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Basic iterator support in for..of statement

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Jason Freeman
2015-02-20 17:09:03 -08:00
parent aa06622695
commit 277c931a0d
1 changed files with 41 additions and 0 deletions
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41
src/compiler/checker.ts
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@@ -8765,6 +8765,8 @@ module ts {
var leftType = checkExpression(varExpr);
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);
var rightType = checkExpression(node.expression);
var iteratedType = getIteratedType(rightType);
checkTypeAssignableTo(iteratedType, leftType, varExpr, /*headMessage*/ undefined);
}
checkSourceElement(node.statement);
@@ -8816,6 +8818,45 @@ module ts {
}
}
function getIteratedType(iterable: Type): Type {
Debug.assert(languageVersion >= ScriptTarget.ES6);
if (allConstituentTypesHaveKind(iterable, TypeFlags.Any)) {
return anyType;
}
// We want to treat type as an iterable, and get the type it is an iterable of. The iterable
// must have the following structure (annotated with the names of the variables below):
//
// { // iterable
// [Symbol.iterator]: { // iteratorFunction
// (): { // iterator
// next: { // iteratorNextFunction
// (): { // iteratorNextResult
// value: T // iteratorNextValue
// }
// }
// }
// }
// }
//
// T is the type we are after. At every level that involves analyzing return types
// of signatures, we union the return types of all the signatures.
var iteratorFunction = getTypeOfPropertyOfType(iterable, getPropertyNameForKnownSymbolName("iterator"));
var iteratorFunctionSignatures = getSignaturesOfType(iteratorFunction, SignatureKind.Call);
var iterator = getUnionType(map(iteratorFunctionSignatures, getReturnTypeOfSignature));
var iteratorNextFunction = getTypeOfPropertyOfType(iterator, "next");
var iteratorNextFunctionSignatures = getSignaturesOfType(iteratorNextFunction, SignatureKind.Call);
var iteratorNextResult = getUnionType(map(iteratorNextFunctionSignatures, getReturnTypeOfSignature));
var iteratorNextValue = getTypeOfPropertyOfType(iteratorNextResult, "value");
return iteratorNextValue;
// TODO
// Now even though we have extracted the iteratorNextValue, we will have to validate that the type
// passed in is actually an Iterable.
}
function checkBreakOrContinueStatement(node: BreakOrContinueStatement) {
// Grammar checking
checkGrammarStatementInAmbientContext(node) || checkGrammarBreakOrContinueStatement(node);