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Fix issue in control flow analysis of nested loops

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This commit is contained in:
Anders Hejlsberg 2016-10-08 15:26:17 -07:00
parent 2f5af2e04b
commit 71b9b33517
1 changed files with 7 additions and 3 deletions
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10
src/compiler/checker.ts
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@ -8797,10 +8797,14 @@ namespace ts {
}
// If this flow loop junction and reference are already being processed, return
// the union of the types computed for each branch so far, marked as incomplete.
// We should never see an empty array here because the first antecedent of a loop
// junction is always the non-looping control flow path that leads to the top.
// It is possible to see an empty array in cases where loops are nested and the
// back edge of the outer loop reaches an inner loop that is already being analyzed.
// In such cases we restart the analysis of the inner loop, which will then see
// a non-empty in-process array for the outer loop and eventually terminate because
// the first antecedent of a loop junction is always the non-looping control flow
// path that leads to the top.
for (let i = flowLoopStart; i < flowLoopCount; i++) {
if (flowLoopNodes[i] === flow && flowLoopKeys[i] === key) {
if (flowLoopNodes[i] === flow && flowLoopKeys[i] === key && flowLoopTypes[i].length) {
return createFlowType(getUnionOrEvolvingArrayType(flowLoopTypes[i], /*subtypeReduction*/ false), /*incomplete*/ true);
}
}