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Preserve type parameter types in narrowing

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This commit is contained in:
Anders Hejlsberg
2016-09-10 07:13:57 -07:00
parent 2305c68560
commit 0f90d880b4
1 changed files with 1 additions and 1 deletions
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src/compiler/checker.ts
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@@ -8682,7 +8682,7 @@ namespace ts {
// type. Otherwise, the types are completely unrelated, so narrow to an intersection of the
// two types.
const targetType = type.flags & TypeFlags.TypeParameter ? getApparentType(type) : type;
return isTypeSubtypeOf(candidate, targetType) ? candidate :
return isTypeSubtypeOf(candidate, type) ? candidate :
isTypeAssignableTo(type, candidate) ? type :
isTypeAssignableTo(candidate, targetType) ? candidate :
getIntersectionType([type, candidate]);