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[framework] remove hashcode override for Element (#96644)

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Jonah Williams 2022-01-14 15:45:18 -08:00 committed by GitHub
parent 49c5871844
commit dafda50c6a
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2 changed files with 16 additions and 22 deletions
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23
packages/flutter/lib/src/widgets/framework.dart
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@ -3137,30 +3137,9 @@ abstract class Element extends DiagnosticableTree implements BuildContext {
/// in a build method if it is known that they will not change.
@nonVirtual
@override
// ignore: avoid_equals_and_hash_code_on_mutable_classes
// ignore: avoid_equals_and_hash_code_on_mutable_classes, hash_and_equals
bool operator ==(Object other) => identical(this, other);
// Custom implementation of hash code optimized for the ".of" pattern used
// with `InheritedWidgets`.
//
// `Element.dependOnInheritedWidgetOfExactType` relies heavily on hash-based
// `Set` look-ups, putting this getter on the performance critical path.
//
// The value is designed to fit within the SMI representation. This makes
// the cached value use less memory (one field and no extra heap objects) and
// cheap to compare (no indirection).
//
// See also:
//
// * https://dart.dev/articles/dart-vm/numeric-computation, which
// explains how numbers are represented in Dart.
@nonVirtual
@override
// ignore: avoid_equals_and_hash_code_on_mutable_classes
int get hashCode => _cachedHash;
final int _cachedHash = _nextHashCode = (_nextHashCode + 1) % 0xffffff;
static int _nextHashCode = 1;
/// Information set by parent to define where this child fits in its parent's
/// child list.
///

15
packages/flutter/test/widgets/framework_test.dart
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@ -1656,6 +1656,21 @@ The findRenderObject() method was called for the following element:
)),
);
});
testWidgets('Elements use the identity hashCode', (WidgetTester tester) async {
final StatefulElement statefulElement = StatefulElement(const _StatefulLeaf());
expect(statefulElement.hashCode, identityHashCode(statefulElement));
final StatelessElement statelessElement = StatelessElement(const Placeholder());
expect(statelessElement.hashCode, identityHashCode(statelessElement));
final InheritedElement inheritedElement = InheritedElement(
const Directionality(textDirection: TextDirection.ltr, child: Placeholder()),
);
expect(inheritedElement.hashCode, identityHashCode(inheritedElement));
});
}
class _WidgetWithNoVisitChildren extends StatelessWidget {