Enable the avoid_final_parameters lint. (#185216)

kallentu · web-flow · commit bf9ce1d43ed5 · 2026-04-28T18:42:18.000Z
`avoid_final_parameters` lint fires when using a `final` modifier in any parameter list. This is a preparatory lint that helps us migrate to Dart 3.13. All violations from this lint will become compile-time errors in Dart 3.13 when the primary constructors feature ships. Fixes: dart-lang/sdk#62590 **Related to breaking changes:** There should be nothing that breaks from adding this lint. Function types with `final` are already a compile-time error and any customers overriding a method with a `final` parameter won't break their code. ``` // Framework code class C { void m(int x) { ... } // Removed var here. } ``` ``` // ... // User code class B implements C { void m(final int x) { ... } // Will still work. } ``` This change should be test exempt. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [AI contribution guidelines] and understand my responsibilities, or I am not using AI tools. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. If this change needs to override an active code freeze, provide a comment explaining why. The code freeze workflow can be overridden by code reviewers. See pinned issues for any active code freezes with guidance. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [AI contribution guidelines]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#ai-contribution-guidelines [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md
diff --git a/analysis_options.yaml b/analysis_options.yaml
@@ -55,7 +55,8 @@ linter:
     - avoid_equals_and_hash_code_on_mutable_classes
     - avoid_escaping_inner_quotes
     - avoid_field_initializers_in_const_classes
-    # - avoid_final_parameters # incompatible with prefer_final_parameters
+    # TODO(kallentu): Remove this lint once the Dart SDK in Flutter is on version 3.13.
+    - avoid_final_parameters
     - avoid_function_literals_in_foreach_calls
     # - avoid_futureor_void # not yet tested
     # - avoid_implementing_value_types # see https://github.com/dart-lang/linter/issues/4558
diff --git a/dev/benchmarks/complex_layout/test/measure_scroll_smoothness.dart b/dev/benchmarks/complex_layout/test/measure_scroll_smoothness.dart
@@ -15,11 +15,11 @@ import 'package:integration_test/integration_test.dart';
 /// Generates the [PointerEvent] to simulate a drag operation from
 /// `center - totalMove/2` to `center + totalMove/2`.
 Iterable<PointerEvent> dragInputEvents(
-  final Duration epoch,
-  final Offset center, {
-  final Offset totalMove = const Offset(0, -400),
-  final Duration totalTime = const Duration(milliseconds: 2000),
-  final double frequency = 90,
+  Duration epoch,
+  Offset center, {
+  Offset totalMove = const Offset(0, -400),
+  Duration totalTime = const Duration(milliseconds: 2000),
+  double frequency = 90,
 }) sync* {
   final Offset startLocation = center - totalMove / 2;
   // The issue is about 120Hz input on 90Hz refresh rate device.
diff --git a/dev/bots/suite_runners/run_test_harness_tests.dart b/dev/bots/suite_runners/run_test_harness_tests.dart
@@ -175,7 +175,7 @@ Future<void> _validateEngineRevision() async {
   }
   final String actualVersion;
   try {
-    actualVersion = result.flattenedStderr!.split('\n').firstWhere((final String line) {
+    actualVersion = result.flattenedStderr!.split('\n').firstWhere((String line) {
       return line.startsWith('Flutter Engine Version:');
     });
   } on StateError {
diff --git a/engine/src/flutter/lib/web_ui/lib/src/engine/text_editing/text_editing.dart b/engine/src/flutter/lib/web_ui/lib/src/engine/text_editing/text_editing.dart
@@ -2716,7 +2716,7 @@ class EditableTextGeometry {
     assert(encodedGeometry.containsKey('transform'));
 
     final transformList = List<double>.from(
-      encodedGeometry.readList('transform').map((final dynamic e) => (e as num).toDouble()),
+      encodedGeometry.readList('transform').map((dynamic e) => (e as num).toDouble()),
     );
     return EditableTextGeometry(
       width: encodedGeometry.readDouble('width'),
diff --git a/engine/src/flutter/lib/web_ui/test/common/matchers.dart b/engine/src/flutter/lib/web_ui/test/common/matchers.dart
@@ -257,7 +257,7 @@ class HtmlPatternMatcher extends Matcher {
   final html.Element pattern;
 
   @override
-  bool matches(final Object? object, Map<Object?, Object?> matchState) {
+  bool matches(Object? object, Map<Object?, Object?> matchState) {
     // TODO(srujzs): Replace this with `!object.isJSAny` once we have that API
     // in `dart:js_interop`.
     // https://github.com/dart-lang/sdk/issues/56905
diff --git a/engine/src/flutter/lib/web_ui/test/ui/scene_builder_test.dart b/engine/src/flutter/lib/web_ui/test/ui/scene_builder_test.dart
@@ -663,7 +663,7 @@ ui.Picture drawPicture(void Function(ui.Canvas) drawCommands) {
   return recorder.endRecording();
 }
 
-ui.Scene backdropBlurWithTileMode(ui.TileMode? tileMode, final double rectSize, final int count) {
+ui.Scene backdropBlurWithTileMode(ui.TileMode? tileMode, double rectSize, int count) {
   final double imgSize = rectSize * count;
 
   const white = ui.Color(0xFFFFFFFF);
diff --git a/engine/src/flutter/shell/platform/windows/fixtures/main.dart b/engine/src/flutter/shell/platform/windows/fixtures/main.dart
@@ -421,11 +421,10 @@ Future<void> sendSemanticsTreeInfo() async {
 
   final Iterable<ui.FlutterView> views = ui.PlatformDispatcher.instance.views;
   final ui.FlutterView view1 = views.firstWhere(
-    (final ui.FlutterView view) => view != ui.PlatformDispatcher.instance.implicitView,
+    (ui.FlutterView view) => view != ui.PlatformDispatcher.instance.implicitView,
   );
   final ui.FlutterView view2 = views.firstWhere(
-    (final ui.FlutterView view) =>
-        view != view1 && view != ui.PlatformDispatcher.instance.implicitView,
+    (ui.FlutterView view) => view != view1 && view != ui.PlatformDispatcher.instance.implicitView,
   );
 
   ui.SemanticsUpdate createSemanticsUpdate(int nodeId) {
diff --git a/examples/image_list/lib/main.dart b/examples/image_list/lib/main.dart
@@ -154,7 +154,7 @@ class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
     });
   }
 
-  Widget createImage(final int index, final Completer<bool> completer) {
+  Widget createImage(int index, Completer<bool> completer) {
     return Image.network(
       'https://localhost:${widget.port}/${_counter * images + index}',
       frameBuilder: (BuildContext context, Widget child, int? frame, bool wasSynchronouslyLoaded) {
diff --git a/examples/multiple_windows/lib/app/popup_button.dart b/examples/multiple_windows/lib/app/popup_button.dart
@@ -32,7 +32,7 @@ class _PopupButtonState extends State<PopupButton> {
     super.dispose();
   }
 
-  void _onPressed(final WindowRegistry windowRegistry, final WindowSettings windowSettings) {
+  void _onPressed(WindowRegistry windowRegistry, WindowSettings windowSettings) {
     // Toggle popup visibility.
     if (_popupWindowEntry != null) {
       _popupWindowEntry!.controller.destroy();
diff --git a/examples/multiple_windows/lib/app/tooltip_button.dart b/examples/multiple_windows/lib/app/tooltip_button.dart
@@ -32,7 +32,7 @@ class _TooltipButtonState extends State<TooltipButton> {
     super.dispose();
   }
 
-  void _onPressed(final WindowRegistry windowRegistry, final WindowSettings windowSettings) {
+  void _onPressed(WindowRegistry windowRegistry, WindowSettings windowSettings) {
     // Toggle tooltip visibility.
     if (_tooltipEntry != null) {
       _tooltipEntry!.controller.destroy();
diff --git a/packages/flutter/lib/src/animation/animation_style.dart b/packages/flutter/lib/src/animation/animation_style.dart
@@ -51,10 +51,10 @@ class AnimationStyle with Diagnosticable {
   /// Creates a new [AnimationStyle] based on the current selection, with the
   /// provided parameters overridden.
   AnimationStyle copyWith({
-    final Curve? curve,
-    final Duration? duration,
-    final Curve? reverseCurve,
-    final Duration? reverseDuration,
+    Curve? curve,
+    Duration? duration,
+    Curve? reverseCurve,
+    Duration? reverseDuration,
   }) {
     return AnimationStyle(
       curve: curve ?? this.curve,
diff --git a/packages/flutter/lib/src/material/about.dart b/packages/flutter/lib/src/material/about.dart
@@ -684,7 +684,7 @@ class _LicensePageState extends State<LicensePage> {
     );
   }
 
-  Widget _packagesView(final BuildContext _, final bool isLateral) {
+  Widget _packagesView(BuildContext _, bool isLateral) {
     final Widget about = _AboutProgram(
       name: widget.applicationName ?? _defaultApplicationName(context),
       icon: widget.applicationIcon ?? _defaultApplicationIcon(context),
@@ -835,10 +835,10 @@ class _PackagesViewState extends State<_PackagesView> {
   }
 
   Widget _packagesList(
-    final BuildContext context,
-    final int? selectedId,
-    final _LicenseData data,
-    final bool drawSelection,
+    BuildContext context,
+    int? selectedId,
+    _LicenseData data,
+    bool drawSelection,
   ) {
     final EdgeInsets safeAreaPadding = MediaQuery.paddingOf(context);
     final padding = EdgeInsets.only(
@@ -971,7 +971,7 @@ class _DetailArguments {
   final List<LicenseEntry> licenseEntries;
 
   @override
-  bool operator ==(final Object other) {
+  bool operator ==(Object other) {
     if (other is _DetailArguments) {
       return other.packageName == packageName;
     }
diff --git a/packages/flutter/lib/src/material/date_picker.dart b/packages/flutter/lib/src/material/date_picker.dart
@@ -219,10 +219,10 @@ Future<DateTime?> showDatePicker({
   String? fieldLabelText,
   TextInputType? keyboardType,
   Offset? anchorPoint,
-  final ValueChanged<DatePickerEntryMode>? onDatePickerModeChange,
-  final Icon? switchToInputEntryModeIcon,
-  final Icon? switchToCalendarEntryModeIcon,
-  final CalendarDelegate<DateTime> calendarDelegate = const GregorianCalendarDelegate(),
+  ValueChanged<DatePickerEntryMode>? onDatePickerModeChange,
+  Icon? switchToInputEntryModeIcon,
+  Icon? switchToCalendarEntryModeIcon,
+  CalendarDelegate<DateTime> calendarDelegate = const GregorianCalendarDelegate(),
 }) async {
   initialDate = initialDate == null ? null : calendarDelegate.dateOnly(initialDate);
   firstDate = calendarDelegate.dateOnly(firstDate);
@@ -1190,8 +1190,8 @@ Future<DateTimeRange?> showDateRangePicker({
   TransitionBuilder? builder,
   Offset? anchorPoint,
   TextInputType keyboardType = TextInputType.datetime,
-  final Icon? switchToInputEntryModeIcon,
-  final Icon? switchToCalendarEntryModeIcon,
+  Icon? switchToInputEntryModeIcon,
+  Icon? switchToCalendarEntryModeIcon,
   SelectableDayForRangePredicate? selectableDayPredicate,
   CalendarDelegate<DateTime> calendarDelegate = const GregorianCalendarDelegate(),
 }) async {
diff --git a/packages/flutter/lib/src/material/scaffold.dart b/packages/flutter/lib/src/material/scaffold.dart
@@ -2715,7 +2715,7 @@ class ScaffoldState extends State<Scaffold>
   }
 
   // Moves the Floating Action Button to the new Floating Action Button Location.
-  void _moveFloatingActionButton(final FloatingActionButtonLocation newLocation) {
+  void _moveFloatingActionButton(FloatingActionButtonLocation newLocation) {
     FloatingActionButtonLocation? previousLocation = _floatingActionButtonLocation;
     var restartAnimationFrom = 0.0;
     // If the Floating Action Button is moving right now, we need to start from a snapshot of the current transition.
diff --git a/packages/flutter/lib/src/widgets/editable_text.dart b/packages/flutter/lib/src/widgets/editable_text.dart
@@ -2140,15 +2140,15 @@ class EditableText extends StatefulWidget {
   /// * [AdaptiveTextSelectionToolbar.getAdaptiveButtons], which builds the button
   ///   Widgets for the current platform given [ContextMenuButtonItem]s.
   static List<ContextMenuButtonItem> getEditableButtonItems({
-    required final ClipboardStatus? clipboardStatus,
-    required final VoidCallback? onCopy,
-    required final VoidCallback? onCut,
-    required final VoidCallback? onPaste,
-    required final VoidCallback? onSelectAll,
-    required final VoidCallback? onLookUp,
-    required final VoidCallback? onSearchWeb,
-    required final VoidCallback? onShare,
-    required final VoidCallback? onLiveTextInput,
+    required ClipboardStatus? clipboardStatus,
+    required VoidCallback? onCopy,
+    required VoidCallback? onCut,
+    required VoidCallback? onPaste,
+    required VoidCallback? onSelectAll,
+    required VoidCallback? onLookUp,
+    required VoidCallback? onSearchWeb,
+    required VoidCallback? onShare,
+    required VoidCallback? onLiveTextInput,
   }) {
     final resultButtonItem = <ContextMenuButtonItem>[];
 
@@ -4574,7 +4574,7 @@ class EditableTextState extends State<EditableText>
     _lastBottomViewInset = view.viewInsets.bottom;
   }
 
-  Future<void> _performSpellCheck(final String text) async {
+  Future<void> _performSpellCheck(String text) async {
     try {
       final Locale? localeForSpellChecking = widget.locale ?? Localizations.maybeLocaleOf(context);
 
diff --git a/packages/flutter/lib/src/widgets/selectable_region.dart b/packages/flutter/lib/src/widgets/selectable_region.dart
@@ -296,10 +296,10 @@ class SelectableRegion extends StatefulWidget {
   /// * [AdaptiveTextSelectionToolbar.getAdaptiveButtons], which builds the button
   ///   Widgets for the current platform given [ContextMenuButtonItem]s.
   static List<ContextMenuButtonItem> getSelectableButtonItems({
-    required final SelectionGeometry selectionGeometry,
-    required final VoidCallback onCopy,
-    required final VoidCallback onSelectAll,
-    required final VoidCallback? onShare,
+    required SelectionGeometry selectionGeometry,
+    required VoidCallback onCopy,
+    required VoidCallback onSelectAll,
+    required VoidCallback? onShare,
   }) {
     final canCopy = selectionGeometry.status == SelectionStatus.uncollapsed;
     final bool canSelectAll = selectionGeometry.hasContent;
diff --git a/packages/flutter/test/foundation/diagnostics_test.dart b/packages/flutter/test/foundation/diagnostics_test.dart
@@ -149,7 +149,7 @@ void validateIterablePropertyJsonSerialization(IterableProperty<Object> property
 }
 
 void validatePropertyJsonSerializationHelper(
-  final Map<String, Object?> json,
+  Map<String, Object?> json,
   DiagnosticsProperty<Object?> property,
 ) {
   if (property.defaultValue != kNoDefaultValue) {
diff --git a/packages/flutter/test/material/text_field_test.dart b/packages/flutter/test/material/text_field_test.dart
@@ -5221,7 +5221,7 @@ void main() {
   testWidgets('Multiline hint text will wrap up to maxLines', (WidgetTester tester) async {
     final Key textFieldKey = UniqueKey();
 
-    Widget builder(int? maxLines, final String hintMsg) {
+    Widget builder(int? maxLines, String hintMsg) {
       return boilerplate(
         child: TextField(
           key: textFieldKey,
diff --git a/packages/flutter/test/material/theme_data_test.dart b/packages/flutter/test/material/theme_data_test.dart
@@ -1849,7 +1849,7 @@ void main() {
     final properties = DiagnosticPropertiesBuilder();
     ThemeData().debugFillProperties(properties);
     final List<String> propertyNameList = properties.properties
-        .map((final DiagnosticsNode node) => node.name)
+        .map((DiagnosticsNode node) => node.name)
         .whereType<String>()
         .toList();
     final Set<String> propertyNames = propertyNameList.toSet();
diff --git a/packages/flutter_tools/lib/src/commands/custom_devices.dart b/packages/flutter_tools/lib/src/commands/custom_devices.dart
@@ -372,7 +372,7 @@ class CustomDevicesAddCommand extends CustomDevicesCommandBase {
 
   /// Check this config by executing some of the commands, see if they run
   /// fine.
-  Future<bool> _checkConfigWithLogging(final CustomDeviceConfig config) async {
+  Future<bool> _checkConfigWithLogging(CustomDeviceConfig config) async {
     final device = CustomDevice(config: config, logger: logger, processManager: _processManager);
 
     var result = true;
diff --git a/packages/flutter_tools/lib/src/commands/validate_project.dart b/packages/flutter_tools/lib/src/commands/validate_project.dart
@@ -91,9 +91,9 @@ class ValidateProject {
   }
 
   void addResultString(
-    final String title,
-    final List<ProjectValidatorResult>? results,
-    final List<String> resultsString,
+    String title,
+    List<ProjectValidatorResult>? results,
+    List<String> resultsString,
   ) {
     if (results != null) {
       for (final ProjectValidatorResult result in results) {
diff --git a/packages/flutter_tools/lib/src/localizations/gen_l10n.dart b/packages/flutter_tools/lib/src/localizations/gen_l10n.dart
@@ -1028,7 +1028,7 @@ class LocalizationsGenerator {
     String className,
     String fileName,
     String header,
-    final LocaleInfo locale,
+    LocaleInfo locale,
   ) {
     final Iterable<String> methods = _allMessages.map((Message message) {
       var localeWithFallback = locale;
diff --git a/packages/flutter_tools/lib/src/test/test_time_recorder.dart b/packages/flutter_tools/lib/src/test/test_time_recorder.dart
@@ -38,11 +38,11 @@ class TestTimeRecorder {
   }
 
   @visibleForTesting
-  Stopwatch getPhaseWallClockStopwatchForTesting(final TestTimePhases phase) {
+  Stopwatch getPhaseWallClockStopwatchForTesting(TestTimePhases phase) {
     return _phaseRecords[phase.index]._wallClockRuntime;
   }
 
-  String _getPrintStringForPhase(final TestTimePhases phase) {
+  String _getPrintStringForPhase(TestTimePhases phase) {
     assert(_phaseRecords[phase.index].isDone());
     return 'Runtime for phase ${phase.name}: ${_phaseRecords[phase.index]}';
   }

Original file line number	Diff line number	Diff line change
`@@ -175,7 +175,7 @@ Future<void> _validateEngineRevision() async {`
`175`	`175`	`}`
`176`	`176`	`final String actualVersion;`
`177`	`177`	`try {`
`178`		`- actualVersion = result.flattenedStderr!.split('\n').firstWhere((final String line) {`
	`178`	`+ actualVersion = result.flattenedStderr!.split('\n').firstWhere((String line) {`
`179`	`179`	`return line.startsWith('Flutter Engine Version:');`
`180`	`180`	`});`
`181`	`181`	`} on StateError {`
Original file line number	Diff line number	Diff line change
`@@ -663,7 +663,7 @@ ui.Picture drawPicture(void Function(ui.Canvas) drawCommands) {`
`663`	`663`	`return recorder.endRecording();`
`664`	`664`	`}`
`665`	`665`
`666`		`-ui.Scene backdropBlurWithTileMode(ui.TileMode? tileMode, final double rectSize, final int count) {`
	`666`	`+ui.Scene backdropBlurWithTileMode(ui.TileMode? tileMode, double rectSize, int count) {`
`667`	`667`	`final double imgSize = rectSize * count;`
`668`	`668`
`669`	`669`	`const white = ui.Color(0xFFFFFFFF);`
Original file line number	Diff line number	Diff line change
`@@ -154,7 +154,7 @@ class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {`
`154`	`154`	`});`
`155`	`155`	`}`
`156`	`156`
`157`		`- Widget createImage(final int index, final Completer<bool> completer) {`
	`157`	`+ Widget createImage(int index, Completer<bool> completer) {`
`158`	`158`	`return Image.network(`
`159`	`159`	`'https://localhost:${widget.port}/${_counter * images + index}',`
`160`	`160`	`frameBuilder: (BuildContext context, Widget child, int? frame, bool wasSynchronouslyLoaded) {`
Original file line number	Diff line number	Diff line change
`@@ -32,7 +32,7 @@ class _PopupButtonState extends State<PopupButton> {`
`32`	`32`	`super.dispose();`
`33`	`33`	`}`
`34`	`34`
`35`		`- void _onPressed(final WindowRegistry windowRegistry, final WindowSettings windowSettings) {`
	`35`	`+ void _onPressed(WindowRegistry windowRegistry, WindowSettings windowSettings) {`
`36`	`36`	`// Toggle popup visibility.`
`37`	`37`	`if (_popupWindowEntry != null) {`
`38`	`38`	`_popupWindowEntry!.controller.destroy();`
Original file line number	Diff line number	Diff line change
`@@ -32,7 +32,7 @@ class _TooltipButtonState extends State<TooltipButton> {`
`32`	`32`	`super.dispose();`
`33`	`33`	`}`
`34`	`34`
`35`		`- void _onPressed(final WindowRegistry windowRegistry, final WindowSettings windowSettings) {`
	`35`	`+ void _onPressed(WindowRegistry windowRegistry, WindowSettings windowSettings) {`
`36`	`36`	`// Toggle tooltip visibility.`
`37`	`37`	`if (_tooltipEntry != null) {`
`38`	`38`	`_tooltipEntry!.controller.destroy();`