Mouse Tracking throwing exceptions for widgets inside a ListView that are listening for hover events  #30744

import 'package:flutter/foundation.dart'
    show debugDefaultTargetPlatformOverride;
import 'package:flutter/material.dart';

void main() {
  debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;
  runApp(new TestApp());
}

class TestApp extends StatelessWidget {
  final ValueNotifier<int> _hoveredListViewIndex = ValueNotifier(-1);
  final ValueNotifier<int> _hoveredColumnIndex = ValueNotifier(-1);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: AnimatedBuilder(
        animation:
            Listenable.merge([_hoveredListViewIndex, _hoveredColumnIndex]),
        builder: (_, __) {
          return Container(
            constraints: BoxConstraints.expand(),
            color: Colors.black,
            child: Row(
              mainAxisSize: MainAxisSize.max,
              children: <Widget>[
                Expanded(
                  child: Container(
                    color: Colors.white,
                    child: ListView(
                      children: List.generate(16, (index) {
                        return Listener(
                          onPointerEnter: (_) {
                            _hoveredListViewIndex.value = index;
                          },
                          onPointerExit: (_) {},
                          child: Container(
                            height: 20.0,
                            color: index == _hoveredListViewIndex.value
                                ? Colors.red
                                : Colors.green,
                          ),
                        );
                      }),
                    ),
                  ),
                ),
                Container(
                  width: 20.0,
                ),
                Expanded(
                  child: Container(
                    color: Colors.grey,
                    child: Column(
                      children: List.generate(16, (index) {
                        return Listener(
                          onPointerEnter: (_) {
                            _hoveredColumnIndex.value = index;
                          },
                          onPointerExit: (_) {},
                          child: Container(
                            height: 20.0,
                            color: index == _hoveredColumnIndex.value
                                ? Colors.red
                                : Colors.green,
                          ),
                        );
                      }),
                    ),
                  ),
                ),
              ],
            ),
          );
        },
      ),
    );
  }
}

══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
flutter: The following assertion was thrown during a scheduler callback:
flutter: Unable to find annotation [MouseTrackerAnnotation30885124 onEnter onExit] in tracked annotations.
flutter: Check that attachAnnotation has been called for all annotated layers.
flutter: 'package:flutter/src/gestures/mouse_tracking.dart': Failed assertion: line 168 pos 9:
flutter: 'trackedAnnotation != null'
flutter: 
flutter: Either the assertion indicates an error in the framework itself, or we should provide substantially
flutter: more information in this error message to help you determine and fix the underlying cause.
flutter: In either case, please report this assertion by filing a bug on GitHub:
flutter:   https://github.com/flutter/flutter/issues/new?template=BUG.md
flutter: 
flutter: When the exception was thrown, this was the stack:
flutter: #2      MouseTracker._findAnnotation (package:flutter/src/gestures/mouse_tracking.dart:168:9)
flutter: #3      MouseTracker.collectMousePositions (package:flutter/src/gestures/mouse_tracking.dart:233:48)
flutter: #4      MouseTracker._scheduleMousePositionCheck.<anonymous closure> (package:flutter/src/gestures/mouse_tracking.dart:131:68)
flutter: #5      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1012:15)
flutter: #6      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:960:9)
flutter: #7      _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:864:5)
flutter: #11     _invoke (dart:ui/hooks.dart:219:10)
flutter: #12     _drawFrame (dart:ui/hooks.dart:178:3)
flutter: (elided 5 frames from class _AssertionError and package dart:async)

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