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Adjust getTypeFromArrayBindingPattern to return an array if inside a rest parameter

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Jason Freeman
2015-03-25 17:20:51 -07:00
parent 6b2d5ceb7c
commit a477b63420
1 changed files with 20 additions and 2 deletions
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22
src/compiler/checker.ts
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@@ -2162,8 +2162,26 @@ module ts {
return languageVersion >= ScriptTarget.ES6 ? createIterableType(anyType) : anyArrayType;
}
else if (hasSpreadElement) {
var unionOfElements = getUnionType(elementTypes);
return languageVersion >= ScriptTarget.ES6 ? createIterableType(unionOfElements) : createArrayType(unionOfElements);
let unionOfElements = getUnionType(elementTypes);
if (languageVersion >= ScriptTarget.ES6) {
// If the user has something like:
//
// function fun(...[a, ...b]) { }
//
// Normally, in ES6, the implied type of an array binding pattern with a rest element is
// an iterable. However, there is a requirement in our grammar checker that all rest
// parameters be array types. To satisfy this, we have an exception to the rule that
// says the type of an array binding pattern with a rest element is an array type
// if it is *itself* in a rest parameter. It will still be compatible with a spreaded
// iterable argument, but within the function it will be an array.
let parent = pattern.parent;
let isRestParameter = parent.kind === SyntaxKind.Parameter &&
pattern === (<ParameterDeclaration>parent).name &&
(<ParameterDeclaration>parent).dotDotDotToken !== undefined;
return isRestParameter ? createArrayType(unionOfElements) : createIterableType(unionOfElements);
}
return createArrayType(unionOfElements);
}
// If the pattern has at least one element, and no rest element, then it should imply a tuple type.