fix overlay entry remove to remove itself from the overlay first if i… (#65126)

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

@@ -123,23 +123,26 @@ class OverlayEntry {
   ///
   /// This should only be called once.
   ///
-  /// If this method is called while the [SchedulerBinding.schedulerPhase] is
-  /// [SchedulerPhase.persistentCallbacks], i.e. during the build, layout, or
-  /// paint phases (see [WidgetsBinding.drawFrame]), then the removal is
-  /// delayed until the post-frame callbacks phase. Otherwise the removal is
-  /// done synchronously. This means that it is safe to call during builds, but
-  /// also that if you do call this during a build, the UI will not update until
-  /// the next frame (i.e. many milliseconds later).
+  /// This method removes this overlay entry from the overlay immediately. The
+  /// UI will be updated in the same frame if this method is called before the
+  /// overlay rebuild in this frame; otherwise, the UI will be updated in the
+  /// next frame. This means that it is safe to call during builds, but	also
+  /// that if you do call this after the overlay rebuild, the UI will not update
+  /// until	the next frame (i.e. many milliseconds later).
   void remove() {
     assert(_overlay != null);
     final OverlayState overlay = _overlay;
     _overlay = null;
+    if (!overlay.mounted)
+      return;
+
+    overlay._entries.remove(this);
     if (SchedulerBinding.instance.schedulerPhase == SchedulerPhase.persistentCallbacks) {
       SchedulerBinding.instance.addPostFrameCallback((Duration duration) {
-        overlay._remove(this);
+        overlay._markDirty();
       });
     } else {
-      overlay._remove(this);
+      overlay._markDirty();
     }
   }
 
@@ -405,11 +408,9 @@ class OverlayState extends State<Overlay> with TickerProviderStateMixin {
     });
   }
 
-  void _remove(OverlayEntry entry) {
+  void _markDirty() {
     if (mounted) {
-      setState(() {
-        _entries.remove(entry);
-      });
+      setState(() {});
     }
   }
 

packages/flutter/test/widgets/navigator_test.dart

@@ -521,6 +521,57 @@ void main() {
     await tester.pumpAndSettle();
   });
 
+  testWidgets('Pages update does update overlay correctly', (WidgetTester tester) async {
+    // Regression Test for https://github.com/flutter/flutter/issues/64941.
+    List<Page<void>> pages = <Page<void>>[
+      MaterialPage<void>(
+        key: const ValueKey<int>(0),
+        builder: (BuildContext context) => const Text('page 0'),
+      ),
+      MaterialPage<void>(
+        key: const ValueKey<int>(1),
+        builder: (BuildContext context) => const Text('page 1'),
+      ),
+    ];
+    Widget buildNavigator() {
+      return Navigator(
+        pages: pages,
+        onPopPage: (Route<dynamic> route, dynamic result) => false,
+      );
+    }
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: buildNavigator(),
+      ),
+    );
+
+    expect(find.text('page 1'), findsOneWidget);
+    expect(find.text('page 0'), findsNothing);
+
+    // Removes the first page.
+    pages = <Page<void>>[
+      MaterialPage<void>(
+        key: const ValueKey<int>(1),
+        builder: (BuildContext context) => const Text('page 1'),
+      ),
+    ];
+
+    await tester.pumpWidget(
+      Directionality(
+        textDirection: TextDirection.ltr,
+        child: buildNavigator(),
+      ),
+    );
+    // Overlay updates correctly.
+    expect(find.text('page 1'), findsOneWidget);
+    expect(find.text('page 0'), findsNothing);
+
+    await tester.pumpAndSettle();
+    expect(find.text('page 1'), findsOneWidget);
+    expect(find.text('page 0'), findsNothing);
+  });
+
   testWidgets('replaceNamed replaces', (WidgetTester tester) async {
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
       '/' : (BuildContext context) => OnTapPage(id: '/', onTap: () { Navigator.pushReplacementNamed(context, '/A'); }),