computeDryLayout access size bad (#164663)

Asserts if `RenderBox.size` is accessed in `computeDryLayout`

Also changes `x is RenderObject` to `x != null` when x's static type is
`RenderObject?`.

## Pre-launch Checklist

- [ ] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [ ] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [ ] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [ ] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [ ] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

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https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[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

packages/flutter/lib/src/rendering/animated_size.dart

@@ -242,6 +242,8 @@ class RenderAnimatedSize extends RenderAligningShiftedBox {
     return _sizeTween.evaluate(_animation);
   }
 
+  late Size _currentSize;
+
   @override
   void performLayout() {
     _lastValue = _controller.value;
@@ -249,7 +251,7 @@ class RenderAnimatedSize extends RenderAligningShiftedBox {
     final BoxConstraints constraints = this.constraints;
     if (child == null || constraints.isTight) {
       _controller.stop();
-      size = _sizeTween.begin = _sizeTween.end = constraints.smallest;
+      size = _currentSize = _sizeTween.begin = _sizeTween.end = constraints.smallest;
       _state = RenderAnimatedSizeState.start;
       child?.layout(constraints);
       return;
@@ -268,7 +270,7 @@ class RenderAnimatedSize extends RenderAligningShiftedBox {
         _layoutUnstable();
     }
 
-    size = constraints.constrain(_animatedSize!);
+    size = _currentSize = constraints.constrain(_animatedSize!);
     alignChild();
 
     if (size.width < _sizeTween.end!.width || size.height < _sizeTween.end!.height) {
@@ -292,7 +294,7 @@ class RenderAnimatedSize extends RenderAligningShiftedBox {
         return constraints.constrain(childSize);
       case RenderAnimatedSizeState.stable:
         if (_sizeTween.end != childSize) {
-          return constraints.constrain(size);
+          return constraints.constrain(_currentSize);
         } else if (_controller.value == _controller.upperBound) {
           return constraints.constrain(childSize);
         }

packages/flutter/lib/src/rendering/box.dart

@@ -2262,7 +2262,6 @@ abstract class RenderBox extends RenderObject {
             !doingRegularLayout ||
             debugDoingThisResize ||
             debugDoingThisLayout ||
-            _computingThisDryLayout ||
             RenderObject.debugActiveLayout == parent && size._canBeUsedByParent;
         assert(
           sizeAccessAllowed,
@@ -2273,16 +2272,29 @@ abstract class RenderBox extends RenderObject {
           'trying to access a child\'s size, pass "parentUsesSize: true" to '
           "that child's layout() in ${objectRuntimeType(this, 'RenderBox')}.performLayout.",
         );
+        final RenderBox? renderBoxDoingDryLayout =
+            _computingThisDryLayout
+                ? this
+                : (parent is RenderBox && parent._computingThisDryLayout ? parent : null);
+
+        assert(
+          renderBoxDoingDryLayout == null,
+          'RenderBox.size accessed in '
+          '${objectRuntimeType(renderBoxDoingDryLayout, 'RenderBox')}.computeDryLayout. '
+          "The computeDryLayout method must not access the RenderBox's own size, or the size of its child, "
+          "because it's established in performLayout or performResize using different BoxConstraints.",
+        );
+
         final RenderBox? renderBoxDoingDryBaseline =
             _computingThisDryBaseline
                 ? this
                 : (parent is RenderBox && parent._computingThisDryBaseline ? parent : null);
         assert(
           renderBoxDoingDryBaseline == null,
+
           'RenderBox.size accessed in '
-          '${objectRuntimeType(renderBoxDoingDryBaseline, 'RenderBox')}.computeDryBaseline.'
+          '${objectRuntimeType(renderBoxDoingDryBaseline, 'RenderBox')}.computeDryBaseline. '
-          'The computeDryBaseline method must not access '
+          "The computeDryBaseline method must not access the RenderBox's own size, or the size of its child, "
-          '${renderBoxDoingDryBaseline == this ? "the RenderBox's own size" : "the size of its child"},'
           "because it's established in performLayout or performResize using different BoxConstraints.",
         );
         assert(size == _size);
@@ -2740,7 +2752,7 @@ abstract class RenderBox extends RenderObject {
         } finally {
           RenderObject.debugCheckingIntrinsics = false;
         }
-        if (_debugDryLayoutCalculationValid && dryLayoutSize != size) {
+        if (_debugDryLayoutCalculationValid && dryLayoutSize != _size) {
           throw FlutterError.fromParts(<DiagnosticsNode>[
             ErrorSummary(
               'The size given to the ${objectRuntimeType(this, 'RenderBox')} class differs from the size computed by computeDryLayout.',

packages/flutter/lib/src/rendering/object.dart

@@ -2594,7 +2594,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
   void scheduleInitialLayout() {
     assert(!_debugDisposed);
     assert(attached);
-    assert(parent is! RenderObject);
+    assert(parent == null);
     assert(!owner!._debugDoingLayout);
     assert(_relayoutBoundary == null);
     _relayoutBoundary = this;
@@ -2712,7 +2712,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
     assert(!_debugDoingThisResize);
     assert(!_debugDoingThisLayout);
     final bool isRelayoutBoundary =
-        !parentUsesSize || sizedByParent || constraints.isTight || parent is! RenderObject;
+        !parentUsesSize || sizedByParent || constraints.isTight || parent == null;
     final RenderObject relayoutBoundary = isRelayoutBoundary ? this : parent!._relayoutBoundary!;
     assert(() {
       _debugCanParentUseSize = parentUsesSize;
@@ -3077,8 +3077,8 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
       return;
     }
     _needsCompositingBitsUpdate = true;
-    if (parent is RenderObject) {
+    final RenderObject? parent = this.parent;
-      final RenderObject parent = this.parent!;
+    if (parent != null) {
       if (parent._needsCompositingBitsUpdate) {
         return;
       }
@@ -3089,9 +3089,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
       }
     }
     // parent is fine (or there isn't one), but we are dirty
-    if (owner != null) {
+    owner?._nodesNeedingCompositingBitsUpdate.add(this);
-      owner!._nodesNeedingCompositingBitsUpdate.add(this);
-    }
   }
 
   late bool _needsCompositing; // initialized in the constructor
@@ -3299,7 +3297,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
     assert(_layerHandle.layer != null);
     assert(!_layerHandle.layer!.attached);
     RenderObject? node = parent;
-    while (node is RenderObject) {
+    while (node != null) {
       if (node.isRepaintBoundary) {
         if (node._layerHandle.layer == null) {
           // Looks like the subtree here has never been painted. Let it handle itself.
@@ -3324,7 +3322,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
   void scheduleInitialPaint(ContainerLayer rootLayer) {
     assert(rootLayer.attached);
     assert(attached);
-    assert(parent is! RenderObject);
+    assert(parent == null);
     assert(!owner!._debugDoingPaint);
     assert(isRepaintBoundary);
     assert(_layerHandle.layer == null);
@@ -3342,7 +3340,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
     assert(!_debugDisposed);
     assert(rootLayer.attached);
     assert(attached);
-    assert(parent is! RenderObject);
+    assert(parent == null);
     assert(!owner!._debugDoingPaint);
     assert(isRepaintBoundary);
     assert(_layerHandle.layer != null); // use scheduleInitialPaint the first time
@@ -3391,8 +3389,8 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
     }
     assert(() {
       if (_needsCompositingBitsUpdate) {
-        if (parent is RenderObject) {
+        final RenderObject? parent = this.parent;
-          final RenderObject parent = this.parent!;
+        if (parent != null) {
           bool visitedByParent = false;
           parent.visitChildren((RenderObject child) {
             if (child == this) {
@@ -3669,7 +3667,7 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
   void scheduleInitialSemantics() {
     assert(!_debugDisposed);
     assert(attached);
-    assert(parent is! RenderObject);
+    assert(parent == null);
     assert(!owner!._debugDoingSemantics);
     assert(_semantics.parentDataDirty || !_semantics.built);
     assert(owner!._semanticsOwner != null);
@@ -4005,14 +4003,12 @@ abstract class RenderObject with DiagnosticableTreeMixin implements HitTestTarge
     Duration duration = Duration.zero,
     Curve curve = Curves.ease,
   }) {
-    if (parent is RenderObject) {
+    parent?.showOnScreen(
-      parent!.showOnScreen(
+      descendant: descendant ?? this,
-        descendant: descendant ?? this,
+      rect: rect,
-        rect: rect,
+      duration: duration,
-        duration: duration,
+      curve: curve,
-        curve: curve,
+    );
-      );
-    }
   }
 
   /// Adds a debug representation of a [RenderObject] optimized for including in

packages/flutter/test/material/list_tile_test.dart

@@ -2605,15 +2605,12 @@ void main() {
     expect(trailingOffset.dy - tileOffset.dy, topPosition);
   });
 
-  testWidgets('Leading/Trailing exceeding list tile width throws exception', (
+  group('Leading/Trailing exceeding list tile width throws exception', () {
-    WidgetTester tester,
+    final List<Object> exceptions = <Object>[];
-  ) async {
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
-    List<dynamic> exceptions = <dynamic>[];
+    tearDown(exceptions.clear);
-    FlutterExceptionHandler? oldHandler = FlutterError.onError;
-    FlutterError.onError = (FlutterErrorDetails details) {
-      exceptions.add(details.exception);
-    };
 
+    void onError(FlutterErrorDetails details) => exceptions.add(details.exception);
     Widget buildListTile({Widget? leading, Widget? trailing}) {
       return MaterialApp(
         home: Material(
@@ -2624,61 +2621,59 @@ void main() {
       );
     }
 
-    // Test a trailing widget that exceeds the list tile width.
+    testWidgets('leading', (WidgetTester tester) async {
-    // 16 (content padding) + 61 (leading width) + 24 (content padding) = 101.
+      // Test a leading widget that exceeds the list tile width.
-    // List tile width is 100 as a result, an exception should be thrown.
+      // 16 (content padding) + 61 (leading width) + 24 (content padding) = 101.
-    await tester.pumpWidget(buildListTile(leading: const SizedBox(width: 61)));
+      // List tile width is 100 as a result, an exception should be thrown.
+      FlutterError.onError = onError;
+      await tester.pumpWidget(buildListTile(leading: const SizedBox(width: 61)));
+      FlutterError.onError = oldHandler;
 
-    FlutterError.onError = oldHandler;
+      final FlutterError error = exceptions.first as FlutterError;
-    expect(exceptions.first.runtimeType, FlutterError);
+      expect(error.diagnostics.length, 3);
-    FlutterError error = exceptions.first as FlutterError;
+      expect(
-    expect(error.diagnostics.length, 3);
+        error.diagnostics[0].toStringDeep(),
-    expect(
+        'Leading widget consumes the entire tile width (including\nListTile.contentPadding).\n',
-      error.diagnostics[0].toStringDeep(),
+      );
-      'Leading widget consumes the entire tile width (including\nListTile.contentPadding).\n',
+      expect(
-    );
+        error.diagnostics[1].toStringDeep(),
-    expect(
+        'Either resize the tile width so that the leading widget plus any\n'
-      error.diagnostics[1].toStringDeep(),
+        'content padding do not exceed the tile width, or use a sized\n'
-      'Either resize the tile width so that the leading widget plus any\n'
+        'widget, or consider replacing ListTile with a custom widget.\n',
-      'content padding do not exceed the tile width, or use a sized\n'
+      );
-      'widget, or consider replacing ListTile with a custom widget.\n',
+      expect(
-    );
+        error.diagnostics[2].toStringDeep(),
-    expect(
+        'See also:\n'
-      error.diagnostics[2].toStringDeep(),
+        'https://api.flutter.dev/flutter/material/ListTile-class.html#material.ListTile.4\n',
-      'See also:\n'
+      );
-      'https://api.flutter.dev/flutter/material/ListTile-class.html#material.ListTile.4\n',
+    });
-    );
 
-    exceptions = <dynamic>[];
+    testWidgets('trailing', (WidgetTester tester) async {
-    oldHandler = FlutterError.onError;
+      // Test a trailing widget that exceeds the list tile width.
-    FlutterError.onError = (FlutterErrorDetails details) {
+      // 16 (content padding) + 61 (trailing width) + 24 (content padding) = 101.
-      exceptions.add(details.exception);
+      // List tile width is 100 as a result, an exception should be thrown.
-    };
+      FlutterError.onError = onError;
+      await tester.pumpWidget(buildListTile(trailing: const SizedBox(width: 61)));
+      FlutterError.onError = oldHandler;
 
-    // Test a trailing widget that exceeds the list tile width.
+      final FlutterError error = exceptions.first as FlutterError;
-    // 16 (content padding) + 61 (trailing width) + 24 (content padding) = 101.
+      expect(error.diagnostics.length, 3);
-    // List tile width is 100 as a result, an exception should be thrown.
+      expect(
-    await tester.pumpWidget(buildListTile(trailing: const SizedBox(width: 61)));
+        error.diagnostics[0].toStringDeep(),
-
+        'Trailing widget consumes the entire tile width (including\nListTile.contentPadding).\n',
-    FlutterError.onError = oldHandler;
+      );
-    expect(exceptions.first.runtimeType, FlutterError);
+      expect(
-    error = exceptions.first as FlutterError;
+        error.diagnostics[1].toStringDeep(),
-    expect(error.diagnostics.length, 3);
+        'Either resize the tile width so that the trailing widget plus any\n'
-    expect(
+        'content padding do not exceed the tile width, or use a sized\n'
-      error.diagnostics[0].toStringDeep(),
+        'widget, or consider replacing ListTile with a custom widget.\n',
-      'Trailing widget consumes the entire tile width (including\nListTile.contentPadding).\n',
+      );
-    );
+      expect(
-    expect(
+        error.diagnostics[2].toStringDeep(),
-      error.diagnostics[1].toStringDeep(),
+        'See also:\n'
-      'Either resize the tile width so that the trailing widget plus any\n'
+        'https://api.flutter.dev/flutter/material/ListTile-class.html#material.ListTile.4\n',
-      'content padding do not exceed the tile width, or use a sized\n'
+      );
-      'widget, or consider replacing ListTile with a custom widget.\n',
+    });
-    );
-    expect(
-      error.diagnostics[2].toStringDeep(),
-      'See also:\n'
-      'https://api.flutter.dev/flutter/material/ListTile-class.html#material.ListTile.4\n',
-    );
   });
 
   group('Material 2', () {

packages/flutter/test/rendering/box_test.dart

@@ -48,6 +48,18 @@ class BadBaselineRenderBox extends RenderBox {
   }
 }
 
+class InvalidSizeAccessInDryLayoutBox extends RenderBox {
+  @override
+  Size computeDryLayout(covariant BoxConstraints constraints) {
+    return constraints.constrain(hasSize ? size : Size.infinite);
+  }
+
+  @override
+  void performLayout() {
+    size = getDryLayout(constraints);
+  }
+}
+
 void main() {
   TestRenderingFlutterBinding.ensureInitialized();
 
@@ -231,6 +243,31 @@ void main() {
     }
   });
 
+  test('Invalid size access error message', () {
+    final InvalidSizeAccessInDryLayoutBox testBox = InvalidSizeAccessInDryLayoutBox();
+
+    late FlutterErrorDetails errorDetails;
+    final FlutterExceptionHandler? oldHandler = FlutterError.onError;
+    FlutterError.onError = (FlutterErrorDetails details) {
+      errorDetails = details;
+    };
+    try {
+      testBox.layout(const BoxConstraints.tightFor(width: 100.0, height: 100.0));
+    } finally {
+      FlutterError.onError = oldHandler;
+    }
+
+    expect(
+      errorDetails.toString().replaceAll('\n', ' '),
+      contains(
+        'RenderBox.size accessed in '
+        'InvalidSizeAccessInDryLayoutBox.computeDryLayout. '
+        "The computeDryLayout method must not access the RenderBox's own size, or the size of its child, "
+        "because it's established in performLayout or performResize using different BoxConstraints.",
+      ),
+    );
+  });
+
   test('Flex and padding', () {
     final RenderBox size = RenderConstrainedBox(
       additionalConstraints: const BoxConstraints().tighten(height: 100.0),

packages/flutter/test/widgets/selectable_region_context_menu_test.dart

@@ -186,21 +186,18 @@ class RenderSelectionSpy extends RenderProxyBox with Selectable, SelectionRegist
   final Set<VoidCallback> listeners = <VoidCallback>{};
   List<SelectionEvent> events = <SelectionEvent>[];
 
-  @override
-  Size get size => _size;
-  Size _size = Size.zero;
-
   @override
   List<Rect> get boundingBoxes => _boundingBoxes;
   final List<Rect> _boundingBoxes = <Rect>[];
 
   @override
-  Size computeDryLayout(BoxConstraints constraints) {
+  void performLayout() {
-    _size = Size(constraints.maxWidth, constraints.maxHeight);
+    _boundingBoxes.add(Offset.zero & (size = computeDryLayout(constraints)));
-    _boundingBoxes.add(Rect.fromLTWH(0.0, 0.0, constraints.maxWidth, constraints.maxHeight));
-    return _size;
   }
 
+  @override
+  Size computeDryLayout(BoxConstraints constraints) => constraints.biggest;
+
   @override
   void addListener(VoidCallback listener) => listeners.add(listener);
 

packages/flutter/test/widgets/selectable_region_test.dart

@@ -6358,18 +6358,14 @@ class RenderSelectionSpy extends RenderProxyBox with Selectable, SelectionRegist
   final Set<VoidCallback> listeners = <VoidCallback>{};
   List<SelectionEvent> events = <SelectionEvent>[];
 
-  @override
-  Size get size => _size;
-  Size _size = Size.zero;
-
   @override
   List<Rect> get boundingBoxes => <Rect>[paintBounds];
 
   @override
-  Size computeDryLayout(BoxConstraints constraints) {
+  Size computeDryLayout(BoxConstraints constraints) => constraints.biggest;
-    _size = Size(constraints.maxWidth, constraints.maxHeight);
+
-    return _size;
+  @override
-  }
+  void performLayout() => size = computeDryLayout(constraints);
 
   @override
   void addListener(VoidCallback listener) => listeners.add(listener);