add missing type parameter on methods (#22096)

diff --git a/dev/manual_tests/lib/animated_icons.dart b/dev/manual_tests/lib/animated_icons.dart
index 3cf6f10..b857423 100644
--- a/dev/manual_tests/lib/animated_icons.dart
+++ b/dev/manual_tests/lib/animated_icons.dart

@@ -22,7 +22,7 @@
   @override
   Widget build(BuildContext context) {
     return ListView(
-      children: samples.map((IconSample s) => IconSampleRow(s)).toList(),
+      children: samples.map<IconSampleRow>((IconSample s) => IconSampleRow(s)).toList(),
     );
   }
 }

diff --git a/dev/manual_tests/lib/material_arc.dart b/dev/manual_tests/lib/material_arc.dart
index 5b7fada..4d9ece5 100644
--- a/dev/manual_tests/lib/material_arc.dart
+++ b/dev/manual_tests/lib/material_arc.dart

@@ -452,7 +452,7 @@
         appBar: AppBar(
           title: const Text('Animation'),
           bottom: TabBar(
-            tabs: _allDemos.map((_ArcDemo demo) => Tab(text: demo.title)).toList(),
+            tabs: _allDemos.map<Tab>((_ArcDemo demo) => Tab(text: demo.title)).toList(),
           ),
         ),
         floatingActionButton: Builder(
@@ -466,7 +466,7 @@
           },
         ),
         body: TabBarView(
-          children: _allDemos.map((_ArcDemo demo) => demo.builder(demo)).toList()
+          children: _allDemos.map<Widget>((_ArcDemo demo) => demo.builder(demo)).toList()
         )
       )
     );

diff --git a/dev/manual_tests/lib/page_view.dart b/dev/manual_tests/lib/page_view.dart
index 5487f08..b882f31 100644
--- a/dev/manual_tests/lib/page_view.dart
+++ b/dev/manual_tests/lib/page_view.dart

@@ -119,7 +119,7 @@
 
   Widget _buildBody(BuildContext context) {
     return PageView(
-      children: cardModels.map(buildCard).toList(),
+      children: cardModels.map<Widget>(buildCard).toList(),
       // TODO(abarth): itemsWrap: itemsWrap,
       scrollDirection: scrollDirection,
     );

diff --git a/dev/manual_tests/lib/text.dart b/dev/manual_tests/lib/text.dart
index 938b532..0244f3e 100644
--- a/dev/manual_tests/lib/text.dart
+++ b/dev/manual_tests/lib/text.dart

@@ -189,7 +189,7 @@
     switch (_random.nextInt(10)) {
       case 0:
         if (value == null)
-          return pickFromList(_random, Colors.primaries)[(_random.nextInt(9) + 1) * 100];
+          return pickFromList<MaterialColor>(_random, Colors.primaries)[(_random.nextInt(9) + 1) * 100];
         switch (_random.nextInt(4)) {
           case 0:
             return value.withAlpha(value.alpha + _random.nextInt(10) - 5);
@@ -240,7 +240,7 @@
       case 0:
         return null;
       case 1:
-        return pickFromList(_random, TextDecorationStyle.values);
+        return pickFromList<TextDecorationStyle>(_random, TextDecorationStyle.values);
     }
     return value;
   }
@@ -250,7 +250,7 @@
       case 0:
         return null;
       case 1:
-        return pickFromList(_random, FontWeight.values);
+        return pickFromList<FontWeight>(_random, FontWeight.values);
     }
     return value;
   }
@@ -260,7 +260,7 @@
       case 0:
         return null;
       case 1:
-        return pickFromList(_random, FontStyle.values);
+        return pickFromList<FontStyle>(_random, FontStyle.values);
     }
     return value;
   }
@@ -938,7 +938,7 @@
       if (mounted && intrinsicKey.currentContext.size.height != controlKey.currentContext.size.height) {
         debugPrint('Found some text that unexpectedly renders at different heights.');
         debugPrint('Text: $_text');
-        debugPrint(_text.runes.map((int index) => 'U+' + index.toRadixString(16).padLeft(4, '0')).join(' '));
+        debugPrint(_text.runes.map<String>((int index) => 'U+' + index.toRadixString(16).padLeft(4, '0')).join(' '));
         setState(() {
           _ticker.stop();
         });
@@ -1045,7 +1045,7 @@
                     FlatButton(
                       onPressed: _ticker.isActive ? null : () {
                         print('The currently visible text is: $_text');
-                        print(_text.runes.map((int value) => 'U+${value.toRadixString(16).padLeft(4, '0').toUpperCase()}').join(' '));
+                        print(_text.runes.map<String>((int value) => 'U+${value.toRadixString(16).padLeft(4, '0').toUpperCase()}').join(' '));
                       },
                       child: const Text('DUMP TEXT TO LOGS'),
                     ),
@@ -2109,7 +2109,7 @@
     Range(0x2ceb0, 0x2ebe0),
     Range(0x2f800, 0x2fa1d),
   ];
-  final Range range = pickFromList(random, characterRanges);
+  final Range range = pickFromList<Range>(random, characterRanges);
   if (range.start == range.end)
     return range.start;
   return range.start + random.nextInt(range.end - range.start);

diff --git a/dev/manual_tests/test/card_collection_test.dart b/dev/manual_tests/test/card_collection_test.dart
index 3ed2a1b..8de4efb 100644
--- a/dev/manual_tests/test/card_collection_test.dart
+++ b/dev/manual_tests/test/card_collection_test.dart

@@ -12,7 +12,7 @@
 
 void main() {
   testWidgets('Card Collection smoke test', (WidgetTester tester) async {
-    HttpOverrides.runZoned(() async {
+    HttpOverrides.runZoned<Future<void>>(() async {
       card_collection.main(); // builds the app and schedules a frame but doesn't trigger one
       await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
       await tester.pump(); // triggers a frame

diff --git a/dev/manual_tests/test/color_testing_demo_test.dart b/dev/manual_tests/test/color_testing_demo_test.dart
index 9c3b16e..eca5509 100644
--- a/dev/manual_tests/test/color_testing_demo_test.dart
+++ b/dev/manual_tests/test/color_testing_demo_test.dart

@@ -12,7 +12,7 @@
 
 void main() {
   testWidgets('Color testing demo smoke test', (WidgetTester tester) async {
-    HttpOverrides.runZoned(() async {
+    HttpOverrides.runZoned<Future<void>>(() async {
       color_testing_demo.main(); // builds the app and schedules a frame but doesn't trigger one
       await tester.pump(); // see https://github.com/flutter/flutter/issues/1865
       await tester.pump(); // triggers a frame