Migrate more tests to null safety (#67360)

packages/flutter/lib/src/painting/image_provider.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:async';
 import 'dart:io';
 import 'dart:typed_data';

packages/flutter/test/painting/flutter_logo_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/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/painting.dart';
@@ -23,26 +21,26 @@ void main() {
   );
 
   test('FlutterLogoDecoration lerp from null to null is null', () {
-    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(null, null, 0.5);
+    final FlutterLogoDecoration? logo = FlutterLogoDecoration.lerp(null, null, 0.5);
     expect(logo, isNull);
   });
 
   test('FlutterLogoDecoration lerp from non-null to null lerps margin', () {
-    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(start, null, 0.4);
+    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(start, null, 0.4)!;
     expect(logo.textColor, start.textColor);
     expect(logo.style, start.style);
     expect(logo.margin, start.margin * 0.4);
   });
 
   test('FlutterLogoDecoration lerp from null to non-null lerps margin', () {
-    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(null, end, 0.6);
+    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(null, end, 0.6)!;
     expect(logo.textColor, end.textColor);
     expect(logo.style, end.style);
     expect(logo.margin, end.margin * 0.6);
   });
 
   test('FlutterLogoDecoration lerps colors and margins', () {
-    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(start, end, 0.5);
+    final FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(start, end, 0.5)!;
     expect(logo.textColor, Color.lerp(start.textColor, end.textColor, 0.5));
     expect(logo.margin, EdgeInsets.lerp(start.margin, end.margin, 0.5));
   });
@@ -55,10 +53,10 @@ void main() {
   });
 
   test('FlutterLogoDecoration lerp changes styles at 0.5', () {
-    FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(start, end, 0.4);
+    FlutterLogoDecoration logo = FlutterLogoDecoration.lerp(start, end, 0.4)!;
     expect(logo.style, start.style);
 
-    logo = FlutterLogoDecoration.lerp(start, end, 0.5);
+    logo = FlutterLogoDecoration.lerp(start, end, 0.5)!;
     expect(logo.style, end.style);
   });
 

packages/flutter/test/painting/fractional_offset_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/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/geometry_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/painting.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/painting/gradient_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/widgets.dart';
@@ -21,7 +19,7 @@ void main() {
         Color(0x44444444),
       ],
     );
-    final LinearGradient actual = LinearGradient.lerp(null, testGradient, 0.25);
+    final LinearGradient? actual = LinearGradient.lerp(null, testGradient, 0.25);
 
     expect(actual, const LinearGradient(
       begin: Alignment.bottomRight,
@@ -52,7 +50,7 @@ void main() {
       ],
     );
 
-    final LinearGradient actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
+    final LinearGradient? actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const LinearGradient(
       begin: Alignment(0.0, -1.0),
       end: Alignment(-1.0, 0.0),
@@ -90,7 +88,7 @@ void main() {
       ],
     );
 
-    final LinearGradient actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
+    final LinearGradient? actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const LinearGradient(
       begin: Alignment(0.0, -1.0),
       end: Alignment(-1.0, 0.0),
@@ -122,7 +120,7 @@ void main() {
       ],
     );
 
-    final LinearGradient actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
+    final LinearGradient? actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const LinearGradient(
       colors: <Color>[
         Color(0x33333333),
@@ -161,7 +159,7 @@ void main() {
       ],
     );
 
-    final LinearGradient actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
+    final LinearGradient? actual = LinearGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const LinearGradient(
       colors: <Color>[
         Color(0x3B3B3B3B),
@@ -291,7 +289,7 @@ void main() {
       ],
     );
 
-    final RadialGradient actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
+    final RadialGradient? actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const RadialGradient(
       center: Alignment(0.0, -1.0),
       radius: 15.0,
@@ -332,9 +330,7 @@ void main() {
       ],
     );
 
-    final RadialGradient actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
-
-    expect(actual.focal, isNull);
+    final RadialGradient? actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
 
     expect(actual, const RadialGradient(
       center: Alignment(0.0, -1.0),
@@ -350,6 +346,8 @@ void main() {
         1.0,
       ],
     ));
+
+    expect(actual!.focal, isNull);
   });
 
   test('RadialGradient lerp test with unequal number of colors', () {
@@ -367,7 +365,7 @@ void main() {
       ],
     );
 
-    final RadialGradient actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
+    final RadialGradient? actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const RadialGradient(
       colors: <Color>[
         Color(0x33333333),
@@ -406,7 +404,7 @@ void main() {
       ],
     );
 
-    final RadialGradient actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
+    final RadialGradient? actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const RadialGradient(
       colors: <Color>[
         Color(0x3B3B3B3B),
@@ -453,7 +451,7 @@ void main() {
       ],
     );
 
-    final RadialGradient actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
+    final RadialGradient? actual = RadialGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const RadialGradient(
       center: Alignment(0.0, -1.0),
       focal: Alignment(0.0, 0.0),
@@ -469,7 +467,7 @@ void main() {
       ],
     ));
 
-    final RadialGradient actual2 = RadialGradient.lerp(testGradient1, testGradient3, 0.5);
+    final RadialGradient? actual2 = RadialGradient.lerp(testGradient1, testGradient3, 0.5);
     expect(actual2, const RadialGradient(
       center: Alignment(0.0, -1.0),
       focal: Alignment(-0.5, 0.0),
@@ -506,7 +504,7 @@ void main() {
       ],
     );
 
-    final SweepGradient actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
+    final SweepGradient? actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const SweepGradient(
       center: Alignment(0.0, -1.0),
       startAngle: math.pi / 4,
@@ -550,7 +548,7 @@ void main() {
       ],
     );
 
-    final SweepGradient actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
+    final SweepGradient? actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const SweepGradient(
       center: Alignment(0.0, -1.0),
       startAngle: math.pi / 4,
@@ -583,7 +581,7 @@ void main() {
       ],
     );
 
-    final SweepGradient actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
+    final SweepGradient? actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const SweepGradient(
       colors: <Color>[
         Color(0x33333333),
@@ -622,7 +620,7 @@ void main() {
       ],
     );
 
-    final SweepGradient actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
+    final SweepGradient? actual = SweepGradient.lerp(testGradient1, testGradient2, 0.5);
     expect(actual, const SweepGradient(
       colors: <Color>[
         Color(0x3B3B3B3B),

packages/flutter/test/painting/image_cache_binding_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';
@@ -13,7 +11,6 @@ import 'package:flutter/services.dart';
 
 import 'package:flutter_test/flutter_test.dart';
 
-
 void main() {
   test('PaintingBinding with memory pressure before initInstances', () {
     // Observed in devicelab: the device sends a memory pressure event to us
@@ -25,7 +22,7 @@ void main() {
     expect(binding.imageCache, null);
     binding.initInstances();
     expect(binding.imageCache, isNotNull);
-    expect(binding.imageCache.currentSize, 0);
+    expect(binding.imageCache!.currentSize, 0);
   });
 }
 
@@ -56,19 +53,19 @@ class TestBindingBase implements BindingBase {
   }
 
   @override
-  void registerBoolServiceExtension({String name, AsyncValueGetter<bool> getter, AsyncValueSetter<bool> setter}) {}
+  void registerBoolServiceExtension({required String name, required AsyncValueGetter<bool> getter, required AsyncValueSetter<bool> setter}) {}
 
   @override
-  void registerNumericServiceExtension({String name, AsyncValueGetter<double> getter, AsyncValueSetter<double> setter}) {}
+  void registerNumericServiceExtension({required String name, required AsyncValueGetter<double> getter, required AsyncValueSetter<double> setter}) {}
 
   @override
-  void registerServiceExtension({String name, ServiceExtensionCallback callback}) {}
+  void registerServiceExtension({required String name, required ServiceExtensionCallback callback}) {}
 
   @override
-  void registerSignalServiceExtension({String name, AsyncCallback callback}) {}
+  void registerSignalServiceExtension({required String name, required AsyncCallback callback}) {}
 
   @override
-  void registerStringServiceExtension({String name, AsyncValueGetter<String> getter, AsyncValueSetter<String> setter}) {}
+  void registerStringServiceExtension({required String name, required AsyncValueGetter<String> getter, required AsyncValueSetter<String> setter}) {}
 
   @override
   void unlocked() {}

packages/flutter/test/painting/image_cache_clearing_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:typed_data';
 
@@ -27,7 +25,7 @@ void main() {
         completer.complete();
       }
     ));
-    imageCache.clearLiveImages();
+    imageCache!.clearLiveImages();
     await completer.future;
   });
 }

packages/flutter/test/painting/image_cache_resize_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/painting.dart';
@@ -16,13 +14,14 @@ void main() {
   TestRenderingFlutterBinding();
 
   tearDown(() {
-    imageCache.clear();
-    imageCache.maximumSize = 1000;
-    imageCache.maximumSizeBytes = 10485760;
+    imageCache!
+      ..clear()
+      ..maximumSize = 1000
+      ..maximumSizeBytes = 10485760;
   });
 
   test('Image cache resizing based on count', () async {
-    imageCache.maximumSize = 2;
+    imageCache!.maximumSize = 2;
 
     final TestImageInfo a = await extractOneFrame(TestImageProvider(1, 1, image: await createTestImage()).resolve(ImageConfiguration.empty)) as TestImageInfo;
     final TestImageInfo b = await extractOneFrame(TestImageProvider(2, 2, image: await createTestImage()).resolve(ImageConfiguration.empty)) as TestImageInfo;
@@ -33,7 +32,7 @@ void main() {
     expect(c.value, equals(3));
     expect(d.value, equals(4));
 
-    imageCache.maximumSize = 0;
+    imageCache!.maximumSize = 0;
 
     final TestImageInfo e = await extractOneFrame(TestImageProvider(1, 5, image: await createTestImage()).resolve(ImageConfiguration.empty)) as TestImageInfo;
     expect(e.value, equals(5));
@@ -41,7 +40,7 @@ void main() {
     final TestImageInfo f = await extractOneFrame(TestImageProvider(1, 6, image: await createTestImage()).resolve(ImageConfiguration.empty)) as TestImageInfo;
     expect(f.value, equals(6));
 
-    imageCache.maximumSize = 3;
+    imageCache!.maximumSize = 3;
 
     final TestImageInfo g = await extractOneFrame(TestImageProvider(1, 7, image: await createTestImage()).resolve(ImageConfiguration.empty)) as TestImageInfo;
     expect(g.value, equals(7));
@@ -52,7 +51,7 @@ void main() {
 
   test('Image cache resizing based on size', () async {
     final ui.Image testImage = await createTestImage(width: 8, height: 8); // 256 B.
-    imageCache.maximumSizeBytes = 256 * 2;
+    imageCache!.maximumSizeBytes = 256 * 2;
 
     final TestImageInfo a = await extractOneFrame(TestImageProvider(1, 1, image: testImage).resolve(ImageConfiguration.empty)) as TestImageInfo;
     final TestImageInfo b = await extractOneFrame(TestImageProvider(2, 2, image: testImage).resolve(ImageConfiguration.empty)) as TestImageInfo;
@@ -63,7 +62,7 @@ void main() {
     expect(c.value, equals(3));
     expect(d.value, equals(4));
 
-    imageCache.maximumSizeBytes = 0;
+    imageCache!.maximumSizeBytes = 0;
 
     final TestImageInfo e = await extractOneFrame(TestImageProvider(1, 5, image: testImage).resolve(ImageConfiguration.empty)) as TestImageInfo;
     expect(e.value, equals(5));
@@ -71,7 +70,7 @@ void main() {
     final TestImageInfo f = await extractOneFrame(TestImageProvider(1, 6, image: testImage).resolve(ImageConfiguration.empty)) as TestImageInfo;
     expect(f.value, equals(6));
 
-    imageCache.maximumSizeBytes = 256 * 3;
+    imageCache!.maximumSizeBytes = 256 * 3;
 
     final TestImageInfo g = await extractOneFrame(TestImageProvider(1, 7, image: testImage).resolve(ImageConfiguration.empty)) as TestImageInfo;
     expect(g.value, equals(7));

packages/flutter/test/painting/image_decoder_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:typed_data';
 import 'dart:ui' as ui;
 

packages/flutter/test/painting/image_provider_and_image_cache_test.dart

@@ -2,14 +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 'dart:async';
 import 'dart:typed_data';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
-import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../image_data.dart';
@@ -19,23 +16,23 @@ import 'mocks_for_image_cache.dart';
 void main() {
   TestRenderingFlutterBinding();
 
-  final DecoderCallback _basicDecoder = (Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) {
-    return PaintingBinding.instance.instantiateImageCodec(bytes, cacheWidth: cacheWidth, cacheHeight: cacheHeight, allowUpscaling: allowUpscaling ?? false);
+  final DecoderCallback _basicDecoder = (Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) {
+    return PaintingBinding.instance!.instantiateImageCodec(bytes, cacheWidth: cacheWidth, cacheHeight: cacheHeight, allowUpscaling: allowUpscaling ?? false);
   };
 
-  FlutterExceptionHandler oldError;
+  FlutterExceptionHandler? oldError;
   setUp(() {
     oldError = FlutterError.onError;
   });
 
   tearDown(() {
     FlutterError.onError = oldError;
-    PaintingBinding.instance.imageCache.clear();
-    PaintingBinding.instance.imageCache.clearLiveImages();
+    PaintingBinding.instance!.imageCache!.clear();
+    PaintingBinding.instance!.imageCache!.clearLiveImages();
   });
 
   tearDown(() {
-    imageCache.clear();
+    imageCache!.clear();
   });
 
   test('AssetImageProvider - evicts on failure to load', () async {
@@ -46,42 +43,20 @@ void main() {
 
     const ImageProvider provider = ExactAssetImage('does-not-exist');
     final Object key = await provider.obtainKey(ImageConfiguration.empty);
-    expect(imageCache.statusForKey(provider).untracked, true);
-    expect(imageCache.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(provider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
 
     provider.resolve(ImageConfiguration.empty);
 
-    expect(imageCache.statusForKey(key).pending, true);
-    expect(imageCache.pendingImageCount, 1);
+    expect(imageCache!.statusForKey(key).pending, true);
+    expect(imageCache!.pendingImageCount, 1);
 
     await error.future;
 
-    expect(imageCache.statusForKey(provider).untracked, true);
-    expect(imageCache.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(provider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/56314
 
-  test('AssetImageProvider - evicts on null load', () async {
-    final Completer<StateError> error = Completer<StateError>();
-    FlutterError.onError = (FlutterErrorDetails details) {
-      error.complete(details.exception as StateError);
-    };
-
-    final ImageProvider provider = ExactAssetImage('does-not-exist', bundle: _TestAssetBundle());
-    final Object key = await provider.obtainKey(ImageConfiguration.empty);
-    expect(imageCache.statusForKey(provider).untracked, true);
-    expect(imageCache.pendingImageCount, 0);
-
-    provider.resolve(ImageConfiguration.empty);
-
-    expect(imageCache.statusForKey(key).pending, true);
-    expect(imageCache.pendingImageCount, 1);
-
-    await error.future;
-
-    expect(imageCache.statusForKey(provider).untracked, true);
-    expect(imageCache.pendingImageCount, 0);
-  });
-
   test('ImageProvider can evict images', () async {
     final Uint8List bytes = Uint8List.fromList(kTransparentImage);
     final MemoryImage imageProvider = MemoryImage(bytes);
@@ -90,9 +65,9 @@ void main() {
     stream.addListener(ImageStreamListener((ImageInfo info, bool syncCall) => completer.complete()));
     await completer.future;
 
-    expect(imageCache.currentSize, 1);
+    expect(imageCache!.currentSize, 1);
     expect(await MemoryImage(bytes).evict(), true);
-    expect(imageCache.currentSize, 0);
+    expect(imageCache!.currentSize, 0);
   });
 
   test('ImageProvider.evict respects the provided ImageCache', () async {
@@ -101,7 +76,7 @@ void main() {
     final MemoryImage imageProvider = MemoryImage(bytes);
     final ImageStreamCompleter cacheStream = otherCache.putIfAbsent(
       imageProvider, () => imageProvider.load(imageProvider, _basicDecoder),
-    );
+    )!;
     final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);
     final Completer<void> completer = Completer<void>();
     final Completer<void> cacheCompleter = Completer<void>();
@@ -114,10 +89,10 @@ void main() {
     await Future.wait(<Future<void>>[completer.future, cacheCompleter.future]);
 
     expect(otherCache.currentSize, 1);
-    expect(imageCache.currentSize, 1);
+    expect(imageCache!.currentSize, 1);
     expect(await imageProvider.evict(cache: otherCache), true);
     expect(otherCache.currentSize, 0);
-    expect(imageCache.currentSize, 1);
+    expect(imageCache!.currentSize, 1);
   });
 
   test('ImageProvider errors can always be caught', () async {
@@ -129,16 +104,9 @@ void main() {
     final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);
     stream.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
       caughtError.complete(false);
-    }, onError: (dynamic error, StackTrace stackTrace) {
+    }, onError: (dynamic error, StackTrace? stackTrace) {
       caughtError.complete(true);
     }));
     expect(await caughtError.future, true);
   });
 }
-
-class _TestAssetBundle extends CachingAssetBundle {
-  @override
-  Future<ByteData> load(String key) async {
-    return null;
-  }
-}

packages/flutter/test/painting/image_provider_network_image_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:io';
 import 'dart:math' as math;
@@ -21,11 +19,11 @@ import '../rendering/rendering_tester.dart';
 void main() {
   TestRenderingFlutterBinding();
 
-  final DecoderCallback _basicDecoder = (Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) {
-    return PaintingBinding.instance.instantiateImageCodec(bytes, cacheWidth: cacheWidth, cacheHeight: cacheHeight, allowUpscaling: allowUpscaling);
+  final DecoderCallback _basicDecoder = (Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) {
+    return PaintingBinding.instance!.instantiateImageCodec(bytes, cacheWidth: cacheWidth, cacheHeight: cacheHeight, allowUpscaling: allowUpscaling ?? false);
   };
 
-  _FakeHttpClient httpClient;
+  late _FakeHttpClient httpClient;
 
   setUp(() {
     httpClient = _FakeHttpClient();
@@ -34,8 +32,8 @@ void main() {
 
   tearDown(() {
     debugNetworkImageHttpClientProvider = null;
-    PaintingBinding.instance.imageCache.clear();
-    PaintingBinding.instance.imageCache.clearLiveImages();
+    PaintingBinding.instance!.imageCache!.clear();
+    PaintingBinding.instance!.imageCache!.clearLiveImages();
   });
 
   test('Expect thrown exception with statusCode - evicts from cache', () async {
@@ -47,23 +45,23 @@ void main() {
     final Completer<dynamic> caughtError = Completer<dynamic>();
 
     final ImageProvider imageProvider = NetworkImage(nonconst(requestUrl));
-    expect(imageCache.pendingImageCount, 0);
-    expect(imageCache.statusForKey(imageProvider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(imageProvider).untracked, true);
 
     final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
 
-    expect(imageCache.pendingImageCount, 1);
-    expect(imageCache.statusForKey(imageProvider).pending, true);
+    expect(imageCache!.pendingImageCount, 1);
+    expect(imageCache!.statusForKey(imageProvider).pending, true);
 
     result.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
-    }, onError: (dynamic error, StackTrace stackTrace) {
+    }, onError: (dynamic error, StackTrace? stackTrace) {
       caughtError.complete(error);
     }));
 
     final dynamic err = await caughtError.future;
 
-    expect(imageCache.pendingImageCount, 0);
-    expect(imageCache.statusForKey(imageProvider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(imageProvider).untracked, true);
 
     expect(
       err,
@@ -73,12 +71,6 @@ void main() {
     );
   }, skip: isBrowser); // Browser implementation does not use HTTP client but an <img> tag.
 
-  test('Disallows null urls', () {
-    expect(() {
-      NetworkImage(nonconst(null));
-    }, throwsAssertionError);
-  });
-
   test('Uses the HttpClient provided by debugNetworkImageHttpClientProvider if set', () async {
     httpClient.thrownError = 'client1';
     final List<dynamic> capturedErrors = <dynamic>[];
@@ -88,7 +80,7 @@ void main() {
       final ImageStreamCompleter completer = networkImage.load(networkImage, _basicDecoder);
       completer.addListener(ImageStreamListener(
         (ImageInfo image, bool synchronousCall) { },
-        onError: (dynamic error, StackTrace stackTrace) {
+        onError: (dynamic error, StackTrace? stackTrace) {
           capturedErrors.add(error);
         },
       ));
@@ -108,7 +100,7 @@ void main() {
     httpClient.thrownError = Error();
     bool uncaught = false;
 
-    final FlutterExceptionHandler oldError = FlutterError.onError;
+    final FlutterExceptionHandler? oldError = FlutterError.onError;
     await runZoned(() async {
       const ImageProvider imageProvider = NetworkImage('asdasdasdas');
       final Completer<bool> caughtError = Completer<bool>();
@@ -117,7 +109,7 @@ void main() {
       };
       final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
       result.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
-      }, onError: (dynamic error, StackTrace stackTrace) {
+      }, onError: (dynamic error, StackTrace? stackTrace) {
         caughtError.complete(true);
       }));
       expect(await caughtError.future, true);
@@ -153,8 +145,8 @@ void main() {
       onChunk: (ImageChunkEvent event) {
         events.add(event);
       },
-      onError: (dynamic error, StackTrace stackTrace) {
-        imageAvailable.completeError(error, stackTrace);
+      onError: (dynamic error, StackTrace? stackTrace) {
+        imageAvailable.completeError(error as Object, stackTrace);
       },
     ));
     await imageAvailable.future;
@@ -171,17 +163,17 @@ void main() {
     debugNetworkImageHttpClientProvider = () => mockHttpClient;
 
     final ImageProvider imageProvider = NetworkImage(nonconst('testing.url'));
-    expect(imageCache.pendingImageCount, 0);
-    expect(imageCache.statusForKey(imageProvider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(imageProvider).untracked, true);
 
     final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
 
-    expect(imageCache.pendingImageCount, 1);
-    expect(imageCache.statusForKey(imageProvider).pending, true);
+    expect(imageCache!.pendingImageCount, 1);
+    expect(imageCache!.statusForKey(imageProvider).pending, true);
     final Completer<dynamic> caughtError = Completer<dynamic>();
     result.addListener(ImageStreamListener(
       (ImageInfo info, bool syncCall) {},
-      onError: (dynamic error, StackTrace stackTrace) {
+      onError: (dynamic error, StackTrace? stackTrace) {
         caughtError.complete(error);
       },
     ));
@@ -190,14 +182,14 @@ void main() {
 
     expect(err, isA<SocketException>());
 
-    expect(imageCache.pendingImageCount, 0);
-    expect(imageCache.statusForKey(imageProvider).untracked, true);
-    expect(imageCache.containsKey(result), isFalse);
+    expect(imageCache!.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(imageProvider).untracked, true);
+    expect(imageCache!.containsKey(result), isFalse);
 
     debugNetworkImageHttpClientProvider = null;
   }, skip: isBrowser); // Browser does not resolve images this way.
 
-  Future<Codec> _decoder(Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) async {
+  Future<Codec> _decoder(Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) async {
     return FakeCodec();
   }
 
@@ -223,12 +215,12 @@ void main() {
 
 class _FakeHttpClient extends Fake implements HttpClient {
   final _FakeHttpClientRequest request = _FakeHttpClientRequest();
-  dynamic thrownError;
+  Object? thrownError;
 
   @override
   Future<HttpClientRequest> getUrl(Uri url) async {
     if (thrownError != null) {
-      throw thrownError;
+      throw thrownError!;
     }
     return request;
   }
@@ -252,10 +244,10 @@ class _FakeHttpClientResponse extends Fake implements HttpClientResponse {
   @override
   HttpClientResponseCompressionState get compressionState => HttpClientResponseCompressionState.notCompressed;
 
-  List<List<int>> content;
+  late List<List<int>> content;
 
   @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}) {
     return Stream<List<int>>.fromIterable(content).listen(
       onData,
       onDone: onDone,

packages/flutter/test/painting/image_provider_resize_image_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:typed_data';
 
@@ -17,8 +15,8 @@ void main() {
   TestRenderingFlutterBinding();
 
   tearDown(() {
-    PaintingBinding.instance.imageCache.clear();
-    PaintingBinding.instance.imageCache.clearLiveImages();
+    PaintingBinding.instance!.imageCache!.clear();
+    PaintingBinding.instance!.imageCache!.clearLiveImages();
   });
 
   test('ResizeImage resizes to the correct dimensions (up)', () async {
@@ -100,11 +98,11 @@ void main() {
     final MemoryImage memoryImage = MemoryImage(bytes);
     final ResizeImage resizeImage = ResizeImage(memoryImage, width: 123, height: 321);
 
-    final DecoderCallback decode = (Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) {
+    final DecoderCallback decode = (Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool allowUpscaling = false}) {
       expect(cacheWidth, 123);
       expect(cacheHeight, 321);
       expect(allowUpscaling, false);
-      return PaintingBinding.instance.instantiateImageCodec(bytes, cacheWidth: cacheWidth, cacheHeight: cacheHeight, allowUpscaling: allowUpscaling);
+      return PaintingBinding.instance!.instantiateImageCodec(bytes, cacheWidth: cacheWidth, cacheHeight: cacheHeight, allowUpscaling: allowUpscaling);
     };
 
     resizeImage.load(await resizeImage.obtainKey(ImageConfiguration.empty), decode);

packages/flutter/test/painting/image_provider_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:io';
 import 'dart:typed_data';
@@ -22,15 +20,15 @@ import 'mocks_for_image_cache.dart';
 void main() {
   TestRenderingFlutterBinding();
 
-  FlutterExceptionHandler oldError;
+  FlutterExceptionHandler? oldError;
   setUp(() {
     oldError = FlutterError.onError;
   });
 
   tearDown(() {
     FlutterError.onError = oldError;
-    PaintingBinding.instance.imageCache.clear();
-    PaintingBinding.instance.imageCache.clearLiveImages();
+    PaintingBinding.instance!.imageCache!.clear();
+    PaintingBinding.instance!.imageCache!.clearLiveImages();
   });
 
   test('obtainKey errors will be caught', () async {
@@ -42,7 +40,7 @@ void main() {
     final ImageStream stream = imageProvider.resolve(ImageConfiguration.empty);
     stream.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
       caughtError.complete(false);
-    }, onError: (dynamic error, StackTrace stackTrace) {
+    }, onError: (dynamic error, StackTrace? stackTrace) {
       caughtError.complete(true);
     }));
     expect(await caughtError.future, true);
@@ -74,7 +72,7 @@ void main() {
       };
       final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
       result.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
-      }, onError: (dynamic error, StackTrace stackTrace) {
+      }, onError: (dynamic error, StackTrace? stackTrace) {
         caughtError.complete(true);
       }));
       expect(await caughtError.future, true);
@@ -97,7 +95,7 @@ void main() {
       };
       final ImageStream result = imageProvider.resolve(ImageConfiguration.empty);
       result.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
-      }, onError: (dynamic error, StackTrace stackTrace) {
+      }, onError: (dynamic error, StackTrace? stackTrace) {
         caughtError.complete(true);
       }));
       expect(await caughtError.future, true);
@@ -114,17 +112,17 @@ void main() {
     final File file = fs.file('/empty.png')..createSync(recursive: true);
     final FileImage provider = FileImage(file);
 
-    expect(imageCache.statusForKey(provider).untracked, true);
-    expect(imageCache.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(provider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
 
     provider.resolve(ImageConfiguration.empty);
 
-    expect(imageCache.statusForKey(provider).pending, true);
-    expect(imageCache.pendingImageCount, 1);
+    expect(imageCache!.statusForKey(provider).pending, true);
+    expect(imageCache!.pendingImageCount, 1);
 
     expect(await error.future, isStateError);
-    expect(imageCache.statusForKey(provider).untracked, true);
-    expect(imageCache.pendingImageCount, 0);
+    expect(imageCache!.statusForKey(provider).untracked, true);
+    expect(imageCache!.pendingImageCount, 0);
   });
 
   test('File image with empty file throws expected error (load)', () async {
@@ -136,14 +134,14 @@ void main() {
     final File file = fs.file('/empty.png')..createSync(recursive: true);
     final FileImage provider = FileImage(file);
 
-    expect(provider.load(provider, (Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) async {
+    expect(provider.load(provider, (Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) async {
       return Future<Codec>.value(FakeCodec());
     }), isA<MultiFrameImageStreamCompleter>());
 
     expect(await error.future, isStateError);
   });
 
-  Future<Codec> _decoder(Uint8List bytes, {int cacheWidth, int cacheHeight, bool allowUpscaling}) async {
+  Future<Codec> _decoder(Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool? allowUpscaling}) async {
     return FakeCodec();
   }
 

packages/flutter/test/painting/image_resolution_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:typed_data';
 

packages/flutter/test/painting/image_stream_test.dart

@@ -2,15 +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
-
 import 'dart:async';
 import 'dart:ui';
 
 import 'package:flutter/painting.dart';
 import 'package:flutter/scheduler.dart' show timeDilation, SchedulerBinding;
 import 'package:flutter_test/flutter_test.dart';
-import 'package:meta/meta.dart';
 
 class FakeFrameInfo implements FrameInfo {
   const FakeFrameInfo(this._duration, this._image);
@@ -24,7 +21,7 @@ class FakeFrameInfo implements FrameInfo {
   @override
   Image get image => _image;
 
-  int get imageHandleCount => image.debugGetOpenHandleStackTraces().length;
+  int get imageHandleCount => image.debugGetOpenHandleStackTraces()!.length;
 
   FakeFrameInfo clone() {
     return FakeFrameInfo(
@@ -35,12 +32,11 @@ class FakeFrameInfo implements FrameInfo {
 }
 
 class MockCodec implements Codec {
-
   @override
-  int frameCount;
+  late int frameCount;
 
   @override
-  int repetitionCount;
+  late int repetitionCount;
 
   int numFramesAsked = 0;
 
@@ -67,7 +63,7 @@ class MockCodec implements Codec {
 }
 
 class FakeEventReportingImageStreamCompleter extends ImageStreamCompleter {
-  FakeEventReportingImageStreamCompleter({Stream<ImageChunkEvent> chunkEvents,}) {
+  FakeEventReportingImageStreamCompleter({Stream<ImageChunkEvent>? chunkEvents}) {
     if (chunkEvents != null) {
       chunkEvents.listen((ImageChunkEvent event) {
           reportImageChunkEvent(event);
@@ -78,8 +74,8 @@ class FakeEventReportingImageStreamCompleter extends ImageStreamCompleter {
 }
 
 void main() {
-  Image image20x10;
-  Image image200x100;
+  late Image image20x10;
+  late Image image200x100;
   setUp(() async {
     image20x10 = await createTestImage(width: 20, height: 10);
     image200x100 = await createTestImage(width: 200, height: 100);
@@ -602,7 +598,7 @@ void main() {
     );
 
     dynamic capturedException;
-    final ImageErrorListener errorListener = (dynamic exception, StackTrace stackTrace) {
+    final ImageErrorListener errorListener = (dynamic exception, StackTrace? stackTrace) {
       capturedException = exception;
     };
 
@@ -660,16 +656,16 @@ void main() {
   testWidgets('ImageStreamListener hashCode and equals', (WidgetTester tester) async {
     void handleImage(ImageInfo image, bool synchronousCall) { }
     void handleImageDifferently(ImageInfo image, bool synchronousCall) { }
-    void handleError(dynamic error, StackTrace stackTrace) { }
+    void handleError(dynamic error, StackTrace? stackTrace) { }
     void handleChunk(ImageChunkEvent event) { }
 
     void compare({
-      @required ImageListener onImage1,
-      @required ImageListener onImage2,
-      ImageChunkListener onChunk1,
-      ImageChunkListener onChunk2,
-      ImageErrorListener onError1,
-      ImageErrorListener onError2,
+      required ImageListener onImage1,
+      required ImageListener onImage2,
+      ImageChunkListener? onChunk1,
+      ImageChunkListener? onChunk2,
+      ImageErrorListener? onError1,
+      ImageErrorListener? onError2,
       bool areEqual = true,
     }) {
       final ImageStreamListener l1 = ImageStreamListener(onImage1, onChunk: onChunk1, onError: onError1);
@@ -690,7 +686,7 @@ void main() {
   });
 
   testWidgets('Keep alive handles do not drive frames or prevent last listener callbacks', (WidgetTester tester) async {
-    final Image image10x10 = await tester.runAsync(() => createTestImage(width: 10, height: 10));
+    final Image image10x10 = (await tester.runAsync(() => createTestImage(width: 10, height: 10)))!;
     final MockCodec mockCodec = MockCodec();
     mockCodec.frameCount = 2;
     mockCodec.repetitionCount = -1;
@@ -713,7 +709,7 @@ void main() {
     expect(lastListenerDropped, false);
     final ImageStreamCompleterHandle handle = imageStream.keepAlive();
     expect(lastListenerDropped, false);
-    SchedulerBinding.instance.debugAssertNoTransientCallbacks('Only passive listeners');
+    SchedulerBinding.instance!.debugAssertNoTransientCallbacks('Only passive listeners');
 
     codecCompleter.complete(mockCodec);
     await tester.idle();
@@ -723,7 +719,7 @@ void main() {
     final FakeFrameInfo frame1 = FakeFrameInfo(Duration.zero, image20x10);
     mockCodec.completeNextFrame(frame1);
     await tester.idle();
-    SchedulerBinding.instance.debugAssertNoTransientCallbacks('Only passive listeners');
+    SchedulerBinding.instance!.debugAssertNoTransientCallbacks('Only passive listeners');
     await tester.pump();
     expect(onImageCount, 0);
 
@@ -732,7 +728,7 @@ void main() {
     final FakeFrameInfo frame2 = FakeFrameInfo(Duration.zero, image10x10);
     mockCodec.completeNextFrame(frame2);
     await tester.idle();
-    expect(SchedulerBinding.instance.transientCallbackCount, 1);
+    expect(SchedulerBinding.instance!.transientCallbackCount, 1);
     await tester.pump();
 
     expect(onImageCount, 1);
@@ -742,16 +738,16 @@ void main() {
 
     mockCodec.completeNextFrame(frame1);
     await tester.idle();
-    expect(SchedulerBinding.instance.transientCallbackCount, 1);
+    expect(SchedulerBinding.instance!.transientCallbackCount, 1);
     await tester.pump();
 
     expect(onImageCount, 1);
 
-    SchedulerBinding.instance.debugAssertNoTransientCallbacks('Only passive listeners');
+    SchedulerBinding.instance!.debugAssertNoTransientCallbacks('Only passive listeners');
 
     mockCodec.completeNextFrame(frame2);
     await tester.idle();
-    SchedulerBinding.instance.debugAssertNoTransientCallbacks('Only passive listeners');
+    SchedulerBinding.instance!.debugAssertNoTransientCallbacks('Only passive listeners');
     await tester.pump();
 
     expect(onImageCount, 1);

packages/flutter/test/painting/matrix_utils_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';
 
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/painting/notched_shapes_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';

packages/flutter/test/painting/paint_image_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';
@@ -20,8 +18,8 @@ class TestCanvas implements Canvas {
 }
 
 void main() {
-  ui.Image image300x300;
-  ui.Image image300x200;
+  late ui.Image image300x300;
+  late ui.Image image300x200;
   setUpAll(() async {
     image300x300 = await createTestImage(width: 300, height: 300, cache: false);
     image300x200 = await createTestImage(width: 300, height: 200, cache: false);
@@ -53,7 +51,7 @@ void main() {
 
   test('debugInvertOversizedImages', () async {
     debugInvertOversizedImages = true;
-    final FlutterExceptionHandler oldFlutterError = FlutterError.onError;
+    final FlutterExceptionHandler? oldFlutterError = FlutterError.onError;
 
     final List<String> messages = <String>[];
     FlutterError.onError = (FlutterErrorDetails details) {
@@ -111,7 +109,7 @@ void main() {
   });
 
   testWidgets('Reports Image painting', (WidgetTester tester) async {
-    ImageSizeInfo imageSizeInfo;
+    late ImageSizeInfo imageSizeInfo;
     int count = 0;
     debugOnPaintImage = (ImageSizeInfo info) {
       count += 1;
@@ -150,7 +148,7 @@ void main() {
   });
 
   testWidgets('Reports Image painting - change per frame', (WidgetTester tester) async {
-    ImageSizeInfo imageSizeInfo;
+    late ImageSizeInfo imageSizeInfo;
     int count = 0;
     debugOnPaintImage = (ImageSizeInfo info) {
       count += 1;
@@ -193,7 +191,7 @@ void main() {
   });
 
   testWidgets('Reports Image painting - no debug label', (WidgetTester tester) async {
-    ImageSizeInfo imageSizeInfo;
+    late ImageSizeInfo imageSizeInfo;
     int count = 0;
     debugOnPaintImage = (ImageSizeInfo info) {
       count += 1;

packages/flutter/test/painting/rounded_rectangle_border_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/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -75,18 +73,18 @@ void main() {
     );
     expect(r.getOuterPath(rect), looksLikeR);
     expect(c.getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(r, c, 0.1).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(r, c, 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.9), r, 0.1).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.9), r, 0.9).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), c, 0.1).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), c, 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), ShapeBorder.lerp(r, c, 0.9), 0.1).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), ShapeBorder.lerp(r, c, 0.9), 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(r, ShapeBorder.lerp(r, c, 0.9), 0.1).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(r, ShapeBorder.lerp(r, c, 0.9), 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(c, ShapeBorder.lerp(r, c, 0.1), 0.1).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(c, ShapeBorder.lerp(r, c, 0.1), 0.9).getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(r, c, 0.1)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(r, c, 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.9), r, 0.1)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.9), r, 0.9)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), c, 0.1)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), c, 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), ShapeBorder.lerp(r, c, 0.9), 0.1)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(r, c, 0.1), ShapeBorder.lerp(r, c, 0.9), 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(r, ShapeBorder.lerp(r, c, 0.9), 0.1)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(r, ShapeBorder.lerp(r, c, 0.9), 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(c, ShapeBorder.lerp(r, c, 0.1), 0.1)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(c, ShapeBorder.lerp(r, c, 0.1), 0.9)!.getOuterPath(rect), looksLikeR);
 
     expect(ShapeBorder.lerp(r, c, 0.1).toString(),
            'RoundedRectangleBorder(BorderSide(Color(0xff000000), 0.0, BorderStyle.none), BorderRadius.circular(10.0), 10.0% of the way to being a CircleBorder)');
@@ -105,8 +103,8 @@ void main() {
     expect(ShapeBorder.lerp(r, c, 0.1), ShapeBorder.lerp(r, c, 0.1));
     expect(ShapeBorder.lerp(r, c, 0.1).hashCode, ShapeBorder.lerp(r, c, 0.1).hashCode);
 
-    final ShapeBorder direct50 = ShapeBorder.lerp(r, c, 0.5);
-    final ShapeBorder indirect50 = ShapeBorder.lerp(ShapeBorder.lerp(c, r, 0.1), ShapeBorder.lerp(c, r, 0.9), 0.5);
+    final ShapeBorder direct50 = ShapeBorder.lerp(r, c, 0.5)!;
+    final ShapeBorder indirect50 = ShapeBorder.lerp(ShapeBorder.lerp(c, r, 0.1), ShapeBorder.lerp(c, r, 0.9), 0.5)!;
     expect(direct50, indirect50);
     expect(direct50.hashCode, indirect50.hashCode);
     expect(direct50.toString(), indirect50.toString());

packages/flutter/test/painting/shader_warm_up_test.dart

@@ -2,32 +2,29 @@
 // Use of 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';
 
 class TestCanvas implements Canvas {
-  TestCanvas([this.invocations]);
+  TestCanvas();
 
-  final List<Invocation> invocations;
+  final List<Invocation> invocations = <Invocation>[];
 
   @override
   void noSuchMethod(Invocation invocation) {
-    invocations?.add(invocation);
+    invocations.add(invocation);
   }
 }
 
 void main() {
   test('DefaultShaderWarmUp has expected canvas invocations', () {
-    final List<Invocation> invocations = <Invocation>[];
-    final TestCanvas canvas = TestCanvas(invocations);
+    final TestCanvas canvas = TestCanvas();
     const DefaultShaderWarmUp s = DefaultShaderWarmUp();
     s.warmUpOnCanvas(canvas);
 
     bool hasDrawRectAfterClipRRect = false;
-    for (int i = 0; i < invocations.length - 1; i += 1) {
-      if (invocations[i].memberName == #clipRRect && invocations[i + 1].memberName == #drawRect) {
+    for (int i = 0; i < canvas.invocations.length - 1; i += 1) {
+      if (canvas.invocations[i].memberName == #clipRRect && canvas.invocations[i + 1].memberName == #drawRect) {
         hasDrawRectAfterClipRRect = true;
         break;
       }

packages/flutter/test/painting/shape_border_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/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 

packages/flutter/test/painting/shape_decoration_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';
@@ -22,7 +20,6 @@ void main() {
     const Gradient gradient = LinearGradient(colors: <Color>[colorR, colorG]);
     expect(const ShapeDecoration(shape: Border()), const ShapeDecoration(shape: Border()));
     expect(() => ShapeDecoration(color: colorR, gradient: nonconst(gradient), shape: const Border()), throwsAssertionError);
-    expect(() => ShapeDecoration(gradient: nonconst(gradient), shape: null), throwsAssertionError);
     expect(
       ShapeDecoration.fromBoxDecoration(const BoxDecoration(shape: BoxShape.circle)),
       const ShapeDecoration(shape: CircleBorder(side: BorderSide.none)),
@@ -52,9 +49,9 @@ void main() {
     expect(Decoration.lerp(a, b, 1.0), b);
     const Size size = Size(200.0, 100.0); // at t=0.5, width will be 150 (x=25 to x=175).
     expect(a.hitTest(size, const Offset(20.0, 50.0)), isFalse);
-    expect(Decoration.lerp(a, b, 0.1).hitTest(size, const Offset(20.0, 50.0)), isFalse);
-    expect(Decoration.lerp(a, b, 0.5).hitTest(size, const Offset(20.0, 50.0)), isFalse);
-    expect(Decoration.lerp(a, b, 0.9).hitTest(size, const Offset(20.0, 50.0)), isTrue);
+    expect(Decoration.lerp(a, b, 0.1)!.hitTest(size, const Offset(20.0, 50.0)), isFalse);
+    expect(Decoration.lerp(a, b, 0.5)!.hitTest(size, const Offset(20.0, 50.0)), isFalse);
+    expect(Decoration.lerp(a, b, 0.9)!.hitTest(size, const Offset(20.0, 50.0)), isTrue);
     expect(b.hitTest(size, const Offset(20.0, 50.0)), isTrue);
   });
 

packages/flutter/test/painting/stadium_border_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/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -63,18 +61,18 @@ void main() {
     );
     expect(stadium.getOuterPath(rect), looksLikeS);
     expect(circle.getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(stadium, circle, 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(stadium, circle, 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.9), stadium, 0.1).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.9), stadium, 0.9).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), circle, 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), circle, 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), ShapeBorder.lerp(stadium, circle, 0.9), 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), ShapeBorder.lerp(stadium, circle, 0.9), 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, circle, 0.9), 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, circle, 0.9), 0.9).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(circle, ShapeBorder.lerp(stadium, circle, 0.1), 0.1).getOuterPath(rect), looksLikeC);
-    expect(ShapeBorder.lerp(circle, ShapeBorder.lerp(stadium, circle, 0.1), 0.9).getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(stadium, circle, 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(stadium, circle, 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.9), stadium, 0.1)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.9), stadium, 0.9)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), circle, 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), circle, 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), ShapeBorder.lerp(stadium, circle, 0.9), 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, circle, 0.1), ShapeBorder.lerp(stadium, circle, 0.9), 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, circle, 0.9), 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, circle, 0.9), 0.9)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(circle, ShapeBorder.lerp(stadium, circle, 0.1), 0.1)!.getOuterPath(rect), looksLikeC);
+    expect(ShapeBorder.lerp(circle, ShapeBorder.lerp(stadium, circle, 0.1), 0.9)!.getOuterPath(rect), looksLikeS);
 
     expect(ShapeBorder.lerp(stadium, circle, 0.1).toString(),
         'StadiumBorder(BorderSide(Color(0xff000000), 0.0, BorderStyle.none), 10.0% of the way to being a CircleBorder)');
@@ -93,8 +91,8 @@ void main() {
     expect(ShapeBorder.lerp(stadium, circle, 0.1), ShapeBorder.lerp(stadium, circle, 0.1));
     expect(ShapeBorder.lerp(stadium, circle, 0.1).hashCode, ShapeBorder.lerp(stadium, circle, 0.1).hashCode);
 
-    final ShapeBorder direct50 = ShapeBorder.lerp(stadium, circle, 0.5);
-    final ShapeBorder indirect50 = ShapeBorder.lerp(ShapeBorder.lerp(circle, stadium, 0.1), ShapeBorder.lerp(circle, stadium, 0.9), 0.5);
+    final ShapeBorder direct50 = ShapeBorder.lerp(stadium, circle, 0.5)!;
+    final ShapeBorder indirect50 = ShapeBorder.lerp(ShapeBorder.lerp(circle, stadium, 0.1), ShapeBorder.lerp(circle, stadium, 0.9), 0.5)!;
     expect(direct50, indirect50);
     expect(direct50.hashCode, indirect50.hashCode);
     expect(direct50.toString(), indirect50.toString());
@@ -130,18 +128,18 @@ void main() {
     );
     expect(stadium.getOuterPath(rect), looksLikeS);
     expect(rrect.getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(stadium, rrect, 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(stadium, rrect, 0.9).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.9), stadium, 0.1).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.9), stadium, 0.9).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), rrect, 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), rrect, 0.9).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), ShapeBorder.lerp(stadium, rrect, 0.9), 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), ShapeBorder.lerp(stadium, rrect, 0.9), 0.9).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, rrect, 0.9), 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, rrect, 0.9), 0.9).getOuterPath(rect), looksLikeR);
-    expect(ShapeBorder.lerp(rrect, ShapeBorder.lerp(stadium, rrect, 0.1), 0.1).getOuterPath(rect), looksLikeS);
-    expect(ShapeBorder.lerp(rrect, ShapeBorder.lerp(stadium, rrect, 0.1), 0.9).getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(stadium, rrect, 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(stadium, rrect, 0.9)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.9), stadium, 0.1)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.9), stadium, 0.9)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), rrect, 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), rrect, 0.9)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), ShapeBorder.lerp(stadium, rrect, 0.9), 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(ShapeBorder.lerp(stadium, rrect, 0.1), ShapeBorder.lerp(stadium, rrect, 0.9), 0.9)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, rrect, 0.9), 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(stadium, ShapeBorder.lerp(stadium, rrect, 0.9), 0.9)!.getOuterPath(rect), looksLikeR);
+    expect(ShapeBorder.lerp(rrect, ShapeBorder.lerp(stadium, rrect, 0.1), 0.1)!.getOuterPath(rect), looksLikeS);
+    expect(ShapeBorder.lerp(rrect, ShapeBorder.lerp(stadium, rrect, 0.1), 0.9)!.getOuterPath(rect), looksLikeS);
 
     expect(ShapeBorder.lerp(stadium, rrect, 0.1).toString(),
         'StadiumBorder(BorderSide(Color(0xff000000), 0.0, BorderStyle.none), '
@@ -166,8 +164,8 @@ void main() {
     expect(ShapeBorder.lerp(stadium, rrect, 0.1), ShapeBorder.lerp(stadium, rrect, 0.1));
     expect(ShapeBorder.lerp(stadium, rrect, 0.1).hashCode, ShapeBorder.lerp(stadium, rrect, 0.1).hashCode);
 
-    final ShapeBorder direct50 = ShapeBorder.lerp(stadium, rrect, 0.5);
-    final ShapeBorder indirect50 = ShapeBorder.lerp(ShapeBorder.lerp(rrect, stadium, 0.1), ShapeBorder.lerp(rrect, stadium, 0.9), 0.5);
+    final ShapeBorder direct50 = ShapeBorder.lerp(stadium, rrect, 0.5)!;
+    final ShapeBorder indirect50 = ShapeBorder.lerp(ShapeBorder.lerp(rrect, stadium, 0.1), ShapeBorder.lerp(rrect, stadium, 0.9), 0.5)!;
     expect(direct50, indirect50);
     expect(direct50.hashCode, indirect50.hashCode);
     expect(direct50.toString(), indirect50.toString());

packages/flutter/test/painting/strut_style_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/painting.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/painting/system_fonts_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/rendering.dart';
 import 'package:flutter/material.dart';
@@ -22,10 +20,10 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-      (ByteData data) { },
+      (ByteData? data) { },
     );
     final RenderObject renderObject = tester.renderObject(find.text('text widget'));
     expect(renderObject.debugNeedsLayout, isTrue);
@@ -40,10 +38,10 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     final EditableTextState state = tester.state(find.byType(EditableText));
     expect(state.renderEditable.debugNeedsLayout, isTrue);
@@ -61,10 +59,10 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     final RenderObject renderObject = tester.renderObject(find.byType(Banner));
     expect(renderObject.debugNeedsPaint, isTrue);
@@ -78,16 +76,16 @@ void main() {
         ),
       ),
     );
-    final dynamic state = tester.state(find.byType(CupertinoDatePicker));
+    final dynamic state = tester.state(find.byType(CupertinoDatePicker)); // ignore: unnecessary_nullable_for_final_variable_declarations
     final Map<int, double> cache = state.estimatedColumnWidths as Map<int, double>;
     expect(cache.isNotEmpty, isTrue);
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     // Cache should be cleaned.
     expect(cache.isEmpty, isTrue);
@@ -104,17 +102,17 @@ void main() {
         ),
       ),
     );
-    final dynamic state = tester.state(find.byType(CupertinoDatePicker));
+    final dynamic state = tester.state(find.byType(CupertinoDatePicker)); // ignore: unnecessary_nullable_for_final_variable_declarations
     final Map<int, double> cache = state.estimatedColumnWidths as Map<int, double>;
     // Simulates font missing.
     cache.clear();
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     // Cache should be replenished
     expect(cache.isNotEmpty, isTrue);
@@ -130,7 +128,7 @@ void main() {
         ),
       ),
     );
-    final dynamic state = tester.state(find.byType(CupertinoTimerPicker));
+    final dynamic state = tester.state(find.byType(CupertinoTimerPicker)); // ignore: unnecessary_nullable_for_final_variable_declarations
     // Simulates wrong metrics due to font missing.
     state.numberLabelWidth = 0.0;
     state.numberLabelHeight = 0.0;
@@ -138,10 +136,10 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     // Metrics should be refreshed
     expect(state.numberLabelWidth - 46.0 < precisionErrorTolerance, isTrue);
@@ -165,14 +163,14 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     final RenderObject renderObject = tester.renderObject(find.byType(RangeSlider));
 
-    bool sliderBoxNeedsLayout;
+    late bool sliderBoxNeedsLayout;
     renderObject.visitChildren((RenderObject child) {sliderBoxNeedsLayout = child.debugNeedsLayout;});
     expect(sliderBoxNeedsLayout, isTrue);
   });
@@ -191,10 +189,10 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     // _RenderSlider is the last render object in the tree.
     final RenderObject renderObject = tester.allRenderObjects.last;
@@ -214,11 +212,11 @@ void main() {
                     showTimePicker(
                       context: context,
                       initialTime: const TimeOfDay(hour: 7, minute: 0),
-                      builder: (BuildContext context, Widget child) {
+                      builder: (BuildContext context, Widget? child) {
                         return Directionality(
                           key: const Key('parent'),
                           textDirection: TextDirection.ltr,
-                          child: child,
+                          child: child!,
                         );
                       },
                     );
@@ -235,10 +233,10 @@ void main() {
     const Map<String, dynamic> data = <String, dynamic>{
       'type': 'fontsChange',
     };
-    await ServicesBinding.instance.defaultBinaryMessenger.handlePlatformMessage(
+    await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage(
       'flutter/system',
       SystemChannels.system.codec.encodeMessage(data),
-        (ByteData data) { },
+        (ByteData? data) { },
     );
     final RenderObject renderObject = tester.renderObject(
       find.descendant(

packages/flutter/test/painting/text_painter_rtl_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/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -46,7 +44,7 @@ void main() {
       style: TextStyle(fontFamily: 'Ahem', fontSize: 10.0),
     );
     TextSpan textSpan = painter.text as TextSpan;
-    expect(textSpan.text.length, 28);
+    expect(textSpan.text!.length, 28);
     painter.layout();
 
     // The skips here are because the old rendering code considers the bidi formatting characters
@@ -131,7 +129,7 @@ void main() {
 
     textSpan = painter.text as TextSpan;
     final List<List<TextBox>> list = <List<TextBox>>[
-      for (int index = 0; index < textSpan.text.length; index += 1)
+      for (int index = 0; index < textSpan.text!.length; index += 1)
         painter.getBoxesForSelection(TextSelection(baseOffset: index, extentOffset: index + 1)),
     ];
     expect(list, const <List<TextBox>>[
@@ -178,7 +176,7 @@ void main() {
       style: TextStyle(fontFamily: 'Ahem', fontSize: 10.0),
     );
     final TextSpan textSpan = painter.text as TextSpan;
-    expect(textSpan.text.length, 28);
+    expect(textSpan.text!.length, 28);
     painter.layout();
 
     final TextRange hebrew1 = painter.getWordBoundary(const TextPosition(offset: 4, affinity: TextAffinity.downstream));
@@ -268,7 +266,7 @@ void main() {
       style: TextStyle(fontFamily: 'Ahem', fontSize: 10.0),
     );
     final TextSpan textSpan = painter.text as TextSpan;
-    expect(textSpan.text.length, 2);
+    expect(textSpan.text!.length, 2);
     painter.layout(maxWidth: 10.0);
 
     for (int index = 0; index <= 2; index += 1) {

packages/flutter/test/painting/text_painter_test.dart

@@ -2,14 +2,14 @@
 // Use 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';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import '../flutter_test_alternative.dart' show Fake;
+
 void main() {
   test('TextPainter caret test', () {
     final TextPainter painter = TextPainter()
@@ -149,7 +149,7 @@ void main() {
 
   test('TextPainter error test', () {
     final TextPainter painter = TextPainter(textDirection: TextDirection.ltr);
-    expect(() { painter.paint(null, Offset.zero); }, anyOf(throwsFlutterError, throwsAssertionError));
+    expect(() { painter.paint(MockCanvas(), Offset.zero); }, anyOf(throwsFlutterError, throwsAssertionError));
   });
 
   test('TextPainter requires textDirection', () {
@@ -730,19 +730,19 @@ void main() {
     caretOffset = painter.getOffsetForCaret(const ui.TextPosition(offset: 23), ui.Rect.zero);
     expect(caretOffset.dx, 250);
 
-    expect(painter.inlinePlaceholderBoxes.length, 14);
-    expect(painter.inlinePlaceholderBoxes[0], const TextBox.fromLTRBD(56, 0, 106, 30, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[2], const TextBox.fromLTRBD(212, 0, 262, 30, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[3], const TextBox.fromLTRBD(318, 0, 368, 30, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[4], const TextBox.fromLTRBD(368, 0, 418, 30, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[5], const TextBox.fromLTRBD(418, 0, 468, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes!.length, 14);
+    expect(painter.inlinePlaceholderBoxes![0], const TextBox.fromLTRBD(56, 0, 106, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![2], const TextBox.fromLTRBD(212, 0, 262, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![3], const TextBox.fromLTRBD(318, 0, 368, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![4], const TextBox.fromLTRBD(368, 0, 418, 30, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![5], const TextBox.fromLTRBD(418, 0, 468, 30, TextDirection.ltr));
     // line should break here
-    expect(painter.inlinePlaceholderBoxes[6], const TextBox.fromLTRBD(0, 30, 50, 60, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[7], const TextBox.fromLTRBD(50, 30, 100, 60, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[10], const TextBox.fromLTRBD(200, 30, 250, 60, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[11], const TextBox.fromLTRBD(250, 30, 300, 60, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[12], const TextBox.fromLTRBD(300, 30, 351, 60, TextDirection.ltr));
-    expect(painter.inlinePlaceholderBoxes[13], const TextBox.fromLTRBD(351, 30, 401, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![6], const TextBox.fromLTRBD(0, 30, 50, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![7], const TextBox.fromLTRBD(50, 30, 100, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![10], const TextBox.fromLTRBD(200, 30, 250, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![11], const TextBox.fromLTRBD(250, 30, 300, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![12], const TextBox.fromLTRBD(300, 30, 351, 60, TextDirection.ltr));
+    expect(painter.inlinePlaceholderBoxes![13], const TextBox.fromLTRBD(351, 30, 401, 60, TextDirection.ltr));
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/42086
 
   // Null values are valid. See https://github.com/flutter/flutter/pull/48346#issuecomment-584839221
@@ -830,7 +830,11 @@ void main() {
     final double caretHeight = painter.getFullHeightForCaret(
       const ui.TextPosition(offset: 0),
       ui.Rect.zero,
-    );
+    )!;
     expect(caretHeight, 50.0);
   }, skip: isBrowser); // https://github.com/flutter/flutter/issues/56308
 }
+
+class MockCanvas extends Fake implements Canvas {
+
+}

packages/flutter/test/painting/text_span_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/painting.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -234,15 +232,4 @@ void main() {
     expect(textSpan.getSpanForPosition(const TextPosition(offset: 2)).runtimeType, WidgetSpan);
     expect(textSpan.getSpanForPosition(const TextPosition(offset: 3)).runtimeType, TextSpan);
   });
-
-  test('TextSpan with a null child should throw FlutterError', () {
-    const TextSpan text = TextSpan(
-      text: 'foo bar',
-      children: <InlineSpan>[
-        null,
-      ],
-    );
-    expect(() => text.computeToPlainText(StringBuffer()), anyOf(throwsFlutterError, throwsAssertionError));
-  });
-
 }

packages/flutter/test/painting/text_style_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 show TextStyle, ParagraphStyle, FontFeature, Shadow;
 
 import 'package:flutter/painting.dart';
@@ -96,7 +94,7 @@ void main() {
     expect(s4.height, 123.0);
     expect(s4.color, const Color(0xFF00FF00));
 
-    final TextStyle s5 = TextStyle.lerp(s1, s3, 0.25);
+    final TextStyle s5 = TextStyle.lerp(s1, s3, 0.25)!;
     expect(s1.fontFamily, isNull);
     expect(s1.fontSize, 10.0);
     expect(s1.fontWeight, FontWeight.w800);
@@ -117,7 +115,7 @@ void main() {
 
     expect(TextStyle.lerp(null, null, 0.5), isNull);
 
-    final TextStyle s6 = TextStyle.lerp(null, s3, 0.25);
+    final TextStyle s6 = TextStyle.lerp(null, s3, 0.25)!;
     expect(s3.fontFamily, isNull);
     expect(s3.fontSize, 18.0);
     expect(s3.fontWeight, FontWeight.w400);
@@ -130,7 +128,7 @@ void main() {
     expect(s6.height, isNull);
     expect(s6.color, isNull);
 
-    final TextStyle s7 = TextStyle.lerp(null, s3, 0.75);
+    final TextStyle s7 = TextStyle.lerp(null, s3, 0.75)!;
     expect(s3.fontFamily, isNull);
     expect(s3.fontSize, 18.0);
     expect(s3.fontWeight, FontWeight.w400);
@@ -143,7 +141,7 @@ void main() {
     expect(s7.height, 123.0);
     expect(s7.color, isNull);
 
-    final TextStyle s8 = TextStyle.lerp(s3, null, 0.25);
+    final TextStyle s8 = TextStyle.lerp(s3, null, 0.25)!;
     expect(s3.fontFamily, isNull);
     expect(s3.fontSize, 18.0);
     expect(s3.fontWeight, FontWeight.w400);
@@ -156,7 +154,7 @@ void main() {
     expect(s8.height, 123.0);
     expect(s8.color, isNull);
 
-    final TextStyle s9 = TextStyle.lerp(s3, null, 0.75);
+    final TextStyle s9 = TextStyle.lerp(s3, null, 0.75)!;
     expect(s3.fontFamily, isNull);
     expect(s3.fontSize, 18.0);
     expect(s3.fontWeight, FontWeight.w400);
@@ -201,9 +199,9 @@ void main() {
     expect(s7.getTextStyle().toString(), 'TextStyle(color: unspecified, decoration: unspecified, decorationColor: unspecified, decorationStyle: unspecified, decorationThickness: unspecified, fontWeight: unspecified, fontStyle: unspecified, textBaseline: unspecified, fontFamily: packages/p/test, fontFamilyFallback: unspecified, fontSize: unspecified, letterSpacing: unspecified, wordSpacing: unspecified, height: unspecified, locale: unspecified, background: unspecified, foreground: unspecified, shadows: unspecified, fontFeatures: unspecified)');
 
     const TextStyle s8 = TextStyle(fontFamilyFallback: <String>['test', 'test2'], package: 'p');
-    expect(s8.fontFamilyFallback[0], 'packages/p/test');
-    expect(s8.fontFamilyFallback[1], 'packages/p/test2');
-    expect(s8.fontFamilyFallback.length, 2);
+    expect(s8.fontFamilyFallback![0], 'packages/p/test');
+    expect(s8.fontFamilyFallback![1], 'packages/p/test2');
+    expect(s8.fontFamilyFallback!.length, 2);
 
     const TextStyle s9 = TextStyle(package: 'p');
     expect(s9.fontFamilyFallback, null);
@@ -214,15 +212,15 @@ void main() {
 
   test('TextStyle font family fallback', () {
     const TextStyle s1 = TextStyle(fontFamilyFallback: <String>['Roboto', 'test']);
-    expect(s1.fontFamilyFallback[0], 'Roboto');
-    expect(s1.fontFamilyFallback[1], 'test');
-    expect(s1.fontFamilyFallback.length, 2);
+    expect(s1.fontFamilyFallback![0], 'Roboto');
+    expect(s1.fontFamilyFallback![1], 'test');
+    expect(s1.fontFamilyFallback!.length, 2);
 
     const TextStyle s2 = TextStyle(fontFamily: 'foo', fontFamilyFallback: <String>['Roboto', 'test']);
-    expect(s2.fontFamilyFallback[0], 'Roboto');
-    expect(s2.fontFamilyFallback[1], 'test');
+    expect(s2.fontFamilyFallback![0], 'Roboto');
+    expect(s2.fontFamilyFallback![1], 'test');
     expect(s2.fontFamily, 'foo');
-    expect(s2.fontFamilyFallback.length, 2);
+    expect(s2.fontFamilyFallback!.length, 2);
 
     const TextStyle s3 = TextStyle(fontFamily: 'foo');
     expect(s3.fontFamily, 'foo');
@@ -231,7 +229,7 @@ void main() {
     const TextStyle s4 = TextStyle(fontFamily: 'foo', fontFamilyFallback: <String>[]);
     expect(s4.fontFamily, 'foo');
     expect(s4.fontFamilyFallback, <String>[]);
-    expect(s4.fontFamilyFallback.isEmpty, true);
+    expect(s4.fontFamilyFallback!.isEmpty, true);
 
     final ui.TextStyle uis1 = s2.getTextStyle();
     expect(uis1.toString(), 'TextStyle(color: unspecified, decoration: unspecified, decorationColor: unspecified, decorationStyle: unspecified, decorationThickness: unspecified, fontWeight: unspecified, fontStyle: unspecified, textBaseline: unspecified, fontFamily: foo, fontFamilyFallback: [Roboto, test], fontSize: unspecified, letterSpacing: unspecified, wordSpacing: unspecified, height: unspecified, locale: unspecified, background: unspecified, foreground: unspecified, shadows: unspecified, fontFeatures: unspecified)');
@@ -259,8 +257,8 @@ void main() {
     expect(foo.merge(bar).merge(baz).debugLabel, '((foo).merge(bar)).merge(baz)');
     expect(foo.copyWith().debugLabel, '(foo).copyWith');
     expect(foo.apply().debugLabel, '(foo).apply');
-    expect(TextStyle.lerp(foo, bar, 0.5).debugLabel, 'lerp(foo ⎯0.5→ bar)');
-    expect(TextStyle.lerp(foo.merge(bar), baz, 0.51).copyWith().debugLabel, '(lerp((foo).merge(bar) ⎯0.5→ baz)).copyWith');
+    expect(TextStyle.lerp(foo, bar, 0.5)!.debugLabel, 'lerp(foo ⎯0.5→ bar)');
+    expect(TextStyle.lerp(foo.merge(bar), baz, 0.51)!.copyWith().debugLabel, '(lerp((foo).merge(bar) ⎯0.5→ baz)).copyWith');
   });
 
   test('TextStyle.hashCode', () {
@@ -297,18 +295,18 @@ void main() {
 
     // apply
     expect(redPaintTextStyle.apply(color: blue).color, isNull);
-    expect(redPaintTextStyle.apply(color: blue).foreground.color, red);
+    expect(redPaintTextStyle.apply(color: blue).foreground!.color, red);
     expect(redTextStyle.apply(color: blue).color, blue);
 
     // lerp
-    expect(TextStyle.lerp(redTextStyle, blueTextStyle, .25).color, Color.lerp(red, blue, .25));
-    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25).color, isNull);
-    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25).foreground.color, red);
-    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .75).foreground.color, blue);
-
-    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).color, isNull);
-    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).foreground.color, red);
-    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .75).foreground.color, blue);
+    expect(TextStyle.lerp(redTextStyle, blueTextStyle, .25)!.color, Color.lerp(red, blue, .25));
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25)!.color, isNull);
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25)!.foreground!.color, red);
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .75)!.foreground!.color, blue);
+
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25)!.color, isNull);
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25)!.foreground!.color, red);
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .75)!.foreground!.color, blue);
   });
 
   test('backgroundColor', () {
@@ -351,18 +349,18 @@ void main() {
 
     // apply
     expect(redPaintTextStyle.apply(backgroundColor: blue).backgroundColor, isNull);
-    expect(redPaintTextStyle.apply(backgroundColor: blue).background.color, red);
+    expect(redPaintTextStyle.apply(backgroundColor: blue).background!.color, red);
     expect(redTextStyle.apply(backgroundColor: blue).backgroundColor, blue);
 
     // lerp
-    expect(TextStyle.lerp(redTextStyle, blueTextStyle, .25).backgroundColor, Color.lerp(red, blue, .25));
-    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25).backgroundColor, isNull);
-    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25).background.color, red);
-    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .75).background.color, blue);
-
-    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).backgroundColor, isNull);
-    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25).background.color, red);
-    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .75).background.color, blue);
+    expect(TextStyle.lerp(redTextStyle, blueTextStyle, .25)!.backgroundColor, Color.lerp(red, blue, .25));
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25)!.backgroundColor, isNull);
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .25)!.background!.color, red);
+    expect(TextStyle.lerp(redTextStyle, bluePaintTextStyle, .75)!.background!.color, blue);
+
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25)!.backgroundColor, isNull);
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .25)!.background!.color, red);
+    expect(TextStyle.lerp(redPaintTextStyle, bluePaintTextStyle, .75)!.background!.color, blue);
   });
 
   test('TextStyle strut textScaleFactor', () {

packages/flutter/test/rendering/annotated_region_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/rendering.dart';
 import 'package:flutter/widgets.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/aspect_ratio_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/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';

packages/flutter/test/rendering/baseline_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/material.dart';
 import 'package:flutter/rendering.dart';
 import '../flutter_test_alternative.dart';

packages/flutter/test/rendering/box_constraints_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/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -70,12 +68,12 @@ void main() {
       minHeight: 11.0,
       maxHeight: 17.0,
     );
-    BoxConstraints copy = BoxConstraints.lerp(null, constraints, 0.5);
+    BoxConstraints copy = BoxConstraints.lerp(null, constraints, 0.5)!;
     expect(copy.minWidth, moreOrLessEquals(1.5));
     expect(copy.maxWidth, moreOrLessEquals(3.5));
     expect(copy.minHeight, moreOrLessEquals(5.5));
     expect(copy.maxHeight, moreOrLessEquals(8.5));
-    copy = BoxConstraints.lerp(constraints, null, 0.5);
+    copy = BoxConstraints.lerp(constraints, null, 0.5)!;
     expect(copy.minWidth, moreOrLessEquals(1.5));
     expect(copy.maxWidth, moreOrLessEquals(3.5));
     expect(copy.minHeight, moreOrLessEquals(5.5));
@@ -85,7 +83,7 @@ void main() {
       maxWidth: 17.0,
       minHeight: 111.0,
       maxHeight: 117.0,
-    ), constraints, 0.2);
+    ), constraints, 0.2)!;
     expect(copy.minWidth, moreOrLessEquals(11.0));
     expect(copy.maxWidth, moreOrLessEquals(15.0));
     expect(copy.minHeight, moreOrLessEquals(91.0));

packages/flutter/test/rendering/box_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/gestures.dart';
 import 'package:flutter/material.dart';
@@ -46,7 +44,7 @@ void main() {
         gradient: RadialGradient(
           center: Alignment.topLeft,
           radius: 1.8,
-          colors: <Color>[Colors.yellow[500], Colors.blue[500]],
+          colors: <Color>[Colors.yellow[500]!, Colors.blue[500]!],
         ),
         boxShadow: kElevationToShadow[3],
       ),
@@ -57,7 +55,7 @@ void main() {
   });
 
   test('performLayout error message', () {
-    FlutterError result;
+    late FlutterError result;
     try {
       MissingPerformLayoutRenderBox().performLayout();
     }  on FlutterError catch (e) {
@@ -95,7 +93,7 @@ void main() {
     // BoxParentData.
     paddingBox.parentData = ParentData();
 
-    FlutterError result;
+    late FlutterError result;
     try {
       root.applyPaintTransform(paddingBox, Matrix4.identity());
     } on FlutterError catch (e) {
@@ -151,7 +149,7 @@ void main() {
 
     final MissingPerformLayoutRenderBox testBox = MissingPerformLayoutRenderBox();
     {
-      FlutterError result;
+      late FlutterError result;
       try {
         testBox.triggerExceptionSettingSizeOutsideOfLayout();
       } on FlutterError catch (e) {
@@ -173,7 +171,7 @@ void main() {
       expect(result.diagnostics.where((DiagnosticsNode node) => node.level == DiagnosticLevel.hint), isEmpty);
     }
     {
-      FlutterError result;
+      late FlutterError result;
       try {
         testBox.debugAdoptSize(root.size);
       } on FlutterError catch (e) {
@@ -392,7 +390,7 @@ void main() {
     layout(unconstrained, constraints: viewport);
 
     {
-      FlutterError result;
+      late FlutterError result;
       try {
         unconstrained.getMinIntrinsicWidth(-1);
       } on FlutterError catch (e) {
@@ -420,7 +418,7 @@ void main() {
     }
 
     {
-      FlutterError result;
+      late FlutterError result;
       try {
         unconstrained.getMinIntrinsicHeight(-1);
       } on FlutterError catch (e) {
@@ -448,7 +446,7 @@ void main() {
     }
 
     {
-      FlutterError result;
+      late FlutterError result;
       try {
         unconstrained.getMaxIntrinsicWidth(-1);
       } on FlutterError catch (e) {
@@ -476,7 +474,7 @@ void main() {
     }
 
     {
-      FlutterError result;
+      late FlutterError result;
       try {
         unconstrained.getMaxIntrinsicHeight(-1);
       } on FlutterError catch (e) {
@@ -934,7 +932,7 @@ void main() {
         final RenderBox renderObject = RenderConstrainedBox(
           additionalConstraints: const BoxConstraints().tighten(height: 100.0),
         );
-        FlutterError result;
+        late FlutterError result;
         try {
           final BoxHitTestResult result = BoxHitTestResult();
           renderObject.hitTest(result, position: Offset.zero);
@@ -971,7 +969,7 @@ void main() {
       }
 
       {
-        FlutterError result;
+        late FlutterError result;
         final FakeMissingSizeRenderBox renderObject = FakeMissingSizeRenderBox();
         layout(renderObject);
         renderObject.fakeMissingSize = true;
@@ -1019,16 +1017,9 @@ void main() {
     });
   });
 
-  test('BoxConstraints parameters should be non-null', () {
-    expect(() => BoxConstraints(minWidth: null), throwsAssertionError);
-    expect(() => BoxConstraints(maxWidth: null), throwsAssertionError);
-    expect(() => BoxConstraints(minHeight: null), throwsAssertionError);
-    expect(() => BoxConstraints(maxHeight: null), throwsAssertionError);
-  });
-
   test('Error message when size has not been set in RenderBox performLayout should be well versed', () {
-    FlutterErrorDetails errorDetails;
-    final FlutterExceptionHandler oldHandler = FlutterError.onError;
+    late FlutterErrorDetails errorDetails;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
     FlutterError.onError = (FlutterErrorDetails details) {
       errorDetails = details;
     };

packages/flutter/test/rendering/cached_intrinsics_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/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/constraints_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/rendering.dart';
 import '../flutter_test_alternative.dart';
 

packages/flutter/test/rendering/debug_overflow_indicator_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/widgets.dart';
 

packages/flutter/test/rendering/debug_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/rendering.dart';
 import 'package:vector_math/vector_math_64.dart';

packages/flutter/test/rendering/dynamic_intrinsics_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/rendering.dart';
 import '../flutter_test_alternative.dart';
 
@@ -33,7 +31,7 @@ class RenderFixedSize extends RenderBox {
 }
 
 class RenderParentSize extends RenderProxyBox {
-  RenderParentSize({ RenderBox child }) : super(child);
+  RenderParentSize({ required RenderBox child }) : super(child);
 
   @override
   bool get sizedByParent => true;
@@ -45,19 +43,19 @@ class RenderParentSize extends RenderProxyBox {
 
   @override
   void performLayout() {
-    child.layout(constraints);
+    child!.layout(constraints);
   }
 }
 
 class RenderIntrinsicSize extends RenderProxyBox {
-  RenderIntrinsicSize({ RenderBox child }) : super(child);
+  RenderIntrinsicSize({ required RenderBox child }) : super(child);
 
   @override
   void performLayout() {
-    child.layout(constraints);
+    child!.layout(constraints);
     size = Size(
-      child.getMinIntrinsicWidth(double.infinity),
-      child.getMinIntrinsicHeight(double.infinity),
+      child!.getMinIntrinsicWidth(double.infinity),
+      child!.getMinIntrinsicHeight(double.infinity),
     );
   }
 }

packages/flutter/test/rendering/editable_gesture_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/gestures.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
@@ -42,7 +40,7 @@ void main() {
     editable.layout(BoxConstraints.loose(const Size(1000.0, 1000.0)));
 
     final PipelineOwner owner = PipelineOwner(onNeedVisualUpdate: () { });
-    final _PointerRouterSpy spy = GestureBinding.instance.pointerRouter as _PointerRouterSpy;
+    final _PointerRouterSpy spy = GestureBinding.instance!.pointerRouter as _PointerRouterSpy;
     editable.attach(owner);
     // This should register pointer into GestureBinding.instance.pointerRouter.
     editable.handleEvent(const PointerDownEvent(), BoxHitTestEntry(editable, const Offset(10,10)));
@@ -64,7 +62,7 @@ class FakeEditableTextState extends TextSelectionDelegate with Fake { }
 class _PointerRouterSpy extends PointerRouter {
   int routeCount = 0;
   @override
-  void addRoute(int pointer, PointerRoute route, [Matrix4 transform]) {
+  void addRoute(int pointer, PointerRoute route, [Matrix4? transform]) {
     super.addRoute(pointer, route, transform);
     routeCount++;
   }