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[dart2wasm] Implement await / for as lowering.
Change-Id: Ic41f016490c993f27c3e5873ad1a4b3e8a902f13 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/255822 Reviewed-by: Aske Simon Christensen <askesc@google.com> Commit-Queue: Joshua Litt <joshualitt@google.com>
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@ -110,8 +110,7 @@ class _WasmTransformer extends Transformer {
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return super.visitClass(cls);
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}
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@override
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TreeNode visitForInStatement(ForInStatement stmt) {
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TreeNode _lowerForIn(ForInStatement stmt) {
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// Transform
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//
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// for ({var/final} T <variable> in <iterable>) { ... }
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@ -126,7 +125,21 @@ class _WasmTransformer extends Transformer {
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// }
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// }
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// }
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final CoreTypes coreTypes = typeContext.typeEnvironment.coreTypes;
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//
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// and:
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//
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// await for ({var/final} T <variable> in <stream>) { ... }
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//
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// Into
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//
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// {
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// final StreamIterator<T> #forIterator = StreamIterator(<stream>);
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// for (; await #forIterator.moveNext() ;) {
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// {var/final} T variable = await #forIterator.current;
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// ...
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// }
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// }
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// }
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// The CFE might invoke this transformation despite the program having
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// compile-time errors. So we will not transform this [stmt] if the
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@ -140,36 +153,65 @@ class _WasmTransformer extends Transformer {
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InvalidExpression('Invalid iterable type in for-in'));
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}
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final isAsync = stmt.isAsync;
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late final Class iteratorClass;
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late final Procedure iteratorMoveNext;
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late final Member iteratorCurrent;
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if (isAsync) {
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iteratorClass = coreTypes.streamIteratorClass;
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iteratorMoveNext = coreTypes.streamIteratorMoveNext;
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iteratorCurrent = coreTypes.streamIteratorCurrent;
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} else {
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iteratorClass = coreTypes.iteratorClass;
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iteratorMoveNext = coreTypes.iteratorMoveNext;
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iteratorCurrent = coreTypes.iteratorGetCurrent;
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}
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final DartType elementType = stmt.getElementType(typeContext);
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final iteratorType = InterfaceType(
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coreTypes.iteratorClass, Nullability.nonNullable, [elementType]);
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final iteratorType =
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InterfaceType(iteratorClass, Nullability.nonNullable, [elementType]);
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late final Expression iteratorInitializer;
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if (isAsync) {
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iteratorInitializer = ConstructorInvocation(
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coreTypes.streamIteratorDefaultConstructor,
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Arguments([iterable], types: [elementType]));
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} else {
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iteratorInitializer = InstanceGet(
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InstanceAccessKind.Instance, iterable, Name('iterator'),
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interfaceTarget: coreTypes.iterableGetIterator,
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resultType: iteratorType);
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}
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final iterator = VariableDeclaration("#forIterator",
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initializer: InstanceGet(
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InstanceAccessKind.Instance, iterable, Name('iterator'),
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interfaceTarget: coreTypes.iterableGetIterator,
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resultType: iteratorType)
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..fileOffset = iterable.fileOffset,
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initializer: iteratorInitializer..fileOffset = iterable.fileOffset,
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type: iteratorType)
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..fileOffset = iterable.fileOffset;
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final condition = InstanceInvocation(InstanceAccessKind.Instance,
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VariableGet(iterator), Name('moveNext'), Arguments(const []),
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interfaceTarget: coreTypes.iteratorMoveNext,
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functionType: coreTypes.iteratorMoveNext.getterType as FunctionType)
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interfaceTarget: iteratorMoveNext,
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functionType: iteratorMoveNext.getterType as FunctionType)
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..fileOffset = iterable.fileOffset;
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final variable = stmt.variable
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..initializer = (InstanceGet(
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InstanceAccessKind.Instance, VariableGet(iterator), Name('current'),
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interfaceTarget: coreTypes.iteratorGetCurrent,
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resultType: elementType)
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interfaceTarget: iteratorCurrent, resultType: elementType)
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..fileOffset = stmt.bodyOffset);
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final Block body = Block([variable, stmt.body])
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..fileOffset = stmt.fileOffset;
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return Block([iterator, ForStatement(const [], condition, const [], body)])
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.accept<TreeNode>(this);
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return Block([
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iterator,
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ForStatement(const [], isAsync ? AwaitExpression(condition) : condition,
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const [], body)
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]).accept<TreeNode>(this);
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}
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@override
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TreeNode visitForInStatement(ForInStatement stmt) {
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return _lowerForIn(stmt);
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}
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}
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