Migrate more material tests (#67591)

packages/flutter/test/material/text_button_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';
@@ -37,10 +35,10 @@ void main() {
     expect(material.elevation, 0.0);
     expect(material.shadowColor, const Color(0xff000000));
     expect(material.shape, RoundedRectangleBorder(borderRadius: BorderRadius.circular(4.0)));
-    expect(material.textStyle.color, colorScheme.primary);
-    expect(material.textStyle.fontFamily, 'Roboto');
-    expect(material.textStyle.fontSize, 14);
-    expect(material.textStyle.fontWeight, FontWeight.w500);
+    expect(material.textStyle!.color, colorScheme.primary);
+    expect(material.textStyle!.fontFamily, 'Roboto');
+    expect(material.textStyle!.fontSize, 14);
+    expect(material.textStyle!.fontWeight, FontWeight.w500);
   });
 
   group('[Theme, TextTheme, TextButton style overrides]', () {
@@ -78,7 +76,7 @@ void main() {
       enableFeedback: enableFeedback,
     );
 
-    Widget buildFrame({ ButtonStyle buttonStyle, ButtonStyle themeStyle, ButtonStyle overallStyle }) {
+    Widget buildFrame({ ButtonStyle? buttonStyle, ButtonStyle? themeStyle, ButtonStyle? overallStyle }) {
       final Widget child = Builder(
         builder: (BuildContext context) {
           return TextButton(
@@ -123,15 +121,15 @@ void main() {
     void checkButton(WidgetTester tester) {
       final Material material = tester.widget<Material>(findMaterial);
       final InkWell inkWell = tester.widget<InkWell>(findInkWell);
-      expect(material.textStyle.color, primaryColor);
-      expect(material.textStyle.fontSize, 12);
+      expect(material.textStyle!.color, primaryColor);
+      expect(material.textStyle!.fontSize, 12);
       expect(material.color, backgroundColor);
       expect(material.shadowColor, shadowColor);
       expect(material.elevation, elevation);
-      expect(MaterialStateProperty.resolveAs<MouseCursor>(inkWell.mouseCursor, enabled), enabledMouseCursor);
-      expect(MaterialStateProperty.resolveAs<MouseCursor>(inkWell.mouseCursor, disabled), disabledMouseCursor);
-      expect(inkWell.overlayColor.resolve(hovered), primaryColor.withOpacity(0.04));
-      expect(inkWell.overlayColor.resolve(focused), primaryColor.withOpacity(0.12));
+      expect(MaterialStateProperty.resolveAs<MouseCursor?>(inkWell.mouseCursor, enabled), enabledMouseCursor);
+      expect(MaterialStateProperty.resolveAs<MouseCursor?>(inkWell.mouseCursor, disabled), disabledMouseCursor);
+      expect(inkWell.overlayColor!.resolve(hovered), primaryColor.withOpacity(0.04));
+      expect(inkWell.overlayColor!.resolve(focused), primaryColor.withOpacity(0.12));
       expect(inkWell.enableFeedback, enableFeedback);
       expect(material.borderRadius, null);
       expect(material.shape, shape);
@@ -183,7 +181,7 @@ void main() {
     const Color shadowColor = Color(0xff000001);
     const Color overiddenColor = Color(0xff000002);
 
-    Widget buildFrame({ Color overallShadowColor, Color themeShadowColor, Color shadowColor }) {
+    Widget buildFrame({ Color? overallShadowColor, Color? themeShadowColor, Color? shadowColor }) {
       return MaterialApp(
         theme: ThemeData.from(colorScheme: colorScheme).copyWith(
           shadowColor: overallShadowColor,

packages/flutter/test/material/text_field_focus_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';
 
@@ -40,7 +38,7 @@ void main() {
 
     expect(tester.testTextInput.isVisible, isFalse);
 
-    Navigator.of(tester.element(find.text('Dialog'))).pop();
+    Navigator.of(tester.element(find.text('Dialog')))!.pop();
     await tester.pump();
 
     expect(focusNode.hasPrimaryFocus, isTrue);
@@ -177,7 +175,7 @@ void main() {
   testWidgets('Focus keep-alive works with GlobalKey reparenting', (WidgetTester tester) async {
     final FocusNode focusNode = FocusNode();
 
-    Widget makeTest(String prefix) {
+    Widget makeTest(String? prefix) {
       return MaterialApp(
         home: Material(
           child: ListView(

packages/flutter/test/material/text_field_helper_text_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';
 

packages/flutter/test/material/text_field_restoration_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';
@@ -74,7 +72,7 @@ Future<void> restoreAndVerify(WidgetTester tester) async {
 }
 
 class TestWidget extends StatefulWidget {
-  const TestWidget({Key key, this.useExternal = false}) : super(key: key);
+  const TestWidget({Key? key, this.useExternal = false}) : super(key: key);
 
   final bool useExternal;
 
@@ -89,7 +87,7 @@ class TestWidgetState extends State<TestWidget> with RestorationMixin {
   String get restorationId => 'widget';
 
   @override
-  void restoreState(RestorationBucket oldBucket, bool initialRestore) {
+  void restoreState(RestorationBucket? oldBucket, bool initialRestore) {
     registerForRestoration(controller, 'controller');
   }
 

packages/flutter/test/material/text_field_splash_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' show kPressTimeout;
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -14,17 +12,17 @@ bool cancelCalled = false;
 
 class TestInkSplash extends InkSplash {
   TestInkSplash({
-    MaterialInkController controller,
-    RenderBox referenceBox,
-    Offset position,
-    Color color,
+    required MaterialInkController controller,
+    required RenderBox referenceBox,
+    Offset? position,
+    required Color color,
     bool containedInkWell = false,
-    RectCallback rectCallback,
-    BorderRadius borderRadius,
-    ShapeBorder customBorder,
-    double radius,
-    VoidCallback onRemoved,
-    TextDirection textDirection,
+    RectCallback? rectCallback,
+    BorderRadius? borderRadius,
+    ShapeBorder? customBorder,
+    double? radius,
+    VoidCallback? onRemoved,
+    required TextDirection textDirection,
   }) : super(
     controller: controller,
     referenceBox: referenceBox,
@@ -57,17 +55,17 @@ class TestInkSplashFactory extends InteractiveInkFeatureFactory {
 
   @override
   InteractiveInkFeature create({
-    MaterialInkController controller,
-    RenderBox referenceBox,
-    Offset position,
-    Color color,
+    required MaterialInkController controller,
+    required RenderBox referenceBox,
+    Offset? position,
+    required Color color,
     bool containedInkWell = false,
-    RectCallback rectCallback,
-    BorderRadius borderRadius,
-    ShapeBorder customBorder,
-    double radius,
-    VoidCallback onRemoved,
-    TextDirection textDirection,
+    RectCallback? rectCallback,
+    BorderRadius? borderRadius,
+    ShapeBorder? customBorder,
+    double? radius,
+    VoidCallback? onRemoved,
+    required TextDirection textDirection,
   }) {
     return TestInkSplash(
       controller: controller,