diff --git a/packages/flutter_tools/test/integration.shard/break_on_framework_exceptions_test.dart b/packages/flutter_tools/test/integration.shard/break_on_framework_exceptions_test.dart
index 1ad607c47b..b127405dde 100644
--- a/packages/flutter_tools/test/integration.shard/break_on_framework_exceptions_test.dart
+++ b/packages/flutter_tools/test/integration.shard/break_on_framework_exceptions_test.dart
@@ -2,8 +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
-
 // TODO(gspencergoog): Remove this tag once this test's state leaks/test
 // dependencies have been fixed.
 // https://github.com/flutter/flutter/issues/85160
@@ -18,7 +16,7 @@ import 'test_driver.dart';
 import 'test_utils.dart';
 
 void main() {
-  Directory tempDir;
+  late Directory tempDir;
 
   setUp(() async {
     tempDir = createResolvedTempDirectorySync('break_on_framework_exceptions.');
@@ -43,7 +41,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'AnimationController listener';"));
   });
 
@@ -62,7 +60,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'AnimationController status listener';"));
   });
 
@@ -81,7 +79,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'ValueNotifier listener';"));
   });
 
@@ -108,7 +106,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'while handling a gesture';"));
   });
 
@@ -126,7 +124,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'platform message callback';"));
   });
 
@@ -147,7 +145,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'cannot build child';"));
   });
 
@@ -171,7 +169,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'onChanged';"));
   });
 
@@ -197,7 +195,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'onEditingComplete';"));
   });
 
@@ -219,7 +217,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'onSelectionChanged';"));
   });
 
@@ -238,7 +236,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'action listener';"));
   });
 
@@ -257,7 +255,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'pointer route';"));
   });
 
@@ -277,7 +275,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'PointerSignalResolver callback';"));
   });
 
@@ -297,7 +295,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'highlight mode listener';"));
   });
 
@@ -324,7 +322,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'onHover';"));
   });
 
@@ -350,7 +348,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'setImage';"));
   });
 
@@ -373,7 +371,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'onError';"));
   });
 
@@ -392,7 +390,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'LayoutBuilder.builder';"));
   });
 
@@ -411,7 +409,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw '_CallbackHookProvider.callback';"));
   });
 
@@ -429,7 +427,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'TimingsCallback';"));
   });
 
@@ -450,7 +448,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'scheduled task';"));
   });
 
@@ -468,7 +466,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'FrameCallback';"));
   });
 
@@ -494,7 +492,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'create element';"));
   });
 
@@ -517,7 +515,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'performLayout';"));
   });
 
@@ -543,7 +541,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'performResize';"));
   });
 
@@ -586,7 +584,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'performLayout without resize';"));
   });
 
@@ -609,7 +607,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'StatelessWidget.build';"));
   });
 
@@ -637,7 +635,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'StatefulWidget.build';"));
   });
 
@@ -669,7 +667,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'dispose';"));
   });
 
@@ -717,7 +715,7 @@ void main() {
     await flutter.test(withDebugger: true, pauseOnExceptions: true);
     await flutter.waitForPause();
 
-    final int breakLine = (await flutter.getSourceLocation()).line;
+    final int? breakLine = (await flutter.getSourceLocation())?.line;
     expect(breakLine, project.lineContaining(project.test, "throw 'rebuild';"));
   });
 }
@@ -726,8 +724,8 @@ class TestProject extends Project {
   TestProject(this.testBody, { this.setup, this.classes });
 
   final String testBody;
-  final String setup;
-  final String classes;
+  final String? setup;
+  final String? classes;
 
   @override
   final String pubspec = '''
diff --git a/packages/flutter_tools/test/integration.shard/test_data/background_project.dart b/packages/flutter_tools/test/integration.shard/test_data/background_project.dart
index 68b9674460..13e37f1ea0 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/background_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/background_project.dart
@@ -2,8 +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
-
 import '../test_utils.dart';
 import 'project.dart';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/basic_project.dart b/packages/flutter_tools/test/integration.shard/test_data/basic_project.dart
index 5f50114692..0090d69003 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/basic_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/basic_project.dart
@@ -2,8 +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
-
 import 'project.dart';
 
 class BasicProject extends Project {
diff --git a/packages/flutter_tools/test/integration.shard/test_data/deferred_components_project.dart b/packages/flutter_tools/test/integration.shard/test_data/deferred_components_project.dart
index ec746a9221..a51b332cca 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/deferred_components_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/deferred_components_project.dart
@@ -2,8 +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
-
 import '../../src/common.dart';
 import 'deferred_components_config.dart';
 import 'project.dart';
@@ -84,7 +82,7 @@ class BasicDeferredComponentsConfig extends DeferredComponentsConfig {
   ''';
 
   @override
-  String get deferredComponentsGolden => r'''
+  String? get deferredComponentsGolden => r'''
   loading-units:
     - id: 2
       libraries:
@@ -604,7 +602,7 @@ class NoAndroidDynamicFeatureModuleDeferredComponentsConfig extends BasicDeferre
 /// Missing golden
 class NoGoldenDeferredComponentsConfig extends BasicDeferredComponentsConfig {
   @override
-  String get deferredComponentsGolden => null;
+  String? get deferredComponentsGolden => null;
 }
 
 /// Missing golden
diff --git a/packages/flutter_tools/test/integration.shard/test_data/gen_l10n_project.dart b/packages/flutter_tools/test/integration.shard/test_data/gen_l10n_project.dart
index d82ea93195..55531ac564 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/gen_l10n_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/gen_l10n_project.dart
@@ -2,10 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:file/file.dart';
-import 'package:meta/meta.dart';
 
 import '../test_utils.dart';
 import 'project.dart';
@@ -750,8 +747,8 @@ void main() {
 ''';
 
   String l10nYaml({
-    @required bool useDeferredLoading,
-    @required bool useSyntheticPackage,
+    required bool useDeferredLoading,
+    required bool useSyntheticPackage,
   }) {
     String l10nYamlString = '';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/hot_reload_const_project.dart b/packages/flutter_tools/test/integration.shard/test_data/hot_reload_const_project.dart
index 1c096af91e..0a2a1456ac 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/hot_reload_const_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/hot_reload_const_project.dart
@@ -2,8 +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
-
 import '../test_utils.dart';
 import 'project.dart';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/hot_reload_project.dart b/packages/flutter_tools/test/integration.shard/test_data/hot_reload_project.dart
index 584fd04491..c0f5e2b76f 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/hot_reload_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/hot_reload_project.dart
@@ -2,8 +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
-
 import '../test_utils.dart';
 import 'project.dart';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/hot_reload_with_asset.dart b/packages/flutter_tools/test/integration.shard/test_data/hot_reload_with_asset.dart
index a7244b6faa..a4111ed4b4 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/hot_reload_with_asset.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/hot_reload_with_asset.dart
@@ -2,8 +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
-
 import '../test_utils.dart';
 import 'project.dart';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/multidex_project.dart b/packages/flutter_tools/test/integration.shard/test_data/multidex_project.dart
index 70fdf0d231..3bd3f82662 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/multidex_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/multidex_project.dart
@@ -2,8 +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
-
 import 'package:file/file.dart';
 
 import '../../src/common.dart';
diff --git a/packages/flutter_tools/test/integration.shard/test_data/project.dart b/packages/flutter_tools/test/integration.shard/test_data/project.dart
index 47d299bc13..69be0b6d42 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/project.dart
@@ -2,8 +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
-
 import 'package:file/file.dart';
 
 import '../test_utils.dart';
@@ -21,31 +19,32 @@ const String _kDefaultHtml  = '''
 ''';
 
 abstract class Project {
-  Directory dir;
+  late Directory dir;
 
   String get pubspec;
-  String get main;
-  String get test => null;
-  String get generatedFile => null;
-  DeferredComponentsConfig get deferredComponents => null;
+  String? get main => null;
+  String? get test => null;
+  String? get generatedFile => null;
+  DeferredComponentsConfig? get deferredComponents => null;
 
   Uri get mainDart => Uri.parse('package:test/main.dart');
 
   Future<void> setUpIn(Directory dir) async {
     this.dir = dir;
     writeFile(fileSystem.path.join(dir.path, 'pubspec.yaml'), pubspec);
+    final String? main = this.main;
     if (main != null) {
       writeFile(fileSystem.path.join(dir.path, 'lib', 'main.dart'), main);
     }
+    final String? test = this.test;
     if (test != null) {
       writeFile(fileSystem.path.join(dir.path, 'test', 'test.dart'), test);
     }
+    final String? generatedFile = this.generatedFile;
     if (generatedFile != null) {
       writeFile(fileSystem.path.join(dir.path, '.dart_tool', 'flutter_gen', 'flutter_gen.dart'), generatedFile);
     }
-    if (deferredComponents != null) {
-      deferredComponents.setUpIn(dir);
-    }
+    deferredComponents?.setUpIn(dir);
     writeFile(fileSystem.path.join(dir.path, 'web', 'index.html'), _kDefaultHtml);
     writePackages(dir.path);
     await getPackages(dir.path);
diff --git a/packages/flutter_tools/test/integration.shard/test_data/project_with_early_error.dart b/packages/flutter_tools/test/integration.shard/test_data/project_with_early_error.dart
index 819d56cac6..10dc33e2bf 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/project_with_early_error.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/project_with_early_error.dart
@@ -2,8 +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
-
 import 'project.dart';
 
 class ProjectWithEarlyError extends Project {
diff --git a/packages/flutter_tools/test/integration.shard/test_data/single_widget_reload_project.dart b/packages/flutter_tools/test/integration.shard/test_data/single_widget_reload_project.dart
index 488958a155..083a0c04d3 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/single_widget_reload_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/single_widget_reload_project.dart
@@ -2,8 +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
-
 import '../test_utils.dart';
 import 'project.dart';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/stateless_stateful_project.dart b/packages/flutter_tools/test/integration.shard/test_data/stateless_stateful_project.dart
index 20430df397..5d89cb914e 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/stateless_stateful_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/stateless_stateful_project.dart
@@ -2,8 +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
-
 import '../test_utils.dart';
 import 'project.dart';
 
diff --git a/packages/flutter_tools/test/integration.shard/test_data/stepping_project.dart b/packages/flutter_tools/test/integration.shard/test_data/stepping_project.dart
index 5722a70c0a..f9161dc5bd 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/stepping_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/stepping_project.dart
@@ -2,8 +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
-
 import 'project.dart';
 
 class SteppingProject extends Project {
diff --git a/packages/flutter_tools/test/integration.shard/test_data/test_project.dart b/packages/flutter_tools/test/integration.shard/test_data/test_project.dart
index 6253e04617..279747afdc 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/test_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/test_project.dart
@@ -2,8 +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
-
 import 'project.dart';
 
 class TestProject extends Project {
diff --git a/packages/flutter_tools/test/integration.shard/test_data/tests_project.dart b/packages/flutter_tools/test/integration.shard/test_data/tests_project.dart
index c29c417b47..c567d6a899 100644
--- a/packages/flutter_tools/test/integration.shard/test_data/tests_project.dart
+++ b/packages/flutter_tools/test/integration.shard/test_data/tests_project.dart
@@ -2,9 +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
-
-
 import 'package:file/file.dart';
 import 'package:flutter_tools/src/base/file_system.dart';