Sound null safety for framework and flutter_test (#68642)

dev/bots/test.dart

@@ -528,7 +528,8 @@ Future<void> _runAddToAppLifeCycleTests() async {
 
 Future<void> _runFrameworkTests() async {
   final bq.BigqueryApi bigqueryApi = await _getBigqueryApi();
-  final List<String> nullSafetyOptions = <String>['--null-assertions', '--no-sound-null-safety'];
+  final List<String> soundNullSafetyOptions     = <String>['--enable-experiment=non-nullable', '--null-assertions', '--sound-null-safety'];
+  final List<String> mixedModeNullSafetyOptions = <String>['--enable-experiment=non-nullable', '--null-assertions', '--no-sound-null-safety'];
   final List<String> trackWidgetCreationAlternatives = <String>['--track-widget-creation', '--no-track-widget-creation'];
 
   Future<void> runWidgets() async {
@@ -536,7 +537,7 @@ Future<void> _runFrameworkTests() async {
     for (final String trackWidgetCreationOption in trackWidgetCreationAlternatives) {
       await _runFlutterTest(
         path.join(flutterRoot, 'packages', 'flutter'),
-        options: <String>[trackWidgetCreationOption, ...nullSafetyOptions],
+        options: <String>[trackWidgetCreationOption, ...soundNullSafetyOptions],
         tableData: bigqueryApi?.tabledata,
         tests: <String>[ path.join('test', 'widgets') + path.separator ],
       );
@@ -562,7 +563,7 @@ Future<void> _runFrameworkTests() async {
     for (final String trackWidgetCreationOption in trackWidgetCreationAlternatives) {
       await _runFlutterTest(
         path.join(flutterRoot, 'packages', 'flutter'),
-        options: <String>[trackWidgetCreationOption, ...nullSafetyOptions],
+        options: <String>[trackWidgetCreationOption, ...soundNullSafetyOptions],
         tableData: bigqueryApi?.tabledata,
         tests: tests,
       );
@@ -613,14 +614,14 @@ Future<void> _runFrameworkTests() async {
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'manual_tests'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'tools', 'vitool'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'examples', 'hello_world'), tableData: bigqueryApi?.tabledata);
-    await _runFlutterTest(path.join(flutterRoot, 'examples', 'layers'), tableData: bigqueryApi?.tabledata);
+    await _runFlutterTest(path.join(flutterRoot, 'examples', 'layers'), tableData: bigqueryApi?.tabledata, options: mixedModeNullSafetyOptions);
     await _runFlutterTest(path.join(flutterRoot, 'dev', 'benchmarks', 'test_apps', 'stocks'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_driver'), tableData: bigqueryApi?.tabledata, tests: <String>[path.join('test', 'src', 'real_tests')]);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_goldens'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_localizations'), tableData: bigqueryApi?.tabledata);
-    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_test'), tableData: bigqueryApi?.tabledata, options: nullSafetyOptions);
+    await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_test'), tableData: bigqueryApi?.tabledata, options: soundNullSafetyOptions);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'fuchsia_remote_debug_protocol'), tableData: bigqueryApi?.tabledata);
-    await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'non_nullable'), options: nullSafetyOptions);
+    await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'non_nullable'), options: mixedModeNullSafetyOptions);
     await _runFlutterTest(
       path.join(flutterRoot, 'dev', 'tracing_tests'),
       options: <String>['--enable-vmservice'],

examples/layers/analysis_options.yaml

+# Use the parent analysis options settings and enable null-experiment.
+
+include: ../../analysis_options.yaml
+
+analyzer:
+  enable-experiment:
+    - non-nullable
+  errors:
+    always_require_non_null_named_parameters: false # not needed with nnbd
+    type_init_formals: false # https://github.com/dart-lang/linter/issues/2192
+    unrelated_type_equality_checks: false # https://github.com/dart-lang/linter/issues/2196
+    void_checks: false # https://github.com/dart-lang/linter/issues/2185
+    unnecessary_null_comparison: false # Turned off until null-safe rollout is complete.

examples/layers/rendering/custom_coordinate_systems.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
+// @dart = 2.10
 
 // This example shows how to build a render tree with a non-cartesian coordinate
 // system. Most of the guts of this examples are in src/sector_layout.dart.

packages/flutter/lib/src/cupertino/context_menu.dart

@@ -731,7 +731,7 @@ class _ContextMenuRoute<T> extends PopupRoute<T> {
   }
 
   @override
-  bool didPop(T result) {
+  bool didPop(T? result) {
     _updateTweenRects();
     return super.didPop(result);
   }

packages/flutter/lib/src/cupertino/route.dart

@@ -1049,7 +1049,7 @@ class _CupertinoModalPopupRoute<T> extends PopupRoute<T> {
 ///  * [CupertinoActionSheet], which is the widget usually returned by the
 ///    `builder` argument to [showCupertinoModalPopup].
 ///  * <https://developer.apple.com/design/human-interface-guidelines/ios/views/action-sheets/>
-Future<T> showCupertinoModalPopup<T>({
+Future<T?> showCupertinoModalPopup<T>({
   required BuildContext context,
   required WidgetBuilder builder,
   ImageFilter? filter,
@@ -1134,7 +1134,7 @@ Widget _buildCupertinoDialogTransitions(BuildContext context, Animation<double>
 ///  * [showDialog], which displays a Material-style dialog.
 ///  * [showGeneralDialog], which allows for customization of the dialog popup.
 ///  * <https://developer.apple.com/ios/human-interface-guidelines/views/alerts/>
-Future<T> showCupertinoDialog<T>({
+Future<T?> showCupertinoDialog<T>({
   required BuildContext context,
   required WidgetBuilder builder,
   bool useRootNavigator = true,

packages/flutter/lib/src/cupertino/tab_scaffold.dart

@@ -619,8 +619,9 @@ class RestorableCupertinoTabController extends RestorableChangeNotifier<Cupertin
   }
 
   @override
-  CupertinoTabController fromPrimitives(Object data) {
-    return CupertinoTabController(initialIndex: data as int);
+  CupertinoTabController fromPrimitives(Object? data) {
+    assert(data != null);
+    return CupertinoTabController(initialIndex: data! as int);
   }
 
   @override

packages/flutter/lib/src/cupertino/text_selection.dart

@@ -781,7 +781,7 @@ class _CupertinoTextSelectionToolbarItemsElement extends RenderObjectElement {
     }
     if (slot is IndexedSlot) {
       assert(renderObject.debugValidateChild(child));
-      renderObject.insert(child as RenderBox, after: slot.value?.renderObject as RenderBox);
+      renderObject.insert(child as RenderBox, after: slot.value?.renderObject as RenderBox?);
       return;
     }
     assert(false, 'slot must be _CupertinoTextSelectionToolbarItemsSlot or IndexedSlot');

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

@@ -166,7 +166,7 @@ void mergeSort<T>(
   final int firstLength = middle - start;
   final int secondLength = end - middle;
   // secondLength is always the same as firstLength, or one greater.
-  final List<T?> scratchSpace = List<T?>.filled(secondLength, null, growable: false);
+  final List<T> scratchSpace = List<T>.filled(secondLength, list[start]);
   _mergeSort<T>(list, compare, middle, end, scratchSpace, 0);
   final int firstTarget = end - firstLength;
   _mergeSort<T>(list, compare, start, middle, list, firstTarget);
@@ -273,7 +273,7 @@ void _mergeSort<T>(
     int Function(T, T) compare,
     int start,
     int end,
-    List<T?> target,
+    List<T> target,
     int targetOffset,
     ) {
   final int length = end - start;
@@ -316,10 +316,10 @@ void _merge<T>(
   List<T> firstList,
   int firstStart,
   int firstEnd,
-  List<T?> secondList,
+  List<T> secondList,
   int secondStart,
   int secondEnd,
-  List<T?> target,
+  List<T> target,
   int targetOffset,
 ) {
   // No empty lists reaches here.
@@ -328,7 +328,7 @@ void _merge<T>(
   int cursor1 = firstStart;
   int cursor2 = secondStart;
   T firstElement = firstList[cursor1++];
-  T secondElement = secondList[cursor2++] as T;
+  T secondElement = secondList[cursor2++];
   while (true) {
     if (compare(firstElement, secondElement) <= 0) {
       target[targetOffset++] = firstElement;
@@ -340,7 +340,7 @@ void _merge<T>(
     } else {
       target[targetOffset++] = secondElement;
       if (cursor2 != secondEnd) {
-        secondElement = secondList[cursor2++] as T;
+        secondElement = secondList[cursor2++];
         continue;
       }
       // Second list empties first. Flushing first list here.

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

@@ -644,7 +644,7 @@ class _BottomSheetSuspendedCurve extends ParametricCurve<double> {
 ///  * [DraggableScrollableSheet], which allows you to create a bottom sheet
 ///    that grows and then becomes scrollable once it reaches its maximum size.
 ///  * <https://material.io/design/components/sheets-bottom.html#modal-bottom-sheet>
-Future<T> showModalBottomSheet<T>({
+Future<T?> showModalBottomSheet<T>({
   required BuildContext context,
   required WidgetBuilder builder,
   Color? backgroundColor,

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

@@ -955,7 +955,7 @@ Widget _buildMaterialDialogTransitions(BuildContext context, Animation<double> a
 ///  * [showCupertinoDialog], which displays an iOS-style dialog.
 ///  * [showGeneralDialog], which allows for customization of the dialog popup.
 ///  * <https://material.io/design/components/dialogs.html>
-Future<T> showDialog<T>({
+Future<T?> showDialog<T>({
   required BuildContext context,
   WidgetBuilder? builder,
   bool barrierDismissible = true,

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

@@ -120,7 +120,7 @@ typedef MaterialPropertyResolver<T> = T Function(Set<MaterialState> states);
 /// }
 /// ```
 /// {@end-tool}
-abstract class MaterialStateColor extends Color implements MaterialStateProperty<Color?> {
+abstract class MaterialStateColor extends Color implements MaterialStateProperty<Color> {
   /// Creates a [MaterialStateColor].
   const MaterialStateColor(int defaultValue) : super(defaultValue);
 

packages/flutter/lib/src/material/pickers/date_picker_dialog.dart

@@ -99,7 +99,7 @@ const double _inputFormLandscapeHeight = 108.0;
 ///  * [CalendarDatePicker], which provides the calendar grid used by the date picker dialog.
 ///  * [InputDatePickerFormField], which provides a text input field for entering dates.
 ///
-Future<DateTime> showDatePicker({
+Future<DateTime?> showDatePicker({
   required BuildContext context,
   required DateTime initialDate,
   required DateTime firstDate,

packages/flutter/lib/src/material/pickers/date_range_picker_dialog.dart

@@ -105,7 +105,7 @@ const double _inputFormLandscapeHeight = 108.0;
 ///    select a single date.
 ///  * [DateTimeRange], which is used to describe a date range.
 ///
-Future<DateTimeRange> showDateRangePicker({
+Future<DateTimeRange?> showDateRangePicker({
   required BuildContext context,
   DateTimeRange? initialDateRange,
   required DateTime firstDate,

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

@@ -829,7 +829,7 @@ class _PopupMenuRoute<T> extends PopupRoute<T> {
 ///    calling this method automatically.
 ///  * [SemanticsConfiguration.namesRoute], for a description of edge triggered
 ///    semantics.
-Future<T> showMenu<T>({
+Future<T?> showMenu<T>({
   required BuildContext context,
   required RelativeRect position,
   required List<PopupMenuEntry<T>> items,
@@ -1088,7 +1088,7 @@ class PopupMenuButtonState<T> extends State<PopupMenuButton<T>> {
     final List<PopupMenuEntry<T>> items = widget.itemBuilder(context);
     // Only show the menu if there is something to show
     if (items.isNotEmpty) {
-      showMenu<T>(
+      showMenu<T?>(
         context: context,
         elevation: widget.elevation ?? popupMenuTheme.elevation,
         items: items,
@@ -1098,7 +1098,7 @@ class PopupMenuButtonState<T> extends State<PopupMenuButton<T>> {
         color: widget.color ?? popupMenuTheme.color,
         captureInheritedThemes: widget.captureInheritedThemes,
       )
-      .then<void>((T newValue) {
+      .then<void>((T? newValue) {
         if (!mounted)
           return null;
         if (newValue == null) {

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

@@ -49,7 +49,7 @@ import 'theme.dart';
 /// See also:
 ///
 ///  * [SearchDelegate] to define the content of the search page.
-Future<T> showSearch<T>({
+Future<T?> showSearch<T>({
   required BuildContext context,
   required SearchDelegate<T> delegate,
   String? query = '',
@@ -387,7 +387,7 @@ class _SearchPageRoute<T> extends PageRoute<T> {
   }
 
   @override
-  void didComplete(T result) {
+  void didComplete(T? result) {
     super.didComplete(result);
     assert(delegate._route == this);
     delegate._route = null;

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

@@ -2175,7 +2175,7 @@ class _TimePickerDialogState extends State<_TimePickerDialog> {
 ///    date picker.
 ///  * [TimePickerThemeData], which allows you to customize the colors,
 ///    typography, and shape of the time picker.
-Future<TimeOfDay> showTimePicker({
+Future<TimeOfDay?> showTimePicker({
   required BuildContext context,
   required TimeOfDay initialTime,
   TransitionBuilder? builder,

packages/flutter/lib/src/painting/image_provider.dart

@@ -379,12 +379,12 @@ abstract class ImageProvider<T extends Object> {
   /// [FlutterError.onError], and the method will return null.
   ///
   /// A completed return value of null indicates that an error has occurred.
-  Future<ImageCacheStatus> obtainCacheStatus({
+  Future<ImageCacheStatus?> obtainCacheStatus({
     required ImageConfiguration configuration,
     ImageErrorListener? handleError,
   }) {
     assert(configuration != null);
-    final Completer<ImageCacheStatus> completer = Completer<ImageCacheStatus>();
+    final Completer<ImageCacheStatus?> completer = Completer<ImageCacheStatus?>();
     _createErrorHandlerAndKey(
       configuration,
       (T key, ImageErrorListener innerHandleError) {

packages/flutter/lib/src/rendering/table.dart

@@ -390,7 +390,7 @@ class RenderTable extends RenderBox {
        _textBaseline = textBaseline,
        _defaultVerticalAlignment = defaultVerticalAlignment,
        _configuration = configuration {
-    _children = <RenderBox>[]..length = _columns * _rows;
+    _children = <RenderBox?>[]..length = _columns * _rows;
     this.rowDecorations = rowDecorations; // must use setter to initialize box painters array
     children?.forEach(addRow);
   }
@@ -645,7 +645,7 @@ class RenderTable extends RenderBox {
     // update our internal values
     _columns = columns;
     _rows = cells.length ~/ columns;
-    _children = cells.toList();
+    _children = List<RenderBox?>.from(cells);
     assert(_children.length == rows * columns);
     markNeedsLayout();
   }

packages/flutter/lib/src/services/restoration.dart

@@ -151,13 +151,13 @@ class RestorationManager extends ChangeNotifier {
       return SynchronousFuture<RestorationBucket?>(_rootBucket);
     }
     if (_pendingRootBucket == null) {
-      _pendingRootBucket = Completer<RestorationBucket>();
+      _pendingRootBucket = Completer<RestorationBucket?>();
       _getRootBucketFromEngine();
     }
     return _pendingRootBucket!.future;
   }
   RestorationBucket? _rootBucket; // May be null to indicate that restoration is turned off.
-  Completer<RestorationBucket>? _pendingRootBucket;
+  Completer<RestorationBucket?>? _pendingRootBucket;
   bool _rootBucketIsValid = false;
 
   /// Returns true for the frame after [rootBucket] has been replaced with a
@@ -186,7 +186,7 @@ class RestorationManager extends ChangeNotifier {
   void _parseAndHandleRestorationUpdateFromEngine(Map<dynamic, dynamic>? update) {
     handleRestorationUpdateFromEngine(
       enabled: update != null && update['enabled'] as bool,
-      data: update == null ? null : update['data'] as Uint8List,
+      data: update == null ? null : update['data'] as Uint8List?,
     );
   }
 
@@ -580,10 +580,10 @@ class RestorationBucket {
   ///  * [remove], which removes a value from the bucket.
   ///  * [contains], which checks whether any value is stored under a given
   ///    restoration ID.
-  P read<P>(String restorationId) {
+  P? read<P>(String restorationId) {
     assert(_debugAssertNotDisposed());
     assert(restorationId != null);
-    return _rawValues[restorationId] as P;
+    return _rawValues[restorationId] as P?;
   }
 
   /// Stores the provided `value` of type `P` under the provided `restorationId`
@@ -624,11 +624,11 @@ class RestorationBucket {
   ///  * [write], which stores a value in the bucket.
   ///  * [contains], which checks whether any value is stored under a given
   ///    restoration ID.
-  P remove<P>(String restorationId) {
+  P? remove<P>(String restorationId) {
     assert(_debugAssertNotDisposed());
     assert(restorationId != null);
     final bool needsUpdate = _rawValues.containsKey(restorationId);
-    final P result = _rawValues.remove(restorationId) as P;
+    final P? result = _rawValues.remove(restorationId) as P?;
     if (_rawValues.isEmpty) {
       _rawData.remove(_valuesMapKey);
     }

packages/flutter/lib/src/widgets/dismissible.dart

@@ -28,7 +28,7 @@ typedef DismissDirectionCallback = void Function(DismissDirection direction);
 /// confirm or veto a dismiss gesture.
 ///
 /// Used by [Dismissible.confirmDismiss].
-typedef ConfirmDismissCallback = Future<bool> Function(DismissDirection direction);
+typedef ConfirmDismissCallback = Future<bool?> Function(DismissDirection direction);
 
 /// The direction in which a [Dismissible] can be dismissed.
 enum DismissDirection {
@@ -120,7 +120,7 @@ class Dismissible extends StatefulWidget {
   /// If the returned Future<bool> completes true, then this widget will be
   /// dismissed, otherwise it will be moved back to its original location.
   ///
-  /// If the returned Future<bool> completes to false or null the [onResize]
+  /// If the returned Future<bool?> completes to false or null the [onResize]
   /// and [onDismissed] callbacks will not run.
   final ConfirmDismissCallback? confirmDismiss;
 
@@ -458,7 +458,7 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
     updateKeepAlive();
   }
 
-  Future<bool> _confirmStartResizeAnimation() async {
+  Future<bool?> _confirmStartResizeAnimation() async {
     if (widget.confirmDismiss != null) {
       final DismissDirection direction = _dismissDirection!;
       assert(direction != null);

packages/flutter/lib/src/widgets/heroes.dart

@@ -300,7 +300,7 @@ class Hero extends StatefulWidget {
           // the Hero is inside a nested Navigator and should only be
           // considered for animation if it is part of the top-most route in
           // that nested Navigator and if that route is also a PageRoute.
-          final ModalRoute<Object>? heroRoute = ModalRoute.of(hero);
+          final ModalRoute<Object?>? heroRoute = ModalRoute.of(hero);
           if (heroRoute != null && heroRoute is PageRoute && heroRoute.isCurrent) {
             inviteHero(hero, tag);
           }

packages/flutter/lib/src/widgets/localizations.dart

@@ -450,7 +450,7 @@ class Localizations extends StatefulWidget {
     assert(context != null);
     assert(type != null);
     final _LocalizationsScope? scope = context.dependOnInheritedWidgetOfExactType<_LocalizationsScope>();
-    return scope?.localizationsState.resourcesFor<T>(type);
+    return scope?.localizationsState.resourcesFor<T?>(type);
   }
 
   @override

packages/flutter/lib/src/widgets/modal_barrier.dart

@@ -159,7 +159,7 @@ class AnimatedModalBarrier extends AnimatedWidget {
   ///
   ///  * [ModalRoute.barrierColor], which controls this property for the
   ///    [AnimatedModalBarrier] built by [ModalRoute] pages.
-  Animation<Color> get color => listenable as Animation<Color>;
+  Animation<Color?> get color => listenable as Animation<Color?>;
 
   /// Whether touching the barrier will pop the current route off the [Navigator].
   ///

packages/flutter/lib/src/widgets/restoration.dart

@@ -425,7 +425,7 @@ abstract class RestorableProperty<T> extends ChangeNotifier {
   /// [RestorableProperty]. Whenever new restoration data has been provided to
   /// the [RestorationMixin] the property is registered to, either this method
   /// or [createDefaultValue] is called before [initWithValue] is invoked.
-  T fromPrimitives(Object data);
+  T fromPrimitives(Object? data);
 
   /// Called by the [RestorationMixin] with the `value` returned by either
   /// [createDefaultValue] or [fromPrimitives] to set the value that this
@@ -884,7 +884,7 @@ mixin RestorationMixin<S extends StatefulWidget> on State<S> {
   /// restore the internal state of a [State] object, it may be removed from the
   /// restoration data by calling this method.
   @protected
-  void unregisterFromRestoration(RestorableProperty<Object> property) {
+  void unregisterFromRestoration(RestorableProperty<Object?> property) {
     assert(property != null);
     assert(property._owner == this);
     _bucket?.remove<Object?>(property._restorationId!);

packages/flutter/lib/src/widgets/restoration_properties.dart

@@ -173,9 +173,9 @@ class _RestorablePrimitiveValue<T extends Object> extends RestorableValue<T> {
   }
 
   @override
-  T fromPrimitives(Object serialized) {
+  T fromPrimitives(Object? serialized) {
     assert(serialized != null);
-    return serialized as T;
+    return serialized! as T;
   }
 
   @override
@@ -360,8 +360,8 @@ class RestorableTextEditingController extends RestorableChangeNotifier<TextEditi
   }
 
   @override
-  TextEditingController fromPrimitives(Object data) {
-    return TextEditingController(text: data as String);
+  TextEditingController fromPrimitives(Object? data) {
+    return TextEditingController(text: data! as String);
   }
 
   @override

packages/flutter/lib/src/widgets/routes.dart

@@ -62,7 +62,7 @@ abstract class OverlayRoute<T> extends Route<T> {
   bool get finishedWhenPopped => true;
 
   @override
-  bool didPop(T result) {
+  bool didPop(T? result) {
     final bool returnValue = super.didPop(result);
     assert(returnValue);
     if (finishedWhenPopped)
@@ -90,8 +90,8 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   /// This future completes once the animation has been dismissed. That will be
   /// after [popped], because [popped] typically completes before the animation
   /// even starts, as soon as the route is popped.
-  Future<T> get completed => _transitionCompleter.future;
-  final Completer<T> _transitionCompleter = Completer<T>();
+  Future<T?> get completed => _transitionCompleter.future;
+  final Completer<T?> _transitionCompleter = Completer<T?>();
 
   /// {@template flutter.widgets.transitionRoute.transitionDuration}
   /// The duration the transition going forwards.
@@ -235,7 +235,7 @@ abstract class TransitionRoute<T> extends OverlayRoute<T> {
   }
 
   @override
-  bool didPop(T result) {
+  bool didPop(T? result) {
     assert(_controller != null, '$runtimeType.didPop called before calling install() or after calling dispose().');
     assert(!_transitionCompleter.isCompleted, 'Cannot reuse a $runtimeType after disposing it.');
     _result = result;
@@ -631,7 +631,7 @@ mixin LocalHistoryRoute<T> on Route<T> {
   }
 
   @override
-  bool didPop(T result) {
+  bool didPop(T? result) {
     if (_localHistory != null && _localHistory!.isNotEmpty) {
       final LocalHistoryEntry entry = _localHistory!.removeLast();
       assert(entry._owner == this);
@@ -1818,7 +1818,7 @@ class _DialogRoute<T> extends PopupRoute<T> {
 ///
 ///  * [showDialog], which displays a Material-style dialog.
 ///  * [showCupertinoDialog], which displays an iOS-style dialog.
-Future<T> showGeneralDialog<T extends Object?>({
+Future<T?> showGeneralDialog<T extends Object?>({
   required BuildContext context,
   required RoutePageBuilder pageBuilder,
   bool barrierDismissible = false,

packages/flutter/lib/src/widgets/scrollable.dart

@@ -1084,8 +1084,8 @@ class _RestorableScrollOffset extends RestorableValue<double?> {
   }
 
   @override
-  double fromPrimitives(Object data) {
-    return data as double;
+  double fromPrimitives(Object? data) {
+    return data! as double;
   }
 
   @override

packages/flutter/lib/src/widgets/table.dart

@@ -303,16 +303,16 @@ class _TableElement extends RenderObjectElement {
   }
 
   @override
-  void insertRenderObjectChild(RenderObject child, IndexedSlot<Element>? slot) {
+  void insertRenderObjectChild(RenderObject child, dynamic slot) {
     renderObject.setupParentData(child);
   }
 
   @override
-  void moveRenderObjectChild(RenderObject child, IndexedSlot<Element>? oldSlot, IndexedSlot<Element>? newSlot) {
+  void moveRenderObjectChild(RenderObject child, dynamic oldSlot, dynamic newSlot) {
   }
 
   @override
-  void removeRenderObjectChild(RenderObject child, IndexedSlot<Element>? slot) {
+  void removeRenderObjectChild(RenderObject child, dynamic slot) {
     final TableCellParentData childParentData = child.parentData! as TableCellParentData;
     renderObject.setChild(childParentData.x!, childParentData.y!, null);
   }

packages/flutter/test/foundation/consolidate_response_test.dart

@@ -111,7 +111,7 @@ void main() {
 
       test('Notifies onBytesReceived with gzipped numbers', () async {
         response.contentLength = gzipped.length;
-        final List<int?> records = <int>[];
+        final List<int?> records = <int?>[];
         await consolidateHttpClientResponseBytes(
           response,
           onBytesReceived: (int cumulative, int? total) {

packages/flutter/test/foundation/diagnostics_json_test.dart

@@ -76,7 +76,7 @@ void main() {
     test('subtreeDepth 1', () {
       final Map<String, Object?> result = testTree.toDiagnosticsNode().toJsonMap(const DiagnosticsSerializationDelegate(subtreeDepth: 1));
       expect(result.containsKey('properties'), isFalse);
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children[0].containsKey('children'), isFalse);
       expect(children[1].containsKey('children'), isFalse);
       expect(children[2].containsKey('children'), isFalse);
@@ -85,7 +85,7 @@ void main() {
     test('subtreeDepth 5', () {
       final Map<String, Object?> result = testTree.toDiagnosticsNode().toJsonMap(const DiagnosticsSerializationDelegate(subtreeDepth: 5));
       expect(result.containsKey('properties'), isFalse);
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children[0]['children'], hasLength(0));
       expect(children[1]['children'], hasLength(3));
       expect(children[2]['children'], hasLength(0));
@@ -103,7 +103,7 @@ void main() {
         subtreeDepth: 1,
       ));
       expect(result['properties'], hasLength(7));
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children, hasLength(3));
       expect(children[0]['properties'], hasLength(0));
       expect(children[1]['properties'], hasLength(2));
@@ -119,13 +119,13 @@ void main() {
         },
       ));
       expect(result['foo'], isTrue);
-      final List<Map<String, Object>> properties = result['properties']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> properties = result['properties']! as List<Map<String, Object?>>;
       expect(properties, hasLength(7));
-      expect(properties.every((Map<String, Object> property) => property['foo'] == true), isTrue);
+      expect(properties.every((Map<String, Object?> property) => property['foo'] == true), isTrue);
 
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children, hasLength(3));
-      expect(children.every((Map<String, Object> child) => child['foo'] == true), isTrue);
+      expect(children.every((Map<String, Object?> child) => child['foo'] == true), isTrue);
     });
 
     test('filterProperties - sublist', () {
@@ -135,9 +135,9 @@ void main() {
             return nodes.whereType<StringProperty>().toList();
           },
       ));
-      final List<Map<String, Object>> properties = result['properties']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> properties = result['properties']! as List<Map<String, Object?>>;
       expect(properties, hasLength(3));
-      expect(properties.every((Map<String, Object> property) => property['type'] == 'StringProperty'), isTrue);
+      expect(properties.every((Map<String, Object?> property) => property['type'] == 'StringProperty'), isTrue);
     });
 
     test('filterProperties - replace', () {
@@ -154,7 +154,7 @@ void main() {
             ];
           },
       ));
-      final List<Map<String, Object>> properties = result['properties']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> properties = result['properties']! as List<Map<String, Object?>>;
       expect(properties, hasLength(1));
       expect(properties.single['name'], 'foo');
     });
@@ -166,7 +166,7 @@ void main() {
             return nodes.where((DiagnosticsNode node) => node.getProperties().isEmpty).toList();
           },
       ));
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children, hasLength(1));
     });
 
@@ -177,7 +177,7 @@ void main() {
             return nodes.expand((DiagnosticsNode node) => node.getChildren()).toList();
           },
       ));
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children, hasLength(3));
       expect(children.first['name'], 'child node B1');
     });
@@ -190,11 +190,11 @@ void main() {
             return nodes.take(2).toList();
           },
       ));
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children, hasLength(3));
       expect(children.last['truncated'], isTrue);
 
-      final List<Map<String, Object>> properties = result['properties']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> properties = result['properties']! as List<Map<String, Object?>>;
       expect(properties, hasLength(3));
       expect(properties.last['truncated'], isTrue);
     });
@@ -207,13 +207,13 @@ void main() {
             return delegate.copyWith(includeProperties: false);
           },
       ));
-      final List<Map<String, Object>> properties = result['properties']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> properties = result['properties']! as List<Map<String, Object?>>;
       expect(properties, hasLength(7));
-      expect(properties.every((Map<String, Object> property) => !property.containsKey('properties')), isTrue);
+      expect(properties.every((Map<String, Object?> property) => !property.containsKey('properties')), isTrue);
 
-      final List<Map<String, Object>> children = result['children']! as List<Map<String, Object>>;
+      final List<Map<String, Object?>> children = result['children']! as List<Map<String, Object?>>;
       expect(children, hasLength(3));
-      expect(children.every((Map<String, Object> child) => !child.containsKey('properties')), isTrue);
+      expect(children.every((Map<String, Object?> child) => !child.containsKey('properties')), isTrue);
     });
   });
 }

packages/flutter/test/foundation/diagnostics_test.dart

@@ -47,15 +47,15 @@ enum ExampleEnum {
 
 /// Encode and decode to JSON to make sure all objects in the JSON for the
 /// [DiagnosticsNode] are valid JSON.
-Map<String, Object> simulateJsonSerialization(DiagnosticsNode node) {
-  return json.decode(json.encode(node.toJsonMap(const DiagnosticsSerializationDelegate()))) as Map<String, Object>;
+Map<String, Object?> simulateJsonSerialization(DiagnosticsNode node) {
+  return json.decode(json.encode(node.toJsonMap(const DiagnosticsSerializationDelegate()))) as Map<String, Object?>;
 }
 
 void validateNodeJsonSerialization(DiagnosticsNode node) {
   validateNodeJsonSerializationHelper(simulateJsonSerialization(node), node);
 }
 
-void validateNodeJsonSerializationHelper(Map<String, Object> json, DiagnosticsNode node) {
+void validateNodeJsonSerializationHelper(Map<String, Object?> json, DiagnosticsNode node) {
   expect(json['name'], equals(node.name));
   expect(json['showSeparator'] ?? true, equals(node.showSeparator));
   expect(json['description'], equals(node.toDescription()));
@@ -67,18 +67,18 @@ void validateNodeJsonSerializationHelper(Map<String, Object> json, DiagnosticsNo
   expect(json['hasChildren'] ?? false, equals(node.getChildren().isNotEmpty));
 }
 
-void validatePropertyJsonSerialization(DiagnosticsProperty<Object> property) {
+void validatePropertyJsonSerialization(DiagnosticsProperty<Object?> property) {
   validatePropertyJsonSerializationHelper(simulateJsonSerialization(property), property);
 }
 
 void validateStringPropertyJsonSerialization(StringProperty property) {
-  final Map<String, Object> json = simulateJsonSerialization(property);
+  final Map<String, Object?> json = simulateJsonSerialization(property);
   expect(json['quoted'], equals(property.quoted));
   validatePropertyJsonSerializationHelper(json, property);
 }
 
 void validateFlagPropertyJsonSerialization(FlagProperty property) {
-  final Map<String, Object> json = simulateJsonSerialization(property);
+  final Map<String, Object?> json = simulateJsonSerialization(property);
   expect(json['ifTrue'], equals(property.ifTrue));
 
   if (property.ifTrue != null) {
@@ -96,7 +96,7 @@ void validateFlagPropertyJsonSerialization(FlagProperty property) {
 }
 
 void validateDoublePropertyJsonSerialization(DoubleProperty property) {
-  final Map<String, Object> json = simulateJsonSerialization(property);
+  final Map<String, Object?> json = simulateJsonSerialization(property);
   if (property.unit != null) {
     expect(json['unit'], equals(property.unit));
   } else {
@@ -109,7 +109,7 @@ void validateDoublePropertyJsonSerialization(DoubleProperty property) {
 }
 
 void validateObjectFlagPropertyJsonSerialization(ObjectFlagProperty<Object> property) {
-  final Map<String, Object> json = simulateJsonSerialization(property);
+  final Map<String, Object?> json = simulateJsonSerialization(property);
   if (property.ifPresent != null) {
     expect(json['ifPresent'], equals(property.ifPresent));
   } else {
@@ -120,7 +120,7 @@ void validateObjectFlagPropertyJsonSerialization(ObjectFlagProperty<Object> prop
 }
 
 void validateIterableFlagsPropertyJsonSerialization(FlagsSummary<Object?> property) {
-  final Map<String, Object> json = simulateJsonSerialization(property);
+  final Map<String, Object?> json = simulateJsonSerialization(property);
   if (property.value.isNotEmpty) {
     expect(json['values'], equals(
       property.value.entries
@@ -135,9 +135,9 @@ void validateIterableFlagsPropertyJsonSerialization(FlagsSummary<Object?> proper
 }
 
 void validateIterablePropertyJsonSerialization(IterableProperty<Object> property) {
-  final Map<String, Object> json = simulateJsonSerialization(property);
+  final Map<String, Object?> json = simulateJsonSerialization(property);
   if (property.value != null) {
-    final List<Object> valuesJson = json['values']! as List<Object>;
+    final List<Object?> valuesJson = json['values']! as List<Object?>;
     final List<String> expectedValues = property.value!.map<String>((Object value) => value.toString()).toList();
     expect(listEquals(valuesJson, expectedValues), isTrue);
   } else {
@@ -147,7 +147,7 @@ void validateIterablePropertyJsonSerialization(IterableProperty<Object> property
   validatePropertyJsonSerializationHelper(json, property);
 }
 
-void validatePropertyJsonSerializationHelper(final Map<String, Object> json, DiagnosticsProperty<Object> property) {
+void validatePropertyJsonSerializationHelper(final Map<String, Object?> json, DiagnosticsProperty<Object?> property) {
   if (property.defaultValue != kNoDefaultValue) {
     expect(json['defaultValue'], equals(property.defaultValue.toString()));
   } else {
@@ -1919,7 +1919,7 @@ void main() {
     expect(messageProperty.name, equals('diagnostics'));
     expect(messageProperty.value, isNull);
     expect(messageProperty.showName, isTrue);
-    validatePropertyJsonSerialization(messageProperty as DiagnosticsProperty<Object>);
+    validatePropertyJsonSerialization(messageProperty as DiagnosticsProperty<Object?>);
   });
 
   test('error message style wrap test', () {
@@ -2246,7 +2246,7 @@ void main() {
 
   test('DiagnosticsProperty for basic types has value in json', () {
     DiagnosticsProperty<int> intProperty = DiagnosticsProperty<int>('int1', 10);
-    Map<String, Object> json = simulateJsonSerialization(intProperty);
+    Map<String, Object?> json = simulateJsonSerialization(intProperty);
     expect(json['name'], 'int1');
     expect(json['value'], 10);
 

packages/flutter/test/material/app_test.dart

@@ -249,7 +249,7 @@ void main() {
   });
 
   testWidgets('Return value from pop is correct', (WidgetTester tester) async {
-    late Future<Object> result;
+    late Future<Object?> result;
     await tester.pumpWidget(
         MaterialApp(
           home: Builder(
@@ -258,7 +258,7 @@ void main() {
                   child: ElevatedButton(
                       child: const Text('X'),
                       onPressed: () async {
-                        result = Navigator.of(context)!.pushNamed('/a');
+                        result = Navigator.of(context)!.pushNamed<Object?>('/a');
                       },
                   ),
                 );

packages/flutter/test/material/dialog_test.dart

@@ -233,7 +233,7 @@ void main() {
 
     final BuildContext context = tester.element(find.text('Go'));
 
-    final Future<int> result = showDialog<int>(
+    final Future<int?> result = showDialog<int>(
       context: context,
       builder: (BuildContext context) {
         return SimpleDialog(
@@ -273,7 +273,7 @@ void main() {
       ),
     );
 
-    final Future<int> result = showDialog<int>(
+    final Future<int?> result = showDialog<int>(
       context: navigator.currentContext!,
       builder: (BuildContext context) {
         return SimpleDialog(
@@ -1382,7 +1382,7 @@ void main() {
     final List<int> dismissedItems = <int>[];
 
     // Dismiss is confirmed IFF confirmDismiss() returns true.
-    Future<bool> confirmDismiss (DismissDirection dismissDirection) {
+    Future<bool?> confirmDismiss (DismissDirection dismissDirection) async {
       return showDialog<bool>(
         context: _scaffoldKey.currentContext!,
         barrierDismissible: true, // showDialog() returns null if tapped outside the dialog
@@ -1762,7 +1762,7 @@ void main() {
     final BuildContext context = tester.element(find.text('Go'));
     const RouteSettings exampleSetting = RouteSettings(name: 'simple');
 
-    final Future<int> result = showDialog<int>(
+    final Future<int?> result = showDialog<int>(
       context: context,
       builder: (BuildContext context) {
         return SimpleDialog(

packages/flutter/test/material/popup_menu_test.dart

@@ -465,7 +465,7 @@ void main() {
     final WidgetPredicate popupMenu = (Widget widget) {
       final String widgetType = widget.runtimeType.toString();
       // TODO(mraleph): Remove the old case below.
-      return widgetType == '_PopupMenu<int>' // normal case
+      return widgetType == '_PopupMenu<int?>' // normal case
           || widgetType == '_PopupMenu'; // for old versions of Dart that don't reify method type arguments
     };
 
@@ -794,7 +794,7 @@ void main() {
     await tester.pumpAndSettle();
 
     // The position is different than the offset because the default position isn't at the origin.
-    expect(tester.getTopLeft(find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_PopupMenu<int>')), const Offset(364.0, 324.0));
+    expect(tester.getTopLeft(find.byWidgetPredicate((Widget w) => '${w.runtimeType}' == '_PopupMenu<int?>')), const Offset(364.0, 324.0));
   });
 
   testWidgets('open PopupMenu has correct semantics', (WidgetTester tester) async {

packages/flutter/test/material/search_test.dart

@@ -80,7 +80,7 @@ void main() {
     // regression test for https://github.com/flutter/flutter/issues/18145
 
     final _TestSearchDelegate delegate = _TestSearchDelegate();
-    final List<String> selectedResults = <String>[];
+    final List<String?> selectedResults = <String?>[];
 
     await tester.pumpWidget(TestHomePage(
       delegate: delegate,
@@ -105,7 +105,7 @@ void main() {
     await ServicesBinding.instance!.defaultBinaryMessenger.handlePlatformMessage('flutter/navigation', message, (_) { });
     await tester.pumpAndSettle();
 
-    expect(selectedResults, <void>[null]);
+    expect(selectedResults, <String?>[null]);
 
     // We are on the homepage again
     expect(find.text('HomeBody'), findsOneWidget);
@@ -374,7 +374,7 @@ void main() {
   });
 
   testWidgets('Closing nested search returns to search', (WidgetTester tester) async {
-    final List<String> nestedSearchResults = <String>[];
+    final List<String?> nestedSearchResults = <String?>[];
     final _TestSearchDelegate nestedSearchDelegate = _TestSearchDelegate(
       suggestions: 'Nested Suggestions',
       result: 'Nested Result',
@@ -389,7 +389,7 @@ void main() {
               tooltip: 'Nested Search',
               icon: const Icon(Icons.search),
               onPressed: () async {
-                final String result = await showSearch(
+                final String? result = await showSearch(
                   context: context,
                   delegate: nestedSearchDelegate,
                 );
@@ -467,7 +467,7 @@ void main() {
               tooltip: 'Nested Search',
               icon: const Icon(Icons.search),
               onPressed: () async {
-                final String result = await showSearch(
+                final String? result = await showSearch(
                   context: context,
                   delegate: nestedSearchDelegate,
                 );
@@ -702,7 +702,7 @@ class TestHomePage extends StatelessWidget {
     this.initialQuery,
   }) : super(key: key);
 
-  final List<String>? results;
+  final List<String?>? results;
   final SearchDelegate<String> delegate;
   final bool passInInitialQuery;
   final String? initialQuery;
@@ -719,7 +719,7 @@ class TestHomePage extends StatelessWidget {
                 tooltip: 'Search',
                 icon: const Icon(Icons.search),
                 onPressed: () async {
-                  String selectedResult;
+                  String? selectedResult;
                   if (passInInitialQuery) {
                     selectedResult = await showSearch<String>(
                       context: context,

packages/flutter/test/material/will_pop_test.dart

@@ -222,8 +222,8 @@ void main() {
   });
 
   testWidgets('Form.willPop callbacks do not accumulate', (WidgetTester tester) async {
-    Future<bool> showYesNoAlert(BuildContext context) {
-      return showDialog<bool>(
+    Future<bool> showYesNoAlert(BuildContext context) async {
+      return (await showDialog<bool>(
         context: context,
         builder: (BuildContext context) {
           return AlertDialog(
@@ -239,7 +239,7 @@ void main() {
             ],
           );
         },
-      );
+      ))!;
     }
 
     Widget buildFrame() {

packages/flutter/test/rendering/mock_canvas.dart

@@ -823,7 +823,6 @@ class _TestRecordingCanvasPatternMatcher extends _TestRecordingCanvasMatcher imp
       while (predicate.moveNext()) {
         predicate.current.match(call);
       }
-      assert(predicate.current == null);
       // We allow painting more than expected.
     } on _MismatchedCall catch (data) {
       description.writeln(data.message);

packages/flutter/test/services/fake_platform_views.dart

@@ -174,11 +174,11 @@ class FakeAndroidPlatformViewsController {
     final Map<dynamic, dynamic> args = call.arguments as Map<dynamic, dynamic>;
     final int id = args['id'] as int;
     final String viewType = args['viewType'] as String;
-    final double width = args['width'] as double;
-    final double height = args['height'] as double;
+    final double? width = args['width'] as double?;
+    final double? height = args['height'] as double?;
     final int layoutDirection = args['direction'] as int;
-    final bool hybrid = args['hybrid'] as bool;
-    final Uint8List creationParams = args['params'] as Uint8List;
+    final bool? hybrid = args['hybrid'] as bool?;
+    final Uint8List? creationParams = args['params'] as Uint8List?;
 
     if (_views.containsKey(id))
       throw PlatformException(
@@ -197,7 +197,7 @@ class FakeAndroidPlatformViewsController {
     }
 
     _views[id] = FakeAndroidPlatformView(id, viewType,
-        width != null || height != null ? Size(width, height) : null,
+        width != null && height != null ? Size(width, height) : null,
         layoutDirection,
         hybrid,
         creationParams,
@@ -344,7 +344,7 @@ class FakeIosPlatformViewsController {
     final Map<dynamic, dynamic> args = call.arguments as Map<dynamic, dynamic>;
     final int id = args['id'] as int;
     final String viewType = args['viewType'] as String;
-    final Uint8List creationParams = args['params'] as Uint8List;
+    final Uint8List? creationParams = args['params'] as Uint8List?;
 
     if (_views.containsKey(id)) {
       throw PlatformException(

packages/flutter/test/services/platform_views_test.dart

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

packages/flutter/test/widgets/custom_paint_test.dart

@@ -58,7 +58,7 @@ class MockPaintingContext extends Fake implements PaintingContext {
 
 void main() {
   testWidgets('Control test for custom painting', (WidgetTester tester) async {
-    final List<String> log = <String>[];
+    final List<String?> log = <String?>[];
     await tester.pumpWidget(CustomPaint(
       painter: TestCustomPainter(
         log: log,
@@ -82,7 +82,7 @@ void main() {
   testWidgets('Throws FlutterError on custom painter incorrect restore/save calls', (
       WidgetTester tester) async {
     final GlobalKey target = GlobalKey();
-    final List<String> log = <String>[];
+    final List<String?> log = <String?>[];
     await tester.pumpWidget(CustomPaint(
       key: target,
       isComplex: true,
@@ -174,7 +174,7 @@ void main() {
   testWidgets('Raster cache hints', (WidgetTester tester) async {
     final GlobalKey target = GlobalKey();
 
-    final List<String> log = <String>[];
+    final List<String?> log = <String?>[];
     await tester.pumpWidget(CustomPaint(
       key: target,
       isComplex: true,

packages/flutter/test/widgets/dismissible_test.dart

@@ -18,7 +18,7 @@ const double crossAxisEndOffset = 0.5;
 Widget buildTest({
   double? startToEndThreshold,
   TextDirection textDirection = TextDirection.ltr,
-  Future<bool> Function(BuildContext context, DismissDirection direction)? confirmDismiss,
+  Future<bool?> Function(BuildContext context, DismissDirection direction)? confirmDismiss,
 }) {
   return Directionality(
     textDirection: textDirection,
@@ -679,7 +679,7 @@ void main() {
       return buildTest(
         confirmDismiss: (BuildContext context, DismissDirection dismissDirection) {
           confirmDismissDirection = dismissDirection;
-          return Future<bool>.value(confirmDismissValue);
+          return Future<bool?>.value(confirmDismissValue);
         }
       );
     }

packages/flutter/test/widgets/image_test.dart

@@ -1516,7 +1516,7 @@ void main() {
     expect(imageCache!.liveImageCount, 1);
     expect(imageCache!.containsKey(provider), false);
 
-    final ImageCacheStatus providerLocation = await provider.obtainCacheStatus(configuration: ImageConfiguration.empty);
+    final ImageCacheStatus providerLocation = (await provider.obtainCacheStatus(configuration: ImageConfiguration.empty))!;
 
     expect(providerLocation, isNotNull);
     expect(providerLocation.live, true);

packages/flutter/test/widgets/navigator_test.dart

@@ -957,7 +957,7 @@ void main() {
   });
 
   testWidgets('replaceNamed returned value', (WidgetTester tester) async {
-    late Future<String> value;
+    late Future<String?> value;
 
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
       '/' : (BuildContext context) => OnTapPage(id: '/', onTap: () { Navigator.pushNamed(context, '/A'); }),
@@ -1001,7 +1001,7 @@ void main() {
     expect(find.text('A'), findsNothing);
     expect(find.text('B'), findsNothing);
 
-    final String replaceNamedValue = await value; // replaceNamed result was 'B'
+    final String? replaceNamedValue = await value; // replaceNamed result was 'B'
     expect(replaceNamedValue, 'B');
   });
 
@@ -1092,7 +1092,7 @@ void main() {
   });
 
   testWidgets('remove a route whose value is awaited', (WidgetTester tester) async {
-    late Future<String> pageValue;
+    late Future<String?> pageValue;
     final Map<String, WidgetBuilder> pageBuilders = <String, WidgetBuilder>{
       '/':  (BuildContext context) => OnTapPage(id: '/', onTap: () { pageValue = Navigator.pushNamed(context, '/A'); }),
       '/A': (BuildContext context) => OnTapPage(id: 'A', onTap: () { Navigator.pop(context, 'A'); }),
@@ -1113,7 +1113,7 @@ void main() {
 
     await tester.tap(find.text('/')); // pushNamed('/A'), stack becomes /, /A
     await tester.pumpAndSettle();
-    pageValue.then((String value) { assert(false); });
+    pageValue.then((String? value) { assert(false); });
 
     final NavigatorState navigator = tester.state<NavigatorState>(find.byType(Navigator));
     navigator.removeRoute(routes['/A']!); // stack becomes /, pageValue will not complete

packages/flutter/test/widgets/restorable_property_test.dart

@@ -285,7 +285,7 @@ void main() {
   });
 }
 
-class _TestRestorableValue extends RestorableValue<Object> {
+class _TestRestorableValue extends RestorableValue<Object?> {
   @override
   Object createDefaultValue() {
     return 55;
@@ -300,12 +300,12 @@ class _TestRestorableValue extends RestorableValue<Object> {
   }
 
   @override
-  Object fromPrimitives(Object data) {
+  Object? fromPrimitives(Object? data) {
     return data;
   }
 
   @override
-  Object toPrimitives() {
+  Object? toPrimitives() {
     return value;
   }
 }

packages/flutter/test/widgets/restoration_mixin_test.dart

@@ -632,7 +632,7 @@ void main() {
   });
 
   test('RestorableProperty throws after disposed', () {
-    final RestorableProperty<Object> property = _TestRestorableProperty(10);
+    final RestorableProperty<Object?> property = _TestRestorableProperty(10);
     property.dispose();
     expect(() => property.dispose(), throwsFlutterError);
   });
@@ -660,8 +660,8 @@ class _TestRestorableWidgetState extends State<_TestRestorableWidget> with Resto
   _TestRestorableProperty? additionalProperty;
   bool _rerigisterAdditionalProperty = false;
 
-  final List<RestorationBucket?> restoreStateLog = <RestorationBucket>[];
-  final List<RestorationBucket?> toggleBucketLog = <RestorationBucket>[];
+  final List<RestorationBucket?> restoreStateLog = <RestorationBucket?>[];
+  final List<RestorationBucket?> toggleBucketLog = <RestorationBucket?>[];
 
   @override
   void restoreState(RestorationBucket? oldBucket, bool initialRestore) {
@@ -737,7 +737,7 @@ Map<String, dynamic> _createRawDataSet() {
   };
 }
 
-class _TestRestorableProperty extends RestorableProperty<Object> {
+class _TestRestorableProperty extends RestorableProperty<Object?> {
   _TestRestorableProperty(this._value);
 
   List<String> log = <String>[];
@@ -751,35 +751,35 @@ class _TestRestorableProperty extends RestorableProperty<Object> {
   }
 
   @override
-  Object createDefaultValue() {
+  Object? createDefaultValue() {
     log.add('createDefaultValue');
     return _value;
   }
 
   @override
-  Object fromPrimitives(Object data) {
+  Object? fromPrimitives(Object? data) {
     log.add('fromPrimitives');
     return data;
   }
 
-  Object get value {
+  Object? get value {
     assert(isRegistered);
     return _value;
   }
-  Object _value;
-  set value(Object value) {
+  Object? _value;
+  set value(Object? value) {
     _value = value;
     notifyListeners();
   }
 
   @override
-  void initWithValue(Object v) {
+  void initWithValue(Object? v) {
     log.add('initWithValue');
     _value = v;
   }
 
   @override
-  Object toPrimitives() {
+  Object? toPrimitives() {
     log.add('toPrimitives');
     return _value;
   }

packages/flutter/test/widgets/restoration_scopes_moving_test.dart

@@ -209,7 +209,7 @@ class TestWidget extends StatefulWidget {
 }
 
 class TestWidgetState extends State<TestWidget> with RestorationMixin {
-  List<RestorationBucket?> buckets = <RestorationBucket>[];
+  List<RestorationBucket?> buckets = <RestorationBucket?>[];
   List<bool> flags = <bool>[];
 
   @override

packages/flutter/test/widgets/root_restoration_scope_test.dart

@@ -302,7 +302,7 @@ void main() {
   });
 
   testWidgets('injects null when rootBucket is null', (WidgetTester tester) async {
-    final Completer<RestorationBucket> completer = Completer<RestorationBucket>();
+    final Completer<RestorationBucket?> completer = Completer<RestorationBucket?>();
     binding.restorationManager.rootBucket = completer.future;
 
     await tester.pumpWidget(

packages/flutter/test/widgets/routes_test.dart

@@ -1319,28 +1319,28 @@ void main() {
       final Finder animatedModalBarrier = find.byType(AnimatedModalBarrier);
       expect(animatedModalBarrier, findsOneWidget);
 
-      Animation<Color> modalBarrierAnimation;
+      Animation<Color?> modalBarrierAnimation;
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(modalBarrierAnimation.value, Colors.transparent);
 
       await tester.pump(const Duration(milliseconds: 25));
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(
-        modalBarrierAnimation.value.alpha,
+        modalBarrierAnimation.value!.alpha,
         closeTo(_getExpectedBarrierTweenAlphaValue(0.25), 1),
       );
 
       await tester.pump(const Duration(milliseconds: 25));
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(
-        modalBarrierAnimation.value.alpha,
+        modalBarrierAnimation.value!.alpha,
         closeTo(_getExpectedBarrierTweenAlphaValue(0.50), 1),
       );
 
       await tester.pump(const Duration(milliseconds: 25));
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(
-        modalBarrierAnimation.value.alpha,
+        modalBarrierAnimation.value!.alpha,
         closeTo(_getExpectedBarrierTweenAlphaValue(0.75), 1),
       );
 
@@ -1382,28 +1382,28 @@ void main() {
       final Finder animatedModalBarrier = find.byType(AnimatedModalBarrier);
       expect(animatedModalBarrier, findsOneWidget);
 
-      Animation<Color> modalBarrierAnimation;
+      Animation<Color?> modalBarrierAnimation;
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(modalBarrierAnimation.value, Colors.transparent);
 
       await tester.pump(const Duration(milliseconds: 25));
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(
-        modalBarrierAnimation.value.alpha,
+        modalBarrierAnimation.value!.alpha,
         closeTo(_getExpectedBarrierTweenAlphaValue(0.25), 1),
       );
 
       await tester.pump(const Duration(milliseconds: 25));
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(
-        modalBarrierAnimation.value.alpha,
+        modalBarrierAnimation.value!.alpha,
         closeTo(_getExpectedBarrierTweenAlphaValue(0.50), 1),
       );
 
       await tester.pump(const Duration(milliseconds: 25));
       modalBarrierAnimation = tester.widget<AnimatedModalBarrier>(animatedModalBarrier).color;
       expect(
-        modalBarrierAnimation.value.alpha,
+        modalBarrierAnimation.value!.alpha,
         closeTo(_getExpectedBarrierTweenAlphaValue(0.75), 1),
       );
 

packages/flutter_test/lib/src/_matchers_io.dart

@@ -49,27 +49,31 @@ class MatchesGoldenFile extends AsyncMatcher {
 
   @override
   Future<String?> matchAsync(dynamic item) async {
-    Future<ui.Image> imageFuture;
-    if (item is Future<ui.Image>) {
+    Future<ui.Image?> imageFuture;
+    if (item is Future<ui.Image?>) {
       imageFuture = item;
     } else if (item is ui.Image) {
       imageFuture = Future<ui.Image>.value(item);
-    } else {
-      final Finder finder = item as Finder;
-      final Iterable<Element> elements = finder.evaluate();
+    } else if (item is Finder) {
+      final Iterable<Element> elements = item.evaluate();
       if (elements.isEmpty) {
         return 'could not be rendered because no widget was found';
       } else if (elements.length > 1) {
         return 'matched too many widgets';
       }
       imageFuture = captureImage(elements.single);
+    } else {
+      throw 'must provide a Finder, Image, or Future<Image>';
     }
 
     final Uri testNameUri = goldenFileComparator.getTestUri(key, version);
 
     final TestWidgetsFlutterBinding binding = TestWidgetsFlutterBinding.ensureInitialized() as TestWidgetsFlutterBinding;
     return binding.runAsync<String?>(() async {
-      final ui.Image image = await imageFuture;
+      final ui.Image? image = await imageFuture;
+      if (image == null) {
+        throw 'Future<Image> completed to null';
+      }
       final ByteData? bytes = await image.toByteData(format: ui.ImageByteFormat.png);
       if (bytes == null)
         return 'could not encode screenshot.';

packages/flutter_test/lib/src/binding.dart

@@ -1011,17 +1011,19 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
 
     addTime(additionalTime);
 
-    return realAsyncZone.run<Future<T>>(() {
+    return realAsyncZone.run<Future<T?>>(() async {
       _pendingAsyncTasks = Completer<void>();
-      return callback().catchError((Object exception, StackTrace stack) {
+      T? result;
+      try {
+        result = await callback();
+      } catch (exception, stack) {
         FlutterError.reportError(FlutterErrorDetails(
           exception: exception,
           stack: stack,
           library: 'Flutter test framework',
           context: ErrorDescription('while running async test code'),
         ));
-        return null;
-      }).whenComplete(() {
+      } finally {
         // We complete the _pendingAsyncTasks future successfully regardless of
         // whether an exception occurred because in the case of an exception,
         // we already reported the exception to FlutterError. Moreover,
@@ -1029,7 +1031,8 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
         // exception due to zone error boundaries.
         _pendingAsyncTasks!.complete();
         _pendingAsyncTasks = null;
-      });
+      }
+      return result;
     });
   }
 

packages/flutter_test/test/test_config/config_test_utils.dart

@@ -11,7 +11,7 @@ void testConfig(
   String? expectedStringValue, {
   Map<Type, dynamic> otherExpectedValues = const <Type, dynamic>{int: isNull},
 }) {
-  final String actualStringValue = Zone.current[String] as String;
+  final String? actualStringValue = Zone.current[String] as String?;
   final Map<Type, dynamic> otherActualValues = otherExpectedValues.map<Type, dynamic>(
     (Type key, dynamic value) {
       return MapEntry<Type, dynamic>(key, Zone.current[key]);