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Reduce intersections that aren't assignable to their constituents to never

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This commit is contained in:
Anders Hejlsberg
2020-03-31 12:47:15 -07:00
parent ef377d5a66
commit 000a25dd92
1 changed files with 6 additions and 1 deletions
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src/compiler/checker.ts
+6 -1
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@@ -12387,6 +12387,11 @@ namespace ts {
return links.resolvedType;
}
function getAssignableIntersectionType(type1: Type, type2: Type) {
const type = getIntersectionType([type1, type2]);
return isTypeAssignableTo(type, type1) && isTypeAssignableTo(type, type2) ? type : neverType;
}
function createIndexType(type: InstantiableType | UnionOrIntersectionType, stringsOnly: boolean) {
const result = <IndexType>createType(TypeFlags.Index);
result.type = type;
@@ -20678,7 +20683,7 @@ namespace ts {
return isTypeSubtypeOf(candidate, type) ? candidate :
isTypeAssignableTo(type, candidate) ? type :
isTypeAssignableTo(candidate, type) ? candidate :
getIntersectionType([type, candidate]);
getAssignableIntersectionType(type, candidate);
}
function narrowTypeByCallExpression(type: Type, callExpression: CallExpression, assumeTrue: boolean): Type {