Revert "Remove duplicate code in Element.rebuild() and BuildOwner.buildScope() (#71940)" (#72120)

This reverts commit c8f07aad.

packages/flutter/lib/src/gestures/pointer_router.dart

@@ -75,7 +75,6 @@ class PointerRouter {
   ///
   /// This is valid in debug builds only. In release builds, this will throw an
   /// [UnsupportedError].
-  @visibleForTesting
   int get debugGlobalRouteCount {
     int? count;
     assert(() {

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

@@ -2651,26 +2651,6 @@ class BuildOwner {
   /// Only valid when asserts are enabled.
   bool get debugBuilding => _debugBuilding;
   bool _debugBuilding = false;
-
-  /// The element currently being built, or null if no element is actively
-  /// being built.
-  ///
-  /// This is valid in debug builds only. In release builds, this will throw an
-  /// [UnsupportedError].
-  @visibleForTesting
-  Element? get debugCurrentBuildTarget {
-    Element? result;
-    bool isSupportedOperation = false;
-    assert(() {
-      result = _debugCurrentBuildTarget;
-      isSupportedOperation = true;
-      return true;
-    }());
-    if (isSupportedOperation) {
-      return result;
-    }
-    throw UnsupportedError('debugCurrentBuildTarget is not supported in release builds');
-  }
   Element? _debugCurrentBuildTarget;
 
   /// Establishes a scope in which calls to [State.setState] are forbidden, and
@@ -2696,25 +2676,6 @@ class BuildOwner {
     assert(_debugStateLockLevel >= 0);
   }
 
-  void _runWithCurrentBuildTarget(Element element, VoidCallback callback) {
-    assert(_debugStateLocked);
-    Element? debugPreviousBuildTarget;
-    assert(() {
-      debugPreviousBuildTarget = _debugCurrentBuildTarget;
-      _debugCurrentBuildTarget = element;
-      return true;
-    }());
-    try {
-      callback();
-    } finally {
-      assert(() {
-        assert(_debugCurrentBuildTarget == element);
-        _debugCurrentBuildTarget = debugPreviousBuildTarget;
-        return true;
-      }());
-    }
-  }
-
   /// Establishes a scope for updating the widget tree, and calls the given
   /// `callback`, if any. Then, builds all the elements that were marked as
   /// dirty using [scheduleBuildFor], in depth order.
@@ -2757,9 +2718,12 @@ class BuildOwner {
     try {
       _scheduledFlushDirtyElements = true;
       if (callback != null) {
-        _runWithCurrentBuildTarget(context, () {
+        assert(_debugStateLocked);
+        Element? debugPreviousBuildTarget;
         assert(() {
           context._debugSetAllowIgnoredCallsToMarkNeedsBuild(true);
+          debugPreviousBuildTarget = _debugCurrentBuildTarget;
+          _debugCurrentBuildTarget = context;
           return true;
         }());
         _dirtyElementsNeedsResorting = false;
@@ -2768,11 +2732,12 @@ class BuildOwner {
         } finally {
           assert(() {
             context._debugSetAllowIgnoredCallsToMarkNeedsBuild(false);
+            assert(_debugCurrentBuildTarget == context);
+            _debugCurrentBuildTarget = debugPreviousBuildTarget;
             _debugElementWasRebuilt(context);
             return true;
           }());
         }
-        });
       }
       _dirtyElements.sort(Element._sort);
       _dirtyElementsNeedsResorting = false;
@@ -4404,7 +4369,19 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
       return true;
     }());
     assert(_lifecycleState == _ElementLifecycle.active);
-    owner!._runWithCurrentBuildTarget(this, performRebuild);
+    assert(owner!._debugStateLocked);
+    Element? debugPreviousBuildTarget;
+    assert(() {
+      debugPreviousBuildTarget = owner!._debugCurrentBuildTarget;
+      owner!._debugCurrentBuildTarget = this;
+      return true;
+    }());
+    performRebuild();
+    assert(() {
+      assert(owner!._debugCurrentBuildTarget == this);
+      owner!._debugCurrentBuildTarget = debugPreviousBuildTarget;
+      return true;
+    }());
     assert(!_dirty);
   }
 
@@ -5609,7 +5586,6 @@ abstract class RenderObjectElement extends Element {
   }
 
   @override
-  @mustCallSuper
   void performRebuild() {
     assert(() {
       _debugDoingBuild = true;

packages/flutter/test/widgets/framework_test.dart

@@ -1494,44 +1494,6 @@ void main() {
     expect(GestureBinding.instance!.pointerRouter.debugGlobalRouteCount, pointerRouterCount);
     expect(RawKeyboard.instance.keyEventHandler, same(rawKeyEventHandler));
   });
-
-  testWidgets('Errors in build', (WidgetTester tester) async {
-    final ErrorWidgetBuilder oldErrorBuilder = ErrorWidget.builder;
-    ErrorWidget.builder = (FlutterErrorDetails detail) => throw AssertionError();
-    try {
-      final FlutterExceptionHandler? oldErrorHandler = FlutterError.onError;
-      FlutterError.onError = (FlutterErrorDetails detail) {};
-      try {
-        int buildCount = 0;
-        void handleBuild() => buildCount++;
-        expect(tester.binding.buildOwner!.debugCurrentBuildTarget, isNull);
-        await tester.pumpWidget(_WidgetThatCanThrowInBuild(onBuild: handleBuild));
-        expect(buildCount, 1);
-        await tester.pumpWidget(_WidgetThatCanThrowInBuild(onBuild: handleBuild, shouldThrow: true));
-        tester.takeException();
-        expect(buildCount, 2);
-        expect(tester.binding.buildOwner!.debugCurrentBuildTarget, isNull);
-      } finally {
-        FlutterError.onError = oldErrorHandler;
-      }
-    } finally {
-      ErrorWidget.builder = oldErrorBuilder;
-    }
-  });
-}
-
-class _WidgetThatCanThrowInBuild extends StatelessWidget {
-  const _WidgetThatCanThrowInBuild({required this.onBuild, this.shouldThrow = false});
-
-  final VoidCallback onBuild;
-  final bool shouldThrow;
-
-  @override
-  Widget build(BuildContext context) {
-    onBuild();
-    assert(!shouldThrow);
-    return Container();
-  }
 }
 
 class _FakeFocusManager implements FocusManager {