Migrate foundation test to nullsafety (#62616)

* Migrate

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

@@ -1897,7 +1897,7 @@ abstract class _NumProperty<T extends num> extends DiagnosticsProperty<T> {
 
   _NumProperty.lazy(
     String name,
-    ComputePropertyValueCallback<T> computeValue, {
+    ComputePropertyValueCallback<T?> computeValue, {
     String? ifNull,
     this.unit,
     bool showName = true,
@@ -1984,7 +1984,7 @@ class DoubleProperty extends _NumProperty<double> {
   /// The [showName] and [level] arguments must not be null.
   DoubleProperty.lazy(
     String name,
-    ComputePropertyValueCallback<double> computeValue, {
+    ComputePropertyValueCallback<double?> computeValue, {
     String? ifNull,
     bool showName = true,
     String? unit,
@@ -2480,7 +2480,7 @@ class ObjectFlagProperty<T> extends DiagnosticsProperty<T> {
 ///    only one flag, and is preferred if there is only one entry.
 ///  * [IterableProperty], which provides similar functionality describing
 ///    the values a collection of objects.
-class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T>> {
+class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T?>> {
   /// Create a summary for multiple properties, indicating whether each of them
   /// is present (non-null) or absent (null).
   ///
@@ -2488,7 +2488,7 @@ class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T>> {
   /// null.
   FlagsSummary(
     String name,
-    Map<String, T> value, {
+    Map<String, T?> value, {
     String? ifEmpty,
     bool showName = true,
     bool showSeparator = true,
@@ -2507,7 +2507,7 @@ class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T>> {
        );
 
   @override
-  Map<String, T> get value => super.value!;
+  Map<String, T?> get value => super.value!;
 
   @override
   String valueToString({TextTreeConfiguration? parentConfiguration}) {
@@ -2545,7 +2545,7 @@ class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T>> {
     return json;
   }
 
-  bool _hasNonNullEntry() => value.values.any((T o) => o != null);
+  bool _hasNonNullEntry() => value.values.any((T? o) => o != null);
 
   // An iterable of each entry's description in [value].
   //
@@ -2554,7 +2554,7 @@ class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T>> {
   // For a null value, it is omitted unless `includeEmtpy` is true and
   // [ifEntryNull] contains a corresponding description.
   Iterable<String> _formattedValues() sync* {
-    for (final MapEntry<String, T> entry in value.entries) {
+    for (final MapEntry<String, T?> entry in value.entries) {
       if (entry.value != null) {
         yield entry.key;
       }
@@ -2567,7 +2567,7 @@ class FlagsSummary<T> extends DiagnosticsProperty<Map<String, T>> {
 /// May throw exception if accessing the property would throw an exception
 /// and callers must handle that case gracefully. For example, accessing a
 /// property may trigger an assert that layout constraints were violated.
-typedef ComputePropertyValueCallback<T> = T Function();
+typedef ComputePropertyValueCallback<T> = T? Function();
 
 /// Property with a [value] of type [T].
 ///
@@ -2651,7 +2651,7 @@ class DiagnosticsProperty<T> extends DiagnosticsNode {
     DiagnosticLevel level = DiagnosticLevel.info,
   }) : assert(showName != null),
        assert(showSeparator != null),
-       assert(defaultValue == kNoDefaultValue || defaultValue is T),
+       assert(defaultValue == kNoDefaultValue || defaultValue is T?),
        assert(missingIfNull != null),
        assert(style != null),
        assert(level != null),
@@ -2848,7 +2848,8 @@ class DiagnosticsProperty<T> extends DiagnosticsNode {
   /// of the property is downgraded to [DiagnosticLevel.fine] as the property
   /// value is uninteresting.
   ///
-  /// [defaultValue] has type [T] or is [kNoDefaultValue].
+  /// The [defaultValue] is [kNoDefaultValue] by default. Otherwise it must be of
+  /// type `T?`.
   final Object? defaultValue;
 
   final DiagnosticLevel _defaultLevel;

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

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-
 import 'dart:ui' as ui show AccessibilityFeatures, SemanticsUpdateBuilder;
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/animation/animation_controller_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
-
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
@@ -19,7 +17,7 @@ import '../scheduler/scheduler_tester.dart';
 void main() {
   setUp(() {
     WidgetsFlutterBinding.ensureInitialized();
-    WidgetsBinding.instance.resetEpoch();
+    WidgetsBinding.instance!.resetEpoch();
     ui.window.onBeginFrame = null;
     ui.window.onDrawFrame = null;
   });
@@ -350,7 +348,7 @@ void main() {
     expect(controller.repeat, throwsFlutterError);
 
     controller.dispose();
-    FlutterError result;
+    FlutterError? result;
     try {
       controller.dispose();
     } on FlutterError catch (e) {
@@ -358,7 +356,7 @@ void main() {
     }
     expect(result, isNotNull);
     expect(
-      result.toStringDeep(),
+      result!.toStringDeep(),
       equalsIgnoringHashCodes(
         'FlutterError\n'
         '   AnimationController.dispose() called more than once.\n'
@@ -482,7 +480,7 @@ void main() {
     controller.forward(from: 0.2);
     expect(controller.value, 0.2);
     controller.animateTo(1.0, duration: Duration.zero);
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0), reason: 'Expected no animation.');
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0), reason: 'Expected no animation.');
     expect(controller.value, 1.0);
   });
 

packages/flutter/test/animation/animation_sheet_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
-
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';
@@ -84,8 +82,8 @@ class _DecuplePixels extends StatefulWidget {
   State<StatefulWidget> createState() => _DecuplePixelsState();
 }
 
-class _DecuplePixelsState extends State<_DecuplePixels> with SingleTickerProviderStateMixin {
-  AnimationController _controller;
+class _DecuplePixelsState extends State<_DecuplePixels> with SingleTickerProviderStateMixin<_DecuplePixels> {
+  late AnimationController _controller;
 
   @override
   void initState() {
@@ -107,7 +105,7 @@ class _DecuplePixelsState extends State<_DecuplePixels> with SingleTickerProvide
   Widget build(BuildContext context) {
     return AnimatedBuilder(
       animation: _controller.view,
-      builder: (BuildContext context, Widget child) {
+      builder: (BuildContext context, Widget? child) {
         return CustomPaint(
           painter: _PaintDecuplePixels(_controller.value),
         );
@@ -132,7 +130,7 @@ class _PaintDecuplePixels extends CustomPainter {
     final Rect rect = RectTween(
       begin: const Rect.fromLTWH(1, 1, 1, 1),
       end: const Rect.fromLTWH(11, 1, 1, 1),
-    ).transform(value);
+    ).transform(value)!;
     canvas.drawRect(rect, Paint()..color = Colors.yellow);
     final Paint black = Paint()..color = Colors.black;
     canvas

packages/flutter/test/animation/animations_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
-
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
@@ -21,7 +19,7 @@ class BogusCurve extends Curve {
 void main() {
   setUp(() {
     WidgetsFlutterBinding.ensureInitialized();
-    WidgetsBinding.instance.resetEpoch();
+    WidgetsBinding.instance!.resetEpoch();
     ui.window.onBeginFrame = null;
     ui.window.onDrawFrame = null;
   });
@@ -240,14 +238,14 @@ void main() {
       vsync: const TestVSync(),
     );
     final CurvedAnimation curved = CurvedAnimation(parent: controller, curve: BogusCurve());
-    FlutterError error;
+    FlutterError? error;
     try {
       curved.value;
     } on FlutterError catch (e) {
       error = e;
     }
     expect(error, isNotNull);
-    expect(error.toStringDeep(), matches(
+    expect(error!.toStringDeep(), matches(
       // RegExp matcher is required here due to flutter web and flutter mobile generating
       // slightly different floating point numbers
       // in Flutter web 0.0 sometimes just appears as 0. or 0

packages/flutter/test/animation/curves_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
-
 import 'dart:math' as math;
 
 import 'package:flutter_test/flutter_test.dart';
@@ -275,9 +273,6 @@ void main() {
   });
 
   test('CatmullRomSpline enforces contract', () {
-    expect(() {
-      CatmullRomSpline(null);
-    }, throwsAssertionError);
     expect(() {
       CatmullRomSpline(const <Offset>[]);
     }, throwsAssertionError);
@@ -327,9 +322,6 @@ void main() {
   });
 
   test('CatmullRomSpline enforces contract when precomputed', () {
-    expect(() {
-      CatmullRomSpline.precompute(null);
-    }, throwsAssertionError);
     expect(() {
       CatmullRomSpline.precompute(const <Offset>[]);
     }, throwsAssertionError);
@@ -395,9 +387,6 @@ void main() {
   });
 
   test('CatmullRomCurve enforces contract', () {
-    expect(() {
-      CatmullRomCurve(null);
-    }, throwsAssertionError);
     expect(() {
       CatmullRomCurve(const <Offset>[]);
     }, throwsAssertionError);
@@ -517,9 +506,6 @@ void main() {
   });
 
   test('CatmullRomCurve enforces contract when precomputed', () {
-    expect(() {
-      CatmullRomCurve.precompute(null);
-    }, throwsAssertionError);
     expect(() {
       CatmullRomCurve.precompute(const <Offset>[]);
     }, throwsAssertionError);

packages/flutter/test/animation/futures_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
-
 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

@@ -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:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';
@@ -11,7 +9,7 @@ import 'package:flutter/widgets.dart';
 void main() {
   setUp(() {
     WidgetsFlutterBinding.ensureInitialized();
-    WidgetsBinding.instance.resetEpoch();
+    WidgetsBinding.instance!.resetEpoch();
   });
 
   test('AnimationController with mutating listener', () {
@@ -92,7 +90,7 @@ void main() {
     final VoidCallback listener1 = () { log.add('listener1'); };
     final VoidCallback badListener = () {
       log.add('badListener');
-      throw null;
+      throw ArgumentError();
     };
     final VoidCallback listener2 = () { log.add('listener2'); };
 
@@ -101,7 +99,7 @@ void main() {
     controller.addListener(listener2);
     controller.value = 0.2;
     expect(log, <String>['listener1', 'badListener', 'listener2']);
-    expect(tester.takeException(), isNullThrownError);
+    expect(tester.takeException(), isArgumentError);
     log.clear();
   });
 
@@ -115,7 +113,7 @@ void main() {
     final AnimationStatusListener listener1 = (AnimationStatus status) { log.add('listener1'); };
     final AnimationStatusListener badListener = (AnimationStatus status) {
       log.add('badListener');
-      throw null;
+      throw ArgumentError();
     };
     final AnimationStatusListener listener2 = (AnimationStatus status) { log.add('listener2'); };
 
@@ -124,7 +122,7 @@ void main() {
     controller.addStatusListener(listener2);
     controller.forward();
     expect(log, <String>['listener1', 'badListener', 'listener2']);
-    expect(tester.takeException(), isNullThrownError);
+    expect(tester.takeException(), isArgumentError);
     log.clear();
     controller.dispose();
   });

packages/flutter/test/animation/tween_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
-
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';

packages/flutter/test/foundation/assertions_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
-
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 
@@ -442,7 +440,7 @@ void main() {
       ],
       replacement: 'test',
     );
-    final List<String> reasons = List<String>(2);
+    final List<String?> reasons = List<String?>.filled(2, null);
     filter.filter(
       const <StackFrame>[
         StackFrame(className: 'TestClass', method: 'test1', packageScheme: 'package', package: 'test', packagePath: 'blah.dart', line: 1, column: 1, number: 0, source: ''),
@@ -450,6 +448,6 @@ void main() {
       ],
       reasons,
     );
-    expect(reasons, List<String>(2));
+    expect(reasons, List<String?>.filled(2, null));
   });
 }

packages/flutter/test/foundation/bit_field_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
-
 @TestOn('!chrome')
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/foundation/caching_iterable_test.dart

@@ -2,13 +2,11 @@
 // Use of 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';
 
-int yieldCount;
+int yieldCount = 0;
 
 Iterable<int> range(int start, int end) sync* {
   assert(yieldCount == 0);

packages/flutter/test/foundation/capture_output.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 'dart:async';
 import 'package:flutter/foundation.dart';
 

packages/flutter/test/foundation/change_notifier_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
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -41,7 +39,7 @@ void main() {
     final VoidCallback listener2 = () { log.add('listener2'); };
     final VoidCallback badListener = () {
       log.add('badListener');
-      throw null;
+      throw ArgumentError();
     };
 
     final TestNotifier test = TestNotifier();
@@ -95,7 +93,7 @@ void main() {
     test.addListener(badListener);
     test.notify();
     expect(log, <String>['listener', 'listener2', 'listener1', 'badListener']);
-    expect(tester.takeException(), isNullThrownError);
+    expect(tester.takeException(), isArgumentError);
     log.clear();
 
     test.addListener(listener1);
@@ -105,7 +103,7 @@ void main() {
     test.addListener(listener2);
     test.notify();
     expect(log, <String>['badListener', 'listener1', 'listener2']);
-    expect(tester.takeException(), isNullThrownError);
+    expect(tester.takeException(), isArgumentError);
     log.clear();
   });
 
@@ -238,7 +236,7 @@ void main() {
     final TestNotifier source2 = TestNotifier();
     final List<String> log = <String>[];
 
-    final Listenable merged = Listenable.merge(<Listenable>[null, source1, null, source2, null]);
+    final Listenable merged = Listenable.merge(<Listenable?>[null, source1, null, source2, null]);
     final VoidCallback listener = () { log.add('listener'); };
 
     merged.addListener(listener);
@@ -300,7 +298,7 @@ void main() {
     Listenable listenableUnderTest = Listenable.merge(<Listenable>[]);
     expect(listenableUnderTest.toString(), 'Listenable.merge([])');
 
-    listenableUnderTest = Listenable.merge(<Listenable>[null]);
+    listenableUnderTest = Listenable.merge(<Listenable?>[null]);
     expect(listenableUnderTest.toString(), 'Listenable.merge([null])');
 
     listenableUnderTest = Listenable.merge(<Listenable>[source1]);
@@ -315,7 +313,7 @@ void main() {
       "Listenable.merge([Instance of 'TestNotifier', Instance of 'TestNotifier'])",
     );
 
-    listenableUnderTest = Listenable.merge(<Listenable>[null, source2]);
+    listenableUnderTest = Listenable.merge(<Listenable?>[null, source2]);
     expect(
       listenableUnderTest.toString(),
       "Listenable.merge([null, Instance of 'TestNotifier'])",
@@ -382,14 +380,14 @@ void main() {
   test('Throws FlutterError when disposed and called', () {
     final TestNotifier testNotifier = TestNotifier();
     testNotifier.dispose();
-    FlutterError error;
+    FlutterError? error;
     try {
       testNotifier.dispose();
     } on FlutterError catch (e) {
       error = e;
     }
     expect(error, isNotNull);
-    expect(error, isFlutterError);
+    expect(error!, isFlutterError);
     expect(error.toStringDeep(), equalsIgnoringHashCodes(
       'FlutterError\n'
       '   A TestNotifier was used after being disposed.\n'

packages/flutter/test/foundation/collections_test.dart

@@ -2,7 +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 'dart:math';
 
 import 'package:flutter/src/foundation/collections.dart';
@@ -64,10 +63,8 @@ void main() {
   test('MergeSortRandom', () {
     final Random random = Random();
     for (int i = 0; i < 250; i += 1) {
-      final List<int> list = List<int>(i);
-      for (int j = 0; j < i; j++) {
-        list[j] = random.nextInt(i); // Expect some equal elements.
-      }
+      // Expect some equal elements.
+      final List<int> list = List<int>.generate(i, (int j) => random.nextInt(i));
       mergeSort(list);
       for (int j = 1; j < i; j++) {
         expect(list[j - 1], lessThanOrEqualTo(list[j]));
@@ -80,14 +77,12 @@ void main() {
     // larger case where the internal moving insertion sort is used
     // larger cases with multiple splittings, numbers just around a power of 2.
     for (final int size in <int>[8, 50, 511, 512, 513]) {
-      final List<OrderedComparable> list = List<OrderedComparable>(size);
       // Class OC compares using id.
       // With size elements with id's in the range 0..size/4, a number of
       // collisions are guaranteed. These should be sorted so that the 'order'
       // part of the objects are still in order.
-      for (int i = 0; i < size; i++) {
-        list[i] = OrderedComparable(random.nextInt(size >> 2), i);
-      }
+      final List<OrderedComparable> list = List<OrderedComparable>.generate(
+          size, (int i) => OrderedComparable(random.nextInt(size >> 2), i));
       mergeSort(list);
       OrderedComparable prev = list[0];
       for (int i = 1; i < size; i++) {
@@ -126,10 +121,8 @@ void main() {
   test('MergeSortSpecialCases', () {
     for (final int size in <int>[511, 512, 513]) {
       // All equal.
-      final List<OrderedComparable> list = List<OrderedComparable>(size);
-      for (int i = 0; i < size; i++) {
-        list[i] = OrderedComparable(0, i);
-      }
+      final List<OrderedComparable> list = List<OrderedComparable>.generate(
+          size, (int i) => OrderedComparable(0, i));
       mergeSort(list);
       for (int i = 0; i < size; i++) {
         expect(list[i].order, equals(i));

packages/flutter/test/foundation/consolidate_response_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
-
 @TestOn('!chrome')
 
 import 'dart:async';
@@ -18,7 +16,7 @@ final Uint8List chunkOne = Uint8List.fromList(<int>[0, 1, 2, 3, 4, 5]);
 final Uint8List chunkTwo = Uint8List.fromList(<int>[6, 7, 8, 9, 10]);
 void main() {
   group(consolidateHttpClientResponseBytes, () {
-    MockHttpClientResponse response;
+    late MockHttpClientResponse response;
 
     setUp(() {
       response = MockHttpClientResponse(
@@ -54,11 +52,11 @@ void main() {
     test('Notifies onBytesReceived for every chunk of bytes', () async {
       final int syntheticTotal = (chunkOne.length + chunkTwo.length) * 2;
       response.contentLength = syntheticTotal;
-      final List<int> records = <int>[];
+      final List<int?> records = <int?>[];
       await consolidateHttpClientResponseBytes(
         response,
-        onBytesReceived: (int cumulative, int total) {
-          records.addAll(<int>[cumulative, total]);
+        onBytesReceived: (int cumulative, int? total) {
+          records.addAll(<int?>[cumulative, total]);
         },
       );
 
@@ -81,7 +79,7 @@ void main() {
       response.contentLength = -1;
       final Future<List<int>> result = consolidateHttpClientResponseBytes(
         response,
-        onBytesReceived: (int cumulative, int total) {
+        onBytesReceived: (int cumulative, int? total) {
           throw 'misbehaving callback';
         },
       );
@@ -113,11 +111,11 @@ void main() {
 
       test('Notifies onBytesReceived with gzipped numbers', () async {
         response.contentLength = gzipped.length;
-        final List<int> records = <int>[];
+        final List<int?> records = <int>[];
         await consolidateHttpClientResponseBytes(
           response,
-          onBytesReceived: (int cumulative, int total) {
-            records.addAll(<int>[cumulative, total]);
+          onBytesReceived: (int cumulative, int? total) {
+            records.addAll(<int?>[cumulative, total]);
           },
         );
 
@@ -133,15 +131,15 @@ void main() {
         final int syntheticTotal = (chunkOne.length + chunkTwo.length) * 2;
         response.compressionState = HttpClientResponseCompressionState.decompressed;
         response.contentLength = syntheticTotal;
-        final List<int> records = <int>[];
+        final List<int?> records = <int?>[];
         await consolidateHttpClientResponseBytes(
           response,
-          onBytesReceived: (int cumulative, int total) {
-            records.addAll(<int>[cumulative, total]);
+          onBytesReceived: (int cumulative, int? total) {
+            records.addAll(<int?>[cumulative, total]);
           },
         );
 
-        expect(records, <int>[
+        expect(records, <int?>[
           gzippedChunkOne.length,
           null,
           gzipped.length,
@@ -153,7 +151,7 @@ void main() {
 }
 
 class MockHttpClientResponse extends Fake implements HttpClientResponse {
-  MockHttpClientResponse({this.error, this.chunkOne, this.chunkTwo});
+  MockHttpClientResponse({this.error, this.chunkOne = const <int>[], this.chunkTwo = const <int>[]});
 
   final dynamic error;
   final List<int> chunkOne;
@@ -166,10 +164,10 @@ class MockHttpClientResponse extends Fake implements HttpClientResponse {
   HttpClientResponseCompressionState compressionState = HttpClientResponseCompressionState.notCompressed;
 
   @override
-  StreamSubscription<List<int>> listen(void Function(List<int> event) onData, {Function onError, void Function() onDone, bool cancelOnError}) {
+  StreamSubscription<List<int>> listen(void Function(List<int> event)? onData, {Function? onError, void Function()? onDone, bool? cancelOnError}) {
     if (error != null) {
       return Stream<List<int>>.fromFuture(
-        Future<List<int>>.error(error)).listen(
+        Future<List<int>>.error(error as Object)).listen(
           onData,
           onDone: onDone,
           onError: onError,

packages/flutter/test/foundation/constants_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
-
 @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

@@ -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:flutter_test/flutter_test.dart';
 
 class X {}
@@ -11,7 +9,7 @@ class X {}
 class Y extends X {}
 
 class A<U extends X> {
-  U u;
+  U? u;
 }
 
 void main() {

packages/flutter/test/foundation/debug_test.dart

@@ -2,21 +2,19 @@
 // Use of 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';
 
 void main() {
   group('debugInstrumentAction', () {
-    DebugPrintCallback originalDebugPrintCallback;
-    StringBuffer printBuffer;
+    late DebugPrintCallback originalDebugPrintCallback;
+    late StringBuffer printBuffer;
 
     setUp(() {
       debugInstrumentationEnabled = true;
       printBuffer = StringBuffer();
       originalDebugPrintCallback = debugPrint;
-      debugPrint = (String message, { int wrapWidth }) {
+      debugPrint = (String? message, { int? wrapWidth }) {
         printBuffer.writeln(message);
       };
     });

packages/flutter/test/foundation/defines_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
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/diagnostics_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
-
 import 'dart:convert';
 import 'dart:ui';
 
@@ -12,7 +10,7 @@ import 'package:flutter_test/flutter_test.dart';
 
 class TestTree extends Object with DiagnosticableTreeMixin {
   TestTree({
-    this.name,
+    this.name = '',
     this.style,
     this.children = const <TestTree>[],
     this.properties = const <DiagnosticsNode>[],
@@ -21,7 +19,7 @@ class TestTree extends Object with DiagnosticableTreeMixin {
   final String name;
   final List<TestTree> children;
   final List<DiagnosticsNode> properties;
-  final DiagnosticsTreeStyle style;
+  final DiagnosticsTreeStyle? style;
 
   @override
   List<DiagnosticsNode> debugDescribeChildren() => <DiagnosticsNode>[
@@ -36,8 +34,7 @@ class TestTree extends Object with DiagnosticableTreeMixin {
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     if (style != null)
-      properties.defaultDiagnosticsTreeStyle = style;
-
+      properties.defaultDiagnosticsTreeStyle = style!;
     this.properties.forEach(properties.add);
   }
 }
@@ -65,7 +62,7 @@ void validateNodeJsonSerializationHelper(Map<String, Object> json, DiagnosticsNo
   expect(json['level'] ?? describeEnum(DiagnosticLevel.info), equals(describeEnum(node.level)));
   expect(json['showName'] ?? true, equals(node.showName));
   expect(json['emptyBodyDescription'], equals(node.emptyBodyDescription));
-  expect(json['style'] ?? describeEnum(DiagnosticsTreeStyle.sparse), equals(describeEnum(node.style)));
+  expect(json['style'] ?? describeEnum(DiagnosticsTreeStyle.sparse), equals(describeEnum(node.style!)));
   expect(json['type'], equals(node.runtimeType.toString()));
   expect(json['hasChildren'] ?? false, equals(node.getChildren().isNotEmpty));
 }
@@ -122,13 +119,13 @@ void validateObjectFlagPropertyJsonSerialization(ObjectFlagProperty<Object> prop
   validatePropertyJsonSerializationHelper(json, property);
 }
 
-void validateIterableFlagsPropertyJsonSerialization(FlagsSummary<Object> property) {
+void validateIterableFlagsPropertyJsonSerialization(FlagsSummary<Object?> property) {
   final Map<String, Object> json = simulateJsonSerialization(property);
   if (property.value.isNotEmpty) {
     expect(json['values'], equals(
       property.value.entries
-        .where((MapEntry<String, Object> entry) => entry.value != null)
-        .map((MapEntry<String, Object> entry) => entry.key).toList(),
+        .where((MapEntry<String, Object?> entry) => entry.value != null)
+        .map((MapEntry<String, Object?> entry) => entry.key).toList(),
     ));
   } else {
     expect(json.containsKey('values'), isFalse);
@@ -141,7 +138,7 @@ void validateIterablePropertyJsonSerialization(IterableProperty<Object> property
   final Map<String, Object> json = simulateJsonSerialization(property);
   if (property.value != null) {
     final List<Object> valuesJson = json['values'] as List<Object>;
-    final List<String> expectedValues = property.value.map<String>((Object value) => value.toString()).toList();
+    final List<String> expectedValues = property.value!.map<String>((Object value) => value.toString()).toList();
     expect(listEquals(valuesJson, expectedValues), isTrue);
   } else {
     expect(json.containsKey('values'), isFalse);
@@ -194,8 +191,8 @@ void main() {
   test('TreeDiagnosticsMixin control test', () async {
     void goldenStyleTest(
       String description, {
-      DiagnosticsTreeStyle style,
-      DiagnosticsTreeStyle lastChildStyle,
+      DiagnosticsTreeStyle? style,
+      DiagnosticsTreeStyle? lastChildStyle,
       String golden = '',
     }) {
       final TestTree tree = TestTree(children: <TestTree>[
@@ -367,11 +364,11 @@ void main() {
   test('TreeDiagnosticsMixin tree with properties test', () async {
     void goldenStyleTest(
       String description, {
-      String name,
-      DiagnosticsTreeStyle style,
-      DiagnosticsTreeStyle lastChildStyle,
+      String? name,
+      DiagnosticsTreeStyle? style,
+      DiagnosticsTreeStyle? lastChildStyle,
       DiagnosticsTreeStyle propertyStyle = DiagnosticsTreeStyle.singleLine,
-      @required String golden,
+      required String golden,
     }) {
       final TestTree tree = TestTree(
         properties: <DiagnosticsNode>[
@@ -1696,7 +1693,7 @@ void main() {
     // Partially empty property
     {
       final Function onClick = () { };
-      final Map<String, Function> value = <String, Function>{
+      final Map<String, Function?> value = <String, Function?>{
         'move': null,
         'click': onClick,
       };
@@ -1711,7 +1708,7 @@ void main() {
 
     // Empty property (without ifEmpty)
     {
-      final Map<String, Function> value = <String, Function>{
+      final Map<String, Function?> value = <String, Function?>{
         'enter': null,
       };
       final FlagsSummary<Function> flags = FlagsSummary<Function>(
@@ -1724,7 +1721,7 @@ void main() {
 
     // Empty property (without ifEmpty)
     {
-      final Map<String, Function> value = <String, Function>{
+      final Map<String, Function?> value = <String, Function?>{
         'enter': null,
       };
       final FlagsSummary<Function> flags = FlagsSummary<Function>(
@@ -1922,14 +1919,14 @@ void main() {
     expect(messageProperty.name, equals('diagnostics'));
     expect(messageProperty.value, isNull);
     expect(messageProperty.showName, isTrue);
-    validatePropertyJsonSerialization(messageProperty as MessageProperty);
+    validatePropertyJsonSerialization(messageProperty as DiagnosticsProperty<Object>);
   });
 
   test('error message style wrap test', () {
     // This tests wrapping of properties with styles typical for error messages.
     DiagnosticsNode createTreeWithWrappingNodes({
-      DiagnosticsTreeStyle rootStyle,
-      DiagnosticsTreeStyle propertyStyle,
+      DiagnosticsTreeStyle? rootStyle,
+      required DiagnosticsTreeStyle propertyStyle,
     }) {
       return TestTree(
         name: 'Test tree',

packages/flutter/test/foundation/double_precision_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
-
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/foundation/error_reporting_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
-
 @TestOn('!chrome') // web has different stack traces
 
 import 'package:flutter/foundation.dart';
@@ -41,13 +39,13 @@ Future<StackTrace> getSampleStack() async {
 }
 
 Future<void> main() async {
-  final List<String> console = <String>[];
+  final List<String?> console = <String?>[];
 
   final StackTrace sampleStack = await getSampleStack();
 
   setUp(() async {
     expect(debugPrint, equals(debugPrintThrottled));
-    debugPrint = (String message, { int wrapWidth }) {
+    debugPrint = (String? message, { int? wrapWidth }) {
       console.add(message);
     };
   });
@@ -160,7 +158,7 @@ Future<void> main() async {
 
   test('Error reporting - NoSuchMethodError', () async {
     expect(console, isEmpty);
-    final dynamic exception = NoSuchMethodError.withInvocation(5,
+    final Object exception = NoSuchMethodError.withInvocation(5,
         Invocation.method(#foo, <dynamic>[2, 4]));
 
     FlutterError.dumpErrorToConsole(FlutterErrorDetails(

packages/flutter/test/foundation/isolates_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
-
 @TestOn('!chrome') // isolates not supported on the web.
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/foundation/licenses_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
-
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 
@@ -11,7 +9,7 @@ void main() {
   test('LicenseEntryWithLineBreaks - most cases', () {
     // There's some trailing spaces in this string.
     // To avoid IDEs stripping them, I've escaped them as \u0020.
-    final List<LicenseParagraph> paragraphs = const LicenseEntryWithLineBreaks(null, '''
+    final List<LicenseParagraph> paragraphs = const LicenseEntryWithLineBreaks(<String>[], '''
 A
 A
 A
@@ -159,17 +157,17 @@ S
   });
 
   test('LicenseEntryWithLineBreaks - leading and trailing whitespace', () {
-    expect(const LicenseEntryWithLineBreaks(null, '    \n\n    ').paragraphs.toList(), isEmpty);
-    expect(const LicenseEntryWithLineBreaks(null, '    \r\n\r\n    ').paragraphs.toList(), isEmpty);
+    expect(const LicenseEntryWithLineBreaks(<String>[], '    \n\n    ').paragraphs.toList(), isEmpty);
+    expect(const LicenseEntryWithLineBreaks(<String>[], '    \r\n\r\n    ').paragraphs.toList(), isEmpty);
 
     List<LicenseParagraph> paragraphs;
 
-    paragraphs = const LicenseEntryWithLineBreaks(null, '    \nA\n    ').paragraphs.toList();
+    paragraphs = const LicenseEntryWithLineBreaks(<String>[], '    \nA\n    ').paragraphs.toList();
     expect(paragraphs[0].text, 'A');
     expect(paragraphs[0].indent, 0);
     expect(paragraphs, hasLength(1));
 
-    paragraphs = const LicenseEntryWithLineBreaks(null, '\n\n\nA\n\n\n').paragraphs.toList();
+    paragraphs = const LicenseEntryWithLineBreaks(<String>[], '\n\n\nA\n\n\n').paragraphs.toList();
     expect(paragraphs[0].text, 'A');
     expect(paragraphs[0].indent, 0);
     expect(paragraphs, hasLength(1));
@@ -178,12 +176,12 @@ S
   test('LicenseRegistry', () async {
     expect(await LicenseRegistry.licenses.toList(), isEmpty);
     LicenseRegistry.addLicense(() async* {
-      yield const LicenseEntryWithLineBreaks(null, 'A');
-      yield const LicenseEntryWithLineBreaks(null, 'B');
+      yield const LicenseEntryWithLineBreaks(<String>[], 'A');
+      yield const LicenseEntryWithLineBreaks(<String>[], 'B');
     });
     LicenseRegistry.addLicense(() async* {
-      yield const LicenseEntryWithLineBreaks(null, 'C');
-      yield const LicenseEntryWithLineBreaks(null, 'D');
+      yield const LicenseEntryWithLineBreaks(<String>[], 'C');
+      yield const LicenseEntryWithLineBreaks(<String>[], 'D');
     });
     expect(await LicenseRegistry.licenses.toList(), hasLength(4));
     final List<LicenseEntry> licenses = await LicenseRegistry.licenses.toList();

packages/flutter/test/foundation/observer_list_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
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/foundation/platform_helper.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 'dart:io' show Platform;
 
 /// Returns [Platform.pathSeparator], suitably escaped so as to be usable in a

packages/flutter/test/foundation/print_test.dart

@@ -2,7 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.10
 import 'package:flutter/foundation.dart';
 import 'package:fake_async/fake_async.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/foundation/reassemble_test.dart

@@ -2,14 +2,12 @@
 // 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';
 import '../flutter_test_alternative.dart';
 
 class TestFoundationFlutterBinding extends BindingBase {
-  bool wasLocked;
+  bool? wasLocked;
 
   @override
   Future<void> performReassemble() async {
@@ -21,8 +19,6 @@ class TestFoundationFlutterBinding extends BindingBase {
 TestFoundationFlutterBinding binding = TestFoundationFlutterBinding();
 
 void main() {
-  binding ??= TestFoundationFlutterBinding();
-
   test('Pointer events are locked during reassemble', () async {
     await binding.reassembleApplication();
     expect(binding.wasLocked, isTrue);

packages/flutter/test/foundation/serialization_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
-
 @TestOn('!chrome') // web does not support certain 64bit behavior
 
 import 'dart:typed_data';

packages/flutter/test/foundation/service_extensions_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
-
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
@@ -31,9 +29,10 @@ class TestServiceExtensionsBinding extends BindingBase
   final Map<String, List<Map<String, dynamic>>> eventsDispatched = <String, List<Map<String, dynamic>>>{};
 
   @override
+  @protected
   void registerServiceExtension({
-    @required String name,
-    @required ServiceExtensionCallback callback,
+    required String name,
+    required ServiceExtensionCallback callback,
   }) {
     expect(extensions.containsKey(name), isFalse);
     extensions[name] = callback;
@@ -55,7 +54,7 @@ class TestServiceExtensionsBinding extends BindingBase
 
   Future<Map<String, dynamic>> testExtension(String name, Map<String, String> arguments) {
     expect(extensions.containsKey(name), isTrue);
-    return extensions[name](arguments);
+    return extensions[name]!(arguments);
   }
 
   int reassembled = 0;
@@ -75,13 +74,10 @@ class TestServiceExtensionsBinding extends BindingBase
   }
   Future<void> doFrame() async {
     frameScheduled = false;
-    if (ui.window.onBeginFrame != null)
-      ui.window.onBeginFrame(Duration.zero);
+    ui.window.onBeginFrame?.call(Duration.zero);
     await flushMicrotasks();
-    if (ui.window.onDrawFrame != null)
-      ui.window.onDrawFrame();
-    if (ui.window.onReportTimings != null)
-      ui.window.onReportTimings(<ui.FrameTiming>[]);
+    ui.window.onDrawFrame?.call();
+    ui.window.onReportTimings?.call(<ui.FrameTiming>[]);
   }
 
   @override
@@ -102,7 +98,7 @@ class TestServiceExtensionsBinding extends BindingBase
   }
 }
 
-TestServiceExtensionsBinding binding;
+late TestServiceExtensionsBinding binding;
 
 Future<Map<String, dynamic>> hasReassemble(Future<Map<String, dynamic>> pendingResult) async {
   bool completed = false;
@@ -120,7 +116,7 @@ Future<Map<String, dynamic>> hasReassemble(Future<Map<String, dynamic>> pendingR
 }
 
 void main() {
-  final List<String> console = <String>[];
+  final List<String?> console = <String?>[];
 
   setUpAll(() async {
     binding = TestServiceExtensionsBinding()..scheduleFrame();
@@ -150,7 +146,7 @@ void main() {
     expect(binding.frameScheduled, isFalse);
 
     expect(debugPrint, equals(debugPrintThrottled));
-    debugPrint = (String message, { int wrapWidth }) {
+    debugPrint = (String? message, { int? wrapWidth }) {
       console.add(message);
     };
   });
@@ -208,7 +204,7 @@ void main() {
 
     bool lastValue = false;
     Future<void> _updateAndCheck(bool newValue) async {
-      Map<String, dynamic> result;
+      Map<String, dynamic>? result;
       binding.testExtension(
         'debugCheckElevationsEnabled',
         <String, String>{'enabled': '$newValue'},
@@ -458,8 +454,8 @@ void main() {
     bool completed;
 
     completed = false;
-    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', (ByteData message) async {
-      expect(utf8.decode(message.buffer.asUint8List()), 'test');
+    ServicesBinding.instance!.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', (ByteData? message) async {
+      expect(utf8.decode(message!.buffer.asUint8List()), 'test');
       completed = true;
       return ByteData(5); // 0x0000000000
     });
@@ -472,8 +468,7 @@ void main() {
     expect(completed, isTrue);
     completed = false;
     data = await rootBundle.loadStructuredData('test', (String value) async {
-      expect(true, isFalse);
-      return null;
+      throw Error();
     });
     expect(data, isTrue);
     expect(completed, isFalse);
@@ -486,7 +481,7 @@ void main() {
     });
     expect(data, isFalse);
     expect(completed, isTrue);
-    ServicesBinding.instance.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', null);
+    ServicesBinding.instance!.defaultBinaryMessenger.setMockMessageHandler('flutter/assets', null);
   });
 
   test('Service extensions - exit', () async {

packages/flutter/test/foundation/stack_frame_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
-
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/foundation/stack_trace_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
-
 @TestOn('!chrome') // web has different stack traces
 
 import 'package:flutter/foundation.dart';

packages/flutter/test/foundation/synchronous_future_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
-
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 
@@ -11,7 +9,7 @@ void main() {
   test('SynchronousFuture control test', () async {
     final Future<int> future = SynchronousFuture<int>(42);
 
-    int result;
+    int? result;
     future.then<void>((int value) { result = value; });
 
     expect(result, equals(42));
@@ -39,16 +37,16 @@ void main() {
 
     expect(await completeResult, equals(42));
 
-    Object exception;
+    Object? exception;
     try {
       await future.whenComplete(() {
-        throw null;
+        throw ArgumentError();
       });
       // Unreached.
       expect(false, isTrue);
     } catch (e) {
       exception = e;
     }
-    expect(exception, isNullThrownError);
+    expect(exception, isArgumentError);
   });
 }