Improve performance of debugCheckHasDirectionality (#81250)

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

@@ -20,6 +20,8 @@ import 'scaffold.dart' show Scaffold, ScaffoldMessenger;
 /// assert(debugCheckHasMaterial(context));
 /// ```
 ///
+/// This method can be expensive (it walks the element tree).
+///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasMaterial(BuildContext context) {
   assert(() {
@@ -62,6 +64,11 @@ bool debugCheckHasMaterial(BuildContext context) {
 /// assert(debugCheckHasMaterialLocalizations(context));
 /// ```
 ///
+/// This function has the side-effect of establishing an inheritance
+/// relationship with the nearest [Localizations] widget (see
+/// [BuildContext.dependOnInheritedWidgetOfExactType]). This is ok if the caller
+/// always also calls [Localizations.of] or [Localizations.localeOf].
+///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasMaterialLocalizations(BuildContext context) {
   assert(() {
@@ -102,6 +109,8 @@ bool debugCheckHasMaterialLocalizations(BuildContext context) {
 /// assert(debugCheckHasScaffold(context));
 /// ```
 ///
+/// This method can be expensive (it walks the element tree).
+///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasScaffold(BuildContext context) {
   assert(() {
@@ -133,6 +142,8 @@ bool debugCheckHasScaffold(BuildContext context) {
 /// assert(debugCheckHasScaffoldMessenger(context));
 /// ```
 ///
+/// This method can be expensive (it walks the element tree).
+///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasScaffoldMessenger(BuildContext context) {
   assert(() {

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

@@ -310,6 +310,8 @@ class Material extends StatefulWidget {
   /// ```dart
   /// MaterialInkController inkController = Material.of(context);
   /// ```
+  ///
+  /// This method can be expensive (it walks the element tree).
   static MaterialInkController? of(BuildContext context) {
     return context.findAncestorRenderObjectOfType<_RenderInkFeatures>();
   }

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

@@ -1820,6 +1820,8 @@ class Scaffold extends StatefulWidget {
   /// If no instance of this class encloses the given context, will cause an
   /// assert in debug mode, and throw an exception in release mode.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// {@tool dartpad --template=freeform}
   /// Typical usage of the [Scaffold.of] function is to call it from within the
   /// `build` method of a child of a [Scaffold].
@@ -1999,6 +2001,8 @@ class Scaffold extends StatefulWidget {
   /// If no instance of this class encloses the given context, will return null.
   /// To throw an exception instead, use [of] instead of this function.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [of], a similar function to this one that throws if no instance
@@ -2066,6 +2070,8 @@ class Scaffold extends StatefulWidget {
   /// [Scaffold] so that the client widget gets rebuilt whenever the [hasDrawer]
   /// value changes.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [Scaffold.of], which provides access to the [ScaffoldState] object as a

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

@@ -392,6 +392,8 @@ class AnimatedList extends StatefulWidget {
   /// If no [AnimatedList] surrounds the context given, then this function will
   /// assert in debug mode and throw an exception in release mode.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [maybeOf], a similar function that will return null if no
@@ -429,6 +431,8 @@ class AnimatedList extends StatefulWidget {
   /// If no [AnimatedList] surrounds the context given, then this function will
   /// return null.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [of], a similar function that will throw if no [AnimatedList] ancestor
@@ -808,6 +812,8 @@ class SliverAnimatedList extends StatefulWidget {
   /// If no [SliverAnimatedList] surrounds the context given, then this function
   /// will assert in debug mode and throw an exception in release mode.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [maybeOf], a similar function that will return null if no
@@ -843,6 +849,8 @@ class SliverAnimatedList extends StatefulWidget {
   /// If no [SliverAnimatedList] surrounds the context given, then this function
   /// will return null.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [of], a similar function that will throw if no [SliverAnimatedList]

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

@@ -184,6 +184,8 @@ bool debugItemsHaveDuplicateKeys(Iterable<Widget> items) {
 /// assert(debugCheckHasTable(context));
 /// ```
 ///
+/// This method can be expensive (it walks the element tree).
+///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasTable(BuildContext context) {
   assert(() {
@@ -215,7 +217,7 @@ bool debugCheckHasTable(BuildContext context) {
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasMediaQuery(BuildContext context) {
   assert(() {
-    if (context.widget is! MediaQuery && context.findAncestorWidgetOfExactType<MediaQuery>() == null) {
+    if (context.widget is! MediaQuery && context.getElementForInheritedWidgetOfExactType<MediaQuery>() == null) {
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No MediaQuery widget ancestor found.'),
         ErrorDescription('${context.widget.runtimeType} widgets require a MediaQuery widget ancestor.'),
@@ -267,7 +269,7 @@ bool debugCheckHasMediaQuery(BuildContext context) {
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasDirectionality(BuildContext context, { String? why, String? hint, String? alternative }) {
   assert(() {
-    if (context.widget is! Directionality && context.findAncestorWidgetOfExactType<Directionality>() == null) {
+    if (context.widget is! Directionality && context.getElementForInheritedWidgetOfExactType<Directionality>() == null) {
       why = why == null ? '' : ' $why';
       throw FlutterError.fromParts(<DiagnosticsNode>[
         ErrorSummary('No Directionality widget found.'),
@@ -373,6 +375,8 @@ bool debugCheckHasWidgetsLocalizations(BuildContext context) {
 /// assert(debugCheckHasOverlay(context));
 /// ```
 ///
+/// This method can be expensive (it walks the element tree).
+///
 /// Does nothing if asserts are disabled. Always returns true.
 bool debugCheckHasOverlay(BuildContext context) {
   assert(() {

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

@@ -146,6 +146,9 @@ abstract class InheritedTheme extends InheritedWidget {
   /// this method is called again to re-capture the updated themes.
   ///
   /// To wrap a [Widget] in the captured themes, call [CapturedThemes.wrap].
+  ///
+  /// This method can be expensive if there are many widgets between `from` and
+  /// `to` (it walks the element tree between those nodes).
   static CapturedThemes capture({ required BuildContext from, required BuildContext? to }) {
     assert(from != null);
 

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

@@ -2712,6 +2712,8 @@ class Navigator extends StatefulWidget {
   ///
   /// If there is no [Navigator] in the give `context`, this function will throw
   /// a [FlutterError] in debug mode, and an exception in release mode.
+  ///
+  /// This method can be expensive (it walks the element tree).
   static NavigatorState of(
     BuildContext context, {
     bool rootNavigator = false,
@@ -2760,6 +2762,8 @@ class Navigator extends StatefulWidget {
   /// subsequent instances of [Navigator].
   ///
   /// Will return null if there is no ancestor [Navigator] in the `context`.
+  ///
+  /// This method can be expensive (it walks the element tree).
   static NavigatorState? maybeOf(
       BuildContext context, {
         bool rootNavigator = false,

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

@@ -284,6 +284,8 @@ class Overlay extends StatefulWidget {
   /// If `rootOverlay` is set to true, the state from the furthest instance of
   /// this class is given instead. Useful for installing overlay entries
   /// above all subsequent instances of [Overlay].
+  ///
+  /// This method can be expensive (it walks the element tree).
   static OverlayState? of(
     BuildContext context, {
     bool rootOverlay = false,

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

@@ -267,6 +267,8 @@ class PageStorage extends StatelessWidget {
   /// ```dart
   /// PageStorageBucket bucket = PageStorage.of(context);
   /// ```
+  ///
+  /// This method can be expensive (it walks the element tree).
   static PageStorageBucket? of(BuildContext context) {
     final PageStorage? widget = context.findAncestorWidgetOfExactType<PageStorage>();
     return widget?.bucket;

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

@@ -220,6 +220,8 @@ class ReorderableList extends StatefulWidget {
   /// If no [ReorderableList] surrounds the given context, then this function
   /// will assert in debug mode and throw an exception in release mode.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [maybeOf], a similar function that will return null if no
@@ -257,6 +259,8 @@ class ReorderableList extends StatefulWidget {
   /// If no [ReorderableList] surrounds the context given, then this function will
   /// return null.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [of], a similar function that will throw if no [ReorderableList] ancestor
@@ -408,6 +412,8 @@ class SliverReorderableList extends StatefulWidget {
   /// If no [SliverReorderableList] surrounds the context given, this function
   /// will assert in debug mode and throw an exception in release mode.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [maybeOf], a similar function that will return null if no
@@ -447,6 +453,8 @@ class SliverReorderableList extends StatefulWidget {
   /// If no [SliverReorderableList] surrounds the context given, this function
   /// will return null.
   ///
+  /// This method can be expensive (it walks the element tree).
+  ///
   /// See also:
   ///
   ///  * [of], a similar function that will throw if no [SliverReorderableList]