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Improve handling of ++ and -- in control flow analysis

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This commit is contained in:
Anders Hejlsberg
2016-09-20 13:22:43 -07:00
parent 798048963c
commit 38d16bb4be
1 changed files with 5 additions and 2 deletions
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7
src/compiler/checker.ts
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@@ -8426,8 +8426,11 @@ namespace ts {
// Assignments only narrow the computed type if the declared type is a union type. Thus, we
// only need to evaluate the assigned type if the declared type is a union type.
if (isMatchingReference(reference, node)) {
const isIncrementOrDecrement = node.parent.kind === SyntaxKind.PrefixUnaryExpression || node.parent.kind === SyntaxKind.PostfixUnaryExpression;
return declaredType.flags & TypeFlags.Union && !isIncrementOrDecrement ?
if (node.parent.kind === SyntaxKind.PrefixUnaryExpression || node.parent.kind === SyntaxKind.PostfixUnaryExpression) {
const flowType = getTypeAtFlowNode(flow.antecedent);
return createFlowType(getBaseTypeOfLiteralType(getTypeFromFlowType(flowType)), isIncomplete(flowType));
}
return declaredType.flags & TypeFlags.Union ?
getAssignmentReducedType(<UnionType>declaredType, getInitialOrAssignedType(node)) :
declaredType;
}