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Support contextual type for property assignments in JS that are not declarations (#18820)

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This commit is contained in:
Andy
2017-10-04 09:32:09 -07:00
committed by GitHub
parent a3853d0774
commit fe9129b1ab
3 changed files with 29 additions and 7 deletions
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24
src/compiler/checker.ts
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@@ -13258,13 +13258,25 @@ namespace ts {
const binaryExpression = <BinaryExpression>node.parent;
const operator = binaryExpression.operatorToken.kind;
if (isAssignmentOperator(operator)) {
// Don't do this for special property assignments to avoid circularity
if (getSpecialPropertyAssignmentKind(binaryExpression) !== SpecialPropertyAssignmentKind.None) {
return undefined;
}
// In an assignment expression, the right operand is contextually typed by the type of the left operand.
if (node === binaryExpression.right) {
// Don't do this for special property assignments to avoid circularity
switch (getSpecialPropertyAssignmentKind(binaryExpression)) {
case SpecialPropertyAssignmentKind.None:
break;
case SpecialPropertyAssignmentKind.Property:
// If `binaryExpression.left` was assigned a symbol, then this is a new declaration; otherwise it is an assignment to an existing declaration.
// See `bindStaticPropertyAssignment` in `binder.ts`.
if (!binaryExpression.left.symbol) {
break;
}
// falls through
case SpecialPropertyAssignmentKind.ExportsProperty:
case SpecialPropertyAssignmentKind.ModuleExports:
case SpecialPropertyAssignmentKind.PrototypeProperty:
case SpecialPropertyAssignmentKind.ThisProperty:
return undefined;
}
// In an assignment expression, the right operand is contextually typed by the type of the left operand.
return getTypeOfExpression(binaryExpression.left);
}
}