding.dart
index 19bd370..2a70f44 100644
--- a/packages/flutter/lib/src/services/binding.dart
+++ b/packages/flutter/lib/src/services/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/lib/src/services/clipboard.dart

diff --git a/packages/flutter/lib/src/services/clipboard.dart b/packages/flutter/lib/src/services/clipboard.dart
index f2df4ca..6560e68 100644
--- a/packages/flutter/lib/src/services/clipboard.dart
+++ b/packages/flutter/lib/src/services/clipboard.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/services/font_loader.dart

diff --git a/packages/flutter/lib/src/services/font_loader.dart b/packages/flutter/lib/src/services/font_loader.dart
index e28bec4..2dce525 100644
--- a/packages/flutter/lib/src/services/font_loader.dart
+++ b/packages/flutter/lib/src/services/font_loader.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui';

packages/flutter/lib/src/services/haptic_feedback.dart

diff --git a/packages/flutter/lib/src/services/haptic_feedback.dart b/packages/flutter/lib/src/services/haptic_feedback.dart
index 1e57f6c..ae8c5c4 100644
--- a/packages/flutter/lib/src/services/haptic_feedback.dart
+++ b/packages/flutter/lib/src/services/haptic_feedback.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'system_channels.dart';

packages/flutter/lib/src/services/keyboard_key.dart

diff --git a/packages/flutter/lib/src/services/keyboard_key.dart b/packages/flutter/lib/src/services/keyboard_key.dart
index efd2800..b3deb38 100644
--- a/packages/flutter/lib/src/services/keyboard_key.dart
+++ b/packages/flutter/lib/src/services/keyboard_key.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
 // This file is generated by dev/tools/gen_keycodes/bin/gen_keycodes.dart and
 // should not be edited directly.

packages/flutter/lib/src/services/keyboard_maps.dart

diff --git a/packages/flutter/lib/src/services/keyboard_maps.dart b/packages/flutter/lib/src/services/keyboard_maps.dart
index edb1425..aceb97a 100644
--- a/packages/flutter/lib/src/services/keyboard_maps.dart
+++ b/packages/flutter/lib/src/services/keyboard_maps.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // DO NOT EDIT -- DO NOT EDIT -- DO NOT EDIT
 // This file is generated by dev/tools/gen_keycodes/bin/gen_keycodes.dart and
 // should not be edited directly.

packages/flutter/lib/src/services/message_codec.dart

diff --git a/packages/flutter/lib/src/services/message_codec.dart b/packages/flutter/lib/src/services/message_codec.dart
index d087af7..0d4a335 100644
--- a/packages/flutter/lib/src/services/message_codec.dart
+++ b/packages/flutter/lib/src/services/message_codec.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/services/message_codecs.dart

diff --git a/packages/flutter/lib/src/services/message_codecs.dart b/packages/flutter/lib/src/services/message_codecs.dart
index 031d2a5..f11c34f 100644
--- a/packages/flutter/lib/src/services/message_codecs.dart
+++ b/packages/flutter/lib/src/services/message_codecs.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert';
 import 'dart:typed_data';
 

packages/flutter/lib/src/services/platform_channel.dart

diff --git a/packages/flutter/lib/src/services/platform_channel.dart b/packages/flutter/lib/src/services/platform_channel.dart
index 0b16c83..cb23d29 100644
--- a/packages/flutter/lib/src/services/platform_channel.dart
+++ b/packages/flutter/lib/src/services/platform_channel.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/lib/src/services/platform_messages.dart

diff --git a/packages/flutter/lib/src/services/platform_messages.dart b/packages/flutter/lib/src/services/platform_messages.dart
index 4581655..c4cd43b 100644
--- a/packages/flutter/lib/src/services/platform_messages.dart
+++ b/packages/flutter/lib/src/services/platform_messages.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/lib/src/services/platform_views.dart

diff --git a/packages/flutter/lib/src/services/platform_views.dart b/packages/flutter/lib/src/services/platform_views.dart
index 040b6f9..75449fb 100644
--- a/packages/flutter/lib/src/services/platform_views.dart
+++ b/packages/flutter/lib/src/services/platform_views.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui';

packages/flutter/lib/src/services/raw_keyboard.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard.dart b/packages/flutter/lib/src/services/raw_keyboard.dart
index 7b744ee..cc552c7 100644
--- a/packages/flutter/lib/src/services/raw_keyboard.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io';
 import 'dart:ui';

packages/flutter/lib/src/services/raw_keyboard_android.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard_android.dart b/packages/flutter/lib/src/services/raw_keyboard_android.dart
index a6a39e6..14802b3 100644
--- a/packages/flutter/lib/src/services/raw_keyboard_android.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard_android.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'keyboard_key.dart';

packages/flutter/lib/src/services/raw_keyboard_fuchsia.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard_fuchsia.dart b/packages/flutter/lib/src/services/raw_keyboard_fuchsia.dart
index b6a901e..ebeb684 100644
--- a/packages/flutter/lib/src/services/raw_keyboard_fuchsia.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard_fuchsia.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'keyboard_key.dart';

packages/flutter/lib/src/services/raw_keyboard_linux.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard_linux.dart b/packages/flutter/lib/src/services/raw_keyboard_linux.dart
index f3c5966..25e9193 100644
--- a/packages/flutter/lib/src/services/raw_keyboard_linux.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard_linux.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'keyboard_key.dart';

packages/flutter/lib/src/services/raw_keyboard_macos.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard_macos.dart b/packages/flutter/lib/src/services/raw_keyboard_macos.dart
index c9f5309..e625436 100644
--- a/packages/flutter/lib/src/services/raw_keyboard_macos.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard_macos.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'keyboard_key.dart';

packages/flutter/lib/src/services/raw_keyboard_web.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard_web.dart b/packages/flutter/lib/src/services/raw_keyboard_web.dart
index fb86513..7f2b1d1 100644
--- a/packages/flutter/lib/src/services/raw_keyboard_web.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard_web.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'keyboard_key.dart';

packages/flutter/lib/src/services/raw_keyboard_windows.dart

diff --git a/packages/flutter/lib/src/services/raw_keyboard_windows.dart b/packages/flutter/lib/src/services/raw_keyboard_windows.dart
index 15a465e..5202672 100644
--- a/packages/flutter/lib/src/services/raw_keyboard_windows.dart
+++ b/packages/flutter/lib/src/services/raw_keyboard_windows.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'keyboard_key.dart';

packages/flutter/lib/src/services/system_channels.dart

diff --git a/packages/flutter/lib/src/services/system_channels.dart b/packages/flutter/lib/src/services/system_channels.dart
index b88a646..ab9dd12 100644
--- a/packages/flutter/lib/src/services/system_channels.dart
+++ b/packages/flutter/lib/src/services/system_channels.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'message_codecs.dart';

packages/flutter/lib/src/services/system_chrome.dart

diff --git a/packages/flutter/lib/src/services/system_chrome.dart b/packages/flutter/lib/src/services/system_chrome.dart
index 8a2da5c..520fd7a 100644
--- a/packages/flutter/lib/src/services/system_chrome.dart
+++ b/packages/flutter/lib/src/services/system_chrome.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui';
 

packages/flutter/lib/src/services/system_navigator.dart

diff --git a/packages/flutter/lib/src/services/system_navigator.dart b/packages/flutter/lib/src/services/system_navigator.dart
index bbaafcc..f61ce7b 100644
--- a/packages/flutter/lib/src/services/system_navigator.dart
+++ b/packages/flutter/lib/src/services/system_navigator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'system_channels.dart';

packages/flutter/lib/src/services/system_sound.dart

diff --git a/packages/flutter/lib/src/services/system_sound.dart b/packages/flutter/lib/src/services/system_sound.dart
index 297efb3..13517e0 100644
--- a/packages/flutter/lib/src/services/system_sound.dart
+++ b/packages/flutter/lib/src/services/system_sound.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'system_channels.dart';

packages/flutter/lib/src/services/text_editing.dart

diff --git a/packages/flutter/lib/src/services/text_editing.dart b/packages/flutter/lib/src/services/text_editing.dart
index b6e6fe6..f770f70 100644
--- a/packages/flutter/lib/src/services/text_editing.dart
+++ b/packages/flutter/lib/src/services/text_editing.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show hashValues, TextAffinity, TextPosition, TextRange;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/services/text_formatter.dart

diff --git a/packages/flutter/lib/src/services/text_formatter.dart b/packages/flutter/lib/src/services/text_formatter.dart
index f9c2974..787bf5d 100644
--- a/packages/flutter/lib/src/services/text_formatter.dart
+++ b/packages/flutter/lib/src/services/text_formatter.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart' show visibleForTesting;

packages/flutter/lib/src/services/text_input.dart

diff --git a/packages/flutter/lib/src/services/text_input.dart b/packages/flutter/lib/src/services/text_input.dart
index b39207c..2f1b758 100644
--- a/packages/flutter/lib/src/services/text_input.dart
+++ b/packages/flutter/lib/src/services/text_input.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io' show Platform;
 import 'dart:ui' show

packages/flutter/lib/src/widgets/actions.dart

diff --git a/packages/flutter/lib/src/widgets/actions.dart b/packages/flutter/lib/src/widgets/actions.dart
index 5bb2188..4aa1715 100644
--- a/packages/flutter/lib/src/widgets/actions.dart
+++ b/packages/flutter/lib/src/widgets/actions.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/widgets/animated_cross_fade.dart

diff --git a/packages/flutter/lib/src/widgets/animated_cross_fade.dart b/packages/flutter/lib/src/widgets/animated_cross_fade.dart
index f23dd52..11b9627 100644
--- a/packages/flutter/lib/src/widgets/animated_cross_fade.dart
+++ b/packages/flutter/lib/src/widgets/animated_cross_fade.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'animated_size.dart';

packages/flutter/lib/src/widgets/animated_list.dart

diff --git a/packages/flutter/lib/src/widgets/animated_list.dart b/packages/flutter/lib/src/widgets/animated_list.dart
index e941cfd..f463dd1 100644
--- a/packages/flutter/lib/src/widgets/animated_list.dart
+++ b/packages/flutter/lib/src/widgets/animated_list.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 import 'package:flutter/foundation.dart';
 

packages/flutter/lib/src/widgets/animated_size.dart

diff --git a/packages/flutter/lib/src/widgets/animated_size.dart b/packages/flutter/lib/src/widgets/animated_size.dart
index 9feda16..d6b8edf 100644
--- a/packages/flutter/lib/src/widgets/animated_size.dart
+++ b/packages/flutter/lib/src/widgets/animated_size.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/scheduler.dart';
 

packages/flutter/lib/src/widgets/animated_switcher.dart

diff --git a/packages/flutter/lib/src/widgets/animated_switcher.dart b/packages/flutter/lib/src/widgets/animated_switcher.dart
index 9e7060f..4a2b5d5 100644
--- a/packages/flutter/lib/src/widgets/animated_switcher.dart
+++ b/packages/flutter/lib/src/widgets/animated_switcher.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 import 'package:flutter/foundation.dart';
 

packages/flutter/lib/src/widgets/annotated_region.dart

diff --git a/packages/flutter/lib/src/widgets/annotated_region.dart b/packages/flutter/lib/src/widgets/annotated_region.dart
index f44e0e7..1a7e4a4 100644
--- a/packages/flutter/lib/src/widgets/annotated_region.dart
+++ b/packages/flutter/lib/src/widgets/annotated_region.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/app.dart

diff --git a/packages/flutter/lib/src/widgets/app.dart b/packages/flutter/lib/src/widgets/app.dart
index 1591789..09c4c7d 100644
--- a/packages/flutter/lib/src/widgets/app.dart
+++ b/packages/flutter/lib/src/widgets/app.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection' show HashMap;
 

packages/flutter/lib/src/widgets/async.dart

diff --git a/packages/flutter/lib/src/widgets/async.dart b/packages/flutter/lib/src/widgets/async.dart
index 2692ad8..5b4aa70 100644
--- a/packages/flutter/lib/src/widgets/async.dart
+++ b/packages/flutter/lib/src/widgets/async.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// Widgets that handle interaction with asynchronous computations.
 ///
 /// Asynchronous computations are represented by [Future]s and [Stream]s.

packages/flutter/lib/src/widgets/autofill.dart

diff --git a/packages/flutter/lib/src/widgets/autofill.dart b/packages/flutter/lib/src/widgets/autofill.dart
index b9a731a..ee89294 100644
--- a/packages/flutter/lib/src/widgets/autofill.dart
+++ b/packages/flutter/lib/src/widgets/autofill.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'framework.dart';
 

packages/flutter/lib/src/widgets/automatic_keep_alive.dart

diff --git a/packages/flutter/lib/src/widgets/automatic_keep_alive.dart b/packages/flutter/lib/src/widgets/automatic_keep_alive.dart
index d6711ce..b2ae057 100644
--- a/packages/flutter/lib/src/widgets/automatic_keep_alive.dart
+++ b/packages/flutter/lib/src/widgets/automatic_keep_alive.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/banner.dart

diff --git a/packages/flutter/lib/src/widgets/banner.dart b/packages/flutter/lib/src/widgets/banner.dart
index 7e70a0a..612dc6e 100644
--- a/packages/flutter/lib/src/widgets/banner.dart
+++ b/packages/flutter/lib/src/widgets/banner.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/basic.dart

diff --git a/packages/flutter/lib/src/widgets/basic.dart b/packages/flutter/lib/src/widgets/basic.dart
index 70e086e..2a01b69 100644
--- a/packages/flutter/lib/src/widgets/basic.dart
+++ b/packages/flutter/lib/src/widgets/basic.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Image, ImageFilter, TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/binding.dart

diff --git a/packages/flutter/lib/src/widgets/binding.dart b/packages/flutter/lib/src/widgets/binding.dart
index 885b181..871c36a 100644
--- a/packages/flutter/lib/src/widgets/binding.dart
+++ b/packages/flutter/lib/src/widgets/binding.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:developer' as developer;
 import 'dart:ui' show AppLifecycleState, Locale, AccessibilityFeatures, FrameTiming, TimingsCallback;

packages/flutter/lib/src/widgets/bottom_navigation_bar_item.dart

diff --git a/packages/flutter/lib/src/widgets/bottom_navigation_bar_item.dart b/packages/flutter/lib/src/widgets/bottom_navigation_bar_item.dart
index 10861fe..036227f 100644
--- a/packages/flutter/lib/src/widgets/bottom_navigation_bar_item.dart
+++ b/packages/flutter/lib/src/widgets/bottom_navigation_bar_item.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color;
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/color_filter.dart

diff --git a/packages/flutter/lib/src/widgets/color_filter.dart b/packages/flutter/lib/src/widgets/color_filter.dart
index 8be10f0..620670b 100644
--- a/packages/flutter/lib/src/widgets/color_filter.dart
+++ b/packages/flutter/lib/src/widgets/color_filter.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/constants.dart

diff --git a/packages/flutter/lib/src/widgets/constants.dart b/packages/flutter/lib/src/widgets/constants.dart
index 49ad496..fd272aa 100644
--- a/packages/flutter/lib/src/widgets/constants.dart
+++ b/packages/flutter/lib/src/widgets/constants.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The minimum dimension of any interactive region according to the Material
 /// guidelines.
 ///

packages/flutter/lib/src/widgets/container.dart

diff --git a/packages/flutter/lib/src/widgets/container.dart b/packages/flutter/lib/src/widgets/container.dart
index e915710..f36632e 100644
--- a/packages/flutter/lib/src/widgets/container.dart
+++ b/packages/flutter/lib/src/widgets/container.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/debug.dart

diff --git a/packages/flutter/lib/src/widgets/debug.dart b/packages/flutter/lib/src/widgets/debug.dart
index 94e2ea2..d69527b 100644
--- a/packages/flutter/lib/src/widgets/debug.dart
+++ b/packages/flutter/lib/src/widgets/debug.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:developer' show Timeline; // to disambiguate reference in dartdocs below
 

packages/flutter/lib/src/widgets/dismissible.dart

diff --git a/packages/flutter/lib/src/widgets/dismissible.dart b/packages/flutter/lib/src/widgets/dismissible.dart
index 0dbf698..e6d1fd7 100644
--- a/packages/flutter/lib/src/widgets/dismissible.dart
+++ b/packages/flutter/lib/src/widgets/dismissible.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 
 import 'automatic_keep_alive.dart';

packages/flutter/lib/src/widgets/disposable_build_context.dart

diff --git a/packages/flutter/lib/src/widgets/disposable_build_context.dart b/packages/flutter/lib/src/widgets/disposable_build_context.dart
index c5b7e0f..5020696 100644
--- a/packages/flutter/lib/src/widgets/disposable_build_context.dart
+++ b/packages/flutter/lib/src/widgets/disposable_build_context.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'framework.dart';
 
 /// Provides non-leaking access to a [BuildContext].

packages/flutter/lib/src/widgets/drag_target.dart

diff --git a/packages/flutter/lib/src/widgets/drag_target.dart b/packages/flutter/lib/src/widgets/drag_target.dart
index 68ff3ae..fc64baf 100644
--- a/packages/flutter/lib/src/widgets/drag_target.dart
+++ b/packages/flutter/lib/src/widgets/drag_target.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart

diff --git a/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart b/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart
index ee3d740..881d3d8 100644
--- a/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart
+++ b/packages/flutter/lib/src/widgets/draggable_scrollable_sheet.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 

packages/flutter/lib/src/widgets/editable_text.dart

diff --git a/packages/flutter/lib/src/widgets/editable_text.dart b/packages/flutter/lib/src/widgets/editable_text.dart
index bb607be..f3ea4b1 100644
--- a/packages/flutter/lib/src/widgets/editable_text.dart
+++ b/packages/flutter/lib/src/widgets/editable_text.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:ui' as ui hide TextStyle;

packages/flutter/lib/src/widgets/fade_in_image.dart

diff --git a/packages/flutter/lib/src/widgets/fade_in_image.dart b/packages/flutter/lib/src/widgets/fade_in_image.dart
index c8d1336..ee605e1 100644
--- a/packages/flutter/lib/src/widgets/fade_in_image.dart
+++ b/packages/flutter/lib/src/widgets/fade_in_image.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/focus_manager.dart

diff --git a/packages/flutter/lib/src/widgets/focus_manager.dart b/packages/flutter/lib/src/widgets/focus_manager.dart
index 087e20a..5c3ad4c 100644
--- a/packages/flutter/lib/src/widgets/focus_manager.dart
+++ b/packages/flutter/lib/src/widgets/focus_manager.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui';
 

packages/flutter/lib/src/widgets/focus_scope.dart

diff --git a/packages/flutter/lib/src/widgets/focus_scope.dart b/packages/flutter/lib/src/widgets/focus_scope.dart
index 2b1fbd3..03dafce 100644
--- a/packages/flutter/lib/src/widgets/focus_scope.dart
+++ b/packages/flutter/lib/src/widgets/focus_scope.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/focus_traversal.dart

diff --git a/packages/flutter/lib/src/widgets/focus_traversal.dart b/packages/flutter/lib/src/widgets/focus_traversal.dart
index 1bfe6f0..1366134 100644
--- a/packages/flutter/lib/src/widgets/focus_traversal.dart
+++ b/packages/flutter/lib/src/widgets/focus_traversal.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:collection/collection.dart';

packages/flutter/lib/src/widgets/form.dart

diff --git a/packages/flutter/lib/src/widgets/form.dart b/packages/flutter/lib/src/widgets/form.dart
index 1204d8f..19473e8 100644
--- a/packages/flutter/lib/src/widgets/form.dart
+++ b/packages/flutter/lib/src/widgets/form.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'framework.dart';
 import 'navigator.dart';
 import 'will_pop_scope.dart';

packages/flutter/lib/src/widgets/framework.dart

diff --git a/packages/flutter/lib/src/widgets/framework.dart b/packages/flutter/lib/src/widgets/framework.dart
index 7aece54..b5a3137 100644
--- a/packages/flutter/lib/src/widgets/framework.dart
+++ b/packages/flutter/lib/src/widgets/framework.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:developer';

packages/flutter/lib/src/widgets/gesture_detector.dart

diff --git a/packages/flutter/lib/src/widgets/gesture_detector.dart b/packages/flutter/lib/src/widgets/gesture_detector.dart
index cfca89e..db38c03 100644
--- a/packages/flutter/lib/src/widgets/gesture_detector.dart
+++ b/packages/flutter/lib/src/widgets/gesture_detector.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/grid_paper.dart

diff --git a/packages/flutter/lib/src/widgets/grid_paper.dart b/packages/flutter/lib/src/widgets/grid_paper.dart
index 888d446..fa1934f 100644
--- a/packages/flutter/lib/src/widgets/grid_paper.dart
+++ b/packages/flutter/lib/src/widgets/grid_paper.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/heroes.dart

diff --git a/packages/flutter/lib/src/widgets/heroes.dart b/packages/flutter/lib/src/widgets/heroes.dart
index 391ba8e..ebd41a7 100644
--- a/packages/flutter/lib/src/widgets/heroes.dart
+++ b/packages/flutter/lib/src/widgets/heroes.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/icon.dart

diff --git a/packages/flutter/lib/src/widgets/icon.dart b/packages/flutter/lib/src/widgets/icon.dart
index b2a261f..3791bda 100644
--- a/packages/flutter/lib/src/widgets/icon.dart
+++ b/packages/flutter/lib/src/widgets/icon.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/icon_data.dart

diff --git a/packages/flutter/lib/src/widgets/icon_data.dart b/packages/flutter/lib/src/widgets/icon_data.dart
index ef390df..a645fc9 100644
--- a/packages/flutter/lib/src/widgets/icon_data.dart
+++ b/packages/flutter/lib/src/widgets/icon_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show hashValues;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/icon_theme.dart

diff --git a/packages/flutter/lib/src/widgets/icon_theme.dart b/packages/flutter/lib/src/widgets/icon_theme.dart
index fc25227..8d3e4df 100644
--- a/packages/flutter/lib/src/widgets/icon_theme.dart
+++ b/packages/flutter/lib/src/widgets/icon_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/icon_theme_data.dart

diff --git a/packages/flutter/lib/src/widgets/icon_theme_data.dart b/packages/flutter/lib/src/widgets/icon_theme_data.dart
index d18d8ff..97f2412 100644
--- a/packages/flutter/lib/src/widgets/icon_theme_data.dart
+++ b/packages/flutter/lib/src/widgets/icon_theme_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Color, hashValues;
 import 'dart:ui' as ui show lerpDouble;
 

packages/flutter/lib/src/widgets/image.dart

diff --git a/packages/flutter/lib/src/widgets/image.dart b/packages/flutter/lib/src/widgets/image.dart
index e16b9d2..6efaa74 100644
--- a/packages/flutter/lib/src/widgets/image.dart
+++ b/packages/flutter/lib/src/widgets/image.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io' show File;
 import 'dart:typed_data';

packages/flutter/lib/src/widgets/image_filter.dart

diff --git a/packages/flutter/lib/src/widgets/image_filter.dart b/packages/flutter/lib/src/widgets/image_filter.dart
index e1e6a8a..db7d83e 100644
--- a/packages/flutter/lib/src/widgets/image_filter.dart
+++ b/packages/flutter/lib/src/widgets/image_filter.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/image_icon.dart

diff --git a/packages/flutter/lib/src/widgets/image_icon.dart b/packages/flutter/lib/src/widgets/image_icon.dart
index 8caab22..fe10956 100644
--- a/packages/flutter/lib/src/widgets/image_icon.dart
+++ b/packages/flutter/lib/src/widgets/image_icon.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/implicit_animations.dart

diff --git a/packages/flutter/lib/src/widgets/implicit_animations.dart b/packages/flutter/lib/src/widgets/implicit_animations.dart
index 6201a2b..b8a01fb 100644
--- a/packages/flutter/lib/src/widgets/implicit_animations.dart
+++ b/packages/flutter/lib/src/widgets/implicit_animations.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show TextHeightBehavior;
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/widgets/inherited_model.dart

diff --git a/packages/flutter/lib/src/widgets/inherited_model.dart b/packages/flutter/lib/src/widgets/inherited_model.dart
index e4c7efe..1c1fc5f 100644
--- a/packages/flutter/lib/src/widgets/inherited_model.dart
+++ b/packages/flutter/lib/src/widgets/inherited_model.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/inherited_notifier.dart

diff --git a/packages/flutter/lib/src/widgets/inherited_notifier.dart b/packages/flutter/lib/src/widgets/inherited_notifier.dart
index e1bc7fb..d70feb8 100644
--- a/packages/flutter/lib/src/widgets/inherited_notifier.dart
+++ b/packages/flutter/lib/src/widgets/inherited_notifier.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/inherited_theme.dart

diff --git a/packages/flutter/lib/src/widgets/inherited_theme.dart b/packages/flutter/lib/src/widgets/inherited_theme.dart
index b218b44..71b08cd 100644
--- a/packages/flutter/lib/src/widgets/inherited_theme.dart
+++ b/packages/flutter/lib/src/widgets/inherited_theme.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/interactive_viewer.dart

diff --git a/packages/flutter/lib/src/widgets/interactive_viewer.dart b/packages/flutter/lib/src/widgets/interactive_viewer.dart
index 48903e7..a37801d 100644
--- a/packages/flutter/lib/src/widgets/interactive_viewer.dart
+++ b/packages/flutter/lib/src/widgets/interactive_viewer.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/widgets/layout_builder.dart

diff --git a/packages/flutter/lib/src/widgets/layout_builder.dart b/packages/flutter/lib/src/widgets/layout_builder.dart
index 86ea24a..1c4be13 100644
--- a/packages/flutter/lib/src/widgets/layout_builder.dart
+++ b/packages/flutter/lib/src/widgets/layout_builder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart

diff --git a/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart b/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
index 40fdc2b..0ca1bb5 100644
--- a/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/list_wheel_scroll_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' as math;

packages/flutter/lib/src/widgets/localizations.dart

diff --git a/packages/flutter/lib/src/widgets/localizations.dart b/packages/flutter/lib/src/widgets/localizations.dart
index 0e8cf5d..9a052b0 100644
--- a/packages/flutter/lib/src/widgets/localizations.dart
+++ b/packages/flutter/lib/src/widgets/localizations.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show Locale;
 

packages/flutter/lib/src/widgets/media_query.dart

diff --git a/packages/flutter/lib/src/widgets/media_query.dart b/packages/flutter/lib/src/widgets/media_query.dart
index eb06f31..90c6036 100644
--- a/packages/flutter/lib/src/widgets/media_query.dart
+++ b/packages/flutter/lib/src/widgets/media_query.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' as ui;
 import 'dart:ui' show Brightness;

packages/flutter/lib/src/widgets/modal_barrier.dart

diff --git a/packages/flutter/lib/src/widgets/modal_barrier.dart b/packages/flutter/lib/src/widgets/modal_barrier.dart
index b83aa18..816ee81 100644
--- a/packages/flutter/lib/src/widgets/modal_barrier.dart
+++ b/packages/flutter/lib/src/widgets/modal_barrier.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/navigation_toolbar.dart

diff --git a/packages/flutter/lib/src/widgets/navigation_toolbar.dart b/packages/flutter/lib/src/widgets/navigation_toolbar.dart
index 119cb1a..868b83c 100644
--- a/packages/flutter/lib/src/widgets/navigation_toolbar.dart
+++ b/packages/flutter/lib/src/widgets/navigation_toolbar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/navigator.dart

diff --git a/packages/flutter/lib/src/widgets/navigator.dart b/packages/flutter/lib/src/widgets/navigator.dart
index 7e73137..bb974d6 100644
--- a/packages/flutter/lib/src/widgets/navigator.dart
+++ b/packages/flutter/lib/src/widgets/navigator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';

packages/flutter/lib/src/widgets/nested_scroll_view.dart

diff --git a/packages/flutter/lib/src/widgets/nested_scroll_view.dart b/packages/flutter/lib/src/widgets/nested_scroll_view.dart
index d552373..ba444c3 100644
--- a/packages/flutter/lib/src/widgets/nested_scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/nested_scroll_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/widgets/notification_listener.dart

diff --git a/packages/flutter/lib/src/widgets/notification_listener.dart b/packages/flutter/lib/src/widgets/notification_listener.dart
index 874becd..8a05bae 100644
--- a/packages/flutter/lib/src/widgets/notification_listener.dart
+++ b/packages/flutter/lib/src/widgets/notification_listener.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/orientation_builder.dart

diff --git a/packages/flutter/lib/src/widgets/orientation_builder.dart b/packages/flutter/lib/src/widgets/orientation_builder.dart
index ad4a93b..a974df8 100644
--- a/packages/flutter/lib/src/widgets/orientation_builder.dart
+++ b/packages/flutter/lib/src/widgets/orientation_builder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'basic.dart';
 import 'framework.dart';
 import 'layout_builder.dart';

packages/flutter/lib/src/widgets/overlay.dart

diff --git a/packages/flutter/lib/src/widgets/overlay.dart b/packages/flutter/lib/src/widgets/overlay.dart
index 3ea523c..a18cd88 100644
--- a/packages/flutter/lib/src/widgets/overlay.dart
+++ b/packages/flutter/lib/src/widgets/overlay.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' as math;

packages/flutter/lib/src/widgets/overscroll_indicator.dart

diff --git a/packages/flutter/lib/src/widgets/overscroll_indicator.dart b/packages/flutter/lib/src/widgets/overscroll_indicator.dart
index b389163..50f7278 100644
--- a/packages/flutter/lib/src/widgets/overscroll_indicator.dart
+++ b/packages/flutter/lib/src/widgets/overscroll_indicator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async' show Timer;
 import 'dart:math' as math;
 

packages/flutter/lib/src/widgets/page_storage.dart

diff --git a/packages/flutter/lib/src/widgets/page_storage.dart b/packages/flutter/lib/src/widgets/page_storage.dart
index ccd6a76..fabeb8b 100644
--- a/packages/flutter/lib/src/widgets/page_storage.dart
+++ b/packages/flutter/lib/src/widgets/page_storage.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/page_view.dart

diff --git a/packages/flutter/lib/src/widgets/page_view.dart b/packages/flutter/lib/src/widgets/page_view.dart
index 80d3f26..f871b72 100644
--- a/packages/flutter/lib/src/widgets/page_view.dart
+++ b/packages/flutter/lib/src/widgets/page_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/widgets/pages.dart

diff --git a/packages/flutter/lib/src/widgets/pages.dart b/packages/flutter/lib/src/widgets/pages.dart
index 89ccfd2..ef9e9a3 100644
--- a/packages/flutter/lib/src/widgets/pages.dart
+++ b/packages/flutter/lib/src/widgets/pages.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'basic.dart';
 import 'framework.dart';
 import 'navigator.dart';

packages/flutter/lib/src/widgets/performance_overlay.dart

diff --git a/packages/flutter/lib/src/widgets/performance_overlay.dart b/packages/flutter/lib/src/widgets/performance_overlay.dart
index 0bedc1a..0efb3f9 100644
--- a/packages/flutter/lib/src/widgets/performance_overlay.dart
+++ b/packages/flutter/lib/src/widgets/performance_overlay.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/placeholder.dart

diff --git a/packages/flutter/lib/src/widgets/placeholder.dart b/packages/flutter/lib/src/widgets/placeholder.dart
index 06789a1..46cc283 100644
--- a/packages/flutter/lib/src/widgets/placeholder.dart
+++ b/packages/flutter/lib/src/widgets/placeholder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/platform_view.dart

diff --git a/packages/flutter/lib/src/widgets/platform_view.dart b/packages/flutter/lib/src/widgets/platform_view.dart
index 2f76007..9ed4a89 100644
--- a/packages/flutter/lib/src/widgets/platform_view.dart
+++ b/packages/flutter/lib/src/widgets/platform_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/preferred_size.dart

diff --git a/packages/flutter/lib/src/widgets/preferred_size.dart b/packages/flutter/lib/src/widgets/preferred_size.dart
index bc2beb4..a9b3275 100644
--- a/packages/flutter/lib/src/widgets/preferred_size.dart
+++ b/packages/flutter/lib/src/widgets/preferred_size.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/primary_scroll_controller.dart

diff --git a/packages/flutter/lib/src/widgets/primary_scroll_controller.dart b/packages/flutter/lib/src/widgets/primary_scroll_controller.dart
index 9ff8a43..b1bcec3 100644
--- a/packages/flutter/lib/src/widgets/primary_scroll_controller.dart
+++ b/packages/flutter/lib/src/widgets/primary_scroll_controller.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/raw_keyboard_listener.dart

diff --git a/packages/flutter/lib/src/widgets/raw_keyboard_listener.dart b/packages/flutter/lib/src/widgets/raw_keyboard_listener.dart
index 8be5c58..87e4256 100644
--- a/packages/flutter/lib/src/widgets/raw_keyboard_listener.dart
+++ b/packages/flutter/lib/src/widgets/raw_keyboard_listener.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 

packages/flutter/lib/src/widgets/route_notification_messages.dart

diff --git a/packages/flutter/lib/src/widgets/route_notification_messages.dart b/packages/flutter/lib/src/widgets/route_notification_messages.dart
index abe59e9..8048315 100644
--- a/packages/flutter/lib/src/widgets/route_notification_messages.dart
+++ b/packages/flutter/lib/src/widgets/route_notification_messages.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 

packages/flutter/lib/src/widgets/routes.dart

diff --git a/packages/flutter/lib/src/widgets/routes.dart b/packages/flutter/lib/src/widgets/routes.dart
index 76b82bd..f901961 100644
--- a/packages/flutter/lib/src/widgets/routes.dart
+++ b/packages/flutter/lib/src/widgets/routes.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui;
 

packages/flutter/lib/src/widgets/safe_area.dart

diff --git a/packages/flutter/lib/src/widgets/safe_area.dart b/packages/flutter/lib/src/widgets/safe_area.dart
index 5e40d79..8190849 100644
--- a/packages/flutter/lib/src/widgets/safe_area.dart
+++ b/packages/flutter/lib/src/widgets/safe_area.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/scroll_activity.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_activity.dart b/packages/flutter/lib/src/widgets/scroll_activity.dart
index 18f9147..b9560ab 100644
--- a/packages/flutter/lib/src/widgets/scroll_activity.dart
+++ b/packages/flutter/lib/src/widgets/scroll_activity.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/widgets/scroll_aware_image_provider.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_aware_image_provider.dart b/packages/flutter/lib/src/widgets/scroll_aware_image_provider.dart
index ae3ec6e..8664927 100644
--- a/packages/flutter/lib/src/widgets/scroll_aware_image_provider.dart
+++ b/packages/flutter/lib/src/widgets/scroll_aware_image_provider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/painting.dart';

packages/flutter/lib/src/widgets/scroll_configuration.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_configuration.dart b/packages/flutter/lib/src/widgets/scroll_configuration.dart
index 2c5cfd3..9ed3690 100644
--- a/packages/flutter/lib/src/widgets/scroll_configuration.dart
+++ b/packages/flutter/lib/src/widgets/scroll_configuration.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/scroll_context.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_context.dart b/packages/flutter/lib/src/widgets/scroll_context.dart
index 0a609b6..6c06c3c 100644
--- a/packages/flutter/lib/src/widgets/scroll_context.dart
+++ b/packages/flutter/lib/src/widgets/scroll_context.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/scroll_controller.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_controller.dart b/packages/flutter/lib/src/widgets/scroll_controller.dart
index a40cf1c..5b7c66a 100644
--- a/packages/flutter/lib/src/widgets/scroll_controller.dart
+++ b/packages/flutter/lib/src/widgets/scroll_controller.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/widgets/scroll_metrics.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_metrics.dart b/packages/flutter/lib/src/widgets/scroll_metrics.dart
index 6bb6f23..14eedf0 100644
--- a/packages/flutter/lib/src/widgets/scroll_metrics.dart
+++ b/packages/flutter/lib/src/widgets/scroll_metrics.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/scroll_notification.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_notification.dart b/packages/flutter/lib/src/widgets/scroll_notification.dart
index 533ef2a..2ab456e 100644
--- a/packages/flutter/lib/src/widgets/scroll_notification.dart
+++ b/packages/flutter/lib/src/widgets/scroll_notification.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/scroll_physics.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_physics.dart b/packages/flutter/lib/src/widgets/scroll_physics.dart
index 855600a..ecfc55b 100644
--- a/packages/flutter/lib/src/widgets/scroll_physics.dart
+++ b/packages/flutter/lib/src/widgets/scroll_physics.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/scroll_position.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_position.dart b/packages/flutter/lib/src/widgets/scroll_position.dart
index aad857a..80bcac7 100644
--- a/packages/flutter/lib/src/widgets/scroll_position.dart
+++ b/packages/flutter/lib/src/widgets/scroll_position.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart b/packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart
index cdb718e..3bc219d 100644
--- a/packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart
+++ b/packages/flutter/lib/src/widgets/scroll_position_with_single_context.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/gestures.dart';

packages/flutter/lib/src/widgets/scroll_simulation.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_simulation.dart b/packages/flutter/lib/src/widgets/scroll_simulation.dart
index 747dac3..2ea0814 100644
--- a/packages/flutter/lib/src/widgets/scroll_simulation.dart
+++ b/packages/flutter/lib/src/widgets/scroll_simulation.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/scroll_view.dart

diff --git a/packages/flutter/lib/src/widgets/scroll_view.dart b/packages/flutter/lib/src/widgets/scroll_view.dart
index 8644e0e..5fc7a17 100644
--- a/packages/flutter/lib/src/widgets/scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/scroll_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/scrollable.dart

diff --git a/packages/flutter/lib/src/widgets/scrollable.dart b/packages/flutter/lib/src/widgets/scrollable.dart
index 807806e..98cec3b 100644
--- a/packages/flutter/lib/src/widgets/scrollable.dart
+++ b/packages/flutter/lib/src/widgets/scrollable.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:ui';

packages/flutter/lib/src/widgets/scrollbar.dart

diff --git a/packages/flutter/lib/src/widgets/scrollbar.dart b/packages/flutter/lib/src/widgets/scrollbar.dart
index 6a324b8..6503e85 100644
--- a/packages/flutter/lib/src/widgets/scrollbar.dart
+++ b/packages/flutter/lib/src/widgets/scrollbar.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/animation.dart';

packages/flutter/lib/src/widgets/semantics_debugger.dart

diff --git a/packages/flutter/lib/src/widgets/semantics_debugger.dart b/packages/flutter/lib/src/widgets/semantics_debugger.dart
index 887416b..b577df7 100644
--- a/packages/flutter/lib/src/widgets/semantics_debugger.dart
+++ b/packages/flutter/lib/src/widgets/semantics_debugger.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show SemanticsFlag;
 

packages/flutter/lib/src/widgets/shortcuts.dart

diff --git a/packages/flutter/lib/src/widgets/shortcuts.dart b/packages/flutter/lib/src/widgets/shortcuts.dart
index db10906..74e56d6 100644
--- a/packages/flutter/lib/src/widgets/shortcuts.dart
+++ b/packages/flutter/lib/src/widgets/shortcuts.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:collection/collection.dart';

packages/flutter/lib/src/widgets/single_child_scroll_view.dart

diff --git a/packages/flutter/lib/src/widgets/single_child_scroll_view.dart b/packages/flutter/lib/src/widgets/single_child_scroll_view.dart
index f4deca6..d906e40 100644
--- a/packages/flutter/lib/src/widgets/single_child_scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/single_child_scroll_view.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/size_changed_layout_notifier.dart

diff --git a/packages/flutter/lib/src/widgets/size_changed_layout_notifier.dart b/packages/flutter/lib/src/widgets/size_changed_layout_notifier.dart
index fbb61a9..2cea79c 100644
--- a/packages/flutter/lib/src/widgets/size_changed_layout_notifier.dart
+++ b/packages/flutter/lib/src/widgets/size_changed_layout_notifier.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/sliver.dart

diff --git a/packages/flutter/lib/src/widgets/sliver.dart b/packages/flutter/lib/src/widgets/sliver.dart
index 3e264ff..40eacdc 100644
--- a/packages/flutter/lib/src/widgets/sliver.dart
+++ b/packages/flutter/lib/src/widgets/sliver.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection' show SplayTreeMap, HashMap;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/sliver_fill.dart

diff --git a/packages/flutter/lib/src/widgets/sliver_fill.dart b/packages/flutter/lib/src/widgets/sliver_fill.dart
index 6261c19..f505980 100644
--- a/packages/flutter/lib/src/widgets/sliver_fill.dart
+++ b/packages/flutter/lib/src/widgets/sliver_fill.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/sliver_layout_builder.dart

diff --git a/packages/flutter/lib/src/widgets/sliver_layout_builder.dart b/packages/flutter/lib/src/widgets/sliver_layout_builder.dart
index 7ff5033..11e350e 100644
--- a/packages/flutter/lib/src/widgets/sliver_layout_builder.dart
+++ b/packages/flutter/lib/src/widgets/sliver_layout_builder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/sliver_persistent_header.dart

diff --git a/packages/flutter/lib/src/widgets/sliver_persistent_header.dart b/packages/flutter/lib/src/widgets/sliver_persistent_header.dart
index 2be682e..b26cc4b 100644
--- a/packages/flutter/lib/src/widgets/sliver_persistent_header.dart
+++ b/packages/flutter/lib/src/widgets/sliver_persistent_header.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 

packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart

diff --git a/packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart b/packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart
index 9afa8df..b6e6c2a 100644
--- a/packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart
+++ b/packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/spacer.dart

diff --git a/packages/flutter/lib/src/widgets/spacer.dart b/packages/flutter/lib/src/widgets/spacer.dart
index f6b8ad8..640495f 100644
--- a/packages/flutter/lib/src/widgets/spacer.dart
+++ b/packages/flutter/lib/src/widgets/spacer.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/status_transitions.dart

diff --git a/packages/flutter/lib/src/widgets/status_transitions.dart b/packages/flutter/lib/src/widgets/status_transitions.dart
index 997f23b..695770c 100644
--- a/packages/flutter/lib/src/widgets/status_transitions.dart
+++ b/packages/flutter/lib/src/widgets/status_transitions.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'basic.dart';
 import 'framework.dart';
 

packages/flutter/lib/src/widgets/table.dart

diff --git a/packages/flutter/lib/src/widgets/table.dart b/packages/flutter/lib/src/widgets/table.dart
index 0d1ea1f..e2d507e 100644
--- a/packages/flutter/lib/src/widgets/table.dart
+++ b/packages/flutter/lib/src/widgets/table.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/text.dart

diff --git a/packages/flutter/lib/src/widgets/text.dart b/packages/flutter/lib/src/widgets/text.dart
index e70cf94..eec5992 100644
--- a/packages/flutter/lib/src/widgets/text.dart
+++ b/packages/flutter/lib/src/widgets/text.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show TextHeightBehavior;
 
 import 'package:flutter/foundation.dart';

packages/flutter/lib/src/widgets/text_selection.dart

diff --git a/packages/flutter/lib/src/widgets/text_selection.dart b/packages/flutter/lib/src/widgets/text_selection.dart
index 09dd32a..4000b61 100644
--- a/packages/flutter/lib/src/widgets/text_selection.dart
+++ b/packages/flutter/lib/src/widgets/text_selection.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 

packages/flutter/lib/src/widgets/texture.dart

diff --git a/packages/flutter/lib/src/widgets/texture.dart b/packages/flutter/lib/src/widgets/texture.dart
index 0d122ea..0d9c86a 100644
--- a/packages/flutter/lib/src/widgets/texture.dart
+++ b/packages/flutter/lib/src/widgets/texture.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'framework.dart';
 

packages/flutter/lib/src/widgets/ticker_provider.dart

diff --git a/packages/flutter/lib/src/widgets/ticker_provider.dart b/packages/flutter/lib/src/widgets/ticker_provider.dart
index 406c991..bad3cc8 100644
--- a/packages/flutter/lib/src/widgets/ticker_provider.dart
+++ b/packages/flutter/lib/src/widgets/ticker_provider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 

packages/flutter/lib/src/widgets/title.dart

diff --git a/packages/flutter/lib/src/widgets/title.dart b/packages/flutter/lib/src/widgets/title.dart
index 5a75d5d..88c577b 100644
--- a/packages/flutter/lib/src/widgets/title.dart
+++ b/packages/flutter/lib/src/widgets/title.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 

packages/flutter/lib/src/widgets/transitions.dart

diff --git a/packages/flutter/lib/src/widgets/transitions.dart b/packages/flutter/lib/src/widgets/transitions.dart
index 0fdac8c..64c370f 100644
--- a/packages/flutter/lib/src/widgets/transitions.dart
+++ b/packages/flutter/lib/src/widgets/transitions.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/lib/src/widgets/tween_animation_builder.dart

diff --git a/packages/flutter/lib/src/widgets/tween_animation_builder.dart b/packages/flutter/lib/src/widgets/tween_animation_builder.dart
index 549bbae..c18e91f 100644
--- a/packages/flutter/lib/src/widgets/tween_animation_builder.dart
+++ b/packages/flutter/lib/src/widgets/tween_animation_builder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/unique_widget.dart

diff --git a/packages/flutter/lib/src/widgets/unique_widget.dart b/packages/flutter/lib/src/widgets/unique_widget.dart
index d2d283f..8934467 100644
--- a/packages/flutter/lib/src/widgets/unique_widget.dart
+++ b/packages/flutter/lib/src/widgets/unique_widget.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'framework.dart';
 
 /// Base class for stateful widgets that have exactly one inflated instance in

packages/flutter/lib/src/widgets/value_listenable_builder.dart

diff --git a/packages/flutter/lib/src/widgets/value_listenable_builder.dart b/packages/flutter/lib/src/widgets/value_listenable_builder.dart
index b82b5a3..a867de4 100644
--- a/packages/flutter/lib/src/widgets/value_listenable_builder.dart
+++ b/packages/flutter/lib/src/widgets/value_listenable_builder.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'framework.dart';

packages/flutter/lib/src/widgets/viewport.dart

diff --git a/packages/flutter/lib/src/widgets/viewport.dart b/packages/flutter/lib/src/widgets/viewport.dart
index 2623ad2..b3b9373 100644
--- a/packages/flutter/lib/src/widgets/viewport.dart
+++ b/packages/flutter/lib/src/widgets/viewport.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/visibility.dart

diff --git a/packages/flutter/lib/src/widgets/visibility.dart b/packages/flutter/lib/src/widgets/visibility.dart
index d039873..48d333b 100644
--- a/packages/flutter/lib/src/widgets/visibility.dart
+++ b/packages/flutter/lib/src/widgets/visibility.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import 'basic.dart';

packages/flutter/lib/src/widgets/widget_inspector.dart

diff --git a/packages/flutter/lib/src/widgets/widget_inspector.dart b/packages/flutter/lib/src/widgets/widget_inspector.dart
index fe655c6..c1d7c26 100644
--- a/packages/flutter/lib/src/widgets/widget_inspector.dart
+++ b/packages/flutter/lib/src/widgets/widget_inspector.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:developer' as developer;

packages/flutter/lib/src/widgets/widget_span.dart

diff --git a/packages/flutter/lib/src/widgets/widget_span.dart b/packages/flutter/lib/src/widgets/widget_span.dart
index f1b89ea..4674414 100644
--- a/packages/flutter/lib/src/widgets/widget_span.dart
+++ b/packages/flutter/lib/src/widgets/widget_span.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show ParagraphBuilder, PlaceholderAlignment;
 
 import 'package:flutter/painting.dart';

packages/flutter/lib/src/widgets/will_pop_scope.dart

diff --git a/packages/flutter/lib/src/widgets/will_pop_scope.dart b/packages/flutter/lib/src/widgets/will_pop_scope.dart
index c8b5d88..7a3aea4 100644
--- a/packages/flutter/lib/src/widgets/will_pop_scope.dart
+++ b/packages/flutter/lib/src/widgets/will_pop_scope.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'framework.dart';
 import 'navigator.dart';
 import 'routes.dart';

packages/flutter/lib/widgets.dart

diff --git a/packages/flutter/lib/widgets.dart b/packages/flutter/lib/widgets.dart
index 2ef12f1..d8cc265 100644
--- a/packages/flutter/lib/widgets.dart
+++ b/packages/flutter/lib/widgets.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// The Flutter widgets framework.
 ///
 /// To use, import `package:flutter/widgets.dart`.

packages/flutter/test/animation/animation_controller_test.dart

diff --git a/packages/flutter/test/animation/animation_controller_test.dart b/packages/flutter/test/animation/animation_controller_test.dart
index a13b1ba..7e0c0e8 100644
--- a/packages/flutter/test/animation/animation_controller_test.dart
+++ b/packages/flutter/test/animation/animation_controller_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/animation/animation_sheet_test.dart

diff --git a/packages/flutter/test/animation/animation_sheet_test.dart b/packages/flutter/test/animation/animation_sheet_test.dart
index 7ff6346..f5a8a2b 100644
--- a/packages/flutter/test/animation/animation_sheet_test.dart
+++ b/packages/flutter/test/animation/animation_sheet_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/animation/animations_test.dart

diff --git a/packages/flutter/test/animation/animations_test.dart b/packages/flutter/test/animation/animations_test.dart
index dec27fb..d6ec66c 100644
--- a/packages/flutter/test/animation/animations_test.dart
+++ b/packages/flutter/test/animation/animations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/animation/curves_test.dart

diff --git a/packages/flutter/test/animation/curves_test.dart b/packages/flutter/test/animation/curves_test.dart
index 9af13ae..608f0bc 100644
--- a/packages/flutter/test/animation/curves_test.dart
+++ b/packages/flutter/test/animation/curves_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/animation/futures_test.dart

diff --git a/packages/flutter/test/animation/futures_test.dart b/packages/flutter/test/animation/futures_test.dart
index e389f1c..3a92903 100644
--- a/packages/flutter/test/animation/futures_test.dart
+++ b/packages/flutter/test/animation/futures_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/scheduler.dart';

packages/flutter/test/animation/iteration_patterns_test.dart

diff --git a/packages/flutter/test/animation/iteration_patterns_test.dart b/packages/flutter/test/animation/iteration_patterns_test.dart
index 59dfec7..9ab1c31 100644
--- a/packages/flutter/test/animation/iteration_patterns_test.dart
+++ b/packages/flutter/test/animation/iteration_patterns_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/animation/listener_helpers_test.dart

diff --git a/packages/flutter/test/animation/listener_helpers_test.dart b/packages/flutter/test/animation/listener_helpers_test.dart
index ddcd3dc..875e220 100644
--- a/packages/flutter/test/animation/listener_helpers_test.dart
+++ b/packages/flutter/test/animation/listener_helpers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/animation/tween_test.dart

diff --git a/packages/flutter/test/animation/tween_test.dart b/packages/flutter/test/animation/tween_test.dart
index 71565fe..6d338d4 100644
--- a/packages/flutter/test/animation/tween_test.dart
+++ b/packages/flutter/test/animation/tween_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/cupertino/action_sheet_test.dart

diff --git a/packages/flutter/test/cupertino/action_sheet_test.dart b/packages/flutter/test/cupertino/action_sheet_test.dart
index a198315..ea9f56f 100644
--- a/packages/flutter/test/cupertino/action_sheet_test.dart
+++ b/packages/flutter/test/cupertino/action_sheet_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/cupertino/activity_indicator_test.dart

diff --git a/packages/flutter/test/cupertino/activity_indicator_test.dart b/packages/flutter/test/cupertino/activity_indicator_test.dart
index 47113a4..7be9448 100644
--- a/packages/flutter/test/cupertino/activity_indicator_test.dart
+++ b/packages/flutter/test/cupertino/activity_indicator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/app_test.dart

diff --git a/packages/flutter/test/cupertino/app_test.dart b/packages/flutter/test/cupertino/app_test.dart
index 1e051e5..4bbd37a 100644
--- a/packages/flutter/test/cupertino/app_test.dart
+++ b/packages/flutter/test/cupertino/app_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/cupertino.dart';
 

packages/flutter/test/cupertino/bottom_tab_bar_test.dart

diff --git a/packages/flutter/test/cupertino/bottom_tab_bar_test.dart b/packages/flutter/test/cupertino/bottom_tab_bar_test.dart
index a51c64e..d1db6aa 100644
--- a/packages/flutter/test/cupertino/bottom_tab_bar_test.dart
+++ b/packages/flutter/test/cupertino/bottom_tab_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/button_test.dart

diff --git a/packages/flutter/test/cupertino/button_test.dart b/packages/flutter/test/cupertino/button_test.dart
index 40ee18a..6ba875f 100644
--- a/packages/flutter/test/cupertino/button_test.dart
+++ b/packages/flutter/test/cupertino/button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/scheduler.dart';

packages/flutter/test/cupertino/colors_test.dart

diff --git a/packages/flutter/test/cupertino/colors_test.dart b/packages/flutter/test/cupertino/colors_test.dart
index e0eef53..29a319e 100644
--- a/packages/flutter/test/cupertino/colors_test.dart
+++ b/packages/flutter/test/cupertino/colors_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/context_menu_action_test.dart

diff --git a/packages/flutter/test/cupertino/context_menu_action_test.dart b/packages/flutter/test/cupertino/context_menu_action_test.dart
index abe0aca..2f09144 100644
--- a/packages/flutter/test/cupertino/context_menu_action_test.dart
+++ b/packages/flutter/test/cupertino/context_menu_action_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/cupertino.dart';
 

packages/flutter/test/cupertino/context_menu_test.dart

diff --git a/packages/flutter/test/cupertino/context_menu_test.dart b/packages/flutter/test/cupertino/context_menu_test.dart
index f63f757..1203b29 100644
--- a/packages/flutter/test/cupertino/context_menu_test.dart
+++ b/packages/flutter/test/cupertino/context_menu_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart' show kIsWeb;

packages/flutter/test/cupertino/date_picker_test.dart

diff --git a/packages/flutter/test/cupertino/date_picker_test.dart b/packages/flutter/test/cupertino/date_picker_test.dart
index 01374e7..598fd4d 100644
--- a/packages/flutter/test/cupertino/date_picker_test.dart
+++ b/packages/flutter/test/cupertino/date_picker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/cupertino/dialog_test.dart

diff --git a/packages/flutter/test/cupertino/dialog_test.dart b/packages/flutter/test/cupertino/dialog_test.dart
index 10c9962..337a8e0 100644
--- a/packages/flutter/test/cupertino/dialog_test.dart
+++ b/packages/flutter/test/cupertino/dialog_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/cupertino/icon_theme_data_test.dart

diff --git a/packages/flutter/test/cupertino/icon_theme_data_test.dart b/packages/flutter/test/cupertino/icon_theme_data_test.dart
index 534a622..bd09dfa 100644
--- a/packages/flutter/test/cupertino/icon_theme_data_test.dart
+++ b/packages/flutter/test/cupertino/icon_theme_data_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/localizations_test.dart

diff --git a/packages/flutter/test/cupertino/localizations_test.dart b/packages/flutter/test/cupertino/localizations_test.dart
index e87d290..a3ecf82 100644
--- a/packages/flutter/test/cupertino/localizations_test.dart
+++ b/packages/flutter/test/cupertino/localizations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/material/tab_scaffold_test.dart

diff --git a/packages/flutter/test/cupertino/material/tab_scaffold_test.dart b/packages/flutter/test/cupertino/material/tab_scaffold_test.dart
index 32b2570..0d29cc0 100644
--- a/packages/flutter/test/cupertino/material/tab_scaffold_test.dart
+++ b/packages/flutter/test/cupertino/material/tab_scaffold_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/nav_bar_test.dart

diff --git a/packages/flutter/test/cupertino/nav_bar_test.dart b/packages/flutter/test/cupertino/nav_bar_test.dart
index 543109b..035dd3c 100644
--- a/packages/flutter/test/cupertino/nav_bar_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/cupertino/nav_bar_transition_test.dart

diff --git a/packages/flutter/test/cupertino/nav_bar_transition_test.dart b/packages/flutter/test/cupertino/nav_bar_transition_test.dart
index f65d4b0..940458b 100644
--- a/packages/flutter/test/cupertino/nav_bar_transition_test.dart
+++ b/packages/flutter/test/cupertino/nav_bar_transition_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/page_test.dart

diff --git a/packages/flutter/test/cupertino/page_test.dart b/packages/flutter/test/cupertino/page_test.dart
index ccc5250..ae15b1c 100644
--- a/packages/flutter/test/cupertino/page_test.dart
+++ b/packages/flutter/test/cupertino/page_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/picker_test.dart

diff --git a/packages/flutter/test/cupertino/picker_test.dart b/packages/flutter/test/cupertino/picker_test.dart
index b5ff312..bb7d7a8 100644
--- a/packages/flutter/test/cupertino/picker_test.dart
+++ b/packages/flutter/test/cupertino/picker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/cupertino/refresh_test.dart

diff --git a/packages/flutter/test/cupertino/refresh_test.dart b/packages/flutter/test/cupertino/refresh_test.dart
index 9081f33..85ed820 100644
--- a/packages/flutter/test/cupertino/refresh_test.dart
+++ b/packages/flutter/test/cupertino/refresh_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/cupertino/route_test.dart

diff --git a/packages/flutter/test/cupertino/route_test.dart b/packages/flutter/test/cupertino/route_test.dart
index bd083fa..c1e39fe 100644
--- a/packages/flutter/test/cupertino/route_test.dart
+++ b/packages/flutter/test/cupertino/route_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/cupertino/scaffold_test.dart

diff --git a/packages/flutter/test/cupertino/scaffold_test.dart b/packages/flutter/test/cupertino/scaffold_test.dart
index 676d248..b005374 100644
--- a/packages/flutter/test/cupertino/scaffold_test.dart
+++ b/packages/flutter/test/cupertino/scaffold_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/scrollbar_paint_test.dart

diff --git a/packages/flutter/test/cupertino/scrollbar_paint_test.dart b/packages/flutter/test/cupertino/scrollbar_paint_test.dart
index e1b1c42..bd2c4a1 100644
--- a/packages/flutter/test/cupertino/scrollbar_paint_test.dart
+++ b/packages/flutter/test/cupertino/scrollbar_paint_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/scrollbar_test.dart

diff --git a/packages/flutter/test/cupertino/scrollbar_test.dart b/packages/flutter/test/cupertino/scrollbar_test.dart
index 2815b5e..3b37145 100644
--- a/packages/flutter/test/cupertino/scrollbar_test.dart
+++ b/packages/flutter/test/cupertino/scrollbar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/segmented_control_test.dart

diff --git a/packages/flutter/test/cupertino/segmented_control_test.dart b/packages/flutter/test/cupertino/segmented_control_test.dart
index cdbd971..d9b8ced 100644
--- a/packages/flutter/test/cupertino/segmented_control_test.dart
+++ b/packages/flutter/test/cupertino/segmented_control_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/cupertino/slider_test.dart

diff --git a/packages/flutter/test/cupertino/slider_test.dart b/packages/flutter/test/cupertino/slider_test.dart
index ac58d77..5f224ee 100644
--- a/packages/flutter/test/cupertino/slider_test.dart
+++ b/packages/flutter/test/cupertino/slider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/cupertino/sliding_segmented_control_test.dart

diff --git a/packages/flutter/test/cupertino/sliding_segmented_control_test.dart b/packages/flutter/test/cupertino/sliding_segmented_control_test.dart
index cd8595b..72663d9 100644
--- a/packages/flutter/test/cupertino/sliding_segmented_control_test.dart
+++ b/packages/flutter/test/cupertino/sliding_segmented_control_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/gestures.dart';

packages/flutter/test/cupertino/switch_test.dart

diff --git a/packages/flutter/test/cupertino/switch_test.dart b/packages/flutter/test/cupertino/switch_test.dart
index 3dc5495..a186670 100644
--- a/packages/flutter/test/cupertino/switch_test.dart
+++ b/packages/flutter/test/cupertino/switch_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/cupertino/tab_scaffold_test.dart

diff --git a/packages/flutter/test/cupertino/tab_scaffold_test.dart b/packages/flutter/test/cupertino/tab_scaffold_test.dart
index fa4d16f..f7bdb25 100644
--- a/packages/flutter/test/cupertino/tab_scaffold_test.dart
+++ b/packages/flutter/test/cupertino/tab_scaffold_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/tab_test.dart

diff --git a/packages/flutter/test/cupertino/tab_test.dart b/packages/flutter/test/cupertino/tab_test.dart
index a08b494..36d972f 100644
--- a/packages/flutter/test/cupertino/tab_test.dart
+++ b/packages/flutter/test/cupertino/tab_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/cupertino/text_field_test.dart

diff --git a/packages/flutter/test/cupertino/text_field_test.dart b/packages/flutter/test/cupertino/text_field_test.dart
index 0781963..893abb5 100644
--- a/packages/flutter/test/cupertino/text_field_test.dart
+++ b/packages/flutter/test/cupertino/text_field_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui show BoxHeightStyle, BoxWidthStyle, Color;
 

packages/flutter/test/cupertino/text_selection_test.dart

diff --git a/packages/flutter/test/cupertino/text_selection_test.dart b/packages/flutter/test/cupertino/text_selection_test.dart
index 770a251..35bed86 100644
--- a/packages/flutter/test/cupertino/text_selection_test.dart
+++ b/packages/flutter/test/cupertino/text_selection_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/cupertino.dart';

packages/flutter/test/cupertino/theme_test.dart

diff --git a/packages/flutter/test/cupertino/theme_test.dart b/packages/flutter/test/cupertino/theme_test.dart
index 7fc0a27..3798c16 100644
--- a/packages/flutter/test/cupertino/theme_test.dart
+++ b/packages/flutter/test/cupertino/theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:collection/collection.dart' show SetEquality;

packages/flutter/test/examples/sector_layout_test.dart

diff --git a/packages/flutter/test/examples/sector_layout_test.dart b/packages/flutter/test/examples/sector_layout_test.dart
index 24944a9..aec1705 100644
--- a/packages/flutter/test/examples/sector_layout_test.dart
+++ b/packages/flutter/test/examples/sector_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 
 import '../../../../examples/layers/rendering/custom_coordinate_systems.dart';

packages/flutter/test/flutter_test_alternative.dart

diff --git a/packages/flutter/test/flutter_test_alternative.dart b/packages/flutter/test/flutter_test_alternative.dart
index a67c1c6..998c4ac 100644
--- a/packages/flutter/test/flutter_test_alternative.dart
+++ b/packages/flutter/test/flutter_test_alternative.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // Defines a 'package:test' shim.
 // TODO(ianh): Remove this file once https://github.com/dart-lang/matcher/issues/98 is fixed
 

packages/flutter/test/flutter_test_config.dart

diff --git a/packages/flutter/test/flutter_test_config.dart b/packages/flutter/test/flutter_test_config.dart
index c75a69e..13680ba 100644
--- a/packages/flutter/test/flutter_test_config.dart
+++ b/packages/flutter/test/flutter_test_config.dart
@@ -2,4 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 export 'package:flutter_goldens/flutter_goldens.dart' show main;

packages/flutter/test/foundation/assertions_test.dart

diff --git a/packages/flutter/test/foundation/assertions_test.dart b/packages/flutter/test/foundation/assertions_test.dart
index 60b5da1..e11f1c5 100644
--- a/packages/flutter/test/foundation/assertions_test.dart
+++ b/packages/flutter/test/foundation/assertions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/foundation/bit_field_test.dart

diff --git a/packages/flutter/test/foundation/bit_field_test.dart b/packages/flutter/test/foundation/bit_field_test.dart
index 977532f..2e54d63 100644
--- a/packages/flutter/test/foundation/bit_field_test.dart
+++ b/packages/flutter/test/foundation/bit_field_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome')
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/foundation/caching_iterable_test.dart

diff --git a/packages/flutter/test/foundation/caching_iterable_test.dart b/packages/flutter/test/foundation/caching_iterable_test.dart
index 37cede8..ca950b9 100644
--- a/packages/flutter/test/foundation/caching_iterable_test.dart
+++ b/packages/flutter/test/foundation/caching_iterable_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/foundation/capture_output.dart

diff --git a/packages/flutter/test/foundation/capture_output.dart b/packages/flutter/test/foundation/capture_output.dart
index bf07652..50b161f 100644
--- a/packages/flutter/test/foundation/capture_output.dart
+++ b/packages/flutter/test/foundation/capture_output.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'package:flutter/foundation.dart';
 

packages/flutter/test/foundation/change_notifier_test.dart

diff --git a/packages/flutter/test/foundation/change_notifier_test.dart b/packages/flutter/test/foundation/change_notifier_test.dart
index 86f0e9a..61c6cd0 100644
--- a/packages/flutter/test/foundation/change_notifier_test.dart
+++ b/packages/flutter/test/foundation/change_notifier_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/collections_test.dart

diff --git a/packages/flutter/test/foundation/collections_test.dart b/packages/flutter/test/foundation/collections_test.dart
index 69c9cb9..d9f03be 100644
--- a/packages/flutter/test/foundation/collections_test.dart
+++ b/packages/flutter/test/foundation/collections_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/src/foundation/collections.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/consolidate_response_test.dart

diff --git a/packages/flutter/test/foundation/consolidate_response_test.dart b/packages/flutter/test/foundation/consolidate_response_test.dart
index 43c4242..c69aac8 100644
--- a/packages/flutter/test/foundation/consolidate_response_test.dart
+++ b/packages/flutter/test/foundation/consolidate_response_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome')
 
 import 'dart:async';

packages/flutter/test/foundation/constants_test.dart

diff --git a/packages/flutter/test/foundation/constants_test.dart b/packages/flutter/test/foundation/constants_test.dart
index f0083d0..c895ede 100644
--- a/packages/flutter/test/foundation/constants_test.dart
+++ b/packages/flutter/test/foundation/constants_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // This test is not intended to run on the web.
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/foundation/covariant_templates_test.dart

diff --git a/packages/flutter/test/foundation/covariant_templates_test.dart b/packages/flutter/test/foundation/covariant_templates_test.dart
index d522000..2342e3d 100644
--- a/packages/flutter/test/foundation/covariant_templates_test.dart
+++ b/packages/flutter/test/foundation/covariant_templates_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 
 class X {}

packages/flutter/test/foundation/debug_test.dart

diff --git a/packages/flutter/test/foundation/debug_test.dart b/packages/flutter/test/foundation/debug_test.dart
index 0004e95..34b8958 100644
--- a/packages/flutter/test/foundation/debug_test.dart
+++ b/packages/flutter/test/foundation/debug_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/defines_test.dart

diff --git a/packages/flutter/test/foundation/defines_test.dart b/packages/flutter/test/foundation/defines_test.dart
index daf5835..41d2d10 100644
--- a/packages/flutter/test/foundation/defines_test.dart
+++ b/packages/flutter/test/foundation/defines_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/diagnostics_json_test.dart

diff --git a/packages/flutter/test/foundation/diagnostics_json_test.dart b/packages/flutter/test/foundation/diagnostics_json_test.dart
index df138a9..33ae10b 100644
--- a/packages/flutter/test/foundation/diagnostics_json_test.dart
+++ b/packages/flutter/test/foundation/diagnostics_json_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/foundation/diagnostics_test.dart

diff --git a/packages/flutter/test/foundation/diagnostics_test.dart b/packages/flutter/test/foundation/diagnostics_test.dart
index ecd824f..2a4d881 100644
--- a/packages/flutter/test/foundation/diagnostics_test.dart
+++ b/packages/flutter/test/foundation/diagnostics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert';
 import 'dart:ui';
 

packages/flutter/test/foundation/double_precision_test.dart

diff --git a/packages/flutter/test/foundation/double_precision_test.dart b/packages/flutter/test/foundation/double_precision_test.dart
index 24f348a..574770f 100644
--- a/packages/flutter/test/foundation/double_precision_test.dart
+++ b/packages/flutter/test/foundation/double_precision_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/foundation/error_reporting_test.dart

diff --git a/packages/flutter/test/foundation/error_reporting_test.dart b/packages/flutter/test/foundation/error_reporting_test.dart
index 3932eff..707ac11 100644
--- a/packages/flutter/test/foundation/error_reporting_test.dart
+++ b/packages/flutter/test/foundation/error_reporting_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // web has different stack traces
 
 import 'dart:async';

packages/flutter/test/foundation/isolates_test.dart

diff --git a/packages/flutter/test/foundation/isolates_test.dart b/packages/flutter/test/foundation/isolates_test.dart
index bbd339d..17a46bc 100644
--- a/packages/flutter/test/foundation/isolates_test.dart
+++ b/packages/flutter/test/foundation/isolates_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // isolates not supported on the web.
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/foundation/licenses_test.dart

diff --git a/packages/flutter/test/foundation/licenses_test.dart b/packages/flutter/test/foundation/licenses_test.dart
index a646c21..d4623e9 100644
--- a/packages/flutter/test/foundation/licenses_test.dart
+++ b/packages/flutter/test/foundation/licenses_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/foundation/observer_list_test.dart

diff --git a/packages/flutter/test/foundation/observer_list_test.dart b/packages/flutter/test/foundation/observer_list_test.dart
index 840214b..a67a8de 100644
--- a/packages/flutter/test/foundation/observer_list_test.dart
+++ b/packages/flutter/test/foundation/observer_list_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/platform_helper.dart

diff --git a/packages/flutter/test/foundation/platform_helper.dart b/packages/flutter/test/foundation/platform_helper.dart
index a30e882..03ff575 100644
--- a/packages/flutter/test/foundation/platform_helper.dart
+++ b/packages/flutter/test/foundation/platform_helper.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:io' show Platform;
 
 /// Returns [Platform.pathSeparator], suitably escaped so as to be usable in a

packages/flutter/test/foundation/print_test.dart

diff --git a/packages/flutter/test/foundation/print_test.dart b/packages/flutter/test/foundation/print_test.dart
index 7e93478..339b75e 100644
--- a/packages/flutter/test/foundation/print_test.dart
+++ b/packages/flutter/test/foundation/print_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:quiver/testing/async.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/foundation/reassemble_test.dart

diff --git a/packages/flutter/test/foundation/reassemble_test.dart b/packages/flutter/test/foundation/reassemble_test.dart
index df29b09..a5d7d56 100644
--- a/packages/flutter/test/foundation/reassemble_test.dart
+++ b/packages/flutter/test/foundation/reassemble_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome')
 import 'dart:async';
 

packages/flutter/test/foundation/serialization_test.dart

diff --git a/packages/flutter/test/foundation/serialization_test.dart b/packages/flutter/test/foundation/serialization_test.dart
index 3d1ed46..053b3b4 100644
--- a/packages/flutter/test/foundation/serialization_test.dart
+++ b/packages/flutter/test/foundation/serialization_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // web does not support certain 64bit behavior
 
 import 'dart:typed_data';

packages/flutter/test/foundation/service_extensions_test.dart

diff --git a/packages/flutter/test/foundation/service_extensions_test.dart b/packages/flutter/test/foundation/service_extensions_test.dart
index 1cfe627..8c8f0a6 100644
--- a/packages/flutter/test/foundation/service_extensions_test.dart
+++ b/packages/flutter/test/foundation/service_extensions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';

packages/flutter/test/foundation/stack_frame_test.dart

diff --git a/packages/flutter/test/foundation/stack_frame_test.dart b/packages/flutter/test/foundation/stack_frame_test.dart
index 87afaaf..4f53495 100644
--- a/packages/flutter/test/foundation/stack_frame_test.dart
+++ b/packages/flutter/test/foundation/stack_frame_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/foundation/stack_trace_test.dart

diff --git a/packages/flutter/test/foundation/stack_trace_test.dart b/packages/flutter/test/foundation/stack_trace_test.dart
index a2b99df..b48a1bd 100644
--- a/packages/flutter/test/foundation/stack_trace_test.dart
+++ b/packages/flutter/test/foundation/stack_trace_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // web has different stack traces
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/foundation/synchronous_future_test.dart

diff --git a/packages/flutter/test/foundation/synchronous_future_test.dart b/packages/flutter/test/foundation/synchronous_future_test.dart
index 5054bae..2ce95ab 100644
--- a/packages/flutter/test/foundation/synchronous_future_test.dart
+++ b/packages/flutter/test/foundation/synchronous_future_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/gestures/arena_test.dart

diff --git a/packages/flutter/test/gestures/arena_test.dart b/packages/flutter/test/gestures/arena_test.dart
index 3ceffbe..a6f1559 100644
--- a/packages/flutter/test/gestures/arena_test.dart
+++ b/packages/flutter/test/gestures/arena_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/gestures/debug_test.dart

diff --git a/packages/flutter/test/gestures/debug_test.dart b/packages/flutter/test/gestures/debug_test.dart
index f51fdc3..bc5b692 100644
--- a/packages/flutter/test/gestures/debug_test.dart
+++ b/packages/flutter/test/gestures/debug_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/double_tap_test.dart

diff --git a/packages/flutter/test/gestures/double_tap_test.dart b/packages/flutter/test/gestures/double_tap_test.dart
index ad40fbf..59da462 100644
--- a/packages/flutter/test/gestures/double_tap_test.dart
+++ b/packages/flutter/test/gestures/double_tap_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:quiver/testing/async.dart';
 

packages/flutter/test/gestures/drag_test.dart

diff --git a/packages/flutter/test/gestures/drag_test.dart b/packages/flutter/test/gestures/drag_test.dart
index 10216e4..c3b4cae 100644
--- a/packages/flutter/test/gestures/drag_test.dart
+++ b/packages/flutter/test/gestures/drag_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/gestures/events_test.dart

diff --git a/packages/flutter/test/gestures/events_test.dart b/packages/flutter/test/gestures/events_test.dart
index 261f999..10ea864 100644
--- a/packages/flutter/test/gestures/events_test.dart
+++ b/packages/flutter/test/gestures/events_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/gestures/force_press_test.dart

diff --git a/packages/flutter/test/gestures/force_press_test.dart b/packages/flutter/test/gestures/force_press_test.dart
index 5c60009..21b8329 100644
--- a/packages/flutter/test/gestures/force_press_test.dart
+++ b/packages/flutter/test/gestures/force_press_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/gestures/gesture_binding_test.dart

diff --git a/packages/flutter/test/gestures/gesture_binding_test.dart b/packages/flutter/test/gestures/gesture_binding_test.dart
index 41574f1..e30080c 100644
--- a/packages/flutter/test/gestures/gesture_binding_test.dart
+++ b/packages/flutter/test/gestures/gesture_binding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/gestures/gesture_tester.dart

diff --git a/packages/flutter/test/gestures/gesture_tester.dart b/packages/flutter/test/gestures/gesture_tester.dart
index 65c922a..5d31894 100644
--- a/packages/flutter/test/gestures/gesture_tester.dart
+++ b/packages/flutter/test/gestures/gesture_tester.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:meta/meta.dart';

packages/flutter/test/gestures/hit_test_test.dart

diff --git a/packages/flutter/test/gestures/hit_test_test.dart b/packages/flutter/test/gestures/hit_test_test.dart
index 0e7b806..be6706f 100644
--- a/packages/flutter/test/gestures/hit_test_test.dart
+++ b/packages/flutter/test/gestures/hit_test_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:vector_math/vector_math_64.dart';
 

packages/flutter/test/gestures/locking_test.dart

diff --git a/packages/flutter/test/gestures/locking_test.dart b/packages/flutter/test/gestures/locking_test.dart
index 8e005a6..6d61129 100644
--- a/packages/flutter/test/gestures/locking_test.dart
+++ b/packages/flutter/test/gestures/locking_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui;
 

packages/flutter/test/gestures/long_press_test.dart

diff --git a/packages/flutter/test/gestures/long_press_test.dart b/packages/flutter/test/gestures/long_press_test.dart
index 4efcfd0..c01211e 100644
--- a/packages/flutter/test/gestures/long_press_test.dart
+++ b/packages/flutter/test/gestures/long_press_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/gestures/lsq_solver_test.dart

diff --git a/packages/flutter/test/gestures/lsq_solver_test.dart b/packages/flutter/test/gestures/lsq_solver_test.dart
index 6fa15a6..467708b 100644
--- a/packages/flutter/test/gestures/lsq_solver_test.dart
+++ b/packages/flutter/test/gestures/lsq_solver_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/gestures/multidrag_test.dart

diff --git a/packages/flutter/test/gestures/multidrag_test.dart b/packages/flutter/test/gestures/multidrag_test.dart
index 72d022e..01ad88d 100644
--- a/packages/flutter/test/gestures/multidrag_test.dart
+++ b/packages/flutter/test/gestures/multidrag_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 

packages/flutter/test/gestures/multitap_test.dart

diff --git a/packages/flutter/test/gestures/multitap_test.dart b/packages/flutter/test/gestures/multitap_test.dart
index 872f9d3..f262c79 100644
--- a/packages/flutter/test/gestures/multitap_test.dart
+++ b/packages/flutter/test/gestures/multitap_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 

packages/flutter/test/gestures/pointer_router_test.dart

diff --git a/packages/flutter/test/gestures/pointer_router_test.dart b/packages/flutter/test/gestures/pointer_router_test.dart
index 228f7d7..07cef48 100644
--- a/packages/flutter/test/gestures/pointer_router_test.dart
+++ b/packages/flutter/test/gestures/pointer_router_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/gestures/pointer_signal_resolver_test.dart

diff --git a/packages/flutter/test/gestures/pointer_signal_resolver_test.dart b/packages/flutter/test/gestures/pointer_signal_resolver_test.dart
index 205c9c4..bbba166 100644
--- a/packages/flutter/test/gestures/pointer_signal_resolver_test.dart
+++ b/packages/flutter/test/gestures/pointer_signal_resolver_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:vector_math/vector_math_64.dart';
 

packages/flutter/test/gestures/recognizer_test.dart

diff --git a/packages/flutter/test/gestures/recognizer_test.dart b/packages/flutter/test/gestures/recognizer_test.dart
index ed7f1e2..2a6c130 100644
--- a/packages/flutter/test/gestures/recognizer_test.dart
+++ b/packages/flutter/test/gestures/recognizer_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 

packages/flutter/test/gestures/scale_test.dart

diff --git a/packages/flutter/test/gestures/scale_test.dart b/packages/flutter/test/gestures/scale_test.dart
index 1a9d85ab..87dcb25 100644
--- a/packages/flutter/test/gestures/scale_test.dart
+++ b/packages/flutter/test/gestures/scale_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/tap_test.dart

diff --git a/packages/flutter/test/gestures/tap_test.dart b/packages/flutter/test/gestures/tap_test.dart
index 7d98b90..7ef3032 100644
--- a/packages/flutter/test/gestures/tap_test.dart
+++ b/packages/flutter/test/gestures/tap_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/team_test.dart

diff --git a/packages/flutter/test/gestures/team_test.dart b/packages/flutter/test/gestures/team_test.dart
index fd3ceda..7c3e0b9 100644
--- a/packages/flutter/test/gestures/team_test.dart
+++ b/packages/flutter/test/gestures/team_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 

packages/flutter/test/gestures/transformed_double_tap.dart

diff --git a/packages/flutter/test/gestures/transformed_double_tap.dart b/packages/flutter/test/gestures/transformed_double_tap.dart
index 04928a7..f182a0c 100644
--- a/packages/flutter/test/gestures/transformed_double_tap.dart
+++ b/packages/flutter/test/gestures/transformed_double_tap.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/transformed_long_press_test.dart

diff --git a/packages/flutter/test/gestures/transformed_long_press_test.dart b/packages/flutter/test/gestures/transformed_long_press_test.dart
index b04e014..78b70da 100644
--- a/packages/flutter/test/gestures/transformed_long_press_test.dart
+++ b/packages/flutter/test/gestures/transformed_long_press_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/transformed_monodrag_test.dart

diff --git a/packages/flutter/test/gestures/transformed_monodrag_test.dart b/packages/flutter/test/gestures/transformed_monodrag_test.dart
index 3dc16080..4cc6619 100644
--- a/packages/flutter/test/gestures/transformed_monodrag_test.dart
+++ b/packages/flutter/test/gestures/transformed_monodrag_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';

packages/flutter/test/gestures/transformed_scale_test.dart

diff --git a/packages/flutter/test/gestures/transformed_scale_test.dart b/packages/flutter/test/gestures/transformed_scale_test.dart
index bd107bc..d78b3de 100644
--- a/packages/flutter/test/gestures/transformed_scale_test.dart
+++ b/packages/flutter/test/gestures/transformed_scale_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/transformed_tap_test.dart

diff --git a/packages/flutter/test/gestures/transformed_tap_test.dart b/packages/flutter/test/gestures/transformed_tap_test.dart
index 950a8c7..27d18b7 100644
--- a/packages/flutter/test/gestures/transformed_tap_test.dart
+++ b/packages/flutter/test/gestures/transformed_tap_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/gestures/velocity_tracker_data.dart

diff --git a/packages/flutter/test/gestures/velocity_tracker_data.dart b/packages/flutter/test/gestures/velocity_tracker_data.dart
index f08ea355..bb02fe6 100644
--- a/packages/flutter/test/gestures/velocity_tracker_data.dart
+++ b/packages/flutter/test/gestures/velocity_tracker_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 
 const List<PointerEvent> velocityEventData = <PointerEvent>[

packages/flutter/test/gestures/velocity_tracker_test.dart

diff --git a/packages/flutter/test/gestures/velocity_tracker_test.dart b/packages/flutter/test/gestures/velocity_tracker_test.dart
index 8032867..03fda2b 100644
--- a/packages/flutter/test/gestures/velocity_tracker_test.dart
+++ b/packages/flutter/test/gestures/velocity_tracker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'velocity_tracker_data.dart';

packages/flutter/test/harness/trivial_test.dart

diff --git a/packages/flutter/test/harness/trivial_test.dart b/packages/flutter/test/harness/trivial_test.dart
index 081e671..5c687f6 100644
--- a/packages/flutter/test/harness/trivial_test.dart
+++ b/packages/flutter/test/harness/trivial_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import '../flutter_test_alternative.dart';
 
 void main() {

packages/flutter/test/material/about_test.dart

diff --git a/packages/flutter/test/material/about_test.dart b/packages/flutter/test/material/about_test.dart
index 401c07f..98f9086 100644
--- a/packages/flutter/test/material/about_test.dart
+++ b/packages/flutter/test/material/about_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/material/animated_icons_private_test.dart

diff --git a/packages/flutter/test/material/animated_icons_private_test.dart b/packages/flutter/test/material/animated_icons_private_test.dart
index fe99560..5abcd68 100644
--- a/packages/flutter/test/material/animated_icons_private_test.dart
+++ b/packages/flutter/test/material/animated_icons_private_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This is the test for the private implementation of animated icons.
 // To make the private API accessible from the test we do not import the
 // material material_animated_icons library, but instead, this test file is an

packages/flutter/test/material/animated_icons_test.dart

diff --git a/packages/flutter/test/material/animated_icons_test.dart b/packages/flutter/test/material/animated_icons_test.dart
index 9c178ea..f013e72 100644
--- a/packages/flutter/test/material/animated_icons_test.dart
+++ b/packages/flutter/test/material/animated_icons_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math show pi;
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/app_bar_test.dart

diff --git a/packages/flutter/test/material/app_bar_test.dart b/packages/flutter/test/material/app_bar_test.dart
index 2af7c94..8638537 100644
--- a/packages/flutter/test/material/app_bar_test.dart
+++ b/packages/flutter/test/material/app_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/app_bar_theme_test.dart

diff --git a/packages/flutter/test/material/app_bar_theme_test.dart b/packages/flutter/test/material/app_bar_theme_test.dart
index 51ef94b..4adaabe 100644
--- a/packages/flutter/test/material/app_bar_theme_test.dart
+++ b/packages/flutter/test/material/app_bar_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/material/app_builder_test.dart

diff --git a/packages/flutter/test/material/app_builder_test.dart b/packages/flutter/test/material/app_builder_test.dart
index 97b3bf2..7398508 100644
--- a/packages/flutter/test/material/app_builder_test.dart
+++ b/packages/flutter/test/material/app_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/app_test.dart

diff --git a/packages/flutter/test/material/app_test.dart b/packages/flutter/test/material/app_test.dart
index f73554a..7ddeb70 100644
--- a/packages/flutter/test/material/app_test.dart
+++ b/packages/flutter/test/material/app_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/semantics.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/cupertino.dart';

packages/flutter/test/material/arc_test.dart

diff --git a/packages/flutter/test/material/arc_test.dart b/packages/flutter/test/material/arc_test.dart
index 008abd9..824347e 100644
--- a/packages/flutter/test/material/arc_test.dart
+++ b/packages/flutter/test/material/arc_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/back_button_test.dart

diff --git a/packages/flutter/test/material/back_button_test.dart b/packages/flutter/test/material/back_button_test.dart
index 281598d..10d83fb 100644
--- a/packages/flutter/test/material/back_button_test.dart
+++ b/packages/flutter/test/material/back_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/banner_test.dart

diff --git a/packages/flutter/test/material/banner_test.dart b/packages/flutter/test/material/banner_test.dart
index f4b13d2..a4025ae 100644
--- a/packages/flutter/test/material/banner_test.dart
+++ b/packages/flutter/test/material/banner_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/banner_theme_test.dart

diff --git a/packages/flutter/test/material/banner_theme_test.dart b/packages/flutter/test/material/banner_theme_test.dart
index 21e383a..7e8bc3f 100644
--- a/packages/flutter/test/material/banner_theme_test.dart
+++ b/packages/flutter/test/material/banner_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/bottom_app_bar_test.dart

diff --git a/packages/flutter/test/material/bottom_app_bar_test.dart b/packages/flutter/test/material/bottom_app_bar_test.dart
index b42bbf0..1d41dd8 100644
--- a/packages/flutter/test/material/bottom_app_bar_test.dart
+++ b/packages/flutter/test/material/bottom_app_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/bottom_app_bar_theme_test.dart

diff --git a/packages/flutter/test/material/bottom_app_bar_theme_test.dart b/packages/flutter/test/material/bottom_app_bar_theme_test.dart
index d3aa222..5078eb9 100644
--- a/packages/flutter/test/material/bottom_app_bar_theme_test.dart
+++ b/packages/flutter/test/material/bottom_app_bar_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/bottom_navigation_bar_test.dart

diff --git a/packages/flutter/test/material/bottom_navigation_bar_test.dart b/packages/flutter/test/material/bottom_navigation_bar_test.dart
index d4ff1cf..6cad771 100644
--- a/packages/flutter/test/material/bottom_navigation_bar_test.dart
+++ b/packages/flutter/test/material/bottom_navigation_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/bottom_navigation_bar_theme_test.dart

diff --git a/packages/flutter/test/material/bottom_navigation_bar_theme_test.dart b/packages/flutter/test/material/bottom_navigation_bar_theme_test.dart
index 54fe98d..b9ce3bf 100644
--- a/packages/flutter/test/material/bottom_navigation_bar_theme_test.dart
+++ b/packages/flutter/test/material/bottom_navigation_bar_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/bottom_sheet_test.dart

diff --git a/packages/flutter/test/material/bottom_sheet_test.dart b/packages/flutter/test/material/bottom_sheet_test.dart
index 79e7e1a..0171f1b 100644
--- a/packages/flutter/test/material/bottom_sheet_test.dart
+++ b/packages/flutter/test/material/bottom_sheet_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/material/bottom_sheet_theme_test.dart

diff --git a/packages/flutter/test/material/bottom_sheet_theme_test.dart b/packages/flutter/test/material/bottom_sheet_theme_test.dart
index eecc1a3..8d46e13 100644
--- a/packages/flutter/test/material/bottom_sheet_theme_test.dart
+++ b/packages/flutter/test/material/bottom_sheet_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/material/button_bar_test.dart

diff --git a/packages/flutter/test/material/button_bar_test.dart b/packages/flutter/test/material/button_bar_test.dart
index 9e1c4e0..693eb10 100644
--- a/packages/flutter/test/material/button_bar_test.dart
+++ b/packages/flutter/test/material/button_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/button_bar_theme_test.dart

diff --git a/packages/flutter/test/material/button_bar_theme_test.dart b/packages/flutter/test/material/button_bar_theme_test.dart
index 46d093f..1e74c0f 100644
--- a/packages/flutter/test/material/button_bar_theme_test.dart
+++ b/packages/flutter/test/material/button_bar_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/button_theme_test.dart

diff --git a/packages/flutter/test/material/button_theme_test.dart b/packages/flutter/test/material/button_theme_test.dart
index 8ccee94..713e9fb 100644
--- a/packages/flutter/test/material/button_theme_test.dart
+++ b/packages/flutter/test/material/button_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/card_test.dart

diff --git a/packages/flutter/test/material/card_test.dart b/packages/flutter/test/material/card_test.dart
index e583c3e..a07751a 100644
--- a/packages/flutter/test/material/card_test.dart
+++ b/packages/flutter/test/material/card_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/card_theme_test.dart

diff --git a/packages/flutter/test/material/card_theme_test.dart b/packages/flutter/test/material/card_theme_test.dart
index 07226b6..f6cfd25 100644
--- a/packages/flutter/test/material/card_theme_test.dart
+++ b/packages/flutter/test/material/card_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/checkbox_list_tile_test.dart

diff --git a/packages/flutter/test/material/checkbox_list_tile_test.dart b/packages/flutter/test/material/checkbox_list_tile_test.dart
index 7c9d9fd..f5913d2 100644
--- a/packages/flutter/test/material/checkbox_list_tile_test.dart
+++ b/packages/flutter/test/material/checkbox_list_tile_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/checkbox_test.dart

diff --git a/packages/flutter/test/material/checkbox_test.dart b/packages/flutter/test/material/checkbox_test.dart
index 7377ab2..d0044eb 100644
--- a/packages/flutter/test/material/checkbox_test.dart
+++ b/packages/flutter/test/material/checkbox_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/material/chip_test.dart

diff --git a/packages/flutter/test/material/chip_test.dart b/packages/flutter/test/material/chip_test.dart
index 997488e..770e4d8 100644
--- a/packages/flutter/test/material/chip_test.dart
+++ b/packages/flutter/test/material/chip_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show window;
 
 import 'package:flutter/gestures.dart';

packages/flutter/test/material/chip_theme_test.dart

diff --git a/packages/flutter/test/material/chip_theme_test.dart b/packages/flutter/test/material/chip_theme_test.dart
index 3133033..1781e9c 100644
--- a/packages/flutter/test/material/chip_theme_test.dart
+++ b/packages/flutter/test/material/chip_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show window;
 
 import 'package:flutter/gestures.dart';

packages/flutter/test/material/circle_avatar_test.dart

diff --git a/packages/flutter/test/material/circle_avatar_test.dart b/packages/flutter/test/material/circle_avatar_test.dart
index 2a434a1..aec85d2 100644
--- a/packages/flutter/test/material/circle_avatar_test.dart
+++ b/packages/flutter/test/material/circle_avatar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/color_scheme_test.dart

diff --git a/packages/flutter/test/material/color_scheme_test.dart b/packages/flutter/test/material/color_scheme_test.dart
index 0e3ba01..351ebdc 100644
--- a/packages/flutter/test/material/color_scheme_test.dart
+++ b/packages/flutter/test/material/color_scheme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/colors_test.dart

diff --git a/packages/flutter/test/material/colors_test.dart b/packages/flutter/test/material/colors_test.dart
index a9f33bb..cc64190 100644
--- a/packages/flutter/test/material/colors_test.dart
+++ b/packages/flutter/test/material/colors_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/material/data_table_test.dart

diff --git a/packages/flutter/test/material/data_table_test.dart b/packages/flutter/test/material/data_table_test.dart
index 115287c..f30dac6 100644
--- a/packages/flutter/test/material/data_table_test.dart
+++ b/packages/flutter/test/material/data_table_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/data_table_test_utils.dart

diff --git a/packages/flutter/test/material/data_table_test_utils.dart b/packages/flutter/test/material/data_table_test_utils.dart
index e6c0846..77ff5d1 100644
--- a/packages/flutter/test/material/data_table_test_utils.dart
+++ b/packages/flutter/test/material/data_table_test_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 class Dessert {
   Dessert(this.name, this.calories, this.fat, this.carbs, this.protein, this.sodium, this.calcium, this.iron);
 

packages/flutter/test/material/date_picker_test.dart

diff --git a/packages/flutter/test/material/date_picker_test.dart b/packages/flutter/test/material/date_picker_test.dart
index dc47a0d..5d25f04 100644
--- a/packages/flutter/test/material/date_picker_test.dart
+++ b/packages/flutter/test/material/date_picker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/date_range_picker_test.dart

diff --git a/packages/flutter/test/material/date_range_picker_test.dart b/packages/flutter/test/material/date_range_picker_test.dart
index 2bcae3a..95bf9d6 100644
--- a/packages/flutter/test/material/date_range_picker_test.dart
+++ b/packages/flutter/test/material/date_range_picker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/debug_test.dart

diff --git a/packages/flutter/test/material/debug_test.dart b/packages/flutter/test/material/debug_test.dart
index 8ed3d7a..2653605 100644
--- a/packages/flutter/test/material/debug_test.dart
+++ b/packages/flutter/test/material/debug_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/dialog_test.dart

diff --git a/packages/flutter/test/material/dialog_test.dart b/packages/flutter/test/material/dialog_test.dart
index cc61d91..531a7e0 100644
--- a/packages/flutter/test/material/dialog_test.dart
+++ b/packages/flutter/test/material/dialog_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/dialog_theme_test.dart

diff --git a/packages/flutter/test/material/dialog_theme_test.dart b/packages/flutter/test/material/dialog_theme_test.dart
index cdc1a93..6a7031f 100644
--- a/packages/flutter/test/material/dialog_theme_test.dart
+++ b/packages/flutter/test/material/dialog_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/divider_test.dart

diff --git a/packages/flutter/test/material/divider_test.dart b/packages/flutter/test/material/divider_test.dart
index 10a5a2b..0489dca 100644
--- a/packages/flutter/test/material/divider_test.dart
+++ b/packages/flutter/test/material/divider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/painting.dart';

packages/flutter/test/material/divider_theme_test.dart

diff --git a/packages/flutter/test/material/divider_theme_test.dart b/packages/flutter/test/material/divider_theme_test.dart
index a1a48f8..9420603 100644
--- a/packages/flutter/test/material/divider_theme_test.dart
+++ b/packages/flutter/test/material/divider_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/drawer_test.dart

diff --git a/packages/flutter/test/material/drawer_test.dart b/packages/flutter/test/material/drawer_test.dart
index 0cdff9d..9f0aa72 100644
--- a/packages/flutter/test/material/drawer_test.dart
+++ b/packages/flutter/test/material/drawer_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/dropdown_form_field_test.dart

diff --git a/packages/flutter/test/material/dropdown_form_field_test.dart b/packages/flutter/test/material/dropdown_form_field_test.dart
index e5e7d6f..5f724c9 100644
--- a/packages/flutter/test/material/dropdown_form_field_test.dart
+++ b/packages/flutter/test/material/dropdown_form_field_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show window;
 

packages/flutter/test/material/dropdown_test.dart

diff --git a/packages/flutter/test/material/dropdown_test.dart b/packages/flutter/test/material/dropdown_test.dart
index 1050e89..c168580 100644
--- a/packages/flutter/test/material/dropdown_test.dart
+++ b/packages/flutter/test/material/dropdown_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui' show window;
 

packages/flutter/test/material/expand_icon_test.dart

diff --git a/packages/flutter/test/material/expand_icon_test.dart b/packages/flutter/test/material/expand_icon_test.dart
index 30fd8d8..dc1a404 100644
--- a/packages/flutter/test/material/expand_icon_test.dart
+++ b/packages/flutter/test/material/expand_icon_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/expansion_panel_test.dart

diff --git a/packages/flutter/test/material/expansion_panel_test.dart b/packages/flutter/test/material/expansion_panel_test.dart
index 05b58d8..a34ab5b 100644
--- a/packages/flutter/test/material/expansion_panel_test.dart
+++ b/packages/flutter/test/material/expansion_panel_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/expansion_tile_test.dart

diff --git a/packages/flutter/test/material/expansion_tile_test.dart b/packages/flutter/test/material/expansion_tile_test.dart
index 9b1c12a..1c004d2 100644
--- a/packages/flutter/test/material/expansion_tile_test.dart
+++ b/packages/flutter/test/material/expansion_tile_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/feedback_test.dart

diff --git a/packages/flutter/test/material/feedback_test.dart b/packages/flutter/test/material/feedback_test.dart
index 84e1433..c7194e8 100644
--- a/packages/flutter/test/material/feedback_test.dart
+++ b/packages/flutter/test/material/feedback_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/feedback_tester.dart

diff --git a/packages/flutter/test/material/feedback_tester.dart b/packages/flutter/test/material/feedback_tester.dart
index 5f1c469..d986af1 100644
--- a/packages/flutter/test/material/feedback_tester.dart
+++ b/packages/flutter/test/material/feedback_tester.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 
 /// Tracks how often feedback has been requested since its instantiation.

packages/flutter/test/material/flat_button_test.dart

diff --git a/packages/flutter/test/material/flat_button_test.dart b/packages/flutter/test/material/flat_button_test.dart
index 13c5f2e..67b0636 100644
--- a/packages/flutter/test/material/flat_button_test.dart
+++ b/packages/flutter/test/material/flat_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/material/flexible_space_bar_collapse_mode_test.dart

diff --git a/packages/flutter/test/material/flexible_space_bar_collapse_mode_test.dart b/packages/flutter/test/material/flexible_space_bar_collapse_mode_test.dart
index 40f37591..d51542a 100644
--- a/packages/flutter/test/material/flexible_space_bar_collapse_mode_test.dart
+++ b/packages/flutter/test/material/flexible_space_bar_collapse_mode_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/flexible_space_bar_stretch_mode_test.dart

diff --git a/packages/flutter/test/material/flexible_space_bar_stretch_mode_test.dart b/packages/flutter/test/material/flexible_space_bar_stretch_mode_test.dart
index 09077fe..694d676 100644
--- a/packages/flutter/test/material/flexible_space_bar_stretch_mode_test.dart
+++ b/packages/flutter/test/material/flexible_space_bar_stretch_mode_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/flexible_space_bar_test.dart

diff --git a/packages/flutter/test/material/flexible_space_bar_test.dart b/packages/flutter/test/material/flexible_space_bar_test.dart
index 2c83547..f8d6c82 100644
--- a/packages/flutter/test/material/flexible_space_bar_test.dart
+++ b/packages/flutter/test/material/flexible_space_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/floating_action_button_location_test.dart

diff --git a/packages/flutter/test/material/floating_action_button_location_test.dart b/packages/flutter/test/material/floating_action_button_location_test.dart
index 14f6652..4cb322d 100644
--- a/packages/flutter/test/material/floating_action_button_location_test.dart
+++ b/packages/flutter/test/material/floating_action_button_location_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/material/floating_action_button_test.dart

diff --git a/packages/flutter/test/material/floating_action_button_test.dart b/packages/flutter/test/material/floating_action_button_test.dart
index 9193935..36ee48a 100644
--- a/packages/flutter/test/material/floating_action_button_test.dart
+++ b/packages/flutter/test/material/floating_action_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // whole file needs triage.
 import 'dart:ui';
 

packages/flutter/test/material/floating_action_button_theme_test.dart

diff --git a/packages/flutter/test/material/floating_action_button_theme_test.dart b/packages/flutter/test/material/floating_action_button_theme_test.dart
index 394c486..1feafb4 100644
--- a/packages/flutter/test/material/floating_action_button_theme_test.dart
+++ b/packages/flutter/test/material/floating_action_button_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/grid_title_test.dart

diff --git a/packages/flutter/test/material/grid_title_test.dart b/packages/flutter/test/material/grid_title_test.dart
index 0e90d90..d1bd664 100644
--- a/packages/flutter/test/material/grid_title_test.dart
+++ b/packages/flutter/test/material/grid_title_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/icon_button_test.dart

diff --git a/packages/flutter/test/material/icon_button_test.dart b/packages/flutter/test/material/icon_button_test.dart
index d582748..ac65041 100644
--- a/packages/flutter/test/material/icon_button_test.dart
+++ b/packages/flutter/test/material/icon_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/icons_test.dart

diff --git a/packages/flutter/test/material/icons_test.dart b/packages/flutter/test/material/icons_test.dart
index 06a30a7..2a1be8d 100644
--- a/packages/flutter/test/material/icons_test.dart
+++ b/packages/flutter/test/material/icons_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/inherited_theme_test.dart

diff --git a/packages/flutter/test/material/inherited_theme_test.dart b/packages/flutter/test/material/inherited_theme_test.dart
index 52b8ac1..52ed3b0 100644
--- a/packages/flutter/test/material/inherited_theme_test.dart
+++ b/packages/flutter/test/material/inherited_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/ink_paint_test.dart

diff --git a/packages/flutter/test/material/ink_paint_test.dart b/packages/flutter/test/material/ink_paint_test.dart
index 01689c1..127be46 100644
--- a/packages/flutter/test/material/ink_paint_test.dart
+++ b/packages/flutter/test/material/ink_paint_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/material/ink_splash_test.dart

diff --git a/packages/flutter/test/material/ink_splash_test.dart b/packages/flutter/test/material/ink_splash_test.dart
index ed34dbe..67b097a 100644
--- a/packages/flutter/test/material/ink_splash_test.dart
+++ b/packages/flutter/test/material/ink_splash_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/ink_well_test.dart

diff --git a/packages/flutter/test/material/ink_well_test.dart b/packages/flutter/test/material/ink_well_test.dart
index 43ba477..2da044e 100644
--- a/packages/flutter/test/material/ink_well_test.dart
+++ b/packages/flutter/test/material/ink_well_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/input_decorator_test.dart

diff --git a/packages/flutter/test/material/input_decorator_test.dart b/packages/flutter/test/material/input_decorator_test.dart
index 723eb46..14f3bb8 100644
--- a/packages/flutter/test/material/input_decorator_test.dart
+++ b/packages/flutter/test/material/input_decorator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/list_tile_test.dart

diff --git a/packages/flutter/test/material/list_tile_test.dart b/packages/flutter/test/material/list_tile_test.dart
index 0b127fa..55ff4d3 100644
--- a/packages/flutter/test/material/list_tile_test.dart
+++ b/packages/flutter/test/material/list_tile_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'dart:ui';
 

packages/flutter/test/material/localizations_test.dart

diff --git a/packages/flutter/test/material/localizations_test.dart b/packages/flutter/test/material/localizations_test.dart
index bd0d98a..0a9bc0a 100644
--- a/packages/flutter/test/material/localizations_test.dart
+++ b/packages/flutter/test/material/localizations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/material_button_test.dart

diff --git a/packages/flutter/test/material/material_button_test.dart b/packages/flutter/test/material/material_button_test.dart
index 7c4ffc7..00ee6dc 100644
--- a/packages/flutter/test/material/material_button_test.dart
+++ b/packages/flutter/test/material/material_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/material_state_property_test.dart

diff --git a/packages/flutter/test/material/material_state_property_test.dart b/packages/flutter/test/material/material_state_property_test.dart
index 8ce450c..79da4d5 100644
--- a/packages/flutter/test/material/material_state_property_test.dart
+++ b/packages/flutter/test/material/material_state_property_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/material_test.dart

diff --git a/packages/flutter/test/material/material_test.dart b/packages/flutter/test/material/material_test.dart
index 4fbe7e1..c35365c 100644
--- a/packages/flutter/test/material/material_test.dart
+++ b/packages/flutter/test/material/material_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/mergeable_material_test.dart

diff --git a/packages/flutter/test/material/mergeable_material_test.dart b/packages/flutter/test/material/mergeable_material_test.dart
index 08254c6..683c8dd 100644
--- a/packages/flutter/test/material/mergeable_material_test.dart
+++ b/packages/flutter/test/material/mergeable_material_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/navigation_rail_test.dart

diff --git a/packages/flutter/test/material/navigation_rail_test.dart b/packages/flutter/test/material/navigation_rail_test.dart
index 2d6ab84..b1211ae 100644
--- a/packages/flutter/test/material/navigation_rail_test.dart
+++ b/packages/flutter/test/material/navigation_rail_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/navigation_rail_theme_test.dart

diff --git a/packages/flutter/test/material/navigation_rail_theme_test.dart b/packages/flutter/test/material/navigation_rail_theme_test.dart
index e613030..2787bb3 100644
--- a/packages/flutter/test/material/navigation_rail_theme_test.dart
+++ b/packages/flutter/test/material/navigation_rail_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/outline_button_test.dart

diff --git a/packages/flutter/test/material/outline_button_test.dart b/packages/flutter/test/material/outline_button_test.dart
index 8a69adb..c787018 100644
--- a/packages/flutter/test/material/outline_button_test.dart
+++ b/packages/flutter/test/material/outline_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/page_selector_test.dart

diff --git a/packages/flutter/test/material/page_selector_test.dart b/packages/flutter/test/material/page_selector_test.dart
index 35e24dc..28028e2 100644
--- a/packages/flutter/test/material/page_selector_test.dart
+++ b/packages/flutter/test/material/page_selector_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/page_test.dart

diff --git a/packages/flutter/test/material/page_test.dart b/packages/flutter/test/material/page_test.dart
index 680742f..4b8e3bd 100644
--- a/packages/flutter/test/material/page_test.dart
+++ b/packages/flutter/test/material/page_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/cupertino.dart' show CupertinoPageRoute;

packages/flutter/test/material/page_transitions_theme_test.dart

diff --git a/packages/flutter/test/material/page_transitions_theme_test.dart b/packages/flutter/test/material/page_transitions_theme_test.dart
index 15ea31f..e823432 100644
--- a/packages/flutter/test/material/page_transitions_theme_test.dart
+++ b/packages/flutter/test/material/page_transitions_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/paginated_data_table_test.dart

diff --git a/packages/flutter/test/material/paginated_data_table_test.dart b/packages/flutter/test/material/paginated_data_table_test.dart
index d2cbcf8..05470da 100644
--- a/packages/flutter/test/material/paginated_data_table_test.dart
+++ b/packages/flutter/test/material/paginated_data_table_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/test/material/persistent_bottom_sheet_test.dart

diff --git a/packages/flutter/test/material/persistent_bottom_sheet_test.dart b/packages/flutter/test/material/persistent_bottom_sheet_test.dart
index b567047..2256a4f 100644
--- a/packages/flutter/test/material/persistent_bottom_sheet_test.dart
+++ b/packages/flutter/test/material/persistent_bottom_sheet_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/popup_menu_test.dart

diff --git a/packages/flutter/test/material/popup_menu_test.dart b/packages/flutter/test/material/popup_menu_test.dart
index 7ae7ed4..9bac482 100644
--- a/packages/flutter/test/material/popup_menu_test.dart
+++ b/packages/flutter/test/material/popup_menu_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show window, SemanticsFlag;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/popup_menu_theme_test.dart

diff --git a/packages/flutter/test/material/popup_menu_theme_test.dart b/packages/flutter/test/material/popup_menu_theme_test.dart
index d89ae6a..a964521 100644
--- a/packages/flutter/test/material/popup_menu_theme_test.dart
+++ b/packages/flutter/test/material/popup_menu_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/progress_indicator_test.dart

diff --git a/packages/flutter/test/material/progress_indicator_test.dart b/packages/flutter/test/material/progress_indicator_test.dart
index fd6ec40..f42763d 100644
--- a/packages/flutter/test/material/progress_indicator_test.dart
+++ b/packages/flutter/test/material/progress_indicator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/radio_list_tile_test.dart

diff --git a/packages/flutter/test/material/radio_list_tile_test.dart b/packages/flutter/test/material/radio_list_tile_test.dart
index 3b03afa..46e663c 100644
--- a/packages/flutter/test/material/radio_list_tile_test.dart
+++ b/packages/flutter/test/material/radio_list_tile_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/material/radio_test.dart

diff --git a/packages/flutter/test/material/radio_test.dart b/packages/flutter/test/material/radio_test.dart
index ef7a378..f3406fd 100644
--- a/packages/flutter/test/material/radio_test.dart
+++ b/packages/flutter/test/material/radio_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/material/raised_button_test.dart

diff --git a/packages/flutter/test/material/raised_button_test.dart b/packages/flutter/test/material/raised_button_test.dart
index 6bdd01c..77b317a 100644
--- a/packages/flutter/test/material/raised_button_test.dart
+++ b/packages/flutter/test/material/raised_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/range_slider_test.dart

diff --git a/packages/flutter/test/material/range_slider_test.dart b/packages/flutter/test/material/range_slider_test.dart
index 69a5a97..b2e9a00 100644
--- a/packages/flutter/test/material/range_slider_test.dart
+++ b/packages/flutter/test/material/range_slider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/material/raw_material_button_test.dart

diff --git a/packages/flutter/test/material/raw_material_button_test.dart b/packages/flutter/test/material/raw_material_button_test.dart
index 9047840..2d59b6d 100644
--- a/packages/flutter/test/material/raw_material_button_test.dart
+++ b/packages/flutter/test/material/raw_material_button_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/refresh_indicator_test.dart

diff --git a/packages/flutter/test/material/refresh_indicator_test.dart b/packages/flutter/test/material/refresh_indicator_test.dart
index 26fed9f..822e444 100644
--- a/packages/flutter/test/material/refresh_indicator_test.dart
+++ b/packages/flutter/test/material/refresh_indicator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/material/reorderable_list_test.dart

diff --git a/packages/flutter/test/material/reorderable_list_test.dart b/packages/flutter/test/material/reorderable_list_test.dart
index b9b2ec3..96a2073 100644
--- a/packages/flutter/test/material/reorderable_list_test.dart
+++ b/packages/flutter/test/material/reorderable_list_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/semantics.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/scaffold_test.dart

diff --git a/packages/flutter/test/material/scaffold_test.dart b/packages/flutter/test/material/scaffold_test.dart
index afcaebe..65166f2 100644
--- a/packages/flutter/test/material/scaffold_test.dart
+++ b/packages/flutter/test/material/scaffold_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'package:flutter/material.dart';

packages/flutter/test/material/scrollbar_paint_test.dart

diff --git a/packages/flutter/test/material/scrollbar_paint_test.dart b/packages/flutter/test/material/scrollbar_paint_test.dart
index c81d935..f82bda0 100644
--- a/packages/flutter/test/material/scrollbar_paint_test.dart
+++ b/packages/flutter/test/material/scrollbar_paint_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/scrollbar_test.dart

diff --git a/packages/flutter/test/material/scrollbar_test.dart b/packages/flutter/test/material/scrollbar_test.dart
index 0566aef..6a63e2a 100644
--- a/packages/flutter/test/material/scrollbar_test.dart
+++ b/packages/flutter/test/material/scrollbar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/search_test.dart

diff --git a/packages/flutter/test/material/search_test.dart b/packages/flutter/test/material/search_test.dart
index 68fee7a..b799666 100644
--- a/packages/flutter/test/material/search_test.dart
+++ b/packages/flutter/test/material/search_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/material/slider_test.dart

diff --git a/packages/flutter/test/material/slider_test.dart b/packages/flutter/test/material/slider_test.dart
index 46fac50..8744d2f 100644
--- a/packages/flutter/test/material/slider_test.dart
+++ b/packages/flutter/test/material/slider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/material/slider_theme_test.dart

diff --git a/packages/flutter/test/material/slider_theme_test.dart b/packages/flutter/test/material/slider_theme_test.dart
index 66169a6..37a53da 100644
--- a/packages/flutter/test/material/slider_theme_test.dart
+++ b/packages/flutter/test/material/slider_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show window;
 
 import 'package:flutter/material.dart';

packages/flutter/test/material/snack_bar_test.dart

diff --git a/packages/flutter/test/material/snack_bar_test.dart b/packages/flutter/test/material/snack_bar_test.dart
index c90ea6d..5275d2a 100644
--- a/packages/flutter/test/material/snack_bar_test.dart
+++ b/packages/flutter/test/material/snack_bar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/snack_bar_theme_test.dart

diff --git a/packages/flutter/test/material/snack_bar_theme_test.dart b/packages/flutter/test/material/snack_bar_theme_test.dart
index 0e92db6..a49f5bc 100644
--- a/packages/flutter/test/material/snack_bar_theme_test.dart
+++ b/packages/flutter/test/material/snack_bar_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/stepper_test.dart

diff --git a/packages/flutter/test/material/stepper_test.dart b/packages/flutter/test/material/stepper_test.dart
index 73a4a50..3fc59dc 100644
--- a/packages/flutter/test/material/stepper_test.dart
+++ b/packages/flutter/test/material/stepper_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/switch_list_tile_test.dart

diff --git a/packages/flutter/test/material/switch_list_tile_test.dart b/packages/flutter/test/material/switch_list_tile_test.dart
index a6bd56a..0098a95 100644
--- a/packages/flutter/test/material/switch_list_tile_test.dart
+++ b/packages/flutter/test/material/switch_list_tile_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/switch_test.dart

diff --git a/packages/flutter/test/material/switch_test.dart b/packages/flutter/test/material/switch_test.dart
index 3361e34..22c4d13 100644
--- a/packages/flutter/test/material/switch_test.dart
+++ b/packages/flutter/test/material/switch_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/material/tab_bar_theme_test.dart

diff --git a/packages/flutter/test/material/tab_bar_theme_test.dart b/packages/flutter/test/material/tab_bar_theme_test.dart
index cbdd97a..e168750 100644
--- a/packages/flutter/test/material/tab_bar_theme_test.dart
+++ b/packages/flutter/test/material/tab_bar_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/tabbed_scrollview_warp_test.dart

diff --git a/packages/flutter/test/material/tabbed_scrollview_warp_test.dart b/packages/flutter/test/material/tabbed_scrollview_warp_test.dart
index ce0f19f..ccbab27 100644
--- a/packages/flutter/test/material/tabbed_scrollview_warp_test.dart
+++ b/packages/flutter/test/material/tabbed_scrollview_warp_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/tabs_test.dart

diff --git a/packages/flutter/test/material/tabs_test.dart b/packages/flutter/test/material/tabs_test.dart
index 86b10fa..4dbdbc7 100644
--- a/packages/flutter/test/material/tabs_test.dart
+++ b/packages/flutter/test/material/tabs_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/text_field_focus_test.dart

diff --git a/packages/flutter/test/material/text_field_focus_test.dart b/packages/flutter/test/material/text_field_focus_test.dart
index 758ffe0..ddfe2bf 100644
--- a/packages/flutter/test/material/text_field_focus_test.dart
+++ b/packages/flutter/test/material/text_field_focus_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/material/text_field_helper_text_test.dart

diff --git a/packages/flutter/test/material/text_field_helper_text_test.dart b/packages/flutter/test/material/text_field_helper_text_test.dart
index a5b4a06..6d4f6ff 100644
--- a/packages/flutter/test/material/text_field_helper_text_test.dart
+++ b/packages/flutter/test/material/text_field_helper_text_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/text_field_splash_test.dart

diff --git a/packages/flutter/test/material/text_field_splash_test.dart b/packages/flutter/test/material/text_field_splash_test.dart
index e7e2069..3c94cac 100644
--- a/packages/flutter/test/material/text_field_splash_test.dart
+++ b/packages/flutter/test/material/text_field_splash_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart' show kPressTimeout;
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/text_field_test.dart

diff --git a/packages/flutter/test/material/text_field_test.dart b/packages/flutter/test/material/text_field_test.dart
index 526e5f5..1175240 100644
--- a/packages/flutter/test/material/text_field_test.dart
+++ b/packages/flutter/test/material/text_field_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // This whole test suite needs triage.
 import 'dart:async';
 import 'dart:math' as math;

packages/flutter/test/material/text_form_field_test.dart

diff --git a/packages/flutter/test/material/text_form_field_test.dart b/packages/flutter/test/material/text_form_field_test.dart
index 0cd68eb..e58e21a 100644
--- a/packages/flutter/test/material/text_form_field_test.dart
+++ b/packages/flutter/test/material/text_form_field_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/text_selection_test.dart

diff --git a/packages/flutter/test/material/text_selection_test.dart b/packages/flutter/test/material/text_selection_test.dart
index 6dba6e1..630e744 100644
--- a/packages/flutter/test/material/text_selection_test.dart
+++ b/packages/flutter/test/material/text_selection_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/text_theme_test.dart

diff --git a/packages/flutter/test/material/text_theme_test.dart b/packages/flutter/test/material/text_theme_test.dart
index 9a2e0c3..44d6734 100644
--- a/packages/flutter/test/material/text_theme_test.dart
+++ b/packages/flutter/test/material/text_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/theme_data_test.dart

diff --git a/packages/flutter/test/material/theme_data_test.dart b/packages/flutter/test/material/theme_data_test.dart
index 986d956..ee667c6 100644
--- a/packages/flutter/test/material/theme_data_test.dart
+++ b/packages/flutter/test/material/theme_data_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/theme_defaults_test.dart

diff --git a/packages/flutter/test/material/theme_defaults_test.dart b/packages/flutter/test/material/theme_defaults_test.dart
index 0fc2ece..ffb5d1c 100644
--- a/packages/flutter/test/material/theme_defaults_test.dart
+++ b/packages/flutter/test/material/theme_defaults_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/theme_test.dart

diff --git a/packages/flutter/test/material/theme_test.dart b/packages/flutter/test/material/theme_test.dart
index 8835aa4..f90ab9c 100644
--- a/packages/flutter/test/material/theme_test.dart
+++ b/packages/flutter/test/material/theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/material/time_picker_test.dart

diff --git a/packages/flutter/test/material/time_picker_test.dart b/packages/flutter/test/material/time_picker_test.dart
index 629fbdd..f5b47ea 100644
--- a/packages/flutter/test/material/time_picker_test.dart
+++ b/packages/flutter/test/material/time_picker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // entire file needs triage.
 import 'dart:async';
 import 'dart:ui' as ui;

packages/flutter/test/material/time_test.dart

diff --git a/packages/flutter/test/material/time_test.dart b/packages/flutter/test/material/time_test.dart
index 62108b2..9e74ec5 100644
--- a/packages/flutter/test/material/time_test.dart
+++ b/packages/flutter/test/material/time_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/material/toggle_buttons_test.dart

diff --git a/packages/flutter/test/material/toggle_buttons_test.dart b/packages/flutter/test/material/toggle_buttons_test.dart
index 992445b..3bddd9c 100644
--- a/packages/flutter/test/material/toggle_buttons_test.dart
+++ b/packages/flutter/test/material/toggle_buttons_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/toggle_buttons_theme_test.dart

diff --git a/packages/flutter/test/material/toggle_buttons_theme_test.dart b/packages/flutter/test/material/toggle_buttons_theme_test.dart
index 384bbfe..05b3983 100644
--- a/packages/flutter/test/material/toggle_buttons_theme_test.dart
+++ b/packages/flutter/test/material/toggle_buttons_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/material/tooltip_test.dart

diff --git a/packages/flutter/test/material/tooltip_test.dart b/packages/flutter/test/material/tooltip_test.dart
index b3667e7..e7bf921 100644
--- a/packages/flutter/test/material/tooltip_test.dart
+++ b/packages/flutter/test/material/tooltip_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/services.dart';

packages/flutter/test/material/tooltip_theme_test.dart

diff --git a/packages/flutter/test/material/tooltip_theme_test.dart b/packages/flutter/test/material/tooltip_theme_test.dart
index c948f3d..2198c13 100644
--- a/packages/flutter/test/material/tooltip_theme_test.dart
+++ b/packages/flutter/test/material/tooltip_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter/src/material/tooltip_theme.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/material/typography_test.dart

diff --git a/packages/flutter/test/material/typography_test.dart b/packages/flutter/test/material/typography_test.dart
index 7447650..a612f95 100644
--- a/packages/flutter/test/material/typography_test.dart
+++ b/packages/flutter/test/material/typography_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/user_accounts_drawer_header_test.dart

diff --git a/packages/flutter/test/material/user_accounts_drawer_header_test.dart b/packages/flutter/test/material/user_accounts_drawer_header_test.dart
index e94aafd..1092e19 100644
--- a/packages/flutter/test/material/user_accounts_drawer_header_test.dart
+++ b/packages/flutter/test/material/user_accounts_drawer_header_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/will_pop_test.dart

diff --git a/packages/flutter/test/material/will_pop_test.dart b/packages/flutter/test/material/will_pop_test.dart
index de08545..545e48d 100644
--- a/packages/flutter/test/material/will_pop_test.dart
+++ b/packages/flutter/test/material/will_pop_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/painting/alignment_test.dart

diff --git a/packages/flutter/test/painting/alignment_test.dart b/packages/flutter/test/painting/alignment_test.dart
index 15691d6..84dc172 100644
--- a/packages/flutter/test/painting/alignment_test.dart
+++ b/packages/flutter/test/painting/alignment_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/painting.dart';

packages/flutter/test/painting/beveled_rectangle_border_test.dart

diff --git a/packages/flutter/test/painting/beveled_rectangle_border_test.dart b/packages/flutter/test/painting/beveled_rectangle_border_test.dart
index 2413c35..c77d465 100644
--- a/packages/flutter/test/painting/beveled_rectangle_border_test.dart
+++ b/packages/flutter/test/painting/beveled_rectangle_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/binding_test.dart

diff --git a/packages/flutter/test/painting/binding_test.dart b/packages/flutter/test/painting/binding_test.dart
index 2d2f3fb..bf9da5b 100644
--- a/packages/flutter/test/painting/binding_test.dart
+++ b/packages/flutter/test/painting/binding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/painting/border_radius_test.dart

diff --git a/packages/flutter/test/painting/border_radius_test.dart b/packages/flutter/test/painting/border_radius_test.dart
index 93f7c1d..375a103 100644
--- a/packages/flutter/test/painting/border_radius_test.dart
+++ b/packages/flutter/test/painting/border_radius_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/border_rtl_test.dart

diff --git a/packages/flutter/test/painting/border_rtl_test.dart b/packages/flutter/test/painting/border_rtl_test.dart
index b4aa9ab..cfa5bad 100644
--- a/packages/flutter/test/painting/border_rtl_test.dart
+++ b/packages/flutter/test/painting/border_rtl_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart' show DiagnosticLevel, FlutterError;
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/border_side_test.dart

diff --git a/packages/flutter/test/painting/border_side_test.dart b/packages/flutter/test/painting/border_side_test.dart
index cd97b15..edb59ab 100644
--- a/packages/flutter/test/painting/border_side_test.dart
+++ b/packages/flutter/test/painting/border_side_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/border_test.dart

diff --git a/packages/flutter/test/painting/border_test.dart b/packages/flutter/test/painting/border_test.dart
index e25a10f..25ffe1a 100644
--- a/packages/flutter/test/painting/border_test.dart
+++ b/packages/flutter/test/painting/border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/box_decoration_test.dart

diff --git a/packages/flutter/test/painting/box_decoration_test.dart b/packages/flutter/test/painting/box_decoration_test.dart
index a9d31fb..6f74976 100644
--- a/packages/flutter/test/painting/box_decoration_test.dart
+++ b/packages/flutter/test/painting/box_decoration_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/test/painting/box_fit_test.dart

diff --git a/packages/flutter/test/painting/box_fit_test.dart b/packages/flutter/test/painting/box_fit_test.dart
index fdc8145..91437c7 100644
--- a/packages/flutter/test/painting/box_fit_test.dart
+++ b/packages/flutter/test/painting/box_fit_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/painting/box_painter_test.dart

diff --git a/packages/flutter/test/painting/box_painter_test.dart b/packages/flutter/test/painting/box_painter_test.dart
index efac723..e9c5141 100644
--- a/packages/flutter/test/painting/box_painter_test.dart
+++ b/packages/flutter/test/painting/box_painter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/test/painting/circle_border_test.dart

diff --git a/packages/flutter/test/painting/circle_border_test.dart b/packages/flutter/test/painting/circle_border_test.dart
index 3cf3bad..99fb87a 100644
--- a/packages/flutter/test/painting/circle_border_test.dart
+++ b/packages/flutter/test/painting/circle_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/colors_test.dart

diff --git a/packages/flutter/test/painting/colors_test.dart b/packages/flutter/test/painting/colors_test.dart
index 1f90b65..c2cbc97 100644
--- a/packages/flutter/test/painting/colors_test.dart
+++ b/packages/flutter/test/painting/colors_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/common_matchers.dart

diff --git a/packages/flutter/test/painting/common_matchers.dart b/packages/flutter/test/painting/common_matchers.dart
index 3a5bf43..81d6762 100644
--- a/packages/flutter/test/painting/common_matchers.dart
+++ b/packages/flutter/test/painting/common_matchers.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/continous_rectangle_border_test.dart

diff --git a/packages/flutter/test/painting/continous_rectangle_border_test.dart b/packages/flutter/test/painting/continous_rectangle_border_test.dart
index 78d0bc4..9631959 100644
--- a/packages/flutter/test/painting/continous_rectangle_border_test.dart
+++ b/packages/flutter/test/painting/continous_rectangle_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/decoration_test.dart

diff --git a/packages/flutter/test/painting/decoration_test.dart b/packages/flutter/test/painting/decoration_test.dart
index 273e874..6eded70 100644
--- a/packages/flutter/test/painting/decoration_test.dart
+++ b/packages/flutter/test/painting/decoration_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome')
 import 'dart:async';
 import 'dart:typed_data';

packages/flutter/test/painting/edge_insets_test.dart

diff --git a/packages/flutter/test/painting/edge_insets_test.dart b/packages/flutter/test/painting/edge_insets_test.dart
index 74d4ba4..e7b13cf 100644
--- a/packages/flutter/test/painting/edge_insets_test.dart
+++ b/packages/flutter/test/painting/edge_insets_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/fake_codec.dart

diff --git a/packages/flutter/test/painting/fake_codec.dart b/packages/flutter/test/painting/fake_codec.dart
index 7ef1479..de7b7ce 100644
--- a/packages/flutter/test/painting/fake_codec.dart
+++ b/packages/flutter/test/painting/fake_codec.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui show Codec, FrameInfo, instantiateImageCodec;

packages/flutter/test/painting/fake_image_provider.dart

diff --git a/packages/flutter/test/painting/fake_image_provider.dart b/packages/flutter/test/painting/fake_image_provider.dart
index 61ac8ff..fe4c63e 100644
--- a/packages/flutter/test/painting/fake_image_provider.dart
+++ b/packages/flutter/test/painting/fake_image_provider.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' as ui show Codec;
 

packages/flutter/test/painting/flutter_logo_test.dart

diff --git a/packages/flutter/test/painting/flutter_logo_test.dart b/packages/flutter/test/painting/flutter_logo_test.dart
index aad7fda..9ac83d6 100644
--- a/packages/flutter/test/painting/flutter_logo_test.dart
+++ b/packages/flutter/test/painting/flutter_logo_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/painting.dart';
 

packages/flutter/test/painting/fractional_offset_test.dart

diff --git a/packages/flutter/test/painting/fractional_offset_test.dart b/packages/flutter/test/painting/fractional_offset_test.dart
index 12ddad5..a7ba3ea 100644
--- a/packages/flutter/test/painting/fractional_offset_test.dart
+++ b/packages/flutter/test/painting/fractional_offset_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/geometry_test.dart

diff --git a/packages/flutter/test/painting/geometry_test.dart b/packages/flutter/test/painting/geometry_test.dart
index 9f20ccc..7f066b4 100644
--- a/packages/flutter/test/painting/geometry_test.dart
+++ b/packages/flutter/test/painting/geometry_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/painting/gradient_test.dart

diff --git a/packages/flutter/test/painting/gradient_test.dart b/packages/flutter/test/painting/gradient_test.dart
index 79c667c..595d9db 100644
--- a/packages/flutter/test/painting/gradient_test.dart
+++ b/packages/flutter/test/painting/gradient_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/widgets.dart';

packages/flutter/test/painting/image_cache_binding_test.dart

diff --git a/packages/flutter/test/painting/image_cache_binding_test.dart b/packages/flutter/test/painting/image_cache_binding_test.dart
index 5f21712..bb0aefa 100644
--- a/packages/flutter/test/painting/image_cache_binding_test.dart
+++ b/packages/flutter/test/painting/image_cache_binding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/painting/image_cache_clearing_test.dart

diff --git a/packages/flutter/test/painting/image_cache_clearing_test.dart b/packages/flutter/test/painting/image_cache_clearing_test.dart
index beb913b..6d0c542 100644
--- a/packages/flutter/test/painting/image_cache_clearing_test.dart
+++ b/packages/flutter/test/painting/image_cache_clearing_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/painting/image_cache_resize_test.dart

diff --git a/packages/flutter/test/painting/image_cache_resize_test.dart b/packages/flutter/test/painting/image_cache_resize_test.dart
index 867ff4c..9c647d3 100644
--- a/packages/flutter/test/painting/image_cache_resize_test.dart
+++ b/packages/flutter/test/painting/image_cache_resize_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/painting/image_cache_test.dart

diff --git a/packages/flutter/test/painting/image_cache_test.dart b/packages/flutter/test/painting/image_cache_test.dart
index 0952c6c..fe8ef5a 100644
--- a/packages/flutter/test/painting/image_cache_test.dart
+++ b/packages/flutter/test/painting/image_cache_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/painting/image_data.dart

diff --git a/packages/flutter/test/painting/image_data.dart b/packages/flutter/test/painting/image_data.dart
index 116b439..fc36144 100644
--- a/packages/flutter/test/painting/image_data.dart
+++ b/packages/flutter/test/painting/image_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 const List<int> kTransparentImage = <int>[
   0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D, 0x49,
   0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x08, 0x06,

packages/flutter/test/painting/image_decoder_test.dart

diff --git a/packages/flutter/test/painting/image_decoder_test.dart b/packages/flutter/test/painting/image_decoder_test.dart
index 9bc3f9f..36ce220 100644
--- a/packages/flutter/test/painting/image_decoder_test.dart
+++ b/packages/flutter/test/painting/image_decoder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 

packages/flutter/test/painting/image_provider_and_image_cache_test.dart

diff --git a/packages/flutter/test/painting/image_provider_and_image_cache_test.dart b/packages/flutter/test/painting/image_provider_and_image_cache_test.dart
index 53724c6..07e87b4 100644
--- a/packages/flutter/test/painting/image_provider_and_image_cache_test.dart
+++ b/packages/flutter/test/painting/image_provider_and_image_cache_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/painting/image_provider_network_image_test.dart

diff --git a/packages/flutter/test/painting/image_provider_network_image_test.dart b/packages/flutter/test/painting/image_provider_network_image_test.dart
index aafe608..d350296 100644
--- a/packages/flutter/test/painting/image_provider_network_image_test.dart
+++ b/packages/flutter/test/painting/image_provider_network_image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io';
 import 'dart:math' as math;

packages/flutter/test/painting/image_provider_resize_image_test.dart

diff --git a/packages/flutter/test/painting/image_provider_resize_image_test.dart b/packages/flutter/test/painting/image_provider_resize_image_test.dart
index 6f8d268..675b32e 100644
--- a/packages/flutter/test/painting/image_provider_resize_image_test.dart
+++ b/packages/flutter/test/painting/image_provider_resize_image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/painting/image_provider_test.dart

diff --git a/packages/flutter/test/painting/image_provider_test.dart b/packages/flutter/test/painting/image_provider_test.dart
index a342d6a..4e2fce5 100644
--- a/packages/flutter/test/painting/image_provider_test.dart
+++ b/packages/flutter/test/painting/image_provider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io';
 

packages/flutter/test/painting/image_resolution_test.dart

diff --git a/packages/flutter/test/painting/image_resolution_test.dart b/packages/flutter/test/painting/image_resolution_test.dart
index 2c86267..50906e4 100644
--- a/packages/flutter/test/painting/image_resolution_test.dart
+++ b/packages/flutter/test/painting/image_resolution_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';

packages/flutter/test/painting/image_stream_test.dart

diff --git a/packages/flutter/test/painting/image_stream_test.dart b/packages/flutter/test/painting/image_stream_test.dart
index 7caf72f..a013b8d 100644
--- a/packages/flutter/test/painting/image_stream_test.dart
+++ b/packages/flutter/test/painting/image_stream_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui';

packages/flutter/test/painting/image_test_utils.dart

diff --git a/packages/flutter/test/painting/image_test_utils.dart b/packages/flutter/test/painting/image_test_utils.dart
index 4fbd7a2..e08a6db 100644
--- a/packages/flutter/test/painting/image_test_utils.dart
+++ b/packages/flutter/test/painting/image_test_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/test/painting/matrix_utils_test.dart

diff --git a/packages/flutter/test/painting/matrix_utils_test.dart b/packages/flutter/test/painting/matrix_utils_test.dart
index a749b73..af69c50 100644
--- a/packages/flutter/test/painting/matrix_utils_test.dart
+++ b/packages/flutter/test/painting/matrix_utils_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/mocks_for_image_cache.dart

diff --git a/packages/flutter/test/painting/mocks_for_image_cache.dart b/packages/flutter/test/painting/mocks_for_image_cache.dart
index 98df538..8e588f7 100644
--- a/packages/flutter/test/painting/mocks_for_image_cache.dart
+++ b/packages/flutter/test/painting/mocks_for_image_cache.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui show Image;

packages/flutter/test/painting/notched_shapes_test.dart

diff --git a/packages/flutter/test/painting/notched_shapes_test.dart b/packages/flutter/test/painting/notched_shapes_test.dart
index 3a350d6..25e668d 100644
--- a/packages/flutter/test/painting/notched_shapes_test.dart
+++ b/packages/flutter/test/painting/notched_shapes_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/paint_image_test.dart

diff --git a/packages/flutter/test/painting/paint_image_test.dart b/packages/flutter/test/painting/paint_image_test.dart
index 4165db1..e0e8446 100644
--- a/packages/flutter/test/painting/paint_image_test.dart
+++ b/packages/flutter/test/painting/paint_image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/test/painting/painting_utils.dart

diff --git a/packages/flutter/test/painting/painting_utils.dart b/packages/flutter/test/painting/painting_utils.dart
index abcb717..28db994 100644
--- a/packages/flutter/test/painting/painting_utils.dart
+++ b/packages/flutter/test/painting/painting_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui' as ui;
 

packages/flutter/test/painting/rounded_rectangle_border_test.dart

diff --git a/packages/flutter/test/painting/rounded_rectangle_border_test.dart b/packages/flutter/test/painting/rounded_rectangle_border_test.dart
index 725cc60..6262d64 100644
--- a/packages/flutter/test/painting/rounded_rectangle_border_test.dart
+++ b/packages/flutter/test/painting/rounded_rectangle_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/shader_warm_up_test.dart

diff --git a/packages/flutter/test/painting/shader_warm_up_test.dart b/packages/flutter/test/painting/shader_warm_up_test.dart
index 11e6313..7c8adb3 100644
--- a/packages/flutter/test/painting/shader_warm_up_test.dart
+++ b/packages/flutter/test/painting/shader_warm_up_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/shape_border_test.dart

diff --git a/packages/flutter/test/painting/shape_border_test.dart b/packages/flutter/test/painting/shape_border_test.dart
index 632db92..eead69f 100644
--- a/packages/flutter/test/painting/shape_border_test.dart
+++ b/packages/flutter/test/painting/shape_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/shape_decoration_test.dart

diff --git a/packages/flutter/test/painting/shape_decoration_test.dart b/packages/flutter/test/painting/shape_decoration_test.dart
index 73edff3..30085f1 100644
--- a/packages/flutter/test/painting/shape_decoration_test.dart
+++ b/packages/flutter/test/painting/shape_decoration_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/test/painting/stadium_border_test.dart

diff --git a/packages/flutter/test/painting/stadium_border_test.dart b/packages/flutter/test/painting/stadium_border_test.dart
index 051a2d0..2960651 100644
--- a/packages/flutter/test/painting/stadium_border_test.dart
+++ b/packages/flutter/test/painting/stadium_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/strut_style_test.dart

diff --git a/packages/flutter/test/painting/strut_style_test.dart b/packages/flutter/test/painting/strut_style_test.dart
index 7f0ac72..bab63dc 100644
--- a/packages/flutter/test/painting/strut_style_test.dart
+++ b/packages/flutter/test/painting/strut_style_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/painting/system_fonts_test.dart

diff --git a/packages/flutter/test/painting/system_fonts_test.dart b/packages/flutter/test/painting/system_fonts_test.dart
index 43c00ef..222e570 100644
--- a/packages/flutter/test/painting/system_fonts_test.dart
+++ b/packages/flutter/test/painting/system_fonts_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/painting/text_painter_rtl_test.dart

diff --git a/packages/flutter/test/painting/text_painter_rtl_test.dart b/packages/flutter/test/painting/text_painter_rtl_test.dart
index 79e9f24..77f999d 100644
--- a/packages/flutter/test/painting/text_painter_rtl_test.dart
+++ b/packages/flutter/test/painting/text_painter_rtl_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/text_painter_test.dart

diff --git a/packages/flutter/test/painting/text_painter_test.dart b/packages/flutter/test/painting/text_painter_test.dart
index d4c73c9..d5de723 100644
--- a/packages/flutter/test/painting/text_painter_test.dart
+++ b/packages/flutter/test/painting/text_painter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/painting.dart';

packages/flutter/test/painting/text_span_test.dart

diff --git a/packages/flutter/test/painting/text_span_test.dart b/packages/flutter/test/painting/text_span_test.dart
index 7d73d11..039dcbc 100644
--- a/packages/flutter/test/painting/text_span_test.dart
+++ b/packages/flutter/test/painting/text_span_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/painting/text_style_test.dart

diff --git a/packages/flutter/test/painting/text_style_test.dart b/packages/flutter/test/painting/text_style_test.dart
index 1884939..d97d418 100644
--- a/packages/flutter/test/painting/text_style_test.dart
+++ b/packages/flutter/test/painting/text_style_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show TextStyle, ParagraphStyle, FontFeature, Shadow;
 
 import 'package:flutter/painting.dart';

packages/flutter/test/physics/clamped_simulation_test.dart

diff --git a/packages/flutter/test/physics/clamped_simulation_test.dart b/packages/flutter/test/physics/clamped_simulation_test.dart
index 592f319..9834521 100644
--- a/packages/flutter/test/physics/clamped_simulation_test.dart
+++ b/packages/flutter/test/physics/clamped_simulation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/physics/friction_simulation_test.dart

diff --git a/packages/flutter/test/physics/friction_simulation_test.dart b/packages/flutter/test/physics/friction_simulation_test.dart
index c3b15f1..19b6a3c 100644
--- a/packages/flutter/test/physics/friction_simulation_test.dart
+++ b/packages/flutter/test/physics/friction_simulation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/physics/gravity_simulation_test.dart

diff --git a/packages/flutter/test/physics/gravity_simulation_test.dart b/packages/flutter/test/physics/gravity_simulation_test.dart
index ccd6874..096a780 100644
--- a/packages/flutter/test/physics/gravity_simulation_test.dart
+++ b/packages/flutter/test/physics/gravity_simulation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/physics/near_equal_test.dart

diff --git a/packages/flutter/test/physics/near_equal_test.dart b/packages/flutter/test/physics/near_equal_test.dart
index 7199333..126b63d 100644
--- a/packages/flutter/test/physics/near_equal_test.dart
+++ b/packages/flutter/test/physics/near_equal_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/physics/newton_test.dart

diff --git a/packages/flutter/test/physics/newton_test.dart b/packages/flutter/test/physics/newton_test.dart
index 49e3012..ebaf476 100644
--- a/packages/flutter/test/physics/newton_test.dart
+++ b/packages/flutter/test/physics/newton_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/physics/tolerance_test.dart

diff --git a/packages/flutter/test/physics/tolerance_test.dart b/packages/flutter/test/physics/tolerance_test.dart
index 543fc3d..d57a0f5 100644
--- a/packages/flutter/test/physics/tolerance_test.dart
+++ b/packages/flutter/test/physics/tolerance_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/physics/utils_test.dart

diff --git a/packages/flutter/test/physics/utils_test.dart b/packages/flutter/test/physics/utils_test.dart
index d538ccc..874e6c7 100644
--- a/packages/flutter/test/physics/utils_test.dart
+++ b/packages/flutter/test/physics/utils_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/physics.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/annotated_region_test.dart

diff --git a/packages/flutter/test/rendering/annotated_region_test.dart b/packages/flutter/test/rendering/annotated_region_test.dart
index fb5d65c..3aad4ce 100644
--- a/packages/flutter/test/rendering/annotated_region_test.dart
+++ b/packages/flutter/test/rendering/annotated_region_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/aspect_ratio_test.dart

diff --git a/packages/flutter/test/rendering/aspect_ratio_test.dart b/packages/flutter/test/rendering/aspect_ratio_test.dart
index 5024b72..15c1ab1 100644
--- a/packages/flutter/test/rendering/aspect_ratio_test.dart
+++ b/packages/flutter/test/rendering/aspect_ratio_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/rendering/baseline_test.dart

diff --git a/packages/flutter/test/rendering/baseline_test.dart b/packages/flutter/test/rendering/baseline_test.dart
index 51a9c5c..5467764 100644
--- a/packages/flutter/test/rendering/baseline_test.dart
+++ b/packages/flutter/test/rendering/baseline_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/box_constraints_test.dart

diff --git a/packages/flutter/test/rendering/box_constraints_test.dart b/packages/flutter/test/rendering/box_constraints_test.dart
index a71107e..db7be12 100644
--- a/packages/flutter/test/rendering/box_constraints_test.dart
+++ b/packages/flutter/test/rendering/box_constraints_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/box_test.dart

diff --git a/packages/flutter/test/rendering/box_test.dart b/packages/flutter/test/rendering/box_test.dart
index 63fd203..1d9dd68 100644
--- a/packages/flutter/test/rendering/box_test.dart
+++ b/packages/flutter/test/rendering/box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/rendering/cached_intrinsics_test.dart

diff --git a/packages/flutter/test/rendering/cached_intrinsics_test.dart b/packages/flutter/test/rendering/cached_intrinsics_test.dart
index 87ecf30..fcba20c 100644
--- a/packages/flutter/test/rendering/cached_intrinsics_test.dart
+++ b/packages/flutter/test/rendering/cached_intrinsics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/constraints_test.dart

diff --git a/packages/flutter/test/rendering/constraints_test.dart b/packages/flutter/test/rendering/constraints_test.dart
index 747333a..398a43d 100644
--- a/packages/flutter/test/rendering/constraints_test.dart
+++ b/packages/flutter/test/rendering/constraints_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/debug_overflow_indicator_test.dart

diff --git a/packages/flutter/test/rendering/debug_overflow_indicator_test.dart b/packages/flutter/test/rendering/debug_overflow_indicator_test.dart
index ef63120..5929fda 100644
--- a/packages/flutter/test/rendering/debug_overflow_indicator_test.dart
+++ b/packages/flutter/test/rendering/debug_overflow_indicator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/rendering/debug_test.dart

diff --git a/packages/flutter/test/rendering/debug_test.dart b/packages/flutter/test/rendering/debug_test.dart
index 1b9b047..b58d327 100644
--- a/packages/flutter/test/rendering/debug_test.dart
+++ b/packages/flutter/test/rendering/debug_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:vector_math/vector_math_64.dart';

packages/flutter/test/rendering/dynamic_intrinsics_test.dart

diff --git a/packages/flutter/test/rendering/dynamic_intrinsics_test.dart b/packages/flutter/test/rendering/dynamic_intrinsics_test.dart
index dfee02e..d797314 100644
--- a/packages/flutter/test/rendering/dynamic_intrinsics_test.dart
+++ b/packages/flutter/test/rendering/dynamic_intrinsics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/editable_gesture_test.dart

diff --git a/packages/flutter/test/rendering/editable_gesture_test.dart b/packages/flutter/test/rendering/editable_gesture_test.dart
index 06cd05f..5288c35 100644
--- a/packages/flutter/test/rendering/editable_gesture_test.dart
+++ b/packages/flutter/test/rendering/editable_gesture_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/editable_test.dart

diff --git a/packages/flutter/test/rendering/editable_test.dart b/packages/flutter/test/rendering/editable_test.dart
index 7f41ef8..0897595 100644
--- a/packages/flutter/test/rendering/editable_test.dart
+++ b/packages/flutter/test/rendering/editable_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/error_test.dart

diff --git a/packages/flutter/test/rendering/error_test.dart b/packages/flutter/test/rendering/error_test.dart
index 4febf7d..a0cff2c 100644
--- a/packages/flutter/test/rendering/error_test.dart
+++ b/packages/flutter/test/rendering/error_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/rendering/flex_overflow_test.dart

diff --git a/packages/flutter/test/rendering/flex_overflow_test.dart b/packages/flutter/test/rendering/flex_overflow_test.dart
index e610086..caf8ae0 100644
--- a/packages/flutter/test/rendering/flex_overflow_test.dart
+++ b/packages/flutter/test/rendering/flex_overflow_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/rendering/flex_test.dart

diff --git a/packages/flutter/test/rendering/flex_test.dart b/packages/flutter/test/rendering/flex_test.dart
index 824aff1..04f5ebb 100644
--- a/packages/flutter/test/rendering/flex_test.dart
+++ b/packages/flutter/test/rendering/flex_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/rendering/image_test.dart

diff --git a/packages/flutter/test/rendering/image_test.dart b/packages/flutter/test/rendering/image_test.dart
index fd1fd26..0e082f1 100644
--- a/packages/flutter/test/rendering/image_test.dart
+++ b/packages/flutter/test/rendering/image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui show Image, ImageByteFormat;

packages/flutter/test/rendering/independent_layout_test.dart

diff --git a/packages/flutter/test/rendering/independent_layout_test.dart b/packages/flutter/test/rendering/independent_layout_test.dart
index 3e263dd..c2bba73 100644
--- a/packages/flutter/test/rendering/independent_layout_test.dart
+++ b/packages/flutter/test/rendering/independent_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/intrinsic_width_test.dart

diff --git a/packages/flutter/test/rendering/intrinsic_width_test.dart b/packages/flutter/test/rendering/intrinsic_width_test.dart
index 2c207c1..3a80320 100644
--- a/packages/flutter/test/rendering/intrinsic_width_test.dart
+++ b/packages/flutter/test/rendering/intrinsic_width_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/layer_annotations_test.dart

diff --git a/packages/flutter/test/rendering/layer_annotations_test.dart b/packages/flutter/test/rendering/layer_annotations_test.dart
index f7b8aa5..b4b052f 100644
--- a/packages/flutter/test/rendering/layer_annotations_test.dart
+++ b/packages/flutter/test/rendering/layer_annotations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/rendering/layers_test.dart

diff --git a/packages/flutter/test/rendering/layers_test.dart b/packages/flutter/test/rendering/layers_test.dart
index 43fc6cd..b7b4e03 100644
--- a/packages/flutter/test/rendering/layers_test.dart
+++ b/packages/flutter/test/rendering/layers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/rendering/limited_box_test.dart

diff --git a/packages/flutter/test/rendering/limited_box_test.dart b/packages/flutter/test/rendering/limited_box_test.dart
index 601d153..76e34a8 100644
--- a/packages/flutter/test/rendering/limited_box_test.dart
+++ b/packages/flutter/test/rendering/limited_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/rendering/localized_fonts_test.dart

diff --git a/packages/flutter/test/rendering/localized_fonts_test.dart b/packages/flutter/test/rendering/localized_fonts_test.dart
index f3eb9f7..38ca773 100644
--- a/packages/flutter/test/rendering/localized_fonts_test.dart
+++ b/packages/flutter/test/rendering/localized_fonts_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/mock_canvas.dart

diff --git a/packages/flutter/test/rendering/mock_canvas.dart b/packages/flutter/test/rendering/mock_canvas.dart
index 869db04..0cfdfb7 100644
--- a/packages/flutter/test/rendering/mock_canvas.dart
+++ b/packages/flutter/test/rendering/mock_canvas.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show Paragraph, Image;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/rendering/mouse_tracking_cursor_test.dart

diff --git a/packages/flutter/test/rendering/mouse_tracking_cursor_test.dart b/packages/flutter/test/rendering/mouse_tracking_cursor_test.dart
index 4bb5c47..c52abd5 100644
--- a/packages/flutter/test/rendering/mouse_tracking_cursor_test.dart
+++ b/packages/flutter/test/rendering/mouse_tracking_cursor_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 import 'dart:ui' show PointerChange;
 

packages/flutter/test/rendering/mouse_tracking_test.dart

diff --git a/packages/flutter/test/rendering/mouse_tracking_test.dart b/packages/flutter/test/rendering/mouse_tracking_test.dart
index 3945fba..2d952fa 100644
--- a/packages/flutter/test/rendering/mouse_tracking_test.dart
+++ b/packages/flutter/test/rendering/mouse_tracking_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 import 'dart:ui' show PointerChange;
 

packages/flutter/test/rendering/mutations_test.dart

diff --git a/packages/flutter/test/rendering/mutations_test.dart b/packages/flutter/test/rendering/mutations_test.dart
index 9919286..2b4ae38 100644
--- a/packages/flutter/test/rendering/mutations_test.dart
+++ b/packages/flutter/test/rendering/mutations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/non_render_object_root_test.dart

diff --git a/packages/flutter/test/rendering/non_render_object_root_test.dart b/packages/flutter/test/rendering/non_render_object_root_test.dart
index f739912..2c1de65 100644
--- a/packages/flutter/test/rendering/non_render_object_root_test.dart
+++ b/packages/flutter/test/rendering/non_render_object_root_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/object_test.dart

diff --git a/packages/flutter/test/rendering/object_test.dart b/packages/flutter/test/rendering/object_test.dart
index 214884d..d545f0c 100644
--- a/packages/flutter/test/rendering/object_test.dart
+++ b/packages/flutter/test/rendering/object_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/offstage_test.dart

diff --git a/packages/flutter/test/rendering/offstage_test.dart b/packages/flutter/test/rendering/offstage_test.dart
index 4afb4a9..bd8eb69 100644
--- a/packages/flutter/test/rendering/offstage_test.dart
+++ b/packages/flutter/test/rendering/offstage_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/overflow_test.dart

diff --git a/packages/flutter/test/rendering/overflow_test.dart b/packages/flutter/test/rendering/overflow_test.dart
index 2bc7b55..0f4819e 100644
--- a/packages/flutter/test/rendering/overflow_test.dart
+++ b/packages/flutter/test/rendering/overflow_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/paint_error_test.dart

diff --git a/packages/flutter/test/rendering/paint_error_test.dart b/packages/flutter/test/rendering/paint_error_test.dart
index 9d5ad93..320d5a1 100644
--- a/packages/flutter/test/rendering/paint_error_test.dart
+++ b/packages/flutter/test/rendering/paint_error_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/rendering/paragraph_intrinsics_test.dart

diff --git a/packages/flutter/test/rendering/paragraph_intrinsics_test.dart b/packages/flutter/test/rendering/paragraph_intrinsics_test.dart
index e960391..8dc726c 100644
--- a/packages/flutter/test/rendering/paragraph_intrinsics_test.dart
+++ b/packages/flutter/test/rendering/paragraph_intrinsics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/paragraph_test.dart

diff --git a/packages/flutter/test/rendering/paragraph_test.dart b/packages/flutter/test/rendering/paragraph_test.dart
index 0f05e78..f610cfd 100644
--- a/packages/flutter/test/rendering/paragraph_test.dart
+++ b/packages/flutter/test/rendering/paragraph_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show TextBox;
 
 import 'package:flutter/gestures.dart';

packages/flutter/test/rendering/platform_view_test.dart

diff --git a/packages/flutter/test/rendering/platform_view_test.dart b/packages/flutter/test/rendering/platform_view_test.dart
index 05ae615..b476a8b 100644
--- a/packages/flutter/test/rendering/platform_view_test.dart
+++ b/packages/flutter/test/rendering/platform_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/positioned_box_test.dart

diff --git a/packages/flutter/test/rendering/positioned_box_test.dart b/packages/flutter/test/rendering/positioned_box_test.dart
index 2182705..4f7bc61 100644
--- a/packages/flutter/test/rendering/positioned_box_test.dart
+++ b/packages/flutter/test/rendering/positioned_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/proxy_box_test.dart

diff --git a/packages/flutter/test/rendering/proxy_box_test.dart b/packages/flutter/test/rendering/proxy_box_test.dart
index 6a49841..a85d133 100644
--- a/packages/flutter/test/rendering/proxy_box_test.dart
+++ b/packages/flutter/test/rendering/proxy_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui' as ui show Gradient, Image, ImageFilter;
 

packages/flutter/test/rendering/proxy_getters_and_setters_test.dart

diff --git a/packages/flutter/test/rendering/proxy_getters_and_setters_test.dart b/packages/flutter/test/rendering/proxy_getters_and_setters_test.dart
index 5b965e1..3464110 100644
--- a/packages/flutter/test/rendering/proxy_getters_and_setters_test.dart
+++ b/packages/flutter/test/rendering/proxy_getters_and_setters_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/proxy_sliver_test.dart

diff --git a/packages/flutter/test/rendering/proxy_sliver_test.dart b/packages/flutter/test/rendering/proxy_sliver_test.dart
index 6285bd2..c310856 100644
--- a/packages/flutter/test/rendering/proxy_sliver_test.dart
+++ b/packages/flutter/test/rendering/proxy_sliver_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/animation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/rendering/reattach_test.dart

diff --git a/packages/flutter/test/rendering/reattach_test.dart b/packages/flutter/test/rendering/reattach_test.dart
index 5159bc5..2f5d3c2 100644
--- a/packages/flutter/test/rendering/reattach_test.dart
+++ b/packages/flutter/test/rendering/reattach_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/recording_canvas.dart

diff --git a/packages/flutter/test/rendering/recording_canvas.dart b/packages/flutter/test/rendering/recording_canvas.dart
index 3b659e7..e4956c4 100644
--- a/packages/flutter/test/rendering/recording_canvas.dart
+++ b/packages/flutter/test/rendering/recording_canvas.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/src/rendering/layer.dart';

packages/flutter/test/rendering/relative_rect_test.dart

diff --git a/packages/flutter/test/rendering/relative_rect_test.dart b/packages/flutter/test/rendering/relative_rect_test.dart
index 307bd5c..cfdaccf 100644
--- a/packages/flutter/test/rendering/relative_rect_test.dart
+++ b/packages/flutter/test/rendering/relative_rect_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/rendering_tester.dart

diff --git a/packages/flutter/test/rendering/rendering_tester.dart b/packages/flutter/test/rendering/rendering_tester.dart
index 6d24df8..4152e30 100644
--- a/packages/flutter/test/rendering/rendering_tester.dart
+++ b/packages/flutter/test/rendering/rendering_tester.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/rendering/repaint_boundary_2_test.dart

diff --git a/packages/flutter/test/rendering/repaint_boundary_2_test.dart b/packages/flutter/test/rendering/repaint_boundary_2_test.dart
index e0d0c60..dc11859 100644
--- a/packages/flutter/test/rendering/repaint_boundary_2_test.dart
+++ b/packages/flutter/test/rendering/repaint_boundary_2_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/rendering/repaint_boundary_test.dart

diff --git a/packages/flutter/test/rendering/repaint_boundary_test.dart b/packages/flutter/test/rendering/repaint_boundary_test.dart
index 0238172..7312dc4 100644
--- a/packages/flutter/test/rendering/repaint_boundary_test.dart
+++ b/packages/flutter/test/rendering/repaint_boundary_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/semantics_and_children_test.dart

diff --git a/packages/flutter/test/rendering/semantics_and_children_test.dart b/packages/flutter/test/rendering/semantics_and_children_test.dart
index 3d6559f..61dce2c 100644
--- a/packages/flutter/test/rendering/semantics_and_children_test.dart
+++ b/packages/flutter/test/rendering/semantics_and_children_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart' show TestVSync;

packages/flutter/test/rendering/simple_semantics_test.dart

diff --git a/packages/flutter/test/rendering/simple_semantics_test.dart b/packages/flutter/test/rendering/simple_semantics_test.dart
index 0966fed..7822b02 100644
--- a/packages/flutter/test/rendering/simple_semantics_test.dart
+++ b/packages/flutter/test/rendering/simple_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/size_test.dart

diff --git a/packages/flutter/test/rendering/size_test.dart b/packages/flutter/test/rendering/size_test.dart
index 1451d6c..0236a71 100644
--- a/packages/flutter/test/rendering/size_test.dart
+++ b/packages/flutter/test/rendering/size_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/sliver_cache_test.dart

diff --git a/packages/flutter/test/rendering/sliver_cache_test.dart b/packages/flutter/test/rendering/sliver_cache_test.dart
index 88dad28..b283ca9 100644
--- a/packages/flutter/test/rendering/sliver_cache_test.dart
+++ b/packages/flutter/test/rendering/sliver_cache_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/sliver_fixed_extent_layout_test.dart

diff --git a/packages/flutter/test/rendering/sliver_fixed_extent_layout_test.dart b/packages/flutter/test/rendering/sliver_fixed_extent_layout_test.dart
index 953f643..1ad34ac 100644
--- a/packages/flutter/test/rendering/sliver_fixed_extent_layout_test.dart
+++ b/packages/flutter/test/rendering/sliver_fixed_extent_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/sliver_persistent_header_test.dart

diff --git a/packages/flutter/test/rendering/sliver_persistent_header_test.dart b/packages/flutter/test/rendering/sliver_persistent_header_test.dart
index 462e159..08264f4 100644
--- a/packages/flutter/test/rendering/sliver_persistent_header_test.dart
+++ b/packages/flutter/test/rendering/sliver_persistent_header_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/slivers_block_test.dart

diff --git a/packages/flutter/test/rendering/slivers_block_test.dart b/packages/flutter/test/rendering/slivers_block_test.dart
index a7a3cc5..985914d 100644
--- a/packages/flutter/test/rendering/slivers_block_test.dart
+++ b/packages/flutter/test/rendering/slivers_block_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/animation.dart';
 import 'package:meta/meta.dart';

packages/flutter/test/rendering/slivers_helpers_test.dart

diff --git a/packages/flutter/test/rendering/slivers_helpers_test.dart b/packages/flutter/test/rendering/slivers_helpers_test.dart
index 5d94252..0b3b9a2 100644
--- a/packages/flutter/test/rendering/slivers_helpers_test.dart
+++ b/packages/flutter/test/rendering/slivers_helpers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/slivers_layout_test.dart

diff --git a/packages/flutter/test/rendering/slivers_layout_test.dart b/packages/flutter/test/rendering/slivers_layout_test.dart
index 3bdb82d..c26cc19 100644
--- a/packages/flutter/test/rendering/slivers_layout_test.dart
+++ b/packages/flutter/test/rendering/slivers_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/slivers_test.dart

diff --git a/packages/flutter/test/rendering/slivers_test.dart b/packages/flutter/test/rendering/slivers_test.dart
index 20123dd..5673bce 100644
--- a/packages/flutter/test/rendering/slivers_test.dart
+++ b/packages/flutter/test/rendering/slivers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/stack_test.dart

diff --git a/packages/flutter/test/rendering/stack_test.dart b/packages/flutter/test/rendering/stack_test.dart
index 1243dc3..9e5a89c 100644
--- a/packages/flutter/test/rendering/stack_test.dart
+++ b/packages/flutter/test/rendering/stack_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/table_border_test.dart

diff --git a/packages/flutter/test/rendering/table_border_test.dart b/packages/flutter/test/rendering/table_border_test.dart
index 4c11638..3cf9842 100644
--- a/packages/flutter/test/rendering/table_border_test.dart
+++ b/packages/flutter/test/rendering/table_border_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/table_test.dart

diff --git a/packages/flutter/test/rendering/table_test.dart b/packages/flutter/test/rendering/table_test.dart
index 0d082e1..bd3641e 100644
--- a/packages/flutter/test/rendering/table_test.dart
+++ b/packages/flutter/test/rendering/table_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/transform_test.dart

diff --git a/packages/flutter/test/rendering/transform_test.dart b/packages/flutter/test/rendering/transform_test.dart
index 24717ca..8852022 100644
--- a/packages/flutter/test/rendering/transform_test.dart
+++ b/packages/flutter/test/rendering/transform_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';

packages/flutter/test/rendering/view_test.dart

diff --git a/packages/flutter/test/rendering/view_test.dart b/packages/flutter/test/rendering/view_test.dart
index 396688c..8599f63 100644
--- a/packages/flutter/test/rendering/view_test.dart
+++ b/packages/flutter/test/rendering/view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/rendering/viewport_caching_test.dart

diff --git a/packages/flutter/test/rendering/viewport_caching_test.dart b/packages/flutter/test/rendering/viewport_caching_test.dart
index 3b0b3c9..6481640 100644
--- a/packages/flutter/test/rendering/viewport_caching_test.dart
+++ b/packages/flutter/test/rendering/viewport_caching_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This file is separate from viewport_test.dart because we can't use both
 // testWidgets and rendering_tester in the same file - testWidgets will
 // initialize a binding, which rendering_tester will attempt to re-initialize

packages/flutter/test/rendering/viewport_test.dart

diff --git a/packages/flutter/test/rendering/viewport_test.dart b/packages/flutter/test/rendering/viewport_test.dart
index 8927c18..c183137 100644
--- a/packages/flutter/test/rendering/viewport_test.dart
+++ b/packages/flutter/test/rendering/viewport_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This file is separate from viewport_caching_test.dart because we can't use
 // both testWidgets and rendering_tester in the same file - testWidgets will
 // initialize a binding, which rendering_tester will attempt to re-initialize

packages/flutter/test/rendering/wrap_test.dart

diff --git a/packages/flutter/test/rendering/wrap_test.dart b/packages/flutter/test/rendering/wrap_test.dart
index e6dac87..39d7a5d 100644
--- a/packages/flutter/test/rendering/wrap_test.dart
+++ b/packages/flutter/test/rendering/wrap_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/scheduler/animation_test.dart

diff --git a/packages/flutter/test/scheduler/animation_test.dart b/packages/flutter/test/scheduler/animation_test.dart
index 441f888..59a2d29 100644
--- a/packages/flutter/test/scheduler/animation_test.dart
+++ b/packages/flutter/test/scheduler/animation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/scheduler/benchmarks_test.dart

diff --git a/packages/flutter/test/scheduler/benchmarks_test.dart b/packages/flutter/test/scheduler/benchmarks_test.dart
index b13d479..27e3713 100644
--- a/packages/flutter/test/scheduler/benchmarks_test.dart
+++ b/packages/flutter/test/scheduler/benchmarks_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/scheduler/debug_test.dart

diff --git a/packages/flutter/test/scheduler/debug_test.dart b/packages/flutter/test/scheduler/debug_test.dart
index 6796124..2ef0c98 100644
--- a/packages/flutter/test/scheduler/debug_test.dart
+++ b/packages/flutter/test/scheduler/debug_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/scheduler.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/scheduler/priority_test.dart

diff --git a/packages/flutter/test/scheduler/priority_test.dart b/packages/flutter/test/scheduler/priority_test.dart
index 6e2e62d..c6c9f6e 100644
--- a/packages/flutter/test/scheduler/priority_test.dart
+++ b/packages/flutter/test/scheduler/priority_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/scheduler.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/scheduler/scheduler_test.dart

diff --git a/packages/flutter/test/scheduler/scheduler_test.dart b/packages/flutter/test/scheduler/scheduler_test.dart
index 11293e4..17bb132 100644
--- a/packages/flutter/test/scheduler/scheduler_test.dart
+++ b/packages/flutter/test/scheduler/scheduler_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui' show window;
 

packages/flutter/test/scheduler/scheduler_tester.dart

diff --git a/packages/flutter/test/scheduler/scheduler_tester.dart b/packages/flutter/test/scheduler/scheduler_tester.dart
index 54b27ea..2f9f68b 100644
--- a/packages/flutter/test/scheduler/scheduler_tester.dart
+++ b/packages/flutter/test/scheduler/scheduler_tester.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/scheduler.dart';
 
 @Deprecated('scheduler_tester is not compatible with dart:async') // ignore: flutter_deprecation_syntax (see analyze.dart)

packages/flutter/test/scheduler/ticker_test.dart

diff --git a/packages/flutter/test/scheduler/ticker_test.dart b/packages/flutter/test/scheduler/ticker_test.dart
index cf3c9ee..e6ac6de 100644
--- a/packages/flutter/test/scheduler/ticker_test.dart
+++ b/packages/flutter/test/scheduler/ticker_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/semantics/custom_semantics_action_test.dart

diff --git a/packages/flutter/test/semantics/custom_semantics_action_test.dart b/packages/flutter/test/semantics/custom_semantics_action_test.dart
index e81cbdb..a581400 100644
--- a/packages/flutter/test/semantics/custom_semantics_action_test.dart
+++ b/packages/flutter/test/semantics/custom_semantics_action_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/semantics.dart';
 
 import '../flutter_test_alternative.dart';

packages/flutter/test/semantics/semantics_elevation_test.dart

diff --git a/packages/flutter/test/semantics/semantics_elevation_test.dart b/packages/flutter/test/semantics/semantics_elevation_test.dart
index 16ce545..bd9a562 100644
--- a/packages/flutter/test/semantics/semantics_elevation_test.dart
+++ b/packages/flutter/test/semantics/semantics_elevation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/semantics/semantics_service_test.dart

diff --git a/packages/flutter/test/semantics/semantics_service_test.dart b/packages/flutter/test/semantics/semantics_service_test.dart
index 9e51d54..fe90467 100644
--- a/packages/flutter/test/semantics/semantics_service_test.dart
+++ b/packages/flutter/test/semantics/semantics_service_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show TextDirection;
 
 import 'package:flutter/semantics.dart';

packages/flutter/test/semantics/semantics_test.dart

diff --git a/packages/flutter/test/semantics/semantics_test.dart b/packages/flutter/test/semantics/semantics_test.dart
index 554e02e..f7a9e7d 100644
--- a/packages/flutter/test/semantics/semantics_test.dart
+++ b/packages/flutter/test/semantics/semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/semantics.dart';
 import 'package:vector_math/vector_math_64.dart';

packages/flutter/test/semantics/traversal_order_test.dart

diff --git a/packages/flutter/test/semantics/traversal_order_test.dart b/packages/flutter/test/semantics/traversal_order_test.dart
index 2aa0423..89ad91e 100644
--- a/packages/flutter/test/semantics/traversal_order_test.dart
+++ b/packages/flutter/test/semantics/traversal_order_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/services/asset_bundle_test.dart

diff --git a/packages/flutter/test/services/asset_bundle_test.dart b/packages/flutter/test/services/asset_bundle_test.dart
index 0cc3ddd..a5c3bef 100644
--- a/packages/flutter/test/services/asset_bundle_test.dart
+++ b/packages/flutter/test/services/asset_bundle_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';

packages/flutter/test/services/autofill_test.dart

diff --git a/packages/flutter/test/services/autofill_test.dart b/packages/flutter/test/services/autofill_test.dart
index c7f85bc..d1a2922 100644
--- a/packages/flutter/test/services/autofill_test.dart
+++ b/packages/flutter/test/services/autofill_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert' show utf8;
 
 import 'package:flutter/services.dart';

packages/flutter/test/services/binding_test.dart

diff --git a/packages/flutter/test/services/binding_test.dart b/packages/flutter/test/services/binding_test.dart
index 8b204e6..af6cfb3 100644
--- a/packages/flutter/test/services/binding_test.dart
+++ b/packages/flutter/test/services/binding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/services/channel_buffers_test.dart

diff --git a/packages/flutter/test/services/channel_buffers_test.dart b/packages/flutter/test/services/channel_buffers_test.dart
index b0e00b2..f671414 100644
--- a/packages/flutter/test/services/channel_buffers_test.dart
+++ b/packages/flutter/test/services/channel_buffers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // TODO(yjbanov): enable Web when https://github.com/flutter/engine/pull/12747 rolls into the framework.
 @TestOn('!chrome')
 

packages/flutter/test/services/default_binary_messenger_test.dart

diff --git a/packages/flutter/test/services/default_binary_messenger_test.dart b/packages/flutter/test/services/default_binary_messenger_test.dart
index 74a16e0..111a50f 100644
--- a/packages/flutter/test/services/default_binary_messenger_test.dart
+++ b/packages/flutter/test/services/default_binary_messenger_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/test/services/fake_platform_views.dart

diff --git a/packages/flutter/test/services/fake_platform_views.dart b/packages/flutter/test/services/fake_platform_views.dart
index f70bca4..8493ae3 100644
--- a/packages/flutter/test/services/fake_platform_views.dart
+++ b/packages/flutter/test/services/fake_platform_views.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/services/font_loader_test.dart

diff --git a/packages/flutter/test/services/font_loader_test.dart b/packages/flutter/test/services/font_loader_test.dart
index 029d7e7..89dd637 100644
--- a/packages/flutter/test/services/font_loader_test.dart
+++ b/packages/flutter/test/services/font_loader_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/services/haptic_feedback_test.dart

diff --git a/packages/flutter/test/services/haptic_feedback_test.dart b/packages/flutter/test/services/haptic_feedback_test.dart
index 6234a97..1da74c2 100644
--- a/packages/flutter/test/services/haptic_feedback_test.dart
+++ b/packages/flutter/test/services/haptic_feedback_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/services/keyboard_key_test.dart

diff --git a/packages/flutter/test/services/keyboard_key_test.dart b/packages/flutter/test/services/keyboard_key_test.dart
index 40abb9c..f4d0cee 100644
--- a/packages/flutter/test/services/keyboard_key_test.dart
+++ b/packages/flutter/test/services/keyboard_key_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/services/lifecycle_test.dart

diff --git a/packages/flutter/test/services/lifecycle_test.dart b/packages/flutter/test/services/lifecycle_test.dart
index 8d9e7a5..cb31e73 100644
--- a/packages/flutter/test/services/lifecycle_test.dart
+++ b/packages/flutter/test/services/lifecycle_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/services.dart';
 

packages/flutter/test/services/message_codecs_test.dart

diff --git a/packages/flutter/test/services/message_codecs_test.dart b/packages/flutter/test/services/message_codecs_test.dart
index 4f11f43..83bb4ef 100644
--- a/packages/flutter/test/services/message_codecs_test.dart
+++ b/packages/flutter/test/services/message_codecs_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This files contains message codec tests that are supported both on the Web
 // and in the VM. For VM-only tests see message_codecs_vm_test.dart.
 

packages/flutter/test/services/message_codecs_testing.dart

diff --git a/packages/flutter/test/services/message_codecs_testing.dart b/packages/flutter/test/services/message_codecs_testing.dart
index 2e2e6d9..bad1436 100644
--- a/packages/flutter/test/services/message_codecs_testing.dart
+++ b/packages/flutter/test/services/message_codecs_testing.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/services.dart';

packages/flutter/test/services/message_codecs_vm_test.dart

diff --git a/packages/flutter/test/services/message_codecs_vm_test.dart b/packages/flutter/test/services/message_codecs_vm_test.dart
index a21fde9..33bccf5 100644
--- a/packages/flutter/test/services/message_codecs_vm_test.dart
+++ b/packages/flutter/test/services/message_codecs_vm_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This file contains tests that are only supported by the Dart VM. For
 // example, on the Web there's no way to express large integers.
 @TestOn('!chrome')

packages/flutter/test/services/platform_channel_test.dart

diff --git a/packages/flutter/test/services/platform_channel_test.dart b/packages/flutter/test/services/platform_channel_test.dart
index e3e01c6..a78bf36 100644
--- a/packages/flutter/test/services/platform_channel_test.dart
+++ b/packages/flutter/test/services/platform_channel_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/services/platform_messages_test.dart

diff --git a/packages/flutter/test/services/platform_messages_test.dart b/packages/flutter/test/services/platform_messages_test.dart
index 18e1bb3..2000d59 100644
--- a/packages/flutter/test/services/platform_messages_test.dart
+++ b/packages/flutter/test/services/platform_messages_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // missing web infrastructure for plugins.
 
 import 'dart:typed_data';

packages/flutter/test/services/platform_views_test.dart

diff --git a/packages/flutter/test/services/platform_views_test.dart b/packages/flutter/test/services/platform_views_test.dart
index 87af3b9..3efbd86 100644
--- a/packages/flutter/test/services/platform_views_test.dart
+++ b/packages/flutter/test/services/platform_views_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/painting.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart' show TestWidgetsFlutterBinding;

packages/flutter/test/services/raw_keyboard_test.dart

diff --git a/packages/flutter/test/services/raw_keyboard_test.dart b/packages/flutter/test/services/raw_keyboard_test.dart
index 2790e85..8e0595e 100644
--- a/packages/flutter/test/services/raw_keyboard_test.dart
+++ b/packages/flutter/test/services/raw_keyboard_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/services/system_chrome_test.dart

diff --git a/packages/flutter/test/services/system_chrome_test.dart b/packages/flutter/test/services/system_chrome_test.dart
index 4c81111..d9f115d 100644
--- a/packages/flutter/test/services/system_chrome_test.dart
+++ b/packages/flutter/test/services/system_chrome_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/services.dart';

packages/flutter/test/services/system_navigator_test.dart

diff --git a/packages/flutter/test/services/system_navigator_test.dart b/packages/flutter/test/services/system_navigator_test.dart
index 40b482d..2219605 100644
--- a/packages/flutter/test/services/system_navigator_test.dart
+++ b/packages/flutter/test/services/system_navigator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/services/system_sound_test.dart

diff --git a/packages/flutter/test/services/system_sound_test.dart b/packages/flutter/test/services/system_sound_test.dart
index f466b1d..c16e593 100644
--- a/packages/flutter/test/services/system_sound_test.dart
+++ b/packages/flutter/test/services/system_sound_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/services/text_formatter_test.dart

diff --git a/packages/flutter/test/services/text_formatter_test.dart b/packages/flutter/test/services/text_formatter_test.dart
index 70c0795..8e0fe8f 100644
--- a/packages/flutter/test/services/text_formatter_test.dart
+++ b/packages/flutter/test/services/text_formatter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/services/text_input_test.dart

diff --git a/packages/flutter/test/services/text_input_test.dart b/packages/flutter/test/services/text_input_test.dart
index 0ff58c1..ce6f699 100644
--- a/packages/flutter/test/services/text_input_test.dart
+++ b/packages/flutter/test/services/text_input_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert' show utf8;
 
 import 'package:flutter/services.dart';

packages/flutter/test/widgets/absorb_pointer_test.dart

diff --git a/packages/flutter/test/widgets/absorb_pointer_test.dart b/packages/flutter/test/widgets/absorb_pointer_test.dart
index 84e9f22..5cfd716 100644
--- a/packages/flutter/test/widgets/absorb_pointer_test.dart
+++ b/packages/flutter/test/widgets/absorb_pointer_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/actions_test.dart

diff --git a/packages/flutter/test/widgets/actions_test.dart b/packages/flutter/test/widgets/actions_test.dart
index 4a51de1..12251c4 100644
--- a/packages/flutter/test/widgets/actions_test.dart
+++ b/packages/flutter/test/widgets/actions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/align_test.dart

diff --git a/packages/flutter/test/widgets/align_test.dart b/packages/flutter/test/widgets/align_test.dart
index 61ffbe3..b6d4e5c 100644
--- a/packages/flutter/test/widgets/align_test.dart
+++ b/packages/flutter/test/widgets/align_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_align_test.dart

diff --git a/packages/flutter/test/widgets/animated_align_test.dart b/packages/flutter/test/widgets/animated_align_test.dart
index 7b9a021..9f99d80 100644
--- a/packages/flutter/test/widgets/animated_align_test.dart
+++ b/packages/flutter/test/widgets/animated_align_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_container_test.dart

diff --git a/packages/flutter/test/widgets/animated_container_test.dart b/packages/flutter/test/widgets/animated_container_test.dart
index caf19c6..d2df68f 100644
--- a/packages/flutter/test/widgets/animated_container_test.dart
+++ b/packages/flutter/test/widgets/animated_container_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_cross_fade_test.dart

diff --git a/packages/flutter/test/widgets/animated_cross_fade_test.dart b/packages/flutter/test/widgets/animated_cross_fade_test.dart
index 5c16496..a1a379b 100644
--- a/packages/flutter/test/widgets/animated_cross_fade_test.dart
+++ b/packages/flutter/test/widgets/animated_cross_fade_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/scheduler.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/animated_list_test.dart

diff --git a/packages/flutter/test/widgets/animated_list_test.dart b/packages/flutter/test/widgets/animated_list_test.dart
index 30e68f8..0cab220 100644
--- a/packages/flutter/test/widgets/animated_list_test.dart
+++ b/packages/flutter/test/widgets/animated_list_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/src/foundation/diagnostics.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_padding_test.dart

diff --git a/packages/flutter/test/widgets/animated_padding_test.dart b/packages/flutter/test/widgets/animated_padding_test.dart
index 90ba6f2..88722e1 100644
--- a/packages/flutter/test/widgets/animated_padding_test.dart
+++ b/packages/flutter/test/widgets/animated_padding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_positioned_test.dart

diff --git a/packages/flutter/test/widgets/animated_positioned_test.dart b/packages/flutter/test/widgets/animated_positioned_test.dart
index 3e543f2..ae9452a 100644
--- a/packages/flutter/test/widgets/animated_positioned_test.dart
+++ b/packages/flutter/test/widgets/animated_positioned_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_size_test.dart

diff --git a/packages/flutter/test/widgets/animated_size_test.dart b/packages/flutter/test/widgets/animated_size_test.dart
index b3f5af5..dd61ddc 100644
--- a/packages/flutter/test/widgets/animated_size_test.dart
+++ b/packages/flutter/test/widgets/animated_size_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/animated_switcher_test.dart

diff --git a/packages/flutter/test/widgets/animated_switcher_test.dart b/packages/flutter/test/widgets/animated_switcher_test.dart
index ea67750..da87bc5 100644
--- a/packages/flutter/test/widgets/animated_switcher_test.dart
+++ b/packages/flutter/test/widgets/animated_switcher_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/annotated_region_test.dart

diff --git a/packages/flutter/test/widgets/annotated_region_test.dart b/packages/flutter/test/widgets/annotated_region_test.dart
index 711efc0..a5ab56f 100644
--- a/packages/flutter/test/widgets/annotated_region_test.dart
+++ b/packages/flutter/test/widgets/annotated_region_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show window;
 
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/app_navigator_key_test.dart

diff --git a/packages/flutter/test/widgets/app_navigator_key_test.dart b/packages/flutter/test/widgets/app_navigator_key_test.dart
index cb4a10f..8ab9931 100644
--- a/packages/flutter/test/widgets/app_navigator_key_test.dart
+++ b/packages/flutter/test/widgets/app_navigator_key_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/app_overrides_test.dart

diff --git a/packages/flutter/test/widgets/app_overrides_test.dart b/packages/flutter/test/widgets/app_overrides_test.dart
index 58d8f7f..6d2564c 100644
--- a/packages/flutter/test/widgets/app_overrides_test.dart
+++ b/packages/flutter/test/widgets/app_overrides_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/app_test.dart

diff --git a/packages/flutter/test/widgets/app_test.dart b/packages/flutter/test/widgets/app_test.dart
index 43d367f..15cdd56 100644
--- a/packages/flutter/test/widgets/app_test.dart
+++ b/packages/flutter/test/widgets/app_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/widgets/app_title_test.dart

diff --git a/packages/flutter/test/widgets/app_title_test.dart b/packages/flutter/test/widgets/app_title_test.dart
index 8548a6c..1662f22 100644
--- a/packages/flutter/test/widgets/app_title_test.dart
+++ b/packages/flutter/test/widgets/app_title_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/aspect_ratio_test.dart

diff --git a/packages/flutter/test/widgets/aspect_ratio_test.dart b/packages/flutter/test/widgets/aspect_ratio_test.dart
index aad114d..8917cba 100644
--- a/packages/flutter/test/widgets/aspect_ratio_test.dart
+++ b/packages/flutter/test/widgets/aspect_ratio_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/async_lifecycle_test.dart

diff --git a/packages/flutter/test/widgets/async_lifecycle_test.dart b/packages/flutter/test/widgets/async_lifecycle_test.dart
index ffdab14..19637d0 100644
--- a/packages/flutter/test/widgets/async_lifecycle_test.dart
+++ b/packages/flutter/test/widgets/async_lifecycle_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/async_test.dart

diff --git a/packages/flutter/test/widgets/async_test.dart b/packages/flutter/test/widgets/async_test.dart
index 41a8997..36e60fb 100644
--- a/packages/flutter/test/widgets/async_test.dart
+++ b/packages/flutter/test/widgets/async_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/autofill_group_test.dart

diff --git a/packages/flutter/test/widgets/autofill_group_test.dart b/packages/flutter/test/widgets/autofill_group_test.dart
index 282edc5..b4d8e86 100644
--- a/packages/flutter/test/widgets/autofill_group_test.dart
+++ b/packages/flutter/test/widgets/autofill_group_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/automatic_keep_alive_test.dart

diff --git a/packages/flutter/test/widgets/automatic_keep_alive_test.dart b/packages/flutter/test/widgets/automatic_keep_alive_test.dart
index 7609908..e0ac362 100644
--- a/packages/flutter/test/widgets/automatic_keep_alive_test.dart
+++ b/packages/flutter/test/widgets/automatic_keep_alive_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/backdrop_filter_test.dart

diff --git a/packages/flutter/test/widgets/backdrop_filter_test.dart b/packages/flutter/test/widgets/backdrop_filter_test.dart
index 6d25448..3703ada 100644
--- a/packages/flutter/test/widgets/backdrop_filter_test.dart
+++ b/packages/flutter/test/widgets/backdrop_filter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/banner_test.dart

diff --git a/packages/flutter/test/widgets/banner_test.dart b/packages/flutter/test/widgets/banner_test.dart
index 06745df..9c2bb4c 100644
--- a/packages/flutter/test/widgets/banner_test.dart
+++ b/packages/flutter/test/widgets/banner_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/baseline_test.dart

diff --git a/packages/flutter/test/widgets/baseline_test.dart b/packages/flutter/test/widgets/baseline_test.dart
index 669aaae..5460bf4 100644
--- a/packages/flutter/test/widgets/baseline_test.dart
+++ b/packages/flutter/test/widgets/baseline_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/basic_test.dart

diff --git a/packages/flutter/test/widgets/basic_test.dart b/packages/flutter/test/widgets/basic_test.dart
index f1c502c..907d497 100644
--- a/packages/flutter/test/widgets/basic_test.dart
+++ b/packages/flutter/test/widgets/basic_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/binding_attach_root_widget_test.dart

diff --git a/packages/flutter/test/widgets/binding_attach_root_widget_test.dart b/packages/flutter/test/widgets/binding_attach_root_widget_test.dart
index c0faa77..06b0344 100644
--- a/packages/flutter/test/widgets/binding_attach_root_widget_test.dart
+++ b/packages/flutter/test/widgets/binding_attach_root_widget_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/scheduler.dart';

packages/flutter/test/widgets/binding_cannot_schedule_frame_test.dart

diff --git a/packages/flutter/test/widgets/binding_cannot_schedule_frame_test.dart b/packages/flutter/test/widgets/binding_cannot_schedule_frame_test.dart
index 1c26f3c..c2cac08 100644
--- a/packages/flutter/test/widgets/binding_cannot_schedule_frame_test.dart
+++ b/packages/flutter/test/widgets/binding_cannot_schedule_frame_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 
 import 'package:flutter/scheduler.dart';

packages/flutter/test/widgets/binding_deferred_first_frame_test.dart

diff --git a/packages/flutter/test/widgets/binding_deferred_first_frame_test.dart b/packages/flutter/test/widgets/binding_deferred_first_frame_test.dart
index 2bb072e..8f5c1fa 100644
--- a/packages/flutter/test/widgets/binding_deferred_first_frame_test.dart
+++ b/packages/flutter/test/widgets/binding_deferred_first_frame_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/binding_first_frame_rasterized_test.dart

diff --git a/packages/flutter/test/widgets/binding_first_frame_rasterized_test.dart b/packages/flutter/test/widgets/binding_first_frame_rasterized_test.dart
index 80113cc..60c77e4 100644
--- a/packages/flutter/test/widgets/binding_first_frame_rasterized_test.dart
+++ b/packages/flutter/test/widgets/binding_first_frame_rasterized_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/binding_frame_scheduling_test.dart

diff --git a/packages/flutter/test/widgets/binding_frame_scheduling_test.dart b/packages/flutter/test/widgets/binding_frame_scheduling_test.dart
index 7d44430..47d7e58 100644
--- a/packages/flutter/test/widgets/binding_frame_scheduling_test.dart
+++ b/packages/flutter/test/widgets/binding_frame_scheduling_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui' show window;
 

packages/flutter/test/widgets/binding_test.dart

diff --git a/packages/flutter/test/widgets/binding_test.dart b/packages/flutter/test/widgets/binding_test.dart
index 0a9c9f3..837e4ef 100644
--- a/packages/flutter/test/widgets/binding_test.dart
+++ b/packages/flutter/test/widgets/binding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 

packages/flutter/test/widgets/box_decoration_test.dart

diff --git a/packages/flutter/test/widgets/box_decoration_test.dart b/packages/flutter/test/widgets/box_decoration_test.dart
index 0c410b4..3cfacf2 100644
--- a/packages/flutter/test/widgets/box_decoration_test.dart
+++ b/packages/flutter/test/widgets/box_decoration_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:typed_data';

packages/flutter/test/widgets/box_sliver_mismatch_test.dart

diff --git a/packages/flutter/test/widgets/box_sliver_mismatch_test.dart b/packages/flutter/test/widgets/box_sliver_mismatch_test.dart
index 426d9ba..d9391dd 100644
--- a/packages/flutter/test/widgets/box_sliver_mismatch_test.dart
+++ b/packages/flutter/test/widgets/box_sliver_mismatch_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/build_fail_test.dart

diff --git a/packages/flutter/test/widgets/build_fail_test.dart b/packages/flutter/test/widgets/build_fail_test.dart
index 307e7f7..004cd90 100644
--- a/packages/flutter/test/widgets/build_fail_test.dart
+++ b/packages/flutter/test/widgets/build_fail_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/build_scope_test.dart

diff --git a/packages/flutter/test/widgets/build_scope_test.dart b/packages/flutter/test/widgets/build_scope_test.dart
index f17d292..abd282b 100644
--- a/packages/flutter/test/widgets/build_scope_test.dart
+++ b/packages/flutter/test/widgets/build_scope_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/center_test.dart

diff --git a/packages/flutter/test/widgets/center_test.dart b/packages/flutter/test/widgets/center_test.dart
index 6be3031..2f52e7f 100644
--- a/packages/flutter/test/widgets/center_test.dart
+++ b/packages/flutter/test/widgets/center_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/clamp_overscrolls_test.dart

diff --git a/packages/flutter/test/widgets/clamp_overscrolls_test.dart b/packages/flutter/test/widgets/clamp_overscrolls_test.dart
index 3df3129..9a7eca9 100644
--- a/packages/flutter/test/widgets/clamp_overscrolls_test.dart
+++ b/packages/flutter/test/widgets/clamp_overscrolls_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/clip_test.dart

diff --git a/packages/flutter/test/widgets/clip_test.dart b/packages/flutter/test/widgets/clip_test.dart
index f127a16..e5aa5be 100644
--- a/packages/flutter/test/widgets/clip_test.dart
+++ b/packages/flutter/test/widgets/clip_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/color_filter_test.dart

diff --git a/packages/flutter/test/widgets/color_filter_test.dart b/packages/flutter/test/widgets/color_filter_test.dart
index 3208225..00e1378 100644
--- a/packages/flutter/test/widgets/color_filter_test.dart
+++ b/packages/flutter/test/widgets/color_filter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/column_test.dart

diff --git a/packages/flutter/test/widgets/column_test.dart b/packages/flutter/test/widgets/column_test.dart
index ef95798..c7f14e2 100644
--- a/packages/flutter/test/widgets/column_test.dart
+++ b/packages/flutter/test/widgets/column_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/composited_transform_test.dart

diff --git a/packages/flutter/test/widgets/composited_transform_test.dart b/packages/flutter/test/widgets/composited_transform_test.dart
index a6029a0..5e40512 100644
--- a/packages/flutter/test/widgets/composited_transform_test.dart
+++ b/packages/flutter/test/widgets/composited_transform_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/constrained_box_test.dart

diff --git a/packages/flutter/test/widgets/constrained_box_test.dart b/packages/flutter/test/widgets/constrained_box_test.dart
index f70fd86..6651b7d 100644
--- a/packages/flutter/test/widgets/constrained_box_test.dart
+++ b/packages/flutter/test/widgets/constrained_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/container_test.dart

diff --git a/packages/flutter/test/widgets/container_test.dart b/packages/flutter/test/widgets/container_test.dart
index a6dac22..e33ca22 100644
--- a/packages/flutter/test/widgets/container_test.dart
+++ b/packages/flutter/test/widgets/container_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/coordinates_test.dart

diff --git a/packages/flutter/test/widgets/coordinates_test.dart b/packages/flutter/test/widgets/coordinates_test.dart
index 462b00d..0784a9b 100644
--- a/packages/flutter/test/widgets/coordinates_test.dart
+++ b/packages/flutter/test/widgets/coordinates_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/custom_multi_child_layout_test.dart

diff --git a/packages/flutter/test/widgets/custom_multi_child_layout_test.dart b/packages/flutter/test/widgets/custom_multi_child_layout_test.dart
index ddd5c33..476daf2 100644
--- a/packages/flutter/test/widgets/custom_multi_child_layout_test.dart
+++ b/packages/flutter/test/widgets/custom_multi_child_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/custom_paint_test.dart

diff --git a/packages/flutter/test/widgets/custom_paint_test.dart b/packages/flutter/test/widgets/custom_paint_test.dart
index 3162f00..9060f19 100644
--- a/packages/flutter/test/widgets/custom_paint_test.dart
+++ b/packages/flutter/test/widgets/custom_paint_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/custom_painter_test.dart

diff --git a/packages/flutter/test/widgets/custom_painter_test.dart b/packages/flutter/test/widgets/custom_painter_test.dart
index abdd4ad..ba0a928 100644
--- a/packages/flutter/test/widgets/custom_painter_test.dart
+++ b/packages/flutter/test/widgets/custom_painter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui';
 

packages/flutter/test/widgets/custom_scroll_view_test.dart

diff --git a/packages/flutter/test/widgets/custom_scroll_view_test.dart b/packages/flutter/test/widgets/custom_scroll_view_test.dart
index 8951653..db78b22 100644
--- a/packages/flutter/test/widgets/custom_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/custom_scroll_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/custom_single_child_layout_test.dart

diff --git a/packages/flutter/test/widgets/custom_single_child_layout_test.dart b/packages/flutter/test/widgets/custom_single_child_layout_test.dart
index cdc6727..020c02d 100644
--- a/packages/flutter/test/widgets/custom_single_child_layout_test.dart
+++ b/packages/flutter/test/widgets/custom_single_child_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/debug_test.dart

diff --git a/packages/flutter/test/widgets/debug_test.dart b/packages/flutter/test/widgets/debug_test.dart
index 7675d4d..d46b0b1 100644
--- a/packages/flutter/test/widgets/debug_test.dart
+++ b/packages/flutter/test/widgets/debug_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/default_text_style_test.dart

diff --git a/packages/flutter/test/widgets/default_text_style_test.dart b/packages/flutter/test/widgets/default_text_style_test.dart
index 9f1536a..804a36a 100644
--- a/packages/flutter/test/widgets/default_text_style_test.dart
+++ b/packages/flutter/test/widgets/default_text_style_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show TextHeightBehavior;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/directionality_test.dart

diff --git a/packages/flutter/test/widgets/directionality_test.dart b/packages/flutter/test/widgets/directionality_test.dart
index 8c77ca1..3f53dc1 100644
--- a/packages/flutter/test/widgets/directionality_test.dart
+++ b/packages/flutter/test/widgets/directionality_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/dismissible_test.dart

diff --git a/packages/flutter/test/widgets/dismissible_test.dart b/packages/flutter/test/widgets/dismissible_test.dart
index 098ccd5..44e102f 100644
--- a/packages/flutter/test/widgets/dismissible_test.dart
+++ b/packages/flutter/test/widgets/dismissible_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/disposable_build_context_test.dart

diff --git a/packages/flutter/test/widgets/disposable_build_context_test.dart b/packages/flutter/test/widgets/disposable_build_context_test.dart
index 9953ceda..5df971f 100644
--- a/packages/flutter/test/widgets/disposable_build_context_test.dart
+++ b/packages/flutter/test/widgets/disposable_build_context_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/dispose_ancestor_lookup_test.dart

diff --git a/packages/flutter/test/widgets/dispose_ancestor_lookup_test.dart b/packages/flutter/test/widgets/dispose_ancestor_lookup_test.dart
index ca4c79d..5c829ab 100644
--- a/packages/flutter/test/widgets/dispose_ancestor_lookup_test.dart
+++ b/packages/flutter/test/widgets/dispose_ancestor_lookup_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart

diff --git a/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart b/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart
index 14ad68c..641e9a9 100644
--- a/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart
+++ b/packages/flutter/test/widgets/draggable_scrollable_sheet_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/draggable_test.dart

diff --git a/packages/flutter/test/widgets/draggable_test.dart b/packages/flutter/test/widgets/draggable_test.dart
index d6a06ff..d378212 100644
--- a/packages/flutter/test/widgets/draggable_test.dart
+++ b/packages/flutter/test/widgets/draggable_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/semantics.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/widgets/drawer_test.dart

diff --git a/packages/flutter/test/widgets/drawer_test.dart b/packages/flutter/test/widgets/drawer_test.dart
index 3a88519..6ad9a77 100644
--- a/packages/flutter/test/widgets/drawer_test.dart
+++ b/packages/flutter/test/widgets/drawer_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/editable_text_cursor_test.dart

diff --git a/packages/flutter/test/widgets/editable_text_cursor_test.dart b/packages/flutter/test/widgets/editable_text_cursor_test.dart
index 45a1c21..e9f13bc 100644
--- a/packages/flutter/test/widgets/editable_text_cursor_test.dart
+++ b/packages/flutter/test/widgets/editable_text_cursor_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/editable_text_show_on_screen_test.dart

diff --git a/packages/flutter/test/widgets/editable_text_show_on_screen_test.dart b/packages/flutter/test/widgets/editable_text_show_on_screen_test.dart
index 5c5d15f..7ef32db 100644
--- a/packages/flutter/test/widgets/editable_text_show_on_screen_test.dart
+++ b/packages/flutter/test/widgets/editable_text_show_on_screen_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/editable_text_test.dart

diff --git a/packages/flutter/test/widgets/editable_text_test.dart b/packages/flutter/test/widgets/editable_text_test.dart
index dc9f0ef..4083ec7 100644
--- a/packages/flutter/test/widgets/editable_text_test.dart
+++ b/packages/flutter/test/widgets/editable_text_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/editable_text_utils.dart

diff --git a/packages/flutter/test/widgets/editable_text_utils.dart b/packages/flutter/test/widgets/editable_text_utils.dart
index 1b9db06..0b5f073 100644
--- a/packages/flutter/test/widgets/editable_text_utils.dart
+++ b/packages/flutter/test/widgets/editable_text_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/ensure_visible_test.dart

diff --git a/packages/flutter/test/widgets/ensure_visible_test.dart b/packages/flutter/test/widgets/ensure_visible_test.dart
index bb8a702..c09c5d1 100644
--- a/packages/flutter/test/widgets/ensure_visible_test.dart
+++ b/packages/flutter/test/widgets/ensure_visible_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/error_widget_builder_test.dart

diff --git a/packages/flutter/test/widgets/error_widget_builder_test.dart b/packages/flutter/test/widgets/error_widget_builder_test.dart
index 5126680..377ec23 100644
--- a/packages/flutter/test/widgets/error_widget_builder_test.dart
+++ b/packages/flutter/test/widgets/error_widget_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/fade_in_image_test.dart

diff --git a/packages/flutter/test/widgets/fade_in_image_test.dart b/packages/flutter/test/widgets/fade_in_image_test.dart
index 5058326..a8103e7 100644
--- a/packages/flutter/test/widgets/fade_in_image_test.dart
+++ b/packages/flutter/test/widgets/fade_in_image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui;

packages/flutter/test/widgets/fade_transition_test.dart

diff --git a/packages/flutter/test/widgets/fade_transition_test.dart b/packages/flutter/test/widgets/fade_transition_test.dart
index 1d4fa87..0858125 100644
--- a/packages/flutter/test/widgets/fade_transition_test.dart
+++ b/packages/flutter/test/widgets/fade_transition_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/fitted_box_test.dart

diff --git a/packages/flutter/test/widgets/fitted_box_test.dart b/packages/flutter/test/widgets/fitted_box_test.dart
index f08cd54..1f14157 100644
--- a/packages/flutter/test/widgets/fitted_box_test.dart
+++ b/packages/flutter/test/widgets/fitted_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/flex_test.dart

diff --git a/packages/flutter/test/widgets/flex_test.dart b/packages/flutter/test/widgets/flex_test.dart
index 993dc7e..f581cf2 100644
--- a/packages/flutter/test/widgets/flex_test.dart
+++ b/packages/flutter/test/widgets/flex_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/flow_test.dart

diff --git a/packages/flutter/test/widgets/flow_test.dart b/packages/flutter/test/widgets/flow_test.dart
index eb21e28..d91724c 100644
--- a/packages/flutter/test/widgets/flow_test.dart
+++ b/packages/flutter/test/widgets/flow_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/focus_manager_test.dart

diff --git a/packages/flutter/test/widgets/focus_manager_test.dart b/packages/flutter/test/widgets/focus_manager_test.dart
index 083ace0..74dc015 100644
--- a/packages/flutter/test/widgets/focus_manager_test.dart
+++ b/packages/flutter/test/widgets/focus_manager_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/focus_scope_test.dart

diff --git a/packages/flutter/test/widgets/focus_scope_test.dart b/packages/flutter/test/widgets/focus_scope_test.dart
index 29d08ba..e3b716e 100644
--- a/packages/flutter/test/widgets/focus_scope_test.dart
+++ b/packages/flutter/test/widgets/focus_scope_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/focus_traversal_test.dart

diff --git a/packages/flutter/test/widgets/focus_traversal_test.dart b/packages/flutter/test/widgets/focus_traversal_test.dart
index 92c7a29..f28c5be 100644
--- a/packages/flutter/test/widgets/focus_traversal_test.dart
+++ b/packages/flutter/test/widgets/focus_traversal_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/form_test.dart

diff --git a/packages/flutter/test/widgets/form_test.dart b/packages/flutter/test/widgets/form_test.dart
index e4d4ad9..98c6176 100644
--- a/packages/flutter/test/widgets/form_test.dart
+++ b/packages/flutter/test/widgets/form_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/fractionally_sized_box_test.dart

diff --git a/packages/flutter/test/widgets/fractionally_sized_box_test.dart b/packages/flutter/test/widgets/fractionally_sized_box_test.dart
index 8b8bf47..cc232ce 100644
--- a/packages/flutter/test/widgets/fractionally_sized_box_test.dart
+++ b/packages/flutter/test/widgets/fractionally_sized_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/framework_test.dart

diff --git a/packages/flutter/test/widgets/framework_test.dart b/packages/flutter/test/widgets/framework_test.dart
index 5f94694..6ef4e5a 100644
--- a/packages/flutter/test/widgets/framework_test.dart
+++ b/packages/flutter/test/widgets/framework_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/gesture_detector_semantics_test.dart

diff --git a/packages/flutter/test/widgets/gesture_detector_semantics_test.dart b/packages/flutter/test/widgets/gesture_detector_semantics_test.dart
index 0700b6e..1dc6fec 100644
--- a/packages/flutter/test/widgets/gesture_detector_semantics_test.dart
+++ b/packages/flutter/test/widgets/gesture_detector_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/gesture_detector_test.dart

diff --git a/packages/flutter/test/widgets/gesture_detector_test.dart b/packages/flutter/test/widgets/gesture_detector_test.dart
index af40089..bc8af0e 100644
--- a/packages/flutter/test/widgets/gesture_detector_test.dart
+++ b/packages/flutter/test/widgets/gesture_detector_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/gesture_disambiguation_test.dart

diff --git a/packages/flutter/test/widgets/gesture_disambiguation_test.dart b/packages/flutter/test/widgets/gesture_disambiguation_test.dart
index 209c42a..9b75de4 100644
--- a/packages/flutter/test/widgets/gesture_disambiguation_test.dart
+++ b/packages/flutter/test/widgets/gesture_disambiguation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/widgets/global_keys_duplicated_test.dart

diff --git a/packages/flutter/test/widgets/global_keys_duplicated_test.dart b/packages/flutter/test/widgets/global_keys_duplicated_test.dart
index 30ccb20..27f54a9 100644
--- a/packages/flutter/test/widgets/global_keys_duplicated_test.dart
+++ b/packages/flutter/test/widgets/global_keys_duplicated_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/global_keys_moving_test.dart

diff --git a/packages/flutter/test/widgets/global_keys_moving_test.dart b/packages/flutter/test/widgets/global_keys_moving_test.dart
index c7c4cb3..370060a 100644
--- a/packages/flutter/test/widgets/global_keys_moving_test.dart
+++ b/packages/flutter/test/widgets/global_keys_moving_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/grid_paper_test.dart

diff --git a/packages/flutter/test/widgets/grid_paper_test.dart b/packages/flutter/test/widgets/grid_paper_test.dart
index 42d4e31..80dfd7d 100644
--- a/packages/flutter/test/widgets/grid_paper_test.dart
+++ b/packages/flutter/test/widgets/grid_paper_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/grid_view_layout_test.dart

diff --git a/packages/flutter/test/widgets/grid_view_layout_test.dart b/packages/flutter/test/widgets/grid_view_layout_test.dart
index 5486a9f..c5ab26d 100644
--- a/packages/flutter/test/widgets/grid_view_layout_test.dart
+++ b/packages/flutter/test/widgets/grid_view_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/grid_view_test.dart

diff --git a/packages/flutter/test/widgets/grid_view_test.dart b/packages/flutter/test/widgets/grid_view_test.dart
index 4c96d02..57baadf 100644
--- a/packages/flutter/test/widgets/grid_view_test.dart
+++ b/packages/flutter/test/widgets/grid_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/test/widgets/heroes_test.dart

diff --git a/packages/flutter/test/widgets/heroes_test.dart b/packages/flutter/test/widgets/heroes_test.dart
index 770e574..490038b 100644
--- a/packages/flutter/test/widgets/heroes_test.dart
+++ b/packages/flutter/test/widgets/heroes_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/hit_testing_test.dart

diff --git a/packages/flutter/test/widgets/hit_testing_test.dart b/packages/flutter/test/widgets/hit_testing_test.dart
index bfe3dd4..9f665df 100644
--- a/packages/flutter/test/widgets/hit_testing_test.dart
+++ b/packages/flutter/test/widgets/hit_testing_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/html_element_view_test.dart

diff --git a/packages/flutter/test/widgets/html_element_view_test.dart b/packages/flutter/test/widgets/html_element_view_test.dart
index e8ea3b3..fb70881 100644
--- a/packages/flutter/test/widgets/html_element_view_test.dart
+++ b/packages/flutter/test/widgets/html_element_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('chrome')
 
 import 'dart:async';

packages/flutter/test/widgets/hyperlink_test.dart

diff --git a/packages/flutter/test/widgets/hyperlink_test.dart b/packages/flutter/test/widgets/hyperlink_test.dart
index 9b56c77..c4264af 100644
--- a/packages/flutter/test/widgets/hyperlink_test.dart
+++ b/packages/flutter/test/widgets/hyperlink_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/icon_data_test.dart

diff --git a/packages/flutter/test/widgets/icon_data_test.dart b/packages/flutter/test/widgets/icon_data_test.dart
index 38a5c3f..2647f43 100644
--- a/packages/flutter/test/widgets/icon_data_test.dart
+++ b/packages/flutter/test/widgets/icon_data_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/icon_test.dart

diff --git a/packages/flutter/test/widgets/icon_test.dart b/packages/flutter/test/widgets/icon_test.dart
index 703905b..b126999 100644
--- a/packages/flutter/test/widgets/icon_test.dart
+++ b/packages/flutter/test/widgets/icon_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/icon_theme_data_test.dart

diff --git a/packages/flutter/test/widgets/icon_theme_data_test.dart b/packages/flutter/test/widgets/icon_theme_data_test.dart
index 83e48c6..50c0984 100644
--- a/packages/flutter/test/widgets/icon_theme_data_test.dart
+++ b/packages/flutter/test/widgets/icon_theme_data_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/image_data.dart

diff --git a/packages/flutter/test/widgets/image_data.dart b/packages/flutter/test/widgets/image_data.dart
index cfb313a..46a898b 100644
--- a/packages/flutter/test/widgets/image_data.dart
+++ b/packages/flutter/test/widgets/image_data.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 const List<int> kTransparentImage = <int>[
   0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0x00, 0x00, 0x0D, 0x49,
   0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x08, 0x06,

packages/flutter/test/widgets/image_filter_test.dart

diff --git a/packages/flutter/test/widgets/image_filter_test.dart b/packages/flutter/test/widgets/image_filter_test.dart
index 7069e1e..4610600 100644
--- a/packages/flutter/test/widgets/image_filter_test.dart
+++ b/packages/flutter/test/widgets/image_filter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui';
 

packages/flutter/test/widgets/image_headers_test.dart

diff --git a/packages/flutter/test/widgets/image_headers_test.dart b/packages/flutter/test/widgets/image_headers_test.dart
index efe379e..427b109 100644
--- a/packages/flutter/test/widgets/image_headers_test.dart
+++ b/packages/flutter/test/widgets/image_headers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:io';
 

packages/flutter/test/widgets/image_icon_test.dart

diff --git a/packages/flutter/test/widgets/image_icon_test.dart b/packages/flutter/test/widgets/image_icon_test.dart
index f4e142b..2a8f8d5 100644
--- a/packages/flutter/test/widgets/image_icon_test.dart
+++ b/packages/flutter/test/widgets/image_icon_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/image_package_asset_test.dart

diff --git a/packages/flutter/test/widgets/image_package_asset_test.dart b/packages/flutter/test/widgets/image_package_asset_test.dart
index 47318dd..922f1b2 100644
--- a/packages/flutter/test/widgets/image_package_asset_test.dart
+++ b/packages/flutter/test/widgets/image_package_asset_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/image_resolution_test.dart

diff --git a/packages/flutter/test/widgets/image_resolution_test.dart b/packages/flutter/test/widgets/image_resolution_test.dart
index 1058f40..63df873 100644
--- a/packages/flutter/test/widgets/image_resolution_test.dart
+++ b/packages/flutter/test/widgets/image_resolution_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // asset bundle behaves differently.
 import 'dart:async';
 import 'dart:typed_data';

packages/flutter/test/widgets/image_rtl_test.dart

diff --git a/packages/flutter/test/widgets/image_rtl_test.dart b/packages/flutter/test/widgets/image_rtl_test.dart
index e42c48f..e284c9c 100644
--- a/packages/flutter/test/widgets/image_rtl_test.dart
+++ b/packages/flutter/test/widgets/image_rtl_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:typed_data';
 import 'dart:ui' as ui show Image, ImageByteFormat;

packages/flutter/test/widgets/image_test.dart

diff --git a/packages/flutter/test/widgets/image_test.dart b/packages/flutter/test/widgets/image_test.dart
index d821046..472181c 100644
--- a/packages/flutter/test/widgets/image_test.dart
+++ b/packages/flutter/test/widgets/image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:math' as math;
 import 'dart:typed_data';

packages/flutter/test/widgets/implicit_animations_test.dart

diff --git a/packages/flutter/test/widgets/implicit_animations_test.dart b/packages/flutter/test/widgets/implicit_animations_test.dart
index 7c680b4..53e7436 100644
--- a/packages/flutter/test/widgets/implicit_animations_test.dart
+++ b/packages/flutter/test/widgets/implicit_animations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/implicit_semantics_test.dart

diff --git a/packages/flutter/test/widgets/implicit_semantics_test.dart b/packages/flutter/test/widgets/implicit_semantics_test.dart
index a32dfce..a8871a0 100644
--- a/packages/flutter/test/widgets/implicit_semantics_test.dart
+++ b/packages/flutter/test/widgets/implicit_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/independent_widget_layout_test.dart

diff --git a/packages/flutter/test/widgets/independent_widget_layout_test.dart b/packages/flutter/test/widgets/independent_widget_layout_test.dart
index f62ba2d..4d55a45 100644
--- a/packages/flutter/test/widgets/independent_widget_layout_test.dart
+++ b/packages/flutter/test/widgets/independent_widget_layout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/inherited_dependencies_test.dart

diff --git a/packages/flutter/test/widgets/inherited_dependencies_test.dart b/packages/flutter/test/widgets/inherited_dependencies_test.dart
index 6532530..404c0f2 100644
--- a/packages/flutter/test/widgets/inherited_dependencies_test.dart
+++ b/packages/flutter/test/widgets/inherited_dependencies_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/src/widgets/basic.dart';
 import 'package:flutter/src/widgets/framework.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/inherited_model_test.dart

diff --git a/packages/flutter/test/widgets/inherited_model_test.dart b/packages/flutter/test/widgets/inherited_model_test.dart
index 03d3e10..09ded2d 100644
--- a/packages/flutter/test/widgets/inherited_model_test.dart
+++ b/packages/flutter/test/widgets/inherited_model_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/inherited_test.dart

diff --git a/packages/flutter/test/widgets/inherited_test.dart b/packages/flutter/test/widgets/inherited_test.dart
index 31a6f61..d44ab93 100644
--- a/packages/flutter/test/widgets/inherited_test.dart
+++ b/packages/flutter/test/widgets/inherited_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/inherited_theme_test.dart

diff --git a/packages/flutter/test/widgets/inherited_theme_test.dart b/packages/flutter/test/widgets/inherited_theme_test.dart
index ade4261..699e161 100644
--- a/packages/flutter/test/widgets/inherited_theme_test.dart
+++ b/packages/flutter/test/widgets/inherited_theme_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/init_state_test.dart

diff --git a/packages/flutter/test/widgets/init_state_test.dart b/packages/flutter/test/widgets/init_state_test.dart
index 9ff423c..2e564a8 100644
--- a/packages/flutter/test/widgets/init_state_test.dart
+++ b/packages/flutter/test/widgets/init_state_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/interactive_viewer_test.dart

diff --git a/packages/flutter/test/widgets/interactive_viewer_test.dart b/packages/flutter/test/widgets/interactive_viewer_test.dart
index 31c3de8..cb4cc0e 100644
--- a/packages/flutter/test/widgets/interactive_viewer_test.dart
+++ b/packages/flutter/test/widgets/interactive_viewer_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/intrinsic_width_test.dart

diff --git a/packages/flutter/test/widgets/intrinsic_width_test.dart b/packages/flutter/test/widgets/intrinsic_width_test.dart
index fa5f32c..e444020 100644
--- a/packages/flutter/test/widgets/intrinsic_width_test.dart
+++ b/packages/flutter/test/widgets/intrinsic_width_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/invert_colors_test.dart

diff --git a/packages/flutter/test/widgets/invert_colors_test.dart b/packages/flutter/test/widgets/invert_colors_test.dart
index f899d60..6a4b9b8 100644
--- a/packages/flutter/test/widgets/invert_colors_test.dart
+++ b/packages/flutter/test/widgets/invert_colors_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/keep_alive_test.dart

diff --git a/packages/flutter/test/widgets/keep_alive_test.dart b/packages/flutter/test/widgets/keep_alive_test.dart
index 8406b99..c4782af 100644
--- a/packages/flutter/test/widgets/keep_alive_test.dart
+++ b/packages/flutter/test/widgets/keep_alive_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // diagnostics use Platform.operatingSystem.
 import 'dart:io' show Platform;
 

packages/flutter/test/widgets/key_test.dart

diff --git a/packages/flutter/test/widgets/key_test.dart b/packages/flutter/test/widgets/key_test.dart
index 47d502fa..52da0a0 100644
--- a/packages/flutter/test/widgets/key_test.dart
+++ b/packages/flutter/test/widgets/key_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/layout_builder_and_global_keys_test.dart

diff --git a/packages/flutter/test/widgets/layout_builder_and_global_keys_test.dart b/packages/flutter/test/widgets/layout_builder_and_global_keys_test.dart
index acb32d4..5a4d050 100644
--- a/packages/flutter/test/widgets/layout_builder_and_global_keys_test.dart
+++ b/packages/flutter/test/widgets/layout_builder_and_global_keys_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/src/rendering/sliver.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/layout_builder_and_parent_data_test.dart

diff --git a/packages/flutter/test/widgets/layout_builder_and_parent_data_test.dart b/packages/flutter/test/widgets/layout_builder_and_parent_data_test.dart
index 2ce19e2..c2a313c 100644
--- a/packages/flutter/test/widgets/layout_builder_and_parent_data_test.dart
+++ b/packages/flutter/test/widgets/layout_builder_and_parent_data_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/layout_builder_and_state_test.dart

diff --git a/packages/flutter/test/widgets/layout_builder_and_state_test.dart b/packages/flutter/test/widgets/layout_builder_and_state_test.dart
index fab59d7..1d5030c 100644
--- a/packages/flutter/test/widgets/layout_builder_and_state_test.dart
+++ b/packages/flutter/test/widgets/layout_builder_and_state_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'test_widgets.dart';

packages/flutter/test/widgets/layout_builder_mutations_test.dart

diff --git a/packages/flutter/test/widgets/layout_builder_mutations_test.dart b/packages/flutter/test/widgets/layout_builder_mutations_test.dart
index 687f0a0..e462654 100644
--- a/packages/flutter/test/widgets/layout_builder_mutations_test.dart
+++ b/packages/flutter/test/widgets/layout_builder_mutations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/src/rendering/sliver.dart';
 import 'package:flutter/src/widgets/basic.dart';
 import 'package:flutter/src/widgets/framework.dart';

packages/flutter/test/widgets/layout_builder_test.dart

diff --git a/packages/flutter/test/widgets/layout_builder_test.dart b/packages/flutter/test/widgets/layout_builder_test.dart
index 067b738..ee54d97 100644
--- a/packages/flutter/test/widgets/layout_builder_test.dart
+++ b/packages/flutter/test/widgets/layout_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/linked_scroll_view_test.dart

diff --git a/packages/flutter/test/widgets/linked_scroll_view_test.dart b/packages/flutter/test/widgets/linked_scroll_view_test.dart
index e8f4129..b2848c7 100644
--- a/packages/flutter/test/widgets/linked_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/linked_scroll_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This file contains a wacky demonstration of creating a custom ScrollPosition
 // setup. It's testing that we don't regress the factoring of the
 // ScrollPosition/ScrollActivity logic into a state where you can no longer

packages/flutter/test/widgets/list_body_test.dart

diff --git a/packages/flutter/test/widgets/list_body_test.dart b/packages/flutter/test/widgets/list_body_test.dart
index e707e23..092cc02 100644
--- a/packages/flutter/test/widgets/list_body_test.dart
+++ b/packages/flutter/test/widgets/list_body_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/src/foundation/assertions.dart';
 import 'package:flutter/src/painting/basic_types.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/list_view_builder_test.dart

diff --git a/packages/flutter/test/widgets/list_view_builder_test.dart b/packages/flutter/test/widgets/list_view_builder_test.dart
index f0bae19..0a6b32e 100644
--- a/packages/flutter/test/widgets/list_view_builder_test.dart
+++ b/packages/flutter/test/widgets/list_view_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/list_view_correction_test.dart

diff --git a/packages/flutter/test/widgets/list_view_correction_test.dart b/packages/flutter/test/widgets/list_view_correction_test.dart
index 4f617d6..facac36 100644
--- a/packages/flutter/test/widgets/list_view_correction_test.dart
+++ b/packages/flutter/test/widgets/list_view_correction_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/list_view_fling_test.dart

diff --git a/packages/flutter/test/widgets/list_view_fling_test.dart b/packages/flutter/test/widgets/list_view_fling_test.dart
index 14b3bfa..9e56b9c 100644
--- a/packages/flutter/test/widgets/list_view_fling_test.dart
+++ b/packages/flutter/test/widgets/list_view_fling_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/list_view_horizontal_test.dart

diff --git a/packages/flutter/test/widgets/list_view_horizontal_test.dart b/packages/flutter/test/widgets/list_view_horizontal_test.dart
index a9730b8..083881e 100644
--- a/packages/flutter/test/widgets/list_view_horizontal_test.dart
+++ b/packages/flutter/test/widgets/list_view_horizontal_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/list_view_misc_test.dart

diff --git a/packages/flutter/test/widgets/list_view_misc_test.dart b/packages/flutter/test/widgets/list_view_misc_test.dart
index 6f343d1..2598fc8 100644
--- a/packages/flutter/test/widgets/list_view_misc_test.dart
+++ b/packages/flutter/test/widgets/list_view_misc_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/list_view_relayout_test.dart

diff --git a/packages/flutter/test/widgets/list_view_relayout_test.dart b/packages/flutter/test/widgets/list_view_relayout_test.dart
index e91a476..61c4807 100644
--- a/packages/flutter/test/widgets/list_view_relayout_test.dart
+++ b/packages/flutter/test/widgets/list_view_relayout_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/list_view_semantics_test.dart

diff --git a/packages/flutter/test/widgets/list_view_semantics_test.dart b/packages/flutter/test/widgets/list_view_semantics_test.dart
index e59c22b..de0de88 100644
--- a/packages/flutter/test/widgets/list_view_semantics_test.dart
+++ b/packages/flutter/test/widgets/list_view_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/list_view_test.dart

diff --git a/packages/flutter/test/widgets/list_view_test.dart b/packages/flutter/test/widgets/list_view_test.dart
index 7696761..fa32738 100644
--- a/packages/flutter/test/widgets/list_view_test.dart
+++ b/packages/flutter/test/widgets/list_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/list_view_vertical_test.dart

diff --git a/packages/flutter/test/widgets/list_view_vertical_test.dart b/packages/flutter/test/widgets/list_view_vertical_test.dart
index 2111dd2..0ff0766 100644
--- a/packages/flutter/test/widgets/list_view_vertical_test.dart
+++ b/packages/flutter/test/widgets/list_view_vertical_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/list_view_viewporting_test.dart

diff --git a/packages/flutter/test/widgets/list_view_viewporting_test.dart b/packages/flutter/test/widgets/list_view_viewporting_test.dart
index 0ee027d..6f39cae 100644
--- a/packages/flutter/test/widgets/list_view_viewporting_test.dart
+++ b/packages/flutter/test/widgets/list_view_viewporting_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/list_view_with_inherited_test.dart

diff --git a/packages/flutter/test/widgets/list_view_with_inherited_test.dart b/packages/flutter/test/widgets/list_view_with_inherited_test.dart
index 31cb0bd..14ef2b6 100644
--- a/packages/flutter/test/widgets/list_view_with_inherited_test.dart
+++ b/packages/flutter/test/widgets/list_view_with_inherited_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/list_wheel_scroll_view_test.dart

diff --git a/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart b/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart
index 4de089f..2bd949d 100644
--- a/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/list_wheel_scroll_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/listener_deprecated_test.dart

diff --git a/packages/flutter/test/widgets/listener_deprecated_test.dart b/packages/flutter/test/widgets/listener_deprecated_test.dart
index 5ce9249..cf2b7e3 100644
--- a/packages/flutter/test/widgets/listener_deprecated_test.dart
+++ b/packages/flutter/test/widgets/listener_deprecated_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/listener_test.dart

diff --git a/packages/flutter/test/widgets/listener_test.dart b/packages/flutter/test/widgets/listener_test.dart
index 09a4075..27ca89d 100644
--- a/packages/flutter/test/widgets/listener_test.dart
+++ b/packages/flutter/test/widgets/listener_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/listview_end_append_test.dart

diff --git a/packages/flutter/test/widgets/listview_end_append_test.dart b/packages/flutter/test/widgets/listview_end_append_test.dart
index d1e5b89..bf23dbe 100644
--- a/packages/flutter/test/widgets/listview_end_append_test.dart
+++ b/packages/flutter/test/widgets/listview_end_append_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/test/widgets/localizations_test.dart

diff --git a/packages/flutter/test/widgets/localizations_test.dart b/packages/flutter/test/widgets/localizations_test.dart
index e538a5f..61dc222 100644
--- a/packages/flutter/test/widgets/localizations_test.dart
+++ b/packages/flutter/test/widgets/localizations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/media_query_test.dart

diff --git a/packages/flutter/test/widgets/media_query_test.dart b/packages/flutter/test/widgets/media_query_test.dart
index 4f290d8..171da41 100644
--- a/packages/flutter/test/widgets/media_query_test.dart
+++ b/packages/flutter/test/widgets/media_query_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Brightness;
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/modal_barrier_test.dart

diff --git a/packages/flutter/test/widgets/modal_barrier_test.dart b/packages/flutter/test/widgets/modal_barrier_test.dart
index d2dbe30..6e1bc76 100644
--- a/packages/flutter/test/widgets/modal_barrier_test.dart
+++ b/packages/flutter/test/widgets/modal_barrier_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/mouse_region_test.dart

diff --git a/packages/flutter/test/widgets/mouse_region_test.dart b/packages/flutter/test/widgets/mouse_region_test.dart
index 8a4f1d0..fb0ef25 100644
--- a/packages/flutter/test/widgets/mouse_region_test.dart
+++ b/packages/flutter/test/widgets/mouse_region_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/multichild_test.dart

diff --git a/packages/flutter/test/widgets/multichild_test.dart b/packages/flutter/test/widgets/multichild_test.dart
index c51429f..23d113d 100644
--- a/packages/flutter/test/widgets/multichild_test.dart
+++ b/packages/flutter/test/widgets/multichild_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/multichildobject_with_keys_test.dart

diff --git a/packages/flutter/test/widgets/multichildobject_with_keys_test.dart b/packages/flutter/test/widgets/multichildobject_with_keys_test.dart
index 186025b..0c41d16 100644
--- a/packages/flutter/test/widgets/multichildobject_with_keys_test.dart
+++ b/packages/flutter/test/widgets/multichildobject_with_keys_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/navigator_and_layers_test.dart

diff --git a/packages/flutter/test/widgets/navigator_and_layers_test.dart b/packages/flutter/test/widgets/navigator_and_layers_test.dart
index 93b7500..7a70041 100644
--- a/packages/flutter/test/widgets/navigator_and_layers_test.dart
+++ b/packages/flutter/test/widgets/navigator_and_layers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/navigator_replacement_test.dart

diff --git a/packages/flutter/test/widgets/navigator_replacement_test.dart b/packages/flutter/test/widgets/navigator_replacement_test.dart
index 89d2d14..cae1ef2 100644
--- a/packages/flutter/test/widgets/navigator_replacement_test.dart
+++ b/packages/flutter/test/widgets/navigator_replacement_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/navigator_test.dart

diff --git a/packages/flutter/test/widgets/navigator_test.dart b/packages/flutter/test/widgets/navigator_test.dart
index f9655a9..16fb138 100644
--- a/packages/flutter/test/widgets/navigator_test.dart
+++ b/packages/flutter/test/widgets/navigator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/nested_scroll_view_test.dart

diff --git a/packages/flutter/test/widgets/nested_scroll_view_test.dart b/packages/flutter/test/widgets/nested_scroll_view_test.dart
index c01c311..cde607c 100644
--- a/packages/flutter/test/widgets/nested_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/nested_scroll_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/notification_test.dart

diff --git a/packages/flutter/test/widgets/notification_test.dart b/packages/flutter/test/widgets/notification_test.dart
index 539885a..38a527e 100644
--- a/packages/flutter/test/widgets/notification_test.dart
+++ b/packages/flutter/test/widgets/notification_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/obscured_animated_image_test.dart

diff --git a/packages/flutter/test/widgets/obscured_animated_image_test.dart b/packages/flutter/test/widgets/obscured_animated_image_test.dart
index ce4e9e4..1a50c99 100644
--- a/packages/flutter/test/widgets/obscured_animated_image_test.dart
+++ b/packages/flutter/test/widgets/obscured_animated_image_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui' as ui show Image;
 

packages/flutter/test/widgets/observer_tester.dart

diff --git a/packages/flutter/test/widgets/observer_tester.dart b/packages/flutter/test/widgets/observer_tester.dart
index 66bcf3a..99a694a 100644
--- a/packages/flutter/test/widgets/observer_tester.dart
+++ b/packages/flutter/test/widgets/observer_tester.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 
 typedef OnObservation = void Function(Route<dynamic> route, Route<dynamic> previousRoute);

packages/flutter/test/widgets/opacity_test.dart

diff --git a/packages/flutter/test/widgets/opacity_test.dart b/packages/flutter/test/widgets/opacity_test.dart
index 044a51f..5687d73 100644
--- a/packages/flutter/test/widgets/opacity_test.dart
+++ b/packages/flutter/test/widgets/opacity_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/overflow_box_test.dart

diff --git a/packages/flutter/test/widgets/overflow_box_test.dart b/packages/flutter/test/widgets/overflow_box_test.dart
index eb91b99..20a8687 100644
--- a/packages/flutter/test/widgets/overflow_box_test.dart
+++ b/packages/flutter/test/widgets/overflow_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/overlay_test.dart

diff --git a/packages/flutter/test/widgets/overlay_test.dart b/packages/flutter/test/widgets/overlay_test.dart
index 850f25f..f3f7918 100644
--- a/packages/flutter/test/widgets/overlay_test.dart
+++ b/packages/flutter/test/widgets/overlay_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/overscroll_indicator_test.dart

diff --git a/packages/flutter/test/widgets/overscroll_indicator_test.dart b/packages/flutter/test/widgets/overscroll_indicator_test.dart
index 68d49c3..c9e3cb6 100644
--- a/packages/flutter/test/widgets/overscroll_indicator_test.dart
+++ b/packages/flutter/test/widgets/overscroll_indicator_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/page_forward_transitions_test.dart

diff --git a/packages/flutter/test/widgets/page_forward_transitions_test.dart b/packages/flutter/test/widgets/page_forward_transitions_test.dart
index ab1a863..5b25df2 100644
--- a/packages/flutter/test/widgets/page_forward_transitions_test.dart
+++ b/packages/flutter/test/widgets/page_forward_transitions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/page_storage_test.dart

diff --git a/packages/flutter/test/widgets/page_storage_test.dart b/packages/flutter/test/widgets/page_storage_test.dart
index 5186eb4..e652226 100644
--- a/packages/flutter/test/widgets/page_storage_test.dart
+++ b/packages/flutter/test/widgets/page_storage_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/page_transitions_test.dart

diff --git a/packages/flutter/test/widgets/page_transitions_test.dart b/packages/flutter/test/widgets/page_transitions_test.dart
index 6f3211d..78cbf5c 100644
--- a/packages/flutter/test/widgets/page_transitions_test.dart
+++ b/packages/flutter/test/widgets/page_transitions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/page_view_test.dart

diff --git a/packages/flutter/test/widgets/page_view_test.dart b/packages/flutter/test/widgets/page_view_test.dart
index 6f47ddc..6149f6a 100644
--- a/packages/flutter/test/widgets/page_view_test.dart
+++ b/packages/flutter/test/widgets/page_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/pageable_list_test.dart

diff --git a/packages/flutter/test/widgets/pageable_list_test.dart b/packages/flutter/test/widgets/pageable_list_test.dart
index 4376678..275e9be 100644
--- a/packages/flutter/test/widgets/pageable_list_test.dart
+++ b/packages/flutter/test/widgets/pageable_list_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/parent_data_test.dart

diff --git a/packages/flutter/test/widgets/parent_data_test.dart b/packages/flutter/test/widgets/parent_data_test.dart
index 52390c1..84bc742 100644
--- a/packages/flutter/test/widgets/parent_data_test.dart
+++ b/packages/flutter/test/widgets/parent_data_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/performance_overlay_test.dart

diff --git a/packages/flutter/test/widgets/performance_overlay_test.dart b/packages/flutter/test/widgets/performance_overlay_test.dart
index e76a324..f633e0a 100644
--- a/packages/flutter/test/widgets/performance_overlay_test.dart
+++ b/packages/flutter/test/widgets/performance_overlay_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/physical_model_test.dart

diff --git a/packages/flutter/test/widgets/physical_model_test.dart b/packages/flutter/test/widgets/physical_model_test.dart
index 979bde2..7d0541c 100644
--- a/packages/flutter/test/widgets/physical_model_test.dart
+++ b/packages/flutter/test/widgets/physical_model_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math show pi;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/placeholder_test.dart

diff --git a/packages/flutter/test/widgets/placeholder_test.dart b/packages/flutter/test/widgets/placeholder_test.dart
index 9c6b0f1..b2765e4 100644
--- a/packages/flutter/test/widgets/placeholder_test.dart
+++ b/packages/flutter/test/widgets/placeholder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/platform_view_test.dart

diff --git a/packages/flutter/test/widgets/platform_view_test.dart b/packages/flutter/test/widgets/platform_view_test.dart
index fd9f388..bef4047 100644
--- a/packages/flutter/test/widgets/platform_view_test.dart
+++ b/packages/flutter/test/widgets/platform_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome')
 import 'dart:async';
 import 'dart:typed_data';

packages/flutter/test/widgets/positioned_test.dart

diff --git a/packages/flutter/test/widgets/positioned_test.dart b/packages/flutter/test/widgets/positioned_test.dart
index 8926a42..6497453 100644
--- a/packages/flutter/test/widgets/positioned_test.dart
+++ b/packages/flutter/test/widgets/positioned_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/range_maintaining_scroll_physics_test.dart

diff --git a/packages/flutter/test/widgets/range_maintaining_scroll_physics_test.dart b/packages/flutter/test/widgets/range_maintaining_scroll_physics_test.dart
index 4e103f4..c110a9d 100644
--- a/packages/flutter/test/widgets/range_maintaining_scroll_physics_test.dart
+++ b/packages/flutter/test/widgets/range_maintaining_scroll_physics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/raw_keyboard_listener_test.dart

diff --git a/packages/flutter/test/widgets/raw_keyboard_listener_test.dart b/packages/flutter/test/widgets/raw_keyboard_listener_test.dart
index bcac58d..12b23e1 100644
--- a/packages/flutter/test/widgets/raw_keyboard_listener_test.dart
+++ b/packages/flutter/test/widgets/raw_keyboard_listener_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/reassemble_test.dart

diff --git a/packages/flutter/test/widgets/reassemble_test.dart b/packages/flutter/test/widgets/reassemble_test.dart
index 32eff20..11e2549 100644
--- a/packages/flutter/test/widgets/reassemble_test.dart
+++ b/packages/flutter/test/widgets/reassemble_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/render_object_widget_test.dart

diff --git a/packages/flutter/test/widgets/render_object_widget_test.dart b/packages/flutter/test/widgets/render_object_widget_test.dart
index 6b781cd..007567c 100644
--- a/packages/flutter/test/widgets/render_object_widget_test.dart
+++ b/packages/flutter/test/widgets/render_object_widget_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/reparent_state_harder_test.dart

diff --git a/packages/flutter/test/widgets/reparent_state_harder_test.dart b/packages/flutter/test/widgets/reparent_state_harder_test.dart
index ad3a943..c42b04c 100644
--- a/packages/flutter/test/widgets/reparent_state_harder_test.dart
+++ b/packages/flutter/test/widgets/reparent_state_harder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/reparent_state_test.dart

diff --git a/packages/flutter/test/widgets/reparent_state_test.dart b/packages/flutter/test/widgets/reparent_state_test.dart
index e31db61..3d61e96 100644
--- a/packages/flutter/test/widgets/reparent_state_test.dart
+++ b/packages/flutter/test/widgets/reparent_state_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/reparent_state_with_layout_builder_test.dart

diff --git a/packages/flutter/test/widgets/reparent_state_with_layout_builder_test.dart b/packages/flutter/test/widgets/reparent_state_with_layout_builder_test.dart
index f5e4c92..899ba03 100644
--- a/packages/flutter/test/widgets/reparent_state_with_layout_builder_test.dart
+++ b/packages/flutter/test/widgets/reparent_state_with_layout_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui show window;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/rotated_box_test.dart

diff --git a/packages/flutter/test/widgets/rotated_box_test.dart b/packages/flutter/test/widgets/rotated_box_test.dart
index c112804..360e4f7 100644
--- a/packages/flutter/test/widgets/rotated_box_test.dart
+++ b/packages/flutter/test/widgets/rotated_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/route_notification_messages_test.dart

diff --git a/packages/flutter/test/widgets/route_notification_messages_test.dart b/packages/flutter/test/widgets/route_notification_messages_test.dart
index 4db5e5b..3752f70 100644
--- a/packages/flutter/test/widgets/route_notification_messages_test.dart
+++ b/packages/flutter/test/widgets/route_notification_messages_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('chrome')
 
 import 'dart:ui';

packages/flutter/test/widgets/routes_test.dart

diff --git a/packages/flutter/test/widgets/routes_test.dart b/packages/flutter/test/widgets/routes_test.dart
index 252d3b9..fd31dcf 100644
--- a/packages/flutter/test/widgets/routes_test.dart
+++ b/packages/flutter/test/widgets/routes_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/row_test.dart

diff --git a/packages/flutter/test/widgets/row_test.dart b/packages/flutter/test/widgets/row_test.dart
index 1572d03..9934cf5 100644
--- a/packages/flutter/test/widgets/row_test.dart
+++ b/packages/flutter/test/widgets/row_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/rtl_test.dart

diff --git a/packages/flutter/test/widgets/rtl_test.dart b/packages/flutter/test/widgets/rtl_test.dart
index 4984e41..4abc46a 100644
--- a/packages/flutter/test/widgets/rtl_test.dart
+++ b/packages/flutter/test/widgets/rtl_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/run_app_async_test.dart

diff --git a/packages/flutter/test/widgets/run_app_async_test.dart b/packages/flutter/test/widgets/run_app_async_test.dart
index 10a1773..3756dea 100644
--- a/packages/flutter/test/widgets/run_app_async_test.dart
+++ b/packages/flutter/test/widgets/run_app_async_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:quiver/testing/async.dart';

packages/flutter/test/widgets/run_app_test.dart

diff --git a/packages/flutter/test/widgets/run_app_test.dart b/packages/flutter/test/widgets/run_app_test.dart
index dbb1a79..8464197 100644
--- a/packages/flutter/test/widgets/run_app_test.dart
+++ b/packages/flutter/test/widgets/run_app_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/safe_area_test.dart

diff --git a/packages/flutter/test/widgets/safe_area_test.dart b/packages/flutter/test/widgets/safe_area_test.dart
index 9879978..d6a342e 100644
--- a/packages/flutter/test/widgets/safe_area_test.dart
+++ b/packages/flutter/test/widgets/safe_area_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/scroll_aware_image_provider_test.dart

diff --git a/packages/flutter/test/widgets/scroll_aware_image_provider_test.dart b/packages/flutter/test/widgets/scroll_aware_image_provider_test.dart
index 18c4856..a68e50c 100644
--- a/packages/flutter/test/widgets/scroll_aware_image_provider_test.dart
+++ b/packages/flutter/test/widgets/scroll_aware_image_provider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/scroll_behavior_test.dart

diff --git a/packages/flutter/test/widgets/scroll_behavior_test.dart b/packages/flutter/test/widgets/scroll_behavior_test.dart
index 2b5d130..933448a 100644
--- a/packages/flutter/test/widgets/scroll_behavior_test.dart
+++ b/packages/flutter/test/widgets/scroll_behavior_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/scroll_controller_test.dart

diff --git a/packages/flutter/test/widgets/scroll_controller_test.dart b/packages/flutter/test/widgets/scroll_controller_test.dart
index 688826b..8ca8a51 100644
--- a/packages/flutter/test/widgets/scroll_controller_test.dart
+++ b/packages/flutter/test/widgets/scroll_controller_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/scroll_events_test.dart

diff --git a/packages/flutter/test/widgets/scroll_events_test.dart b/packages/flutter/test/widgets/scroll_events_test.dart
index 93c7785..90d2a43 100644
--- a/packages/flutter/test/widgets/scroll_events_test.dart
+++ b/packages/flutter/test/widgets/scroll_events_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/scroll_interaction_test.dart

diff --git a/packages/flutter/test/widgets/scroll_interaction_test.dart b/packages/flutter/test/widgets/scroll_interaction_test.dart
index 7afdf1a..1cf1049 100644
--- a/packages/flutter/test/widgets/scroll_interaction_test.dart
+++ b/packages/flutter/test/widgets/scroll_interaction_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/scroll_notification_test.dart

diff --git a/packages/flutter/test/widgets/scroll_notification_test.dart b/packages/flutter/test/widgets/scroll_notification_test.dart
index adb0598..e71e625 100644
--- a/packages/flutter/test/widgets/scroll_notification_test.dart
+++ b/packages/flutter/test/widgets/scroll_notification_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/scroll_physics_test.dart

diff --git a/packages/flutter/test/widgets/scroll_physics_test.dart b/packages/flutter/test/widgets/scroll_physics_test.dart
index 8a88fb5..18a1b98 100644
--- a/packages/flutter/test/widgets/scroll_physics_test.dart
+++ b/packages/flutter/test/widgets/scroll_physics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/scroll_position_test.dart

diff --git a/packages/flutter/test/widgets/scroll_position_test.dart b/packages/flutter/test/widgets/scroll_position_test.dart
index 3655bf5..11aa00a 100644
--- a/packages/flutter/test/widgets/scroll_position_test.dart
+++ b/packages/flutter/test/widgets/scroll_position_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:ui';
 

packages/flutter/test/widgets/scroll_simulation_test.dart

diff --git a/packages/flutter/test/widgets/scroll_simulation_test.dart b/packages/flutter/test/widgets/scroll_simulation_test.dart
index fc2a705..7ad4b26 100644
--- a/packages/flutter/test/widgets/scroll_simulation_test.dart
+++ b/packages/flutter/test/widgets/scroll_simulation_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/scroll_view_test.dart

diff --git a/packages/flutter/test/widgets/scroll_view_test.dart b/packages/flutter/test/widgets/scroll_view_test.dart
index 0bf0497..ca84be7 100644
--- a/packages/flutter/test/widgets/scroll_view_test.dart
+++ b/packages/flutter/test/widgets/scroll_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/test/widgets/scrollable_animations_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_animations_test.dart b/packages/flutter/test/widgets/scrollable_animations_test.dart
index d34183f..3b8c27b 100644
--- a/packages/flutter/test/widgets/scrollable_animations_test.dart
+++ b/packages/flutter/test/widgets/scrollable_animations_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/scrollable_dispose_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_dispose_test.dart b/packages/flutter/test/widgets/scrollable_dispose_test.dart
index e0bdc0a..6500c19 100644
--- a/packages/flutter/test/widgets/scrollable_dispose_test.dart
+++ b/packages/flutter/test/widgets/scrollable_dispose_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/scrollable_fling_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_fling_test.dart b/packages/flutter/test/widgets/scrollable_fling_test.dart
index 87515f3..a4b5c35 100644
--- a/packages/flutter/test/widgets/scrollable_fling_test.dart
+++ b/packages/flutter/test/widgets/scrollable_fling_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/gestures.dart' show DragStartBehavior;

packages/flutter/test/widgets/scrollable_grid_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_grid_test.dart b/packages/flutter/test/widgets/scrollable_grid_test.dart
index 03bb4d7..24e773e 100644
--- a/packages/flutter/test/widgets/scrollable_grid_test.dart
+++ b/packages/flutter/test/widgets/scrollable_grid_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/scrollable_in_overlay_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_in_overlay_test.dart b/packages/flutter/test/widgets/scrollable_in_overlay_test.dart
index c67d261..fbbc83f 100644
--- a/packages/flutter/test/widgets/scrollable_in_overlay_test.dart
+++ b/packages/flutter/test/widgets/scrollable_in_overlay_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart b/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart
index 56a2b84..793c152 100644
--- a/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart
+++ b/packages/flutter/test/widgets/scrollable_list_hit_testing_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/scrollable_of_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_of_test.dart b/packages/flutter/test/widgets/scrollable_of_test.dart
index f7724e7..c480b78 100644
--- a/packages/flutter/test/widgets/scrollable_of_test.dart
+++ b/packages/flutter/test/widgets/scrollable_of_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/scrollable_semantics_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_semantics_test.dart b/packages/flutter/test/widgets/scrollable_semantics_test.dart
index d7f992f..6c1c4cf 100644
--- a/packages/flutter/test/widgets/scrollable_semantics_test.dart
+++ b/packages/flutter/test/widgets/scrollable_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/scrollable_semantics_traversal_order_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_semantics_traversal_order_test.dart b/packages/flutter/test/widgets/scrollable_semantics_traversal_order_test.dart
index db00d3c..0d75a69 100644
--- a/packages/flutter/test/widgets/scrollable_semantics_traversal_order_test.dart
+++ b/packages/flutter/test/widgets/scrollable_semantics_traversal_order_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/scrollable_test.dart

diff --git a/packages/flutter/test/widgets/scrollable_test.dart b/packages/flutter/test/widgets/scrollable_test.dart
index e2b2420..b9b4ec2 100644
--- a/packages/flutter/test/widgets/scrollable_test.dart
+++ b/packages/flutter/test/widgets/scrollable_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/scrollbar_test.dart

diff --git a/packages/flutter/test/widgets/scrollbar_test.dart b/packages/flutter/test/widgets/scrollbar_test.dart
index 0ad1a7e..e9c3c9ec 100644
--- a/packages/flutter/test/widgets/scrollbar_test.dart
+++ b/packages/flutter/test/widgets/scrollbar_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/src/physics/utils.dart' show nearEqual;
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/selectable_text_test.dart

diff --git a/packages/flutter/test/widgets/selectable_text_test.dart b/packages/flutter/test/widgets/selectable_text_test.dart
index 6bf9b06..a95af67 100644
--- a/packages/flutter/test/widgets/selectable_text_test.dart
+++ b/packages/flutter/test/widgets/selectable_text_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/cupertino.dart';

packages/flutter/test/widgets/semantics_10_test.dart

diff --git a/packages/flutter/test/widgets/semantics_10_test.dart b/packages/flutter/test/widgets/semantics_10_test.dart
index 5f625dc..7c8d00f 100644
--- a/packages/flutter/test/widgets/semantics_10_test.dart
+++ b/packages/flutter/test/widgets/semantics_10_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/semantics_11_test.dart

diff --git a/packages/flutter/test/widgets/semantics_11_test.dart b/packages/flutter/test/widgets/semantics_11_test.dart
index 67c6bec..e270d06 100644
--- a/packages/flutter/test/widgets/semantics_11_test.dart
+++ b/packages/flutter/test/widgets/semantics_11_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/semantics_1_test.dart

diff --git a/packages/flutter/test/widgets/semantics_1_test.dart b/packages/flutter/test/widgets/semantics_1_test.dart
index b95e973..9fa9d99 100644
--- a/packages/flutter/test/widgets/semantics_1_test.dart
+++ b/packages/flutter/test/widgets/semantics_1_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/semantics_2_test.dart

diff --git a/packages/flutter/test/widgets/semantics_2_test.dart b/packages/flutter/test/widgets/semantics_2_test.dart
index 1c4f1a9..8642f94 100644
--- a/packages/flutter/test/widgets/semantics_2_test.dart
+++ b/packages/flutter/test/widgets/semantics_2_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/semantics_3_test.dart

diff --git a/packages/flutter/test/widgets/semantics_3_test.dart b/packages/flutter/test/widgets/semantics_3_test.dart
index b0df811..e52481a 100644
--- a/packages/flutter/test/widgets/semantics_3_test.dart
+++ b/packages/flutter/test/widgets/semantics_3_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/semantics_4_test.dart

diff --git a/packages/flutter/test/widgets/semantics_4_test.dart b/packages/flutter/test/widgets/semantics_4_test.dart
index 9d34de4..0cab288 100644
--- a/packages/flutter/test/widgets/semantics_4_test.dart
+++ b/packages/flutter/test/widgets/semantics_4_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/semantics_5_test.dart

diff --git a/packages/flutter/test/widgets/semantics_5_test.dart b/packages/flutter/test/widgets/semantics_5_test.dart
index 16859cb..5d67c6b 100644
--- a/packages/flutter/test/widgets/semantics_5_test.dart
+++ b/packages/flutter/test/widgets/semantics_5_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/semantics_6_test.dart

diff --git a/packages/flutter/test/widgets/semantics_6_test.dart b/packages/flutter/test/widgets/semantics_6_test.dart
index 9ff67fb..3e477dc 100644
--- a/packages/flutter/test/widgets/semantics_6_test.dart
+++ b/packages/flutter/test/widgets/semantics_6_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/semantics_7_test.dart

diff --git a/packages/flutter/test/widgets/semantics_7_test.dart b/packages/flutter/test/widgets/semantics_7_test.dart
index 2ad88a3..b755c73 100644
--- a/packages/flutter/test/widgets/semantics_7_test.dart
+++ b/packages/flutter/test/widgets/semantics_7_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/semantics_8_test.dart

diff --git a/packages/flutter/test/widgets/semantics_8_test.dart b/packages/flutter/test/widgets/semantics_8_test.dart
index 9bd70bc..0afc48a 100644
--- a/packages/flutter/test/widgets/semantics_8_test.dart
+++ b/packages/flutter/test/widgets/semantics_8_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/semantics_9_test.dart

diff --git a/packages/flutter/test/widgets/semantics_9_test.dart b/packages/flutter/test/widgets/semantics_9_test.dart
index a7a6dde..1fdfbe4 100644
--- a/packages/flutter/test/widgets/semantics_9_test.dart
+++ b/packages/flutter/test/widgets/semantics_9_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/semantics_clipping_test.dart

diff --git a/packages/flutter/test/widgets/semantics_clipping_test.dart b/packages/flutter/test/widgets/semantics_clipping_test.dart
index c1811b1..16fc46e 100644
--- a/packages/flutter/test/widgets/semantics_clipping_test.dart
+++ b/packages/flutter/test/widgets/semantics_clipping_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/semantics_debugger_test.dart

diff --git a/packages/flutter/test/widgets/semantics_debugger_test.dart b/packages/flutter/test/widgets/semantics_debugger_test.dart
index f80cfaa..fb86995 100644
--- a/packages/flutter/test/widgets/semantics_debugger_test.dart
+++ b/packages/flutter/test/widgets/semantics_debugger_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show window;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/semantics_event_test.dart

diff --git a/packages/flutter/test/widgets/semantics_event_test.dart b/packages/flutter/test/widgets/semantics_event_test.dart
index dcf473d..87dbba3 100644
--- a/packages/flutter/test/widgets/semantics_event_test.dart
+++ b/packages/flutter/test/widgets/semantics_event_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/semantics.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/semantics_keep_alive_offstage_test.dart

diff --git a/packages/flutter/test/widgets/semantics_keep_alive_offstage_test.dart b/packages/flutter/test/widgets/semantics_keep_alive_offstage_test.dart
index f7dfd00..6ceccf8 100644
--- a/packages/flutter/test/widgets/semantics_keep_alive_offstage_test.dart
+++ b/packages/flutter/test/widgets/semantics_keep_alive_offstage_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/semantics_merge_test.dart

diff --git a/packages/flutter/test/widgets/semantics_merge_test.dart b/packages/flutter/test/widgets/semantics_merge_test.dart
index a4a997d..d1bf5b5 100644
--- a/packages/flutter/test/widgets/semantics_merge_test.dart
+++ b/packages/flutter/test/widgets/semantics_merge_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/semantics_test.dart

diff --git a/packages/flutter/test/widgets/semantics_test.dart b/packages/flutter/test/widgets/semantics_test.dart
index b4cff76..0f485d4 100644
--- a/packages/flutter/test/widgets/semantics_test.dart
+++ b/packages/flutter/test/widgets/semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math';
 import 'dart:ui';
 

packages/flutter/test/widgets/semantics_tester.dart

diff --git a/packages/flutter/test/widgets/semantics_tester.dart b/packages/flutter/test/widgets/semantics_tester.dart
index d944475..2a36463 100644
--- a/packages/flutter/test/widgets/semantics_tester.dart
+++ b/packages/flutter/test/widgets/semantics_tester.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show SemanticsFlag;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart

diff --git a/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart b/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart
index b94bb2d..a7f1022 100644
--- a/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart
+++ b/packages/flutter/test/widgets/semantics_tester_generateTestSemanticsExpressionForCurrentSemanticsTree_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome')
 import 'dart:async';
 import 'dart:io';

packages/flutter/test/widgets/semantics_tester_test.dart

diff --git a/packages/flutter/test/widgets/semantics_tester_test.dart b/packages/flutter/test/widgets/semantics_tester_test.dart
index d5d8d33..4024d95 100644
--- a/packages/flutter/test/widgets/semantics_tester_test.dart
+++ b/packages/flutter/test/widgets/semantics_tester_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/gestures.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/semantics_traversal_test.dart

diff --git a/packages/flutter/test/widgets/semantics_traversal_test.dart b/packages/flutter/test/widgets/semantics_traversal_test.dart
index b7ee4d0..5cb4042 100644
--- a/packages/flutter/test/widgets/semantics_traversal_test.dart
+++ b/packages/flutter/test/widgets/semantics_traversal_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:collection';
 import 'dart:math' as math;
 import 'dart:ui';

packages/flutter/test/widgets/semantics_zero_surface_size_test.dart

diff --git a/packages/flutter/test/widgets/semantics_zero_surface_size_test.dart b/packages/flutter/test/widgets/semantics_zero_surface_size_test.dart
index 7529e7e..3b801c0 100644
--- a/packages/flutter/test/widgets/semantics_zero_surface_size_test.dart
+++ b/packages/flutter/test/widgets/semantics_zero_surface_size_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/set_state_1_test.dart

diff --git a/packages/flutter/test/widgets/set_state_1_test.dart b/packages/flutter/test/widgets/set_state_1_test.dart
index e38629e..150ddd2 100644
--- a/packages/flutter/test/widgets/set_state_1_test.dart
+++ b/packages/flutter/test/widgets/set_state_1_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/set_state_2_test.dart

diff --git a/packages/flutter/test/widgets/set_state_2_test.dart b/packages/flutter/test/widgets/set_state_2_test.dart
index 60eb3f6..5b2cf13 100644
--- a/packages/flutter/test/widgets/set_state_2_test.dart
+++ b/packages/flutter/test/widgets/set_state_2_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/set_state_3_test.dart

diff --git a/packages/flutter/test/widgets/set_state_3_test.dart b/packages/flutter/test/widgets/set_state_3_test.dart
index d391225..1e9b537 100644
--- a/packages/flutter/test/widgets/set_state_3_test.dart
+++ b/packages/flutter/test/widgets/set_state_3_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/set_state_4_test.dart

diff --git a/packages/flutter/test/widgets/set_state_4_test.dart b/packages/flutter/test/widgets/set_state_4_test.dart
index 843cdd0..c65d6ea 100644
--- a/packages/flutter/test/widgets/set_state_4_test.dart
+++ b/packages/flutter/test/widgets/set_state_4_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/set_state_5_test.dart

diff --git a/packages/flutter/test/widgets/set_state_5_test.dart b/packages/flutter/test/widgets/set_state_5_test.dart
index 052032b..27969d3 100644
--- a/packages/flutter/test/widgets/set_state_5_test.dart
+++ b/packages/flutter/test/widgets/set_state_5_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/shader_mask_test.dart

diff --git a/packages/flutter/test/widgets/shader_mask_test.dart b/packages/flutter/test/widgets/shader_mask_test.dart
index 363475e..6400baa 100644
--- a/packages/flutter/test/widgets/shader_mask_test.dart
+++ b/packages/flutter/test/widgets/shader_mask_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' show Shader;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/shadow_test.dart

diff --git a/packages/flutter/test/widgets/shadow_test.dart b/packages/flutter/test/widgets/shadow_test.dart
index 3fdfca1..9f49651 100644
--- a/packages/flutter/test/widgets/shadow_test.dart
+++ b/packages/flutter/test/widgets/shadow_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 

packages/flutter/test/widgets/shape_decoration_test.dart

diff --git a/packages/flutter/test/widgets/shape_decoration_test.dart b/packages/flutter/test/widgets/shape_decoration_test.dart
index ab48e48..dbfc9ed 100644
--- a/packages/flutter/test/widgets/shape_decoration_test.dart
+++ b/packages/flutter/test/widgets/shape_decoration_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:typed_data';
 import 'dart:ui' as ui show Image;
 

packages/flutter/test/widgets/shortcuts_test.dart

diff --git a/packages/flutter/test/widgets/shortcuts_test.dart b/packages/flutter/test/widgets/shortcuts_test.dart
index 2f8d3c0..2f9fbfa 100644
--- a/packages/flutter/test/widgets/shortcuts_test.dart
+++ b/packages/flutter/test/widgets/shortcuts_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/widgets/simple_semantics_test.dart

diff --git a/packages/flutter/test/widgets/simple_semantics_test.dart b/packages/flutter/test/widgets/simple_semantics_test.dart
index b9b2c4e..dd9cdc1 100644
--- a/packages/flutter/test/widgets/simple_semantics_test.dart
+++ b/packages/flutter/test/widgets/simple_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/single_child_scroll_view_test.dart

diff --git a/packages/flutter/test/widgets/single_child_scroll_view_test.dart b/packages/flutter/test/widgets/single_child_scroll_view_test.dart
index be96c1c..d1071d7 100644
--- a/packages/flutter/test/widgets/single_child_scroll_view_test.dart
+++ b/packages/flutter/test/widgets/single_child_scroll_view_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/size_changed_layout_notification_test.dart

diff --git a/packages/flutter/test/widgets/size_changed_layout_notification_test.dart b/packages/flutter/test/widgets/size_changed_layout_notification_test.dart
index 6f8c8c8..2690cd5 100644
--- a/packages/flutter/test/widgets/size_changed_layout_notification_test.dart
+++ b/packages/flutter/test/widgets/size_changed_layout_notification_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/sized_box_test.dart

diff --git a/packages/flutter/test/widgets/sized_box_test.dart b/packages/flutter/test/widgets/sized_box_test.dart
index 76a46ae..c986ee8 100644
--- a/packages/flutter/test/widgets/sized_box_test.dart
+++ b/packages/flutter/test/widgets/sized_box_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/sliver_appbar_opacity_test.dart

diff --git a/packages/flutter/test/widgets/sliver_appbar_opacity_test.dart b/packages/flutter/test/widgets/sliver_appbar_opacity_test.dart
index 6b90e5b..f9bca3e 100644
--- a/packages/flutter/test/widgets/sliver_appbar_opacity_test.dart
+++ b/packages/flutter/test/widgets/sliver_appbar_opacity_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/sliver_constraints_test.dart

diff --git a/packages/flutter/test/widgets/sliver_constraints_test.dart b/packages/flutter/test/widgets/sliver_constraints_test.dart
index fc0fd30..804d91c 100644
--- a/packages/flutter/test/widgets/sliver_constraints_test.dart
+++ b/packages/flutter/test/widgets/sliver_constraints_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/sliver_fill_remaining_test.dart

diff --git a/packages/flutter/test/widgets/sliver_fill_remaining_test.dart b/packages/flutter/test/widgets/sliver_fill_remaining_test.dart
index 2f86b71..2c4b039 100644
--- a/packages/flutter/test/widgets/sliver_fill_remaining_test.dart
+++ b/packages/flutter/test/widgets/sliver_fill_remaining_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/sliver_fill_viewport_test.dart

diff --git a/packages/flutter/test/widgets/sliver_fill_viewport_test.dart b/packages/flutter/test/widgets/sliver_fill_viewport_test.dart
index 00b9abf..e329d17 100644
--- a/packages/flutter/test/widgets/sliver_fill_viewport_test.dart
+++ b/packages/flutter/test/widgets/sliver_fill_viewport_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/sliver_list_test.dart

diff --git a/packages/flutter/test/widgets/sliver_list_test.dart b/packages/flutter/test/widgets/sliver_list_test.dart
index 2549194..0ad1bfe 100644
--- a/packages/flutter/test/widgets/sliver_list_test.dart
+++ b/packages/flutter/test/widgets/sliver_list_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/sliver_prototype_item_extent_test.dart

diff --git a/packages/flutter/test/widgets/sliver_prototype_item_extent_test.dart b/packages/flutter/test/widgets/sliver_prototype_item_extent_test.dart
index cfe354e..963fcde 100644
--- a/packages/flutter/test/widgets/sliver_prototype_item_extent_test.dart
+++ b/packages/flutter/test/widgets/sliver_prototype_item_extent_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/sliver_semantics_test.dart

diff --git a/packages/flutter/test/widgets/sliver_semantics_test.dart b/packages/flutter/test/widgets/sliver_semantics_test.dart
index 84a44b5..53f03b8 100644
--- a/packages/flutter/test/widgets/sliver_semantics_test.dart
+++ b/packages/flutter/test/widgets/sliver_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/sliver_visibility_test.dart

diff --git a/packages/flutter/test/widgets/sliver_visibility_test.dart b/packages/flutter/test/widgets/sliver_visibility_test.dart
index 10a3699..6218541 100644
--- a/packages/flutter/test/widgets/sliver_visibility_test.dart
+++ b/packages/flutter/test/widgets/sliver_visibility_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/slivers_appbar_floating_pinned_test.dart

diff --git a/packages/flutter/test/widgets/slivers_appbar_floating_pinned_test.dart b/packages/flutter/test/widgets/slivers_appbar_floating_pinned_test.dart
index 19e56b9..ec4c086 100644
--- a/packages/flutter/test/widgets/slivers_appbar_floating_pinned_test.dart
+++ b/packages/flutter/test/widgets/slivers_appbar_floating_pinned_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/slivers_appbar_floating_test.dart

diff --git a/packages/flutter/test/widgets/slivers_appbar_floating_test.dart b/packages/flutter/test/widgets/slivers_appbar_floating_test.dart
index 8a50a82..ff21465 100644
--- a/packages/flutter/test/widgets/slivers_appbar_floating_test.dart
+++ b/packages/flutter/test/widgets/slivers_appbar_floating_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/slivers_appbar_pinned_test.dart

diff --git a/packages/flutter/test/widgets/slivers_appbar_pinned_test.dart b/packages/flutter/test/widgets/slivers_appbar_pinned_test.dart
index 6fe3f4d..abcd0e0 100644
--- a/packages/flutter/test/widgets/slivers_appbar_pinned_test.dart
+++ b/packages/flutter/test/widgets/slivers_appbar_pinned_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/slivers_appbar_scrolling_test.dart

diff --git a/packages/flutter/test/widgets/slivers_appbar_scrolling_test.dart b/packages/flutter/test/widgets/slivers_appbar_scrolling_test.dart
index 9728410..3b62cda 100644
--- a/packages/flutter/test/widgets/slivers_appbar_scrolling_test.dart
+++ b/packages/flutter/test/widgets/slivers_appbar_scrolling_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/slivers_appbar_stretch_test.dart

diff --git a/packages/flutter/test/widgets/slivers_appbar_stretch_test.dart b/packages/flutter/test/widgets/slivers_appbar_stretch_test.dart
index 87c7baa..8293837 100644
--- a/packages/flutter/test/widgets/slivers_appbar_stretch_test.dart
+++ b/packages/flutter/test/widgets/slivers_appbar_stretch_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/widgets/slivers_block_global_key_test.dart

diff --git a/packages/flutter/test/widgets/slivers_block_global_key_test.dart b/packages/flutter/test/widgets/slivers_block_global_key_test.dart
index 3975559..b9bab1f 100644
--- a/packages/flutter/test/widgets/slivers_block_global_key_test.dart
+++ b/packages/flutter/test/widgets/slivers_block_global_key_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/slivers_block_test.dart

diff --git a/packages/flutter/test/widgets/slivers_block_test.dart b/packages/flutter/test/widgets/slivers_block_test.dart
index 85a1f1e..afac7c4 100644
--- a/packages/flutter/test/widgets/slivers_block_test.dart
+++ b/packages/flutter/test/widgets/slivers_block_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/slivers_evil_test.dart

diff --git a/packages/flutter/test/widgets/slivers_evil_test.dart b/packages/flutter/test/widgets/slivers_evil_test.dart
index 4574f25..d4b22e9 100644
--- a/packages/flutter/test/widgets/slivers_evil_test.dart
+++ b/packages/flutter/test/widgets/slivers_evil_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/physics.dart';

packages/flutter/test/widgets/slivers_keepalive_test.dart

diff --git a/packages/flutter/test/widgets/slivers_keepalive_test.dart b/packages/flutter/test/widgets/slivers_keepalive_test.dart
index c16b787..c0e58ac 100644
--- a/packages/flutter/test/widgets/slivers_keepalive_test.dart
+++ b/packages/flutter/test/widgets/slivers_keepalive_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/slivers_padding_test.dart

diff --git a/packages/flutter/test/widgets/slivers_padding_test.dart b/packages/flutter/test/widgets/slivers_padding_test.dart
index 58728dc..93abafc 100644
--- a/packages/flutter/test/widgets/slivers_padding_test.dart
+++ b/packages/flutter/test/widgets/slivers_padding_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/slivers_protocol_test.dart

diff --git a/packages/flutter/test/widgets/slivers_protocol_test.dart b/packages/flutter/test/widgets/slivers_protocol_test.dart
index deb480d..983329e 100644
--- a/packages/flutter/test/widgets/slivers_protocol_test.dart
+++ b/packages/flutter/test/widgets/slivers_protocol_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/slivers_test.dart

diff --git a/packages/flutter/test/widgets/slivers_test.dart b/packages/flutter/test/widgets/slivers_test.dart
index 7bb16a8..412a986 100644
--- a/packages/flutter/test/widgets/slivers_test.dart
+++ b/packages/flutter/test/widgets/slivers_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/spacer_test.dart

diff --git a/packages/flutter/test/widgets/spacer_test.dart b/packages/flutter/test/widgets/spacer_test.dart
index 15fccf3..354b6c2 100644
--- a/packages/flutter/test/widgets/spacer_test.dart
+++ b/packages/flutter/test/widgets/spacer_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/stack_test.dart

diff --git a/packages/flutter/test/widgets/stack_test.dart b/packages/flutter/test/widgets/stack_test.dart
index 7447140..839915b 100644
--- a/packages/flutter/test/widgets/stack_test.dart
+++ b/packages/flutter/test/widgets/stack_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/state_setting_in_scrollables_test.dart

diff --git a/packages/flutter/test/widgets/state_setting_in_scrollables_test.dart b/packages/flutter/test/widgets/state_setting_in_scrollables_test.dart
index 8855579..071af41 100644
--- a/packages/flutter/test/widgets/state_setting_in_scrollables_test.dart
+++ b/packages/flutter/test/widgets/state_setting_in_scrollables_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/stateful_component_test.dart

diff --git a/packages/flutter/test/widgets/stateful_component_test.dart b/packages/flutter/test/widgets/stateful_component_test.dart
index b67042c..9b9b550 100644
--- a/packages/flutter/test/widgets/stateful_component_test.dart
+++ b/packages/flutter/test/widgets/stateful_component_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/stateful_components_test.dart

diff --git a/packages/flutter/test/widgets/stateful_components_test.dart b/packages/flutter/test/widgets/stateful_components_test.dart
index 0b4fd27..777a820 100644
--- a/packages/flutter/test/widgets/stateful_components_test.dart
+++ b/packages/flutter/test/widgets/stateful_components_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/states.dart

diff --git a/packages/flutter/test/widgets/states.dart b/packages/flutter/test/widgets/states.dart
index 02d38fe..76064a6 100644
--- a/packages/flutter/test/widgets/states.dart
+++ b/packages/flutter/test/widgets/states.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 const List<String> kStates = <String>[
   'Alabama',
   'Alaska',

packages/flutter/test/widgets/status_transitions_test.dart

diff --git a/packages/flutter/test/widgets/status_transitions_test.dart b/packages/flutter/test/widgets/status_transitions_test.dart
index bd8a51d..ce15813 100644
--- a/packages/flutter/test/widgets/status_transitions_test.dart
+++ b/packages/flutter/test/widgets/status_transitions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/syncing_test.dart

diff --git a/packages/flutter/test/widgets/syncing_test.dart b/packages/flutter/test/widgets/syncing_test.dart
index 7a947e2..56c4920 100644
--- a/packages/flutter/test/widgets/syncing_test.dart
+++ b/packages/flutter/test/widgets/syncing_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/table_test.dart

diff --git a/packages/flutter/test/widgets/table_test.dart b/packages/flutter/test/widgets/table_test.dart
index 46df669..4852d81 100644
--- a/packages/flutter/test/widgets/table_test.dart
+++ b/packages/flutter/test/widgets/table_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/test_border.dart

diff --git a/packages/flutter/test/widgets/test_border.dart b/packages/flutter/test/widgets/test_border.dart
index e811064..26b9dac 100644
--- a/packages/flutter/test/widgets/test_border.dart
+++ b/packages/flutter/test/widgets/test_border.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/material.dart';
 
 typedef Logger = void Function(String caller);

packages/flutter/test/widgets/test_widgets.dart

diff --git a/packages/flutter/test/widgets/test_widgets.dart b/packages/flutter/test/widgets/test_widgets.dart
index c847ff4..3ec1db9 100644
--- a/packages/flutter/test/widgets/test_widgets.dart
+++ b/packages/flutter/test/widgets/test_widgets.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/text.dart

diff --git a/packages/flutter/test/widgets/text.dart b/packages/flutter/test/widgets/text.dart
index 04cf7be..deb8bde 100644
--- a/packages/flutter/test/widgets/text.dart
+++ b/packages/flutter/test/widgets/text.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/text_formatter_test.dart

diff --git a/packages/flutter/test/widgets/text_formatter_test.dart b/packages/flutter/test/widgets/text_formatter_test.dart
index 83844ff..b37d8a3 100644
--- a/packages/flutter/test/widgets/text_formatter_test.dart
+++ b/packages/flutter/test/widgets/text_formatter_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/text_golden_test.dart

diff --git a/packages/flutter/test/widgets/text_golden_test.dart b/packages/flutter/test/widgets/text_golden_test.dart
index 2247518..3f38ee1 100644
--- a/packages/flutter/test/widgets/text_golden_test.dart
+++ b/packages/flutter/test/widgets/text_golden_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 @TestOn('!chrome') // Flaky on web
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/text_selection_test.dart

diff --git a/packages/flutter/test/widgets/text_selection_test.dart b/packages/flutter/test/widgets/text_selection_test.dart
index 4fae7a1..38ab7db 100644
--- a/packages/flutter/test/widgets/text_selection_test.dart
+++ b/packages/flutter/test/widgets/text_selection_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart' show PointerDeviceKind;
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/text_semantics_test.dart

diff --git a/packages/flutter/test/widgets/text_semantics_test.dart b/packages/flutter/test/widgets/text_semantics_test.dart
index dc7e0ff..da71911 100644
--- a/packages/flutter/test/widgets/text_semantics_test.dart
+++ b/packages/flutter/test/widgets/text_semantics_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/gestures.dart';

packages/flutter/test/widgets/text_test.dart

diff --git a/packages/flutter/test/widgets/text_test.dart b/packages/flutter/test/widgets/text_test.dart
index c307c4e..c9982b9 100644
--- a/packages/flutter/test/widgets/text_test.dart
+++ b/packages/flutter/test/widgets/text_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:ui' as ui;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/ticker_mode_test.dart

diff --git a/packages/flutter/test/widgets/ticker_mode_test.dart b/packages/flutter/test/widgets/ticker_mode_test.dart
index b6d3ba8..cb32eb3 100644
--- a/packages/flutter/test/widgets/ticker_mode_test.dart
+++ b/packages/flutter/test/widgets/ticker_mode_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/ticker_provider_test.dart

diff --git a/packages/flutter/test/widgets/ticker_provider_test.dart b/packages/flutter/test/widgets/ticker_provider_test.dart
index ffc17d9..70ea6a5 100644
--- a/packages/flutter/test/widgets/ticker_provider_test.dart
+++ b/packages/flutter/test/widgets/ticker_provider_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/title_test.dart

diff --git a/packages/flutter/test/widgets/title_test.dart b/packages/flutter/test/widgets/title_test.dart
index 03e907b..9385269 100644
--- a/packages/flutter/test/widgets/title_test.dart
+++ b/packages/flutter/test/widgets/title_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/services.dart';

packages/flutter/test/widgets/tracking_scroll_controller_test.dart

diff --git a/packages/flutter/test/widgets/tracking_scroll_controller_test.dart b/packages/flutter/test/widgets/tracking_scroll_controller_test.dart
index 14b22ce..018cb3e 100644
--- a/packages/flutter/test/widgets/tracking_scroll_controller_test.dart
+++ b/packages/flutter/test/widgets/tracking_scroll_controller_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/transform_test.dart

diff --git a/packages/flutter/test/widgets/transform_test.dart b/packages/flutter/test/widgets/transform_test.dart
index a310fdb..510d48c 100644
--- a/packages/flutter/test/widgets/transform_test.dart
+++ b/packages/flutter/test/widgets/transform_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/widgets/transformed_scrollable_test.dart

diff --git a/packages/flutter/test/widgets/transformed_scrollable_test.dart b/packages/flutter/test/widgets/transformed_scrollable_test.dart
index 5f78398..144e673 100644
--- a/packages/flutter/test/widgets/transformed_scrollable_test.dart
+++ b/packages/flutter/test/widgets/transformed_scrollable_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/transitions_test.dart

diff --git a/packages/flutter/test/widgets/transitions_test.dart b/packages/flutter/test/widgets/transitions_test.dart
index 82662c4..a01e41d 100644
--- a/packages/flutter/test/widgets/transitions_test.dart
+++ b/packages/flutter/test/widgets/transitions_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';

packages/flutter/test/widgets/tween_animation_builder_test.dart

diff --git a/packages/flutter/test/widgets/tween_animation_builder_test.dart b/packages/flutter/test/widgets/tween_animation_builder_test.dart
index b8bd545..44beab2 100644
--- a/packages/flutter/test/widgets/tween_animation_builder_test.dart
+++ b/packages/flutter/test/widgets/tween_animation_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/unique_widget_test.dart

diff --git a/packages/flutter/test/widgets/unique_widget_test.dart b/packages/flutter/test/widgets/unique_widget_test.dart
index 1ca079b..20c42cf 100644
--- a/packages/flutter/test/widgets/unique_widget_test.dart
+++ b/packages/flutter/test/widgets/unique_widget_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 

packages/flutter/test/widgets/value_listenable_builder_test.dart

diff --git a/packages/flutter/test/widgets/value_listenable_builder_test.dart b/packages/flutter/test/widgets/value_listenable_builder_test.dart
index 717e2ad..a2b472a 100644
--- a/packages/flutter/test/widgets/value_listenable_builder_test.dart
+++ b/packages/flutter/test/widgets/value_listenable_builder_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/widgets/visibility_test.dart

diff --git a/packages/flutter/test/widgets/visibility_test.dart b/packages/flutter/test/widgets/visibility_test.dart
index 3e5a9ad..3ad71a6 100644
--- a/packages/flutter/test/widgets/visibility_test.dart
+++ b/packages/flutter/test/widgets/visibility_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/widgets/widget_inspector_init_with_structured_error_test.dart

diff --git a/packages/flutter/test/widgets/widget_inspector_init_with_structured_error_test.dart b/packages/flutter/test/widgets/widget_inspector_init_with_structured_error_test.dart
index 50fe302..3053570 100644
--- a/packages/flutter/test/widgets/widget_inspector_init_with_structured_error_test.dart
+++ b/packages/flutter/test/widgets/widget_inspector_init_with_structured_error_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';

packages/flutter/test/widgets/widget_inspector_structure_error_test.dart

diff --git a/packages/flutter/test/widgets/widget_inspector_structure_error_test.dart b/packages/flutter/test/widgets/widget_inspector_structure_error_test.dart
index c87746d..bf05b09 100644
--- a/packages/flutter/test/widgets/widget_inspector_structure_error_test.dart
+++ b/packages/flutter/test/widgets/widget_inspector_structure_error_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 

packages/flutter/test/widgets/widget_inspector_test.dart

diff --git a/packages/flutter/test/widgets/widget_inspector_test.dart b/packages/flutter/test/widgets/widget_inspector_test.dart
index 55df87a..c470bdd 100644
--- a/packages/flutter/test/widgets/widget_inspector_test.dart
+++ b/packages/flutter/test/widgets/widget_inspector_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:math';
@@ -1673,7 +1675,7 @@
       _CreationLocation location = knownLocations[id];
       expect(location.file, equals(file));
       // ClockText widget.
-      expect(location.line, equals(53));
+      expect(location.line, equals(55));
       expect(location.column, equals(9));
       expect(count, equals(1));
 
@@ -1682,7 +1684,7 @@
       location = knownLocations[id];
       expect(location.file, equals(file));
       // Text widget in _ClockTextState build method.
-      expect(location.line, equals(91));
+      expect(location.line, equals(93));
       expect(location.column, equals(12));
       expect(count, equals(1));
 
@@ -1707,7 +1709,7 @@
       location = knownLocations[id];
       expect(location.file, equals(file));
       // ClockText widget.
-      expect(location.line, equals(53));
+      expect(location.line, equals(55));
       expect(location.column, equals(9));
       expect(count, equals(3)); // 3 clock widget instances rebuilt.
 
@@ -1716,7 +1718,7 @@
       location = knownLocations[id];
       expect(location.file, equals(file));
       // Text widget in _ClockTextState build method.
-      expect(location.line, equals(91));
+      expect(location.line, equals(93));
       expect(location.column, equals(12));
       expect(count, equals(3)); // 3 clock widget instances rebuilt.
 

packages/flutter/test/widgets/widget_inspector_test_utils.dart

diff --git a/packages/flutter/test/widgets/widget_inspector_test_utils.dart b/packages/flutter/test/widgets/widget_inspector_test_utils.dart
index f5d3184..3ce8dd4 100644
--- a/packages/flutter/test/widgets/widget_inspector_test_utils.dart
+++ b/packages/flutter/test/widgets/widget_inspector_test_utils.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:async';
 import 'dart:convert';
 

packages/flutter/test/widgets/wrap_test.dart

diff --git a/packages/flutter/test/widgets/wrap_test.dart b/packages/flutter/test/widgets/wrap_test.dart
index 46b7b83..66eba8f 100644
--- a/packages/flutter/test/widgets/wrap_test.dart
+++ b/packages/flutter/test/widgets/wrap_test.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';