enable lint prefer_generic_function_type_aliases (#21680)

diff --git a/dev/bots/analyze.dart b/dev/bots/analyze.dart
index e9e8a76..ec41f2c 100644
--- a/dev/bots/analyze.dart
+++ b/dev/bots/analyze.dart

@@ -11,7 +11,7 @@
 
 import 'run_command.dart';
 
-typedef Future<Null> ShardRunner();
+typedef ShardRunner = Future<Null> Function();
 
 final String flutterRoot = path.dirname(path.dirname(path.dirname(path.fromUri(Platform.script))));
 final String flutter = path.join(flutterRoot, 'bin', Platform.isWindows ? 'flutter.bat' : 'flutter');

diff --git a/dev/bots/prepare_package.dart b/dev/bots/prepare_package.dart
index 64f8ed6..6926763 100644
--- a/dev/bots/prepare_package.dart
+++ b/dev/bots/prepare_package.dart

@@ -175,7 +175,7 @@
   }
 }
 
-typedef Future<Uint8List> HttpReader(Uri url, {Map<String, String> headers});
+typedef HttpReader = Future<Uint8List> Function(Uri url, {Map<String, String> headers});
 
 /// Creates a pre-populated Flutter archive from a git repo.
 class ArchiveCreator {

diff --git a/dev/bots/test.dart b/dev/bots/test.dart
index 983f796..32e083a 100644
--- a/dev/bots/test.dart
+++ b/dev/bots/test.dart

@@ -9,7 +9,7 @@
 
 import 'run_command.dart';
 
-typedef Future<Null> ShardRunner();
+typedef ShardRunner = Future<Null> Function();
 
 final String flutterRoot = path.dirname(path.dirname(path.dirname(path.fromUri(Platform.script))));
 final String flutter = path.join(flutterRoot, 'bin', Platform.isWindows ? 'flutter.bat' : 'flutter');

diff --git a/dev/bots/test/fake_process_manager.dart b/dev/bots/test/fake_process_manager.dart
index 719cf6e..779d7a5 100644
--- a/dev/bots/test/fake_process_manager.dart
+++ b/dev/bots/test/fake_process_manager.dart

@@ -151,7 +151,7 @@
 }
 
 /// Callback used to receive stdin input when it occurs.
-typedef void StringReceivedCallback(String received);
+typedef StringReceivedCallback = void Function(String received);
 
 /// A stream consumer class that consumes UTF8 strings as lists of ints.
 class StringStreamConsumer implements StreamConsumer<List<int>> {

diff --git a/dev/devicelab/lib/framework/framework.dart b/dev/devicelab/lib/framework/framework.dart
index 5bf7edb..f3583f0 100644
--- a/dev/devicelab/lib/framework/framework.dart
+++ b/dev/devicelab/lib/framework/framework.dart

@@ -20,7 +20,7 @@
 
 /// Represents a unit of work performed in the CI environment that can
 /// succeed, fail and be retried independently of others.
-typedef Future<TaskResult> TaskFunction();
+typedef TaskFunction = Future<TaskResult> Function();
 
 bool _isTaskRegistered = false;
 

diff --git a/dev/devicelab/test/adb_test.dart b/dev/devicelab/test/adb_test.dart
index 525746f..17c0736 100644
--- a/dev/devicelab/test/adb_test.dart
+++ b/dev/devicelab/test/adb_test.dart

@@ -122,7 +122,7 @@
   );
 }
 
-typedef dynamic ExitErrorFactory();
+typedef ExitErrorFactory = dynamic Function();
 
 class CommandArgs {
   CommandArgs({ this.command, this.arguments, this.environment });

diff --git a/dev/integration_tests/channels/lib/src/test_step.dart b/dev/integration_tests/channels/lib/src/test_step.dart
index 04394f2..39caab2 100644
--- a/dev/integration_tests/channels/lib/src/test_step.dart
+++ b/dev/integration_tests/channels/lib/src/test_step.dart

@@ -11,7 +11,7 @@
 
 enum TestStatus { ok, pending, failed, complete }
 
-typedef Future<TestStepResult> TestStep();
+typedef TestStep = Future<TestStepResult> Function();
 
 const String nothing = '-';
 

diff --git a/dev/integration_tests/platform_interaction/lib/src/test_step.dart b/dev/integration_tests/platform_interaction/lib/src/test_step.dart
index 7313e57..1da4766 100644
--- a/dev/integration_tests/platform_interaction/lib/src/test_step.dart
+++ b/dev/integration_tests/platform_interaction/lib/src/test_step.dart

@@ -8,7 +8,7 @@
 
 enum TestStatus { ok, pending, failed, complete }
 
-typedef Future<TestStepResult> TestStep();
+typedef TestStep = Future<TestStepResult> Function();
 
 const String nothing = '-';
 

diff --git a/dev/manual_tests/lib/material_arc.dart b/dev/manual_tests/lib/material_arc.dart
index e4afb81..06cdf9f 100644
--- a/dev/manual_tests/lib/material_arc.dart
+++ b/dev/manual_tests/lib/material_arc.dart

@@ -396,7 +396,7 @@
   }
 }
 
-typedef Widget _DemoBuilder(_ArcDemo demo);
+typedef _DemoBuilder = Widget Function(_ArcDemo demo);
 
 class _ArcDemo {
   _ArcDemo(this.title, this.builder, TickerProvider vsync)

diff --git a/dev/manual_tests/lib/overlay_geometry.dart b/dev/manual_tests/lib/overlay_geometry.dart
index e73cb75..3f1cb37 100644
--- a/dev/manual_tests/lib/overlay_geometry.dart
+++ b/dev/manual_tests/lib/overlay_geometry.dart

@@ -92,7 +92,7 @@
   OverlayGeometryAppState createState() => OverlayGeometryAppState();
 }
 
-typedef void CardTapCallback(GlobalKey targetKey, Offset globalPosition);
+typedef CardTapCallback = void Function(GlobalKey targetKey, Offset globalPosition);
 
 class CardBuilder extends SliverChildDelegate {
   CardBuilder({ this.cardModels, this.onTapUp });