Basic iterator support in for..of statement
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@ -8765,6 +8765,8 @@ module ts {
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var leftType = checkExpression(varExpr);
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checkReferenceExpression(varExpr, Diagnostics.Invalid_left_hand_side_in_for_of_statement, Diagnostics.The_left_hand_side_of_a_for_of_statement_cannot_be_a_previously_defined_constant);
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var rightType = checkExpression(node.expression);
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var iteratedType = getIteratedType(rightType);
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checkTypeAssignableTo(iteratedType, leftType, varExpr, /*headMessage*/ undefined);
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}
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checkSourceElement(node.statement);
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@ -8816,6 +8818,45 @@ module ts {
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}
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}
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function getIteratedType(iterable: Type): Type {
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Debug.assert(languageVersion >= ScriptTarget.ES6);
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if (allConstituentTypesHaveKind(iterable, TypeFlags.Any)) {
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return anyType;
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}
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// We want to treat type as an iterable, and get the type it is an iterable of. The iterable
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// must have the following structure (annotated with the names of the variables below):
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//
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// { // iterable
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// [Symbol.iterator]: { // iteratorFunction
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// (): { // iterator
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// next: { // iteratorNextFunction
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// (): { // iteratorNextResult
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// value: T // iteratorNextValue
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// }
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// }
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// }
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// }
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// }
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//
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// T is the type we are after. At every level that involves analyzing return types
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// of signatures, we union the return types of all the signatures.
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var iteratorFunction = getTypeOfPropertyOfType(iterable, getPropertyNameForKnownSymbolName("iterator"));
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var iteratorFunctionSignatures = getSignaturesOfType(iteratorFunction, SignatureKind.Call);
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var iterator = getUnionType(map(iteratorFunctionSignatures, getReturnTypeOfSignature));
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var iteratorNextFunction = getTypeOfPropertyOfType(iterator, "next");
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var iteratorNextFunctionSignatures = getSignaturesOfType(iteratorNextFunction, SignatureKind.Call);
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var iteratorNextResult = getUnionType(map(iteratorNextFunctionSignatures, getReturnTypeOfSignature));
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var iteratorNextValue = getTypeOfPropertyOfType(iteratorNextResult, "value");
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return iteratorNextValue;
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// TODO
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// Now even though we have extracted the iteratorNextValue, we will have to validate that the type
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// passed in is actually an Iterable.
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}
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function checkBreakOrContinueStatement(node: BreakOrContinueStatement) {
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// Grammar checking
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checkGrammarStatementInAmbientContext(node) || checkGrammarBreakOrContinueStatement(node);
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