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Add single-element fastpath to getSupertypeOrUnion (#43934)

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Wesley Wigham 2021-05-05 13:32:23 -07:00 committed by GitHub
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commit 84da19efc8
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src/compiler/checker.ts
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@ -19954,6 +19954,9 @@ namespace ts {
// of those literal types. Otherwise, return the leftmost type for which no type to the
// right is a supertype.
function getSupertypeOrUnion(types: Type[]): Type {
if (types.length === 1) {
return types[0];
}
return literalTypesWithSameBaseType(types) ?
getUnionType(types) :
reduceLeft(types, (s, t) => isTypeSubtypeOf(s, t) ? t : s)!;