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Optimize relationship checks for arrays and tuples

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Anders Hejlsberg
2018-08-30 13:13:21 -07:00
parent 1fb6f11a88
commit a2928b8fd3
1 changed files with 3 additions and 0 deletions
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src/compiler/checker.ts
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@@ -11829,6 +11829,9 @@ namespace ts {
errorInfo = saveErrorInfo;
}
}
else if (isTupleType(source) && (isArrayType(target) || isReadonlyArrayType(target)) || isArrayType(source) && isReadonlyArrayType(target)) {
return isRelatedTo(getIndexTypeOfType(source, IndexKind.Number) || anyType, getIndexTypeOfType(target, IndexKind.Number) || anyType, reportErrors);
}
// Even if relationship doesn't hold for unions, intersections, or generic type references,
// it may hold in a structural comparison.
// In a check of the form X = A & B, we will have previously checked if A relates to X or B relates