Enable strict-inference (#135043)

Avoids that dynamic accidentally sneaks in, see https://dart.dev/tools/analysis#enabling-additional-type-checks

analysis_options.yaml

@@ -17,6 +17,7 @@
 analyzer:
   language:
     strict-casts: true
+    strict-inference: true
     strict-raw-types: true
   errors:
     # allow self-reference to deprecated members (we do this because otherwise we have

dev/bots/test/analyze-snippet-code-test-dart-ui/ui.dart

@@ -11,7 +11,7 @@ library dart.ui;
 ///
 /// ```dart
 /// class MyStringBuffer {
-///   error; // error (missing_const_final_var_or_type, always_specify_types)
+///   error; // error (prefer_typing_uninitialized_variables, inference_failure_on_uninitialized_variable, missing_const_final_var_or_type)
 ///
 ///   StringBuffer _buffer = StringBuffer(); // error (prefer_final_fields, unused_field)
 /// }

dev/bots/test/analyze-snippet-code-test-input/custom_imports_broken.dart

@@ -16,6 +16,6 @@ String? bar;
 
 /// error: widgets library was not imported (not even implicitly).
 /// ```dart
-/// print(Widget);
+/// print(Widget); // error (undefined_identifier)
 /// ```
 String? foo;

dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart

@@ -131,7 +131,7 @@
 /// Widget build(BuildContext context) {
 ///   final String title;
 ///   return Opacity(
-///     key: globalKey, // error (undefined_identifier, argument_type_not_assignable)
+///     key: globalKey, // error (undefined_identifier)
 ///     opacity: _visible ? 1.0 : 0.0,
 ///     child: Text(title), // error (read_potentially_unassigned_final)
 ///   );
@@ -144,13 +144,14 @@
 /// ```
 ///
 /// ```dart
-/// import 'dart:io'; // error (unused_import)/// final Widget p = Placeholder(); // error (undefined_class, undefined_function)
+/// import 'dart:io'; // error (unused_import)
+/// final Widget p = Placeholder(); // error (undefined_class, undefined_function)
 /// ```
 ///
 /// ```dart
 /// // (e.g. in a stateful widget)
 /// void initState() { // error (must_call_super, annotate_overrides)
-///   widget.toString(); // error (undefined_identifier, return_of_invalid_type)
+///   widget.toString();
 /// }
 /// ```
 ///

dev/bots/test/analyze_snippet_code_test.dart

@@ -21,16 +21,19 @@ const List<String> expectedMainErrors = <String>[
   'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:134:14: (top-level declaration) (undefined_identifier)',
   'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:136:21: (top-level declaration) (read_potentially_unassigned_final)',
   'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:147:12: (self-contained program) (unused_import)',
-  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:152:10: (stateful widget) (annotate_overrides)',
-  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:152:10: (stateful widget) (must_call_super)',
-  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:160:7: (top-level declaration) (undefined_identifier)',
-  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:164: Found "```" in code but it did not match RegExp: pattern=^ */// *```dart\$ flags= so something is wrong. Line was: "/// ```"',
+  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:148:11: (self-contained program) (undefined_class)',
+  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:148:22: (self-contained program) (undefined_function)',
+  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:153:10: (stateful widget) (annotate_overrides)',
+  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:153:10: (stateful widget) (must_call_super)',
+  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:161:7: (top-level declaration) (undefined_identifier)',
+  'dev/bots/test/analyze-snippet-code-test-input/known_broken_documentation.dart:165: Found "```" in code but it did not match RegExp: pattern=^ */// *```dart\$ flags= so something is wrong. Line was: "/// ```"',
   'dev/bots/test/analyze-snippet-code-test-input/short_but_still_broken.dart:9:12: (statement) (invalid_assignment)',
   'dev/bots/test/analyze-snippet-code-test-input/short_but_still_broken.dart:18:4: Empty ```dart block in snippet code.',
 ];
 
 const List<String> expectedUiErrors = <String>[
   'dev/bots/test/analyze-snippet-code-test-dart-ui/ui.dart:14:7: (top-level declaration) (prefer_typing_uninitialized_variables)',
+  'dev/bots/test/analyze-snippet-code-test-dart-ui/ui.dart:14:7: (top-level declaration) (inference_failure_on_uninitialized_variable)',
   'dev/bots/test/analyze-snippet-code-test-dart-ui/ui.dart:14:7: (top-level declaration) (missing_const_final_var_or_type)',
   'dev/bots/test/analyze-snippet-code-test-dart-ui/ui.dart:16:20: (top-level declaration) (prefer_final_fields)',
   'dev/bots/test/analyze-snippet-code-test-dart-ui/ui.dart:16:20: (top-level declaration) (unused_field)',
@@ -69,7 +72,7 @@ void main() {
     final List<String> stderrNoDescriptions = stderrLines.map(removeLintDescriptions).toList();
     expect(stderrNoDescriptions, <String>[
       ...expectedMainErrors,
-      'Found 16 snippet code errors.',
+      'Found 18 snippet code errors.',
       'See the documentation at the top of dev/bots/analyze_snippet_code.dart for details.',
       '', // because we end with a newline, split gives us an extra blank line
     ]);
@@ -93,7 +96,7 @@ void main() {
     expect(stderrNoDescriptions, <String>[
       ...expectedUiErrors,
       ...expectedMainErrors,
-      'Found 20 snippet code errors.',
+      'Found 23 snippet code errors.',
       'See the documentation at the top of dev/bots/analyze_snippet_code.dart for details.',
       '', // because we end with a newline, split gives us an extra blank line
     ]);

dev/conductor/core/test/packages_autoroller_test.dart

@@ -170,7 +170,7 @@ void main() {
     await expectLater(
       () async {
         final Future<void> rollFuture = autoroller.roll();
-        await controller.stream.drain();
+        await controller.stream.drain<Object?>();
         await rollFuture;
       },
       throwsA(isA<Exception>().having(
@@ -214,7 +214,7 @@ void main() {
       ], stdout: '[{"number": 123}]'),
     ]);
     final Future<void> rollFuture = autoroller.roll();
-    await controller.stream.drain();
+    await controller.stream.drain<Object?>();
     await rollFuture;
     expect(processManager, hasNoRemainingExpectations);
     expect(stdio.stdout, contains('flutter-pub-roller-bot already has open tool PRs'));
@@ -312,7 +312,7 @@ void main() {
       ]),
     ]);
     final Future<void> rollFuture = autoroller.roll();
-    await controller.stream.drain();
+    await controller.stream.drain<Object?>();
     await rollFuture;
     expect(processManager, hasNoRemainingExpectations);
   });

dev/devicelab/bin/tasks/flutter_engine_group_performance.dart

@@ -16,7 +16,7 @@ const String _activityName = 'MainActivity';
 const int _numberOfIterations = 10;
 
 Future<void> _withApkInstall(
-    String apkPath, String bundleName, Function(AndroidDevice) body) async {
+    String apkPath, String bundleName, Future<void> Function(AndroidDevice) body) async {
   final DeviceDiscovery devices = DeviceDiscovery();
   final AndroidDevice device = await devices.workingDevice as AndroidDevice;
   await device.unlock();

dev/devicelab/lib/framework/runner.dart

@@ -42,7 +42,7 @@ Future<void> runTasks(
   List<String>? taskArgs,
   bool useEmulator = false,
   @visibleForTesting Map<String, String>? isolateParams,
-  @visibleForTesting Function(String) print = print,
+  @visibleForTesting void Function(String) print = print,
   @visibleForTesting List<String>? logs,
 }) async {
   for (final String taskName in taskNames) {

dev/integration_tests/ios_platform_view_tests/lib/main.dart

@@ -201,7 +201,7 @@ class _ZOrderTestPageState extends State<ZOrderTestPage> {
                 )),
             TextButton(
                 onPressed: () {
-                  showDialog(
+                  showDialog<void>(
                       context: context,
                       builder: (BuildContext context) {
                         return const SizedBox(

examples/api/lib/material/bottom_navigation_bar/bottom_navigation_bar.2.dart

@@ -91,7 +91,7 @@ class _BottomNavigationBarExampleState extends State<BottomNavigationBarExample>
   }
 
   void showModal(BuildContext context) {
-    showDialog(
+    showDialog<void>(
       context: context,
       builder: (BuildContext context) => AlertDialog(
         content: const Text('Example Dialog'),

examples/api/lib/material/navigation_bar/navigation_bar.2.dart

@@ -174,7 +174,7 @@ class RootPage extends StatelessWidget {
             ElevatedButton(
               style: buttonStyle,
               onPressed: () {
-                showDialog(
+                showDialog<void>(
                   context: context,
                   useRootNavigator: false,
                   builder: _buildDialog,
@@ -186,9 +186,9 @@ class RootPage extends StatelessWidget {
             ElevatedButton(
               style: buttonStyle,
               onPressed: () {
-                showDialog(
+                showDialog<void>(
                   context: context,
-                  useRootNavigator: true,
+                  useRootNavigator: true, // ignore: avoid_redundant_argument_values
                   builder: _buildDialog,
                 );
               },
@@ -200,7 +200,7 @@ class RootPage extends StatelessWidget {
                 return ElevatedButton(
                   style: buttonStyle,
                   onPressed: () {
-                    showBottomSheet(
+                    showBottomSheet<void>(
                       context: context,
                       builder: (BuildContext context) {
                         return Container(

examples/api/lib/widgets/scroll_view/list_view.0.dart

@@ -136,7 +136,7 @@ class GridBuilder extends StatefulWidget {
   });
 
   final bool isSelectionMode;
-  final Function(bool)? onSelectionChange;
+  final ValueChanged<bool>? onSelectionChange;
   final List<bool> selectedList;
 
   @override
@@ -189,7 +189,7 @@ class ListBuilder extends StatefulWidget {
 
   final bool isSelectionMode;
   final List<bool> selectedList;
-  final Function(bool)? onSelectionChange;
+  final ValueChanged<bool>? onSelectionChange;
 
   @override
   State<ListBuilder> createState() => _ListBuilderState();

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

@@ -111,7 +111,7 @@ mixin ToggleableStateMixin<S extends StatefulWidget> on TickerProviderStateMixin
   /// build method - potentially after wrapping it in other widgets.
   Widget buildToggleable({
     FocusNode? focusNode,
-    Function(bool)? onFocusChange,
+    ValueChanged<bool>? onFocusChange,
     bool autofocus = false,
     required Size size,
     required CustomPainter painter,

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

@@ -440,7 +440,7 @@ class _DragHandle extends StatelessWidget {
   });
 
   final VoidCallback? onSemanticsTap;
-  final Function(bool) handleHover;
+  final ValueChanged<bool> handleHover;
   final Set<MaterialState> materialState;
   final Color? dragHandleColor;
   final Size? dragHandleSize;

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

@@ -710,7 +710,7 @@ class _MaterialSwitch extends StatefulWidget {
   final MaterialStateProperty<Color?>? overlayColor;
   final double? splashRadius;
   final FocusNode? focusNode;
-  final Function(bool)? onFocusChange;
+  final ValueChanged<bool>? onFocusChange;
   final bool autofocus;
   final Size size;
 

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

@@ -302,7 +302,7 @@ mixin ToggleableStateMixin<S extends StatefulWidget> on TickerProviderStateMixin
   /// build method - potentially after wrapping it in other widgets.
   Widget buildToggleable({
     FocusNode? focusNode,
-    Function(bool)? onFocusChange,
+    ValueChanged<bool>? onFocusChange,
     bool autofocus = false,
     required MaterialStateProperty<MouseCursor> mouseCursor,
     required Size size,

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

@@ -5470,7 +5470,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin, Res
   }
 
   /// Gets first route entry satisfying the predicate, or null if not found.
-  _RouteEntry? _firstRouteEntryWhereOrNull<T>(_RouteEntryPredicate test) {
+  _RouteEntry? _firstRouteEntryWhereOrNull(_RouteEntryPredicate test) {
     for (final _RouteEntry element in _history) {
       if (test(element)) {
         return element;
@@ -5480,7 +5480,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin, Res
   }
 
   /// Gets last route entry satisfying the predicate, or null if not found.
-  _RouteEntry? _lastRouteEntryWhereOrNull<T>(_RouteEntryPredicate test) {
+  _RouteEntry? _lastRouteEntryWhereOrNull(_RouteEntryPredicate test) {
     _RouteEntry? result;
     for (final _RouteEntry element in _history) {
       if (test(element)) {

packages/flutter/test/material/popup_menu_test.dart

@@ -3352,7 +3352,7 @@ void main() {
                 itemBuilder: (BuildContext context) => <PopupMenuItem<int>>[
                   PopupMenuItem<int>(
                     onTap: () {
-                      showModalBottomSheet(
+                      showModalBottomSheet<void>(
                         context: context,
                         builder: (BuildContext context) {
                           return const SizedBox(

packages/flutter/test/painting/colors_test.dart

@@ -464,7 +464,7 @@ void main() {
   });
 
   test('ColorSwatch.lerp identical a,b', () {
-    expect(ColorSwatch.lerp(null, null, 0), null);
+    expect(ColorSwatch.lerp<Object?>(null, null, 0), null);
     const ColorSwatch<int> color = ColorSwatch<int>(0x00000000, <int, Color>{1: Color(0x00000000)});
     expect(identical(ColorSwatch.lerp(color, color, 0.5), color), true);
   });

packages/flutter/test/rendering/proxy_box_test.dart

@@ -881,7 +881,7 @@ void main() {
   });
 
   // Simulate painting a RenderBox as if 'debugPaintSizeEnabled == true'
-  Function(PaintingContext, Offset) debugPaint(RenderBox renderBox) {
+  DebugPaintCallback debugPaint(RenderBox renderBox) {
     layout(renderBox);
     pumpFrame(phase: EnginePhase.compositingBits);
     return (PaintingContext context, Offset offset) {
@@ -891,7 +891,7 @@ void main() {
   }
 
   test('RenderClipPath.debugPaintSize draws a path and a debug text when clipBehavior is not Clip.none', () {
-    Function(PaintingContext, Offset) debugPaintClipRect(Clip clip) {
+    DebugPaintCallback debugPaintClipRect(Clip clip) {
       final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
       final RenderClipPath renderClipPath = RenderClipPath(clipBehavior: clip, child: child);
       return debugPaint(renderClipPath);
@@ -908,7 +908,7 @@ void main() {
   });
 
   test('RenderClipRect.debugPaintSize draws a rect and a debug text when clipBehavior is not Clip.none', () {
-    Function(PaintingContext, Offset) debugPaintClipRect(Clip clip) {
+    DebugPaintCallback debugPaintClipRect(Clip clip) {
       final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
       final RenderClipRect renderClipRect = RenderClipRect(clipBehavior: clip, child: child);
       return debugPaint(renderClipRect);
@@ -924,7 +924,7 @@ void main() {
   });
 
   test('RenderClipRRect.debugPaintSize draws a rounded rect and a debug text when clipBehavior is not Clip.none', () {
-    Function(PaintingContext, Offset) debugPaintClipRRect(Clip clip) {
+    DebugPaintCallback debugPaintClipRRect(Clip clip) {
       final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
       final RenderClipRRect renderClipRRect = RenderClipRRect(clipBehavior: clip, child: child);
       return debugPaint(renderClipRRect);
@@ -940,7 +940,7 @@ void main() {
   });
 
   test('RenderClipOval.debugPaintSize draws a path and a debug text when clipBehavior is not Clip.none', () {
-    Function(PaintingContext, Offset) debugPaintClipOval(Clip clip) {
+    DebugPaintCallback debugPaintClipOval(Clip clip) {
       final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
       final RenderClipOval renderClipOval = RenderClipOval(clipBehavior: clip, child: child);
       return debugPaint(renderClipOval);
@@ -1085,3 +1085,5 @@ void expectAssertionError() {
     FlutterError.reportError(errorDetails);
   }
 }
+
+typedef DebugPaintCallback = void Function(PaintingContext context, Offset offset);

packages/flutter/test/widgets/media_query_test.dart

@@ -11,7 +11,7 @@ import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 class _MediaQueryAspectCase {
   const _MediaQueryAspectCase(this.method, this.data);
-  final Function(BuildContext) method;
+  final void Function(BuildContext) method;
   final MediaQueryData data;
 }
 

packages/flutter/test/widgets/sliver_cross_axis_group_test.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -327,7 +328,7 @@ void main() {
 
   testWidgets('Assertion error when SliverExpanded is used outside of SliverCrossAxisGroup', (WidgetTester tester) async {
     final List<FlutterErrorDetails> errors = <FlutterErrorDetails>[];
-    final Function(FlutterErrorDetails)? oldHandler = FlutterError.onError;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
     FlutterError.onError = (FlutterErrorDetails error) => errors.add(error);
 
     await tester.pumpWidget(
@@ -459,7 +460,7 @@ void main() {
 
   testWidgetsWithLeakTracking('Assertion error when constrained widget runs out of cross axis extent', (WidgetTester tester) async {
     final List<FlutterErrorDetails> errors = <FlutterErrorDetails>[];
-    final Function(FlutterErrorDetails)? oldHandler = FlutterError.onError;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
     FlutterError.onError = (FlutterErrorDetails error) => errors.add(error);
 
     final List<int> items = List<int>.generate(20, (int i) => i);
@@ -481,7 +482,7 @@ void main() {
 
   testWidgetsWithLeakTracking('Assertion error when expanded widget runs out of cross axis extent', (WidgetTester tester) async {
     final List<FlutterErrorDetails> errors = <FlutterErrorDetails>[];
-    final Function(FlutterErrorDetails)? oldHandler = FlutterError.onError;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
     FlutterError.onError = (FlutterErrorDetails error) => errors.add(error);
 
     final List<int> items = List<int>.generate(20, (int i) => i);

packages/flutter_test/lib/src/_binding_io.dart

@@ -128,7 +128,7 @@ class _MockHttpClient implements HttpClient {
   bool Function(X509Certificate cert, String host, int port)? badCertificateCallback;
 
   @override
-  Function(String line)? keyLog;
+  void Function(String line)? keyLog;
 
   @override
   void close({ bool force = false }) { }

packages/flutter_test/test/utils/fake_and_mock_utils.dart

@@ -19,7 +19,7 @@ void verifyPropertyFaked<TProperty>({
   required TProperty realValue,
   required TProperty fakeValue,
   required TProperty Function() propertyRetriever,
-  required Function(TestWidgetsFlutterBinding, TProperty fakeValue) propertyFaker,
+  required void Function(TestWidgetsFlutterBinding, TProperty fakeValue) propertyFaker,
   Matcher Function(TProperty) matcher = equals,
 }) {
   TProperty propertyBeforeFaking;
@@ -45,8 +45,8 @@ void verifyPropertyReset<TProperty>({
   required WidgetTester tester,
   required TProperty fakeValue,
   required TProperty Function() propertyRetriever,
-  required Function() propertyResetter,
-  required Function(TProperty fakeValue) propertyFaker,
+  required VoidCallback propertyResetter,
+  required ValueSetter<TProperty> propertyFaker,
   Matcher Function(TProperty) matcher = equals,
 }) {
   TProperty propertyBeforeFaking;

packages/flutter_tools/test/general.shard/ios/ios_deploy_test.dart

@@ -80,7 +80,7 @@ void main () {
 
       expect(iosDeployDebugger.logLines, emits('Did finish launching.'));
       expect(await iosDeployDebugger.launchAndAttach(), isTrue);
-      await iosDeployDebugger.logLines.drain();
+      await iosDeployDebugger.logLines.drain<Object?>();
       expect(processManager, hasNoRemainingExpectations);
       expect(appDeltaDirectory, exists);
     });
@@ -141,7 +141,7 @@ void main () {
           'process detach',
         ]));
         expect(await iosDeployDebugger.launchAndAttach(), isTrue);
-        await logLines.drain();
+        await logLines.drain<Object?>();
 
         expect(logger.traceText, contains('PROCESS_STOPPED'));
         expect(logger.traceText, contains('thread backtrace all'));
@@ -189,7 +189,7 @@ void main () {
 
         expect(iosDeployDebugger.logLines, emitsDone);
         expect(await iosDeployDebugger.launchAndAttach(), isFalse);
-        await iosDeployDebugger.logLines.drain();
+        await iosDeployDebugger.logLines.drain<Object?>();
       });
 
       testWithoutContext('app exit', () async {
@@ -209,7 +209,7 @@ void main () {
         ]));
 
         expect(await iosDeployDebugger.launchAndAttach(), isTrue);
-        await iosDeployDebugger.logLines.drain();
+        await iosDeployDebugger.logLines.drain<Object?>();
       });
 
       testWithoutContext('app crash', () async {
@@ -239,7 +239,7 @@ void main () {
         ]));
 
         expect(await iosDeployDebugger.launchAndAttach(), isTrue);
-        await iosDeployDebugger.logLines.drain();
+        await iosDeployDebugger.logLines.drain<Object?>();
 
         expect(logger.traceText, contains('Process 6156 stopped'));
         expect(logger.traceText, contains('thread backtrace all'));
@@ -263,7 +263,7 @@ void main () {
         expect(iosDeployDebugger.logLines, emitsDone);
 
         expect(await iosDeployDebugger.launchAndAttach(), isFalse);
-        await iosDeployDebugger.logLines.drain();
+        await iosDeployDebugger.logLines.drain<Object?>();
       });
 
       testWithoutContext('no provisioning profile 1, stdout', () async {
@@ -364,7 +364,7 @@ void main () {
           'Log on attach2',
         ]));
         expect(await iosDeployDebugger.launchAndAttach(), isTrue);
-        await logLines.drain();
+        await logLines.drain<Object?>();
 
         expect(LineSplitter.split(logger.traceText), containsOnce('Received logs from ios-deploy.'));
       });

packages/flutter_tools/test/integration.shard/debug_adapter/test_server.dart

@@ -19,7 +19,7 @@ abstract class DapTestServer {
   Future<void> stop();
   StreamSink<List<int>> get sink;
   Stream<List<int>> get stream;
-  Function(String message)? onStderrOutput;
+  void Function(String message)? onStderrOutput;
 }
 
 /// An instance of a DAP server running in-process (to aid debugging).
@@ -83,7 +83,7 @@ class OutOfProcessDapTestServer extends DapTestServer {
         .listen((String error) {
       logger?.call(error);
       if (!_isShuttingDown) {
-        final Function(String message)? stderrHandler = onStderrOutput;
+        final void Function(String message)? stderrHandler = onStderrOutput;
         if (stderrHandler != null) {
           stderrHandler(error);
         } else {

packages/flutter_tools/test/src/fake_http_client.dart

@@ -147,7 +147,7 @@ class FakeHttpClient implements HttpClient {
   bool Function(X509Certificate cert, String host, int port)? badCertificateCallback;
 
   @override
-  Function(String line)? keyLog;
+  void Function(String line)? keyLog;
 
   @override
   void close({bool force = false}) { }