Migrated the Slider widget and tests to null safety. (#68232)

packages/flutter/lib/src/material/range_slider.dart

@@ -1317,6 +1317,7 @@ class _RenderRangeSlider extends RenderBox with RelayoutWhenSystemFontsChangeMix
 
     final bool startThumbSelected = _lastThumbSelection == Thumb.start;
     final bool endThumbSelected = _lastThumbSelection == Thumb.end;
+    final Size resolvedscreenSize = screenSize.isEmpty ? size : screenSize;
 
     if (!_overlayAnimation.isDismissed) {
       if (startThumbSelected) {
@@ -1331,6 +1332,8 @@ class _RenderRangeSlider extends RenderBox with RelayoutWhenSystemFontsChangeMix
           sliderTheme: _sliderTheme,
           textDirection: _textDirection,
           value: startValue,
+          textScaleFactor: _textScaleFactor,
+          sizeWithOverflow: resolvedscreenSize,
         );
       }
       if (endThumbSelected) {
@@ -1345,6 +1348,8 @@ class _RenderRangeSlider extends RenderBox with RelayoutWhenSystemFontsChangeMix
           sliderTheme: _sliderTheme,
           textDirection: _textDirection,
           value: endValue,
+          textScaleFactor: _textScaleFactor,
+          sizeWithOverflow: resolvedscreenSize,
         );
       }
     }
@@ -1392,7 +1397,6 @@ class _RenderRangeSlider extends RenderBox with RelayoutWhenSystemFontsChangeMix
     final double bottomValue = isLastThumbStart ? endValue : startValue;
     final double topValue = isLastThumbStart ? startValue : endValue;
     final bool shouldPaintValueIndicators = isEnabled && labels != null && !_valueIndicatorAnimation.isDismissed && showValueIndicator;
-    final Size resolvedscreenSize = screenSize.isEmpty ? size : screenSize;
 
     if (shouldPaintValueIndicators) {
       _state.paintBottomValueIndicator = (PaintingContext context, Offset offset) {

packages/flutter/lib/src/material/slider.dart

@@ -1385,6 +1385,8 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
         sliderTheme: _sliderTheme,
         textDirection: _textDirection,
         value: _value,
+        textScaleFactor: _textScaleFactor,
+        sizeWithOverflow: screenSize.isEmpty ? size : screenSize,
       );
     }
 
@@ -1451,8 +1453,9 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
       parentBox: this,
       sliderTheme: _sliderTheme,
       textDirection: _textDirection,
-      sizeWithOverflow: screenSize.isEmpty ? size : screenSize,
       value: _value,
+      textScaleFactor: textScaleFactor,
+      sizeWithOverflow: screenSize.isEmpty ? size : screenSize,
     );
   }
 

packages/flutter/lib/src/material/slider_theme.dart

@@ -870,14 +870,14 @@ abstract class SliderComponentShape {
     Offset center, {
     required Animation<double> activationAnimation,
     required Animation<double> enableAnimation,
-    bool isDiscrete,
+    required bool isDiscrete,
     required TextPainter labelPainter,
     required RenderBox parentBox,
     required SliderThemeData sliderTheme,
     required TextDirection textDirection,
     required double value,
-    double textScaleFactor,
-    Size sizeWithOverflow,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   });
 
   /// Special instance of [SliderComponentShape] to skip the thumb drawing.
@@ -927,7 +927,7 @@ abstract class SliderTickMarkShape {
   /// {@endtemplate}
   Size getPreferredSize({
     required SliderThemeData sliderTheme,
-    bool isEnabled,
+    required bool isEnabled,
   });
 
   /// Paints the slider track.
@@ -958,7 +958,7 @@ abstract class SliderTickMarkShape {
     required SliderThemeData sliderTheme,
     required Animation<double> enableAnimation,
     required Offset thumbCenter,
-    bool isEnabled,
+    required bool isEnabled,
     required TextDirection textDirection,
   });
 
@@ -2012,7 +2012,7 @@ class RoundSliderTickMarkShape extends SliderTickMarkShape {
   @override
   Size getPreferredSize({
     required SliderThemeData sliderTheme,
-    bool isEnabled = false,
+    required bool isEnabled,
   }) {
     assert(sliderTheme != null);
     assert(sliderTheme.trackHeight != null);
@@ -2032,7 +2032,7 @@ class RoundSliderTickMarkShape extends SliderTickMarkShape {
     required Animation<double> enableAnimation,
     required TextDirection textDirection,
     required Offset thumbCenter,
-    bool isEnabled = false,
+    required bool isEnabled,
   }) {
     assert(context != null);
     assert(center != null);
@@ -2178,8 +2178,8 @@ class RoundRangeSliderTickMarkShape extends RangeSliderTickMarkShape {
 class _EmptySliderTickMarkShape extends SliderTickMarkShape {
   @override
   Size getPreferredSize({
-    SliderThemeData? sliderTheme,
-    bool? isEnabled,
+    required SliderThemeData sliderTheme,
+    required bool isEnabled,
   }) {
     return Size.zero;
   }
@@ -2192,7 +2192,7 @@ class _EmptySliderTickMarkShape extends SliderTickMarkShape {
     required SliderThemeData sliderTheme,
     required Animation<double> enableAnimation,
     required Offset thumbCenter,
-    bool? isEnabled,
+    required bool isEnabled,
     required TextDirection textDirection,
   }) {
     // no-op.
@@ -2216,16 +2216,16 @@ class _EmptySliderComponentShape extends SliderComponentShape {
   void paint(
     PaintingContext context,
     Offset center, {
-    Animation<double>? activationAnimation,
-    Animation<double>? enableAnimation,
-    bool? isDiscrete,
-    TextPainter? labelPainter,
-    RenderBox? parentBox,
-    SliderThemeData? sliderTheme,
-    TextDirection? textDirection,
-    double? value,
-    double? textScaleFactor,
-    Size? sizeWithOverflow,
+    required Animation<double> activationAnimation,
+    required Animation<double> enableAnimation,
+    required bool isDiscrete,
+    required TextPainter labelPainter,
+    required RenderBox parentBox,
+    required SliderThemeData sliderTheme,
+    required TextDirection textDirection,
+    required double value,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   }) {
     // no-op.
   }
@@ -2290,16 +2290,16 @@ class RoundSliderThumbShape extends SliderComponentShape {
   void paint(
     PaintingContext context,
     Offset center, {
-    Animation<double>? activationAnimation,
+    required Animation<double> activationAnimation,
     required Animation<double> enableAnimation,
-    bool? isDiscrete,
-    TextPainter? labelPainter,
-    RenderBox? parentBox,
+    required bool isDiscrete,
+    required TextPainter labelPainter,
+    required RenderBox parentBox,
     required SliderThemeData sliderTheme,
-    TextDirection? textDirection,
-    double? value,
-    double? textScaleFactor,
-    Size? sizeWithOverflow,
+    required TextDirection textDirection,
+    required double value,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   }) {
     assert(context != null);
     assert(center != null);
@@ -2326,7 +2326,7 @@ class RoundSliderThumbShape extends SliderComponentShape {
       end: pressedElevation,
     );
 
-    final double evaluatedElevation = elevationTween.evaluate(activationAnimation!);
+    final double evaluatedElevation = elevationTween.evaluate(activationAnimation);
     final Path path = Path()
       ..addArc(Rect.fromCenter(center: center, width: 2 * radius, height: 2 * radius), 0, math.pi * 2);
     canvas.drawShadow(path, Colors.black, evaluatedElevation, true);
@@ -2484,14 +2484,14 @@ class RoundSliderOverlayShape extends SliderComponentShape {
     Offset center, {
     required Animation<double> activationAnimation,
     required Animation<double> enableAnimation,
-    bool isDiscrete = false,
+    required bool isDiscrete,
     required TextPainter labelPainter,
     required RenderBox parentBox,
     required SliderThemeData sliderTheme,
     required TextDirection textDirection,
     required double value,
-    double? textScaleFactor,
-    Size? sizeWithOverflow,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   }) {
     assert(context != null);
     assert(center != null);
@@ -2549,28 +2549,28 @@ class RectangularSliderValueIndicatorShape extends SliderComponentShape {
   void paint(
     PaintingContext context,
     Offset center, {
-    Animation<double>? activationAnimation,
-    Animation<double>? enableAnimation,
-    bool? isDiscrete,
-    TextPainter? labelPainter,
+    required Animation<double> activationAnimation,
+    required Animation<double> enableAnimation,
+    required bool isDiscrete,
+    required TextPainter labelPainter,
     required RenderBox parentBox,
-    SliderThemeData? sliderTheme,
-    TextDirection? textDirection,
-    double? value,
-    double? textScaleFactor,
-    Size? sizeWithOverflow,
+    required SliderThemeData sliderTheme,
+    required TextDirection textDirection,
+    required double value,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   }) {
     final Canvas canvas = context.canvas;
-    final double scale = activationAnimation!.value;
+    final double scale = activationAnimation.value;
     _pathPainter.paint(
       parentBox: parentBox,
       canvas: canvas,
       center: center,
       scale: scale,
-      labelPainter: labelPainter!,
-      textScaleFactor: textScaleFactor!,
-      sizeWithOverflow: sizeWithOverflow!,
-      backgroundPaintColor: sliderTheme!.valueIndicatorColor!);
+      labelPainter: labelPainter,
+      textScaleFactor: textScaleFactor,
+      sizeWithOverflow: sizeWithOverflow,
+      backgroundPaintColor: sliderTheme.valueIndicatorColor!);
   }
 }
 
@@ -2815,16 +2815,16 @@ class PaddleSliderValueIndicatorShape extends SliderComponentShape {
   void paint(
     PaintingContext context,
     Offset center, {
-    Animation<double>? activationAnimation,
-    Animation<double>? enableAnimation,
-    bool? isDiscrete,
-    TextPainter? labelPainter,
-    RenderBox? parentBox,
-    SliderThemeData? sliderTheme,
-    TextDirection? textDirection,
-    double? value,
-    double? textScaleFactor,
-    Size? sizeWithOverflow,
+    required Animation<double> activationAnimation,
+    required Animation<double> enableAnimation,
+    required bool isDiscrete,
+    required TextPainter labelPainter,
+    required RenderBox parentBox,
+    required SliderThemeData sliderTheme,
+    required TextDirection textDirection,
+    required double value,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   }) {
     assert(context != null);
     assert(center != null);
@@ -2833,19 +2833,19 @@ class PaddleSliderValueIndicatorShape extends SliderComponentShape {
     assert(labelPainter != null);
     assert(parentBox != null);
     assert(sliderTheme != null);
-    assert(!sizeWithOverflow!.isEmpty);
+    assert(!sizeWithOverflow.isEmpty);
     final ColorTween enableColor = ColorTween(
-      begin: sliderTheme!.disabledThumbColor,
+      begin: sliderTheme.disabledThumbColor,
       end: sliderTheme.valueIndicatorColor,
     );
     _pathPainter.paint(
       context.canvas,
       center,
-      Paint()..color = enableColor.evaluate(enableAnimation!)!,
-      activationAnimation!.value,
-      labelPainter!,
-      textScaleFactor!,
-      sizeWithOverflow!,
+      Paint()..color = enableColor.evaluate(enableAnimation)!,
+      activationAnimation.value,
+      labelPainter,
+      textScaleFactor,
+      sizeWithOverflow,
       null,
     );
   }

packages/flutter/test/material/slider_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:ui';
 
 import 'package:flutter/cupertino.dart';
@@ -33,18 +31,16 @@ class LoggingThumbShape extends SliderComponentShape {
   void paint(
     PaintingContext context,
     Offset thumbCenter, {
-    Animation<double> activationAnimation,
-    Animation<double> enableAnimation,
-    bool isEnabled,
-    bool isDiscrete,
-    bool onActiveTrack,
-    TextPainter labelPainter,
-    RenderBox parentBox,
-    SliderThemeData sliderTheme,
-    TextDirection textDirection,
-    double value,
-    double textScaleFactor,
-    Size sizeWithOverflow,
+    required Animation<double> activationAnimation,
+    required Animation<double> enableAnimation,
+    required bool isDiscrete,
+    required TextPainter labelPainter,
+    required RenderBox parentBox,
+    required SliderThemeData sliderTheme,
+    required TextDirection textDirection,
+    required double value,
+    required double textScaleFactor,
+    required Size sizeWithOverflow,
   }) {
     log.add(thumbCenter);
     final Paint thumbPaint = Paint()..color = Colors.red;
@@ -54,7 +50,7 @@ class LoggingThumbShape extends SliderComponentShape {
 
 class TallSliderTickMarkShape extends SliderTickMarkShape {
   @override
-  Size getPreferredSize({SliderThemeData sliderTheme, bool isEnabled}) {
+  Size getPreferredSize({required SliderThemeData sliderTheme, required bool isEnabled}) {
     return const Size(10.0, 200.0);
   }
 
@@ -62,12 +58,12 @@ class TallSliderTickMarkShape extends SliderTickMarkShape {
   void paint(
     PaintingContext context,
     Offset offset, {
-    Offset thumbCenter,
-    RenderBox parentBox,
-    SliderThemeData sliderTheme,
-    Animation<double> enableAnimation,
-    bool isEnabled,
-    TextDirection textDirection,
+    required Offset thumbCenter,
+    required RenderBox parentBox,
+    required SliderThemeData sliderTheme,
+    required Animation<double> enableAnimation,
+    required bool isEnabled,
+    required TextDirection textDirection,
   }) {
     final Paint paint = Paint()..color = Colors.red;
     context.canvas.drawRect(Rect.fromLTWH(offset.dx, offset.dy, 10.0, 20.0), paint);
@@ -78,8 +74,8 @@ void main() {
   testWidgets('Slider can move when tapped (LTR)', (WidgetTester tester) async {
     final Key sliderKey = UniqueKey();
     double value = 0.0;
-    double startValue;
-    double endValue;
+    double? startValue;
+    double? endValue;
 
     await tester.pumpWidget(
       MaterialApp(
@@ -123,7 +119,7 @@ void main() {
     startValue = null;
     endValue = null;
     await tester.pump(); // No animation should start.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
 
     final Offset topLeft = tester.getTopLeft(find.byKey(sliderKey));
     final Offset bottomRight = tester.getBottomRight(find.byKey(sliderKey));
@@ -134,7 +130,7 @@ void main() {
     expect(startValue, equals(0.5));
     expect(endValue, moreOrLessEquals(0.25, epsilon: 0.05));
     await tester.pump(); // No animation should start.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider can move when tapped (RTL)', (WidgetTester tester) async {
@@ -173,7 +169,7 @@ void main() {
     await tester.tap(find.byKey(sliderKey));
     expect(value, equals(0.5));
     await tester.pump(); // No animation should start.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
 
     final Offset topLeft = tester.getTopLeft(find.byKey(sliderKey));
     final Offset bottomRight = tester.getBottomRight(find.byKey(sliderKey));
@@ -182,14 +178,14 @@ void main() {
     await tester.tapAt(target);
     expect(value, moreOrLessEquals(0.75, epsilon: 0.05));
     await tester.pump(); // No animation should start.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets("Slider doesn't send duplicate change events if tapped on the same value", (WidgetTester tester) async {
     final Key sliderKey = UniqueKey();
     double value = 0.0;
-    double startValue;
-    double endValue;
+    late double startValue;
+    late double endValue;
     int updates = 0;
     int startValueUpdates = 0;
     int endValueUpdates = 0;
@@ -284,19 +280,19 @@ void main() {
     expect(value, equals(0.5));
     await tester.pump(const Duration(milliseconds: 100));
     // Starts with the position animation and value indicator
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
     await tester.pump(const Duration(milliseconds: 100));
     // Value indicator is longer than position.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(1));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(1));
     await tester.pump(const Duration(milliseconds: 100));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
     await tester.pump(const Duration(milliseconds: 100));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
     await tester.pump(const Duration(milliseconds: 100));
     // Shown for long enough, value indicator is animated closed.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(1));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(1));
     await tester.pump(const Duration(milliseconds: 101));
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Discrete Slider repaints and animates when dragged', (WidgetTester tester) async {
@@ -532,13 +528,13 @@ void main() {
     expect(value, equals(80.0));
 
     await tester.pump(); // Starts animation.
-    expect(SchedulerBinding.instance.transientCallbackCount, greaterThan(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, greaterThan(0));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     await tester.pump(const Duration(milliseconds: 200));
     // Animation complete.
-    expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+    expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
   });
 
   testWidgets('Slider can be given zero values', (WidgetTester tester) async {
@@ -618,12 +614,12 @@ void main() {
     final SliderThemeData sliderTheme = theme.sliderTheme;
     double value = 0.45;
     Widget buildApp({
-      Color activeColor,
-      Color inactiveColor,
-      int divisions,
+      Color? activeColor,
+      Color? inactiveColor,
+      int? divisions,
       bool enabled = true,
     }) {
-      final ValueChanged<double> onChanged = !enabled
+      final ValueChanged<double>? onChanged = !enabled
         ? null
         : (double d) {
             value = d;
@@ -655,7 +651,7 @@ void main() {
 
     await tester.pumpWidget(buildApp());
 
-    final MaterialInkController material = Material.of(tester.element(find.byType(Slider)));
+    final MaterialInkController material = Material.of(tester.element(find.byType(Slider)))!;
     final RenderBox valueIndicatorBox = tester.renderObject(find.byType(Overlay));
 
     // Check default theme for enabled widget.
@@ -982,7 +978,7 @@ void main() {
     double value = 0.0;
 
     Widget buildSlider({
-      double textScaleFactor,
+      required double textScaleFactor,
       bool isDiscrete = true,
       ShowValueIndicator show = ShowValueIndicator.onlyForDiscrete,
     }) {
@@ -995,8 +991,8 @@ void main() {
                 data: MediaQueryData(textScaleFactor: textScaleFactor),
                 child: Material(
                   child: Theme(
-                    data: Theme.of(context).copyWith(
-                      sliderTheme: Theme.of(context).sliderTheme.copyWith(showValueIndicator: show),
+                    data: Theme.of(context)!.copyWith(
+                      sliderTheme: Theme.of(context)!.sliderTheme.copyWith(showValueIndicator: show),
                     ),
                     child: Center(
                       child: OverflowBox(
@@ -1129,7 +1125,7 @@ void main() {
 
   testWidgets('Tick marks are skipped when they are too dense', (WidgetTester tester) async {
     Widget buildSlider({
-      int divisions,
+      required int divisions,
     }) {
       return MaterialApp(
         home: Directionality(
@@ -1160,7 +1156,7 @@ void main() {
       ),
     );
 
-    final MaterialInkController material = Material.of(tester.element(find.byType(Slider)));
+    final MaterialInkController material = Material.of(tester.element(find.byType(Slider)))!;
 
     // 5 tick marks and a thumb.
     expect(material, paintsExactlyCountTimes(#drawCircle, 6));
@@ -1219,14 +1215,14 @@ void main() {
     }
 
     Future<void> testReparenting(bool reparent) async {
-      final MaterialInkController material = Material.of(tester.element(find.byType(Slider)));
+      final MaterialInkController material = Material.of(tester.element(find.byType(Slider)))!;
       final Offset center = tester.getCenter(find.byType(Slider));
       // Move to 0.0.
       TestGesture gesture = await tester.startGesture(Offset.zero);
       await tester.pump();
       await gesture.up();
       await tester.pumpAndSettle();
-      expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+      expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
       expect(
         material,
         paints
@@ -1242,7 +1238,7 @@ void main() {
       await tester.pump();
       // Wait for animations to start.
       await tester.pump(const Duration(milliseconds: 25));
-      expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+      expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
       expect(
         material,
         paints
@@ -1262,7 +1258,7 @@ void main() {
 
       // Move a little further in the animations.
       await tester.pump(const Duration(milliseconds: 10));
-      expect(SchedulerBinding.instance.transientCallbackCount, equals(2));
+      expect(SchedulerBinding.instance!.transientCallbackCount, equals(2));
       expect(
         material,
         paints
@@ -1276,7 +1272,7 @@ void main() {
       );
       // Wait for animations to finish.
       await tester.pumpAndSettle();
-      expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+      expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
       expect(
         material,
         paints
@@ -1290,7 +1286,7 @@ void main() {
       );
       await gesture.up();
       await tester.pumpAndSettle();
-      expect(SchedulerBinding.instance.transientCallbackCount, equals(0));
+      expect(SchedulerBinding.instance!.transientCallbackCount, equals(0));
       expect(
         material,
         paints
@@ -1933,8 +1929,8 @@ void main() {
     );
     SliderThemeData theme = baseTheme.sliderTheme;
     double value = 0.45;
-    Widget buildApp({ SliderThemeData sliderTheme, int divisions, bool enabled = true }) {
-      final ValueChanged<double> onChanged = enabled ? (double d) => value = d : null;
+    Widget buildApp({ required SliderThemeData sliderTheme, int? divisions, bool enabled = true }) {
+      final ValueChanged<double>? onChanged = enabled ? (double d) => value = d : null;
       return MaterialApp(
         home: Directionality(
           textDirection: TextDirection.ltr,
@@ -1962,9 +1958,9 @@ void main() {
     }
 
     Future<void> expectValueIndicator({
-      bool isVisible,
-      SliderThemeData theme,
-      int divisions,
+      required bool isVisible,
+      required SliderThemeData theme,
+      int? divisions,
       bool enabled = true,
     }) async {
       // Discrete enabled widget.
@@ -2062,9 +2058,7 @@ void main() {
     double value = 0.0;
 
     Widget buildApp({
-      Color activeColor,
-      Color inactiveColor,
-      int divisions,
+      int? divisions,
       bool enabled = true,
     }) {
       return MaterialApp(
@@ -2090,12 +2084,12 @@ void main() {
                   ElevatedButton(
                     child: const Text('Next'),
                     onPressed: () {
-                      Navigator.of(context).pushReplacement(
+                      Navigator.of(context)!.pushReplacement(
                         MaterialPageRoute<void>(
                           builder: (BuildContext context) {
                             return ElevatedButton(
                               child: const Text('Inner page'),
-                              onPressed: () { Navigator.of(context).pop(); },
+                              onPressed: () { Navigator.of(context)!.pop(); },
                             );
                           },
                         ),
@@ -2280,7 +2274,7 @@ void main() {
 
     await tester.pump();
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
     // Test Slider.adaptive() constructor
     await tester.pumpWidget(
@@ -2303,7 +2297,7 @@ void main() {
       )
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.text);
 
     // Test default cursor
     await tester.pumpWidget(
@@ -2325,7 +2319,7 @@ void main() {
       )
     );
 
-    expect(RendererBinding.instance.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
+    expect(RendererBinding.instance!.mouseTracker.debugDeviceActiveCursor(1), SystemMouseCursors.click);
   });
 
   testWidgets('Slider implements debugFillProperties', (WidgetTester tester) async {
@@ -2459,7 +2453,7 @@ void main() {
     await tester.pumpWidget(buildFrame(15));
     await tester.pumpAndSettle(); // Finish the animation.
 
-    RRect activeTrackRRect;
+    late RRect activeTrackRRect;
     expect(renderObject, paints..something((Symbol method, List<dynamic> arguments) {
       if (method != #drawRRect)
         return false;