Migrate more material tests to NNBD (#67674)

This migrates more material tests to NNBD.

packages/flutter/test/material/about_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 'package:flutter/foundation.dart';
@@ -733,7 +731,7 @@ class LicensePageObserver extends NavigatorObserver {
   int licensePageCount = 0;
 
   @override
-  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     if (route is MaterialPageRoute<dynamic>) {
       licensePageCount++;
     }
@@ -745,7 +743,7 @@ class AboutDialogObserver extends NavigatorObserver {
   int dialogCount = 0;
 
   @override
-  void didPush(Route<dynamic> route, Route<dynamic> previousRoute) {
+  void didPush(Route<dynamic> route, Route<dynamic>? previousRoute) {
     if (route.toString().contains('_DialogRoute')) {
       dialogCount++;
     }

packages/flutter/test/material/animated_icons_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 show pi;
 
 import 'package:flutter/material.dart';
@@ -13,8 +11,8 @@ import '../flutter_test_alternative.dart' show Fake;
 import '../widgets/semantics_tester.dart';
 
 class MockCanvas extends Fake implements Canvas {
-  Path capturedPath;
-  Paint capturedPaint;
+  late Path capturedPath;
+  late Paint capturedPaint;
 
   @override
   void drawPath(Path path, Paint paint) {
@@ -22,13 +20,13 @@ class MockCanvas extends Fake implements Canvas {
     capturedPaint = paint;
   }
 
-  double capturedSx;
-  double capturedSy;
+  late double capturedSx;
+  late double capturedSy;
 
   @override
-  void scale(double sx, [double sy]) {
+  void scale(double sx, [double? sy]) {
     capturedSx = sx;
-    capturedSy = sy;
+    capturedSy = sy!;
   }
 
   final List<RecordedCanvasCall> invocations = <RecordedCanvasCall>[];
@@ -96,7 +94,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.capturedPaint, hasColor(0xFF666666));
   });
 
@@ -118,7 +116,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.capturedPaint, hasColor(0x80666666));
   });
 
@@ -140,7 +138,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.capturedPaint, hasColor(0xFF0000FF));
   });
 
@@ -162,7 +160,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(12.0, 12.0));
+    customPaint.painter!.paint(canvas, const Size(12.0, 12.0));
     // arrow_menu default size is 48x48 so we expect it to be scaled by 0.25.
     expect(canvas.capturedSx, 0.25);
     expect(canvas.capturedSy, 0.25);
@@ -187,7 +185,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(12.0, 12.0));
+    customPaint.painter!.paint(canvas, const Size(12.0, 12.0));
     // arrow_menu default size is 48x48 so we expect it to be scaled by 2.
     expect(canvas.capturedSx, 2);
     expect(canvas.capturedSy, 2);
@@ -230,7 +228,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.invocations, const <RecordedCanvasCall>[
       RecordedRotate(math.pi),
       RecordedTranslate(-48, -48),
@@ -254,7 +252,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.invocations, isEmpty);
   });
 
@@ -276,7 +274,7 @@ void main() {
     );
     final CustomPaint customPaint = tester.widget(find.byType(CustomPaint));
     final MockCanvas canvas = MockCanvas();
-    customPaint.painter.paint(canvas, const Size(48.0, 48.0));
+    customPaint.painter!.paint(canvas, const Size(48.0, 48.0));
     expect(canvas.invocations, const <RecordedCanvasCall>[
       RecordedRotate(math.pi),
       RecordedTranslate(-48, -48),

packages/flutter/test/material/app_bar_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/material.dart';
 import 'package:flutter/rendering.dart';
@@ -14,10 +12,10 @@ import '../rendering/mock_canvas.dart';
 import '../widgets/semantics_tester.dart';
 
 Widget buildSliverAppBarApp({
-  bool floating,
-  bool pinned,
-  double collapsedHeight,
-  double expandedHeight,
+  bool floating = false,
+  bool pinned = false,
+  double? collapsedHeight,
+  double? expandedHeight,
   bool snap = false,
   double toolbarHeight = kToolbarHeight,
 }) {
@@ -65,7 +63,7 @@ Widget buildSliverAppBarApp({
 }
 
 ScrollController primaryScrollController(WidgetTester tester) {
-  return PrimaryScrollController.of(tester.element(find.byType(CustomScrollView)));
+  return PrimaryScrollController.of(tester.element(find.byType(CustomScrollView)))!;
 }
 
 double appBarHeight(WidgetTester tester) => tester.getSize(find.byType(AppBar, skipOffstage: false)).height;
@@ -303,7 +301,7 @@ void main() {
 
     final Key titleKey = UniqueKey();
     Widget leading = Container();
-    List<Widget> actions;
+    List<Widget> actions = <Widget>[];
 
     Widget buildApp() {
       return MaterialApp(
@@ -360,8 +358,8 @@ void main() {
 
     final Key titleKey = UniqueKey();
     double titleWidth = 700.0;
-    Widget leading = Container();
-    List<Widget> actions;
+    Widget? leading = Container();
+    List<Widget> actions = <Widget>[];
 
     Widget buildApp() {
       return MaterialApp(
@@ -412,8 +410,8 @@ void main() {
 
     final Key titleKey = UniqueKey();
     double titleWidth = 700.0;
-    Widget leading = Container();
-    List<Widget> actions;
+    Widget? leading = Container();
+    List<Widget> actions = <Widget>[];
 
     Widget buildApp() {
       return MaterialApp(
@@ -1952,14 +1950,14 @@ void main() {
   });
 
   testWidgets('AppBars title has upper limit on text scaling, textScaleFactor = 1, 1.34, 2', (WidgetTester tester) async {
-    double textScaleFactor;
+    late double textScaleFactor;
 
     Widget buildFrame() {
       return MaterialApp(
         home: Builder(
           builder: (BuildContext context) {
             return MediaQuery(
-              data: MediaQuery.of(context).copyWith(textScaleFactor: textScaleFactor),
+              data: MediaQuery.of(context)!.copyWith(textScaleFactor: textScaleFactor),
               child: Scaffold(
                 appBar: AppBar(
                   centerTitle: false,
@@ -1988,9 +1986,9 @@ void main() {
   });
 
   testWidgets('AppBars with jumbo titles, textScaleFactor = 3, 3.5, 4', (WidgetTester tester) async {
-    double textScaleFactor;
-    TextDirection textDirection;
-    bool centerTitle;
+    double textScaleFactor = 1.0;
+    TextDirection textDirection = TextDirection.ltr;
+    bool centerTitle = false;
 
     Widget buildFrame() {
       return MaterialApp(
@@ -2004,7 +2002,7 @@ void main() {
                     appBar: AppBar(
                       centerTitle: centerTitle,
                       title: MediaQuery(
-                        data: MediaQuery.of(context).copyWith(textScaleFactor: textScaleFactor),
+                        data: MediaQuery.of(context)!.copyWith(textScaleFactor: textScaleFactor),
                         child: const Text('Jumbo'),
                       ),
                     ),
@@ -2023,10 +2021,8 @@ void main() {
     // Overall screen size is 800x600
     // Left or right justified title is padded by 16 on the "start" side.
     // Toolbar height is 56.
+    // "Jumbo" title is 100x20.
 
-    textScaleFactor = 1; // "Jumbo" title is 100x20.
-    textDirection = TextDirection.ltr;
-    centerTitle = false;
     await tester.pumpWidget(buildFrame());
     expect(tester.getRect(appBarTitle), const Rect.fromLTRB(16, 18, 116, 38));
     expect(tester.getCenter(appBarTitle).dy, tester.getCenter(toolbar).dy);
@@ -2058,7 +2054,7 @@ void main() {
   });
 
   testWidgets('SliverAppBar configures the delegate properly', (WidgetTester tester) async {
-    Future<void> buildAndVerifyDelegate({ bool pinned, bool floating, bool snap }) async {
+    Future<void> buildAndVerifyDelegate({ required bool pinned, required bool floating, required bool snap }) async {
       await tester.pumpWidget(
         MaterialApp(
           home: CustomScrollView(
@@ -2150,17 +2146,6 @@ void main() {
     expect(appBarHeight(tester), collapsedHeight + initialTabBarHeight);
   });
 
-  test('SliverApp toolbarHeight cannot be null', () {
-    try{
-       SliverAppBar(
-        toolbarHeight: null,
-      );
-    } on AssertionError catch (error) {
-      expect(error.toString(), contains('toolbarHeight != null'));
-      expect(error.toString(), contains('is not true'));
-    }
-  });
-
   testWidgets('AppBar respects leadingWidth', (WidgetTester tester) async {
     const Key key = Key('leading');
     await tester.pumpWidget(MaterialApp(

packages/flutter/test/material/app_bar_theme_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 'package:flutter/services.dart';
@@ -31,14 +29,14 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, Brightness.dark);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, Brightness.dark);
     expect(widget.color, Colors.blue);
     expect(widget.elevation, 4.0);
     expect(widget.shadowColor, Colors.black);
     expect(iconTheme.data, const IconThemeData(color: Colors.white));
     expect(actionsIconTheme.data, const IconThemeData(color: Colors.white));
-    expect(actionIconText.text.style.color, Colors.white);
-    expect(text.style, Typography.material2014().englishLike.bodyText2.merge(Typography.material2014().white.bodyText2));
+    expect(actionIconText.text.style!.color, Colors.white);
+    expect(text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().white.bodyText2));
   });
 
   testWidgets('AppBar uses values from AppBarTheme', (WidgetTester tester) async {
@@ -60,14 +58,14 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, appBarTheme.brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, appBarTheme.brightness);
     expect(widget.color, appBarTheme.color);
     expect(widget.elevation, appBarTheme.elevation);
     expect(widget.shadowColor, appBarTheme.shadowColor);
     expect(iconTheme.data, appBarTheme.iconTheme);
     expect(actionsIconTheme.data, appBarTheme.actionsIconTheme);
-    expect(actionIconText.text.style.color, appBarTheme.actionsIconTheme.color);
-    expect(text.style, appBarTheme.textTheme.bodyText2);
+    expect(actionIconText.text.style!.color, appBarTheme.actionsIconTheme!.color);
+    expect(text.style, appBarTheme.textTheme!.bodyText2);
   });
 
   testWidgets('AppBar widget properties take priority over theme', (WidgetTester tester) async {
@@ -103,13 +101,13 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, brightness);
     expect(widget.color, color);
     expect(widget.elevation, elevation);
     expect(widget.shadowColor, shadowColor);
     expect(iconTheme.data, iconThemeData);
     expect(actionsIconTheme.data, actionsIconThemeData);
-    expect(actionIconText.text.style.color, actionsIconThemeData.color);
+    expect(actionIconText.text.style!.color, actionsIconThemeData.color);
     expect(text.style, textTheme.bodyText2);
   });
 
@@ -132,7 +130,7 @@ void main() {
     ));
 
     final RichText actionIconText = _getAppBarIconRichText(tester);
-    expect(actionIconText.text.style.color, color);
+    expect(actionIconText.text.style!.color, color);
   });
 
   testWidgets('AppBarTheme properties take priority over ThemeData properties', (WidgetTester tester) async {
@@ -154,14 +152,14 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, appBarTheme.brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, appBarTheme.brightness);
     expect(widget.color, appBarTheme.color);
     expect(widget.elevation, appBarTheme.elevation);
     expect(widget.shadowColor, appBarTheme.shadowColor);
     expect(iconTheme.data, appBarTheme.iconTheme);
     expect(actionsIconTheme.data, appBarTheme.actionsIconTheme);
-    expect(actionIconText.text.style.color, appBarTheme.actionsIconTheme.color);
-    expect(text.style, appBarTheme.textTheme.bodyText2);
+    expect(actionIconText.text.style!.color, appBarTheme.actionsIconTheme!.color);
+    expect(text.style, appBarTheme.textTheme!.bodyText2);
   });
 
   testWidgets('ThemeData properties are used when no AppBarTheme is set', (WidgetTester tester) async {
@@ -182,15 +180,15 @@ void main() {
     final RichText actionIconText = _getAppBarIconRichText(tester);
     final DefaultTextStyle text = _getAppBarText(tester);
 
-    expect(SystemChrome.latestStyle.statusBarBrightness, themeData.brightness);
+    expect(SystemChrome.latestStyle!.statusBarBrightness, themeData.brightness);
     expect(widget.color, themeData.primaryColor);
     expect(widget.elevation, 4.0);
     expect(widget.shadowColor, Colors.black);
     expect(iconTheme.data, themeData.primaryIconTheme);
     expect(actionsIconTheme.data, themeData.primaryIconTheme);
-    expect(actionIconText.text.style.color, themeData.primaryIconTheme.color);
+    expect(actionIconText.text.style!.color, themeData.primaryIconTheme.color);
     // Default value for ThemeData.typography is Typography.material2014()
-    expect(text.style, Typography.material2014().englishLike.bodyText2.merge(Typography.material2014().white.bodyText2).merge(themeData.primaryTextTheme.bodyText2));
+    expect(text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().white.bodyText2).merge(themeData.primaryTextTheme.bodyText2));
   });
 
   testWidgets('AppBar uses AppBarTheme.centerTitle when centerTitle is null', (WidgetTester tester) async {

packages/flutter/test/material/app_builder_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/material.dart';
 
@@ -15,9 +13,9 @@ void main() {
         primarySwatch: Colors.green,
       ),
       home: const Placeholder(),
-      builder: (BuildContext context, Widget child) {
+      builder: (BuildContext context, Widget? child) {
         log.add('build');
-        expect(Theme.of(context).primaryColor, Colors.green);
+        expect(Theme.of(context)!.primaryColor, Colors.green);
         expect(Directionality.of(context), TextDirection.ltr);
         expect(child, isA<Navigator>());
         return const Placeholder();
@@ -49,15 +47,15 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             log.add('build');
-            expect(Theme.of(context).primaryColor, Colors.yellow);
+            expect(Theme.of(context)!.primaryColor, Colors.yellow);
             expect(Directionality.of(context), TextDirection.rtl);
             return const Placeholder();
           },
         ),
-        builder: (BuildContext context, Widget child) {
+        builder: (BuildContext context, Widget? child) {
           return Directionality(
             textDirection: TextDirection.rtl,
-            child: child,
+            child: child!,
           );
         },
       ),

packages/flutter/test/material/arc_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/material.dart';
 

packages/flutter/test/material/back_button_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 'package:flutter_test/flutter_test.dart';
@@ -132,7 +130,7 @@ void main() {
         of: find.byType(BackButton),
         matching: find.byType(RichText)
     ));
-    expect(iconText.text.style.color, Colors.blue);
+    expect(iconText.text.style!.color, Colors.blue);
   });
 
   testWidgets('BackButton semantics', (WidgetTester tester) async {
@@ -182,7 +180,7 @@ void main() {
         of: find.byType(CloseButton),
         matching: find.byType(RichText)
     ));
-    expect(iconText.text.style.color, Colors.red);
+    expect(iconText.text.style!.color, Colors.red);
   });
 
   testWidgets('CloseButton onPressed overrides default pop behavior', (WidgetTester tester) async {

packages/flutter/test/material/banner_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 'package:flutter_test/flutter_test.dart';
@@ -260,5 +258,5 @@ Container _getContainerFromBanner(WidgetTester tester) {
 }
 
 RenderParagraph _getTextRenderObjectFromDialog(WidgetTester tester, String text) {
-  return tester.element<StatelessElement>(find.descendant(of: find.byType(MaterialBanner), matching: find.text(text))).renderObject as RenderParagraph;
+  return tester.element<StatelessElement>(find.descendant(of: find.byType(MaterialBanner), matching: find.text(text))).renderObject! as RenderParagraph;
 }

packages/flutter/test/material/banner_theme_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 'package:flutter_test/flutter_test.dart';
@@ -70,7 +68,7 @@ void main() {
     final RenderParagraph content = _getTextRenderObjectFromDialog(tester, contentText);
     expect(container.color, const Color(0xffffffff));
     // Default value for ThemeData.typography is Typography.material2014()
-    expect(content.text.style, Typography.material2014().englishLike.bodyText2.merge(Typography.material2014().black.bodyText2));
+    expect(content.text.style, Typography.material2014().englishLike.bodyText2!.merge(Typography.material2014().black.bodyText2));
   });
 
   testWidgets('MaterialBanner uses values from MaterialBannerThemeData', (WidgetTester tester) async {
@@ -185,7 +183,7 @@ Finder _containerFinder() {
 }
 
 RenderParagraph _getTextRenderObjectFromDialog(WidgetTester tester, String text) {
-  return tester.element<StatelessElement>(_textFinder(text)).renderObject as RenderParagraph;
+  return tester.element<StatelessElement>(_textFinder(text)).renderObject! as RenderParagraph;
 }
 
 Finder _textFinder(String text) {

packages/flutter/test/material/bottom_app_bar_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/material.dart';
 import 'package:flutter/rendering.dart';
@@ -90,7 +88,7 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             return Theme(
-              data: Theme.of(context).copyWith(bottomAppBarColor: const Color(0xffffff00)),
+              data: Theme.of(context)!.copyWith(bottomAppBarColor: const Color(0xffffff00)),
               child: const Scaffold(
                 floatingActionButton: FloatingActionButton(
                   onPressed: null,
@@ -115,7 +113,7 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             return Theme(
-              data: Theme.of(context).copyWith(bottomAppBarColor: const Color(0xffffff00)),
+              data: Theme.of(context)!.copyWith(bottomAppBarColor: const Color(0xffffff00)),
               child: const Scaffold(
                 floatingActionButton: FloatingActionButton(
                   onPressed: null,
@@ -392,19 +390,19 @@ void main() {
 class ClipCachePainter extends CustomPainter {
   ClipCachePainter(this.context);
 
-  Path value;
+  late Path value;
   BuildContext context;
 
   @override
   void paint(Canvas canvas, Size size) {
-    final RenderPhysicalShape physicalShape = findPhysicalShapeChild(context);
-    value = physicalShape.clipper.getClip(size);
+    final RenderPhysicalShape physicalShape = findPhysicalShapeChild(context)!;
+    value = physicalShape.clipper!.getClip(size);
   }
 
-  RenderPhysicalShape findPhysicalShapeChild(BuildContext context) {
-    RenderPhysicalShape result;
+  RenderPhysicalShape? findPhysicalShapeChild(BuildContext context) {
+    RenderPhysicalShape? result;
     context.visitChildElements((Element e) {
-      final RenderObject renderObject = e.findRenderObject();
+      final RenderObject renderObject = e.findRenderObject()!;
       if (renderObject.runtimeType == RenderPhysicalShape) {
         assert(result == null);
         result = renderObject as RenderPhysicalShape;
@@ -422,7 +420,7 @@ class ClipCachePainter extends CustomPainter {
 }
 
 class ShapeListener extends StatefulWidget {
-  const ShapeListener(this.child, { Key key }) : super(key: key);
+  const ShapeListener(this.child, { Key? key }) : super(key: key);
 
   final Widget child;
 
@@ -440,7 +438,7 @@ class ShapeListenerState extends State<ShapeListener> {
     );
   }
 
-  ClipCachePainter cache;
+  late ClipCachePainter cache;
 
   @override
   void didChangeDependencies() {
@@ -454,7 +452,7 @@ class RectangularNotch extends NotchedShape {
   const RectangularNotch();
 
   @override
-  Path getOuterPath(Rect host, Rect guest) {
+  Path getOuterPath(Rect host, Rect? guest) {
     if (guest == null)
       return Path()..addRect(host);
     return Path()

packages/flutter/test/material/bottom_app_bar_theme_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 'package:flutter_test/flutter_test.dart';

packages/flutter/test/material/bottom_navigation_bar_theme_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 'package:flutter_test/flutter_test.dart';
@@ -139,14 +137,14 @@ void main() {
       ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
     final TextStyle selectedIcon = _iconStyle(tester, Icons.ac_unit);
     final TextStyle unselectedIcon = _iconStyle(tester, Icons.access_alarm);
     expect(selectedFontStyle.fontSize, selectedFontStyle.fontSize);
     // Unselected label has a font size of 22 but is scaled down to be font size 21.
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
-      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize / selectedTextStyle.fontSize))),
+      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize! / selectedTextStyle.fontSize!))),
     );
     expect(selectedIcon.color, equals(selectedItemColor));
     expect(selectedIcon.fontSize, equals(selectedIconTheme.size));
@@ -232,14 +230,14 @@ void main() {
       ),
     );
 
-    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style;
+    final TextStyle selectedFontStyle = tester.renderObject<RenderParagraph>(find.text('AC')).text.style!;
     final TextStyle selectedIcon = _iconStyle(tester, Icons.ac_unit);
     final TextStyle unselectedIcon = _iconStyle(tester, Icons.access_alarm);
     expect(selectedFontStyle.fontSize, selectedFontStyle.fontSize);
     // Unselected label has a font size of 22 but is scaled down to be font size 21.
     expect(
       tester.firstWidget<Transform>(find.ancestor(of: find.text('Alarm'), matching: find.byType(Transform))).transform,
-      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize / selectedTextStyle.fontSize))),
+      equals(Matrix4.diagonal3(Vector3.all(unselectedTextStyle.fontSize! / selectedTextStyle.fontSize!))),
     );
     expect(selectedIcon.color, equals(selectedItemColor));
     expect(selectedIcon.fontSize, equals(selectedIconTheme.size));
@@ -266,7 +264,7 @@ TextStyle _iconStyle(WidgetTester tester, IconData icon) {
   final RichText iconRichText = tester.widget<RichText>(
     find.descendant(of: find.byIcon(icon), matching: find.byType(RichText)),
   );
-  return iconRichText.text.style;
+  return iconRichText.text.style!;
 }
 
 Material _material(WidgetTester tester) {

packages/flutter/test/material/bottom_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 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
@@ -28,7 +26,7 @@ void main() {
   }
 
   testWidgets('Tapping on a modal BottomSheet should not dismiss it', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -64,7 +62,7 @@ void main() {
   });
 
   testWidgets('Tapping outside a modal BottomSheet should dismiss it by default', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -98,7 +96,7 @@ void main() {
   });
 
   testWidgets('Tapping outside a modal BottomSheet should dismiss it when isDismissible=true', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -133,7 +131,7 @@ void main() {
   });
 
   testWidgets('Verify that the BottomSheet animates non-linearly', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -165,7 +163,7 @@ void main() {
   });
 
   testWidgets('Tapping outside a modal BottomSheet should not dismiss it when isDismissible=false', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -202,7 +200,7 @@ void main() {
   });
 
   testWidgets('Swiping down a modal BottomSheet should dismiss it by default', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -237,7 +235,7 @@ void main() {
   });
 
   testWidgets('Swiping down a modal BottomSheet should not dismiss it when enableDrag is false', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -273,7 +271,7 @@ void main() {
   });
 
   testWidgets('Swiping down a modal BottomSheet should dismiss it when enableDrag is true', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -309,7 +307,7 @@ void main() {
   });
 
   testWidgets('Modal BottomSheet builder should only be called once', (WidgetTester tester) async {
-    BuildContext savedContext;
+    late BuildContext savedContext;
 
     await tester.pumpWidget(MaterialApp(
       home: Builder(
@@ -354,7 +352,7 @@ void main() {
     expect(showBottomSheetThenCalled, isFalse);
     expect(find.text('BottomSheet'), findsNothing);
 
-    scaffoldKey.currentState.showBottomSheet<void>((BuildContext context) {
+    scaffoldKey.currentState!.showBottomSheet<void>((BuildContext context) {
       return Container(
         margin: const EdgeInsets.all(40.0),
         child: const Text('BottomSheet'),
@@ -408,7 +406,7 @@ void main() {
       ),
     ));
 
-    scaffoldKey.currentState.showBottomSheet<void>((BuildContext context) {
+    scaffoldKey.currentState!.showBottomSheet<void>((BuildContext context) {
       return Container(
         margin: const EdgeInsets.all(40.0),
         child: const Text('BottomSheet'),
@@ -428,8 +426,8 @@ void main() {
   });
 
   testWidgets('modal BottomSheet has no top MediaQuery', (WidgetTester tester) async {
-    BuildContext outerContext;
-    BuildContext innerContext;
+    late BuildContext outerContext;
+    late BuildContext innerContext;
 
     await tester.pumpWidget(Localizations(
       locale: const Locale('en', 'US'),
@@ -469,11 +467,11 @@ void main() {
     await tester.pump(const Duration(seconds: 1));
 
     expect(
-      MediaQuery.of(outerContext).padding,
+      MediaQuery.of(outerContext)!.padding,
       const EdgeInsets.all(50.0),
     );
     expect(
-      MediaQuery.of(innerContext).padding,
+      MediaQuery.of(innerContext)!.padding,
       const EdgeInsets.only(left: 50.0, right: 50.0, bottom: 50.0),
     );
   });
@@ -490,7 +488,7 @@ void main() {
     ));
 
 
-    showModalBottomSheet<void>(context: scaffoldKey.currentContext, builder: (BuildContext context) {
+    showModalBottomSheet<void>(context: scaffoldKey.currentContext!, builder: (BuildContext context) {
       return Container(
         child: const Text('BottomSheet'),
       );
@@ -545,7 +543,7 @@ void main() {
     ));
 
     showModalBottomSheet<void>(
-      context: scaffoldKey.currentContext,
+      context: scaffoldKey.currentContext!,
       backgroundColor: color,
       barrierColor: barrierColor,
       elevation: elevation,
@@ -584,7 +582,7 @@ void main() {
 
 
     showModalBottomSheet<void>(
-      context: scaffoldKey.currentContext,
+      context: scaffoldKey.currentContext!,
       builder: (BuildContext context) {
         return DraggableScrollableSheet(
           expand: false,
@@ -710,13 +708,13 @@ void main() {
       ),
     ));
 
-    RouteSettings retrievedRouteSettings;
+    late RouteSettings retrievedRouteSettings;
 
     showModalBottomSheet<void>(
-      context: scaffoldKey.currentContext,
+      context: scaffoldKey.currentContext!,
       routeSettings: routeSettings,
       builder: (BuildContext context) {
-        retrievedRouteSettings = ModalRoute.of(context).settings;
+        retrievedRouteSettings = ModalRoute.of(context)!.settings;
         return Container(
           child: const Text('BottomSheet'),
         );
@@ -731,9 +729,9 @@ void main() {
 }
 
 class _TestPage extends StatelessWidget {
-  const _TestPage({Key key, this.useRootNavigator}) : super(key: key);
+  const _TestPage({Key? key, this.useRootNavigator}) : super(key: key);
 
-  final bool useRootNavigator;
+  final bool? useRootNavigator;
 
   @override
   Widget build(BuildContext context) {
@@ -743,7 +741,7 @@ class _TestPage extends StatelessWidget {
         onPressed: () {
           if (useRootNavigator != null) {
             showModalBottomSheet<void>(
-              useRootNavigator: useRootNavigator,
+              useRootNavigator: useRootNavigator!,
               context: context,
               builder: (_) => const Text('Modal bottom sheet'),
             );

packages/flutter/test/material/bottom_sheet_theme_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 'package:flutter/services.dart';

packages/flutter/test/material/button_bar_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_test/flutter_test.dart';
 
@@ -243,7 +241,7 @@ void main() {
   group('button properties override ButtonTheme', () {
 
     testWidgets('default button properties override ButtonTheme properties', (WidgetTester tester) async {
-      BuildContext capturedContext;
+      late BuildContext capturedContext;
       await tester.pumpWidget(
         MaterialApp(
           home: ButtonBar(
@@ -266,7 +264,7 @@ void main() {
     });
 
     testWidgets('ButtonBarTheme button properties override defaults and ButtonTheme properties', (WidgetTester tester) async {
-      BuildContext capturedContext;
+      late BuildContext capturedContext;
       await tester.pumpWidget(
         MaterialApp(
           home: ButtonBarTheme(
@@ -299,7 +297,7 @@ void main() {
     });
 
     testWidgets('ButtonBar button properties override ButtonBarTheme, defaults and ButtonTheme properties', (WidgetTester tester) async {
-      BuildContext capturedContext;
+      late BuildContext capturedContext;
       await tester.pumpWidget(
         MaterialApp(
           home: ButtonBarTheme(