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Undo extra subtype reduction in getWidenedType

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This commit is contained in:
Anders Hejlsberg
2017-10-27 17:18:49 -07:00
parent 39383cadb1
commit 73802be004
1 changed files with 1 additions and 5 deletions
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6
src/compiler/checker.ts
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@@ -10551,11 +10551,7 @@ namespace ts {
}
if (type.flags & TypeFlags.Union) {
const unionContext = context || createWideningContext(/*parent*/ undefined, /*propertyName*/ undefined, (<UnionType>type).types);
const widenedTypes = sameMap((<UnionType>type).types, t => t.flags & TypeFlags.Nullable ? t : getWidenedTypeWithContext(t, unionContext));
// Widening an empty object literal transitions from a highly restrictive type to
// a highly inclusive one. For that reason we perform subtype reduction here if the
// union includes empty object types (e.g. reducing {} | string to just {}).
return getUnionType(widenedTypes, some(widenedTypes, isEmptyObjectType));
return getUnionType(sameMap((<UnionType>type).types, t => t.flags & TypeFlags.Nullable ? t : getWidenedTypeWithContext(t, unionContext)));
}
if (isArrayType(type) || isTupleType(type)) {
return createTypeReference((<TypeReference>type).target, sameMap((<TypeReference>type).typeArguments, getWidenedType));