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Use nominal check in isTypeInstanceOf

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This commit is contained in:
Anders Hejlsberg 2017-10-30 12:36:25 -07:00
parent 7798f69558
commit a01df0f20b
1 changed files with 7 additions and 4 deletions
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11
src/compiler/checker.ts
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@ -8556,11 +8556,14 @@ namespace ts {
return isTypeRelatedTo(source, target, assignableRelation);
}
// A type S is considered to be an instance of a type T if S and T are the same type or if S is a
// subtype of T but not structurally identical to T. This specifically means that two distinct but
// structurally identical types (such as two classes) are not considered instances of each other.
// An object type S is considered to be an instance of an object type T if
// S is a union type and every constituent of S is an instance of T,
// T is a union type and S is an instance of at least one constituent of T, or
// T occurs directly or indirectly in an 'extends' clause of S.
function isTypeInstanceOf(source: Type, target: Type): boolean {
return getTargetType(source) === getTargetType(target) || isTypeSubtypeOf(source, target) && !isTypeIdenticalTo(source, target);
return source.flags & TypeFlags.Union ? every((<UnionType>source).types, t => isTypeInstanceOf(t, target)) :
target.flags & TypeFlags.Union ? some((<UnionType>target).types, t => isTypeInstanceOf(source, t)) :
hasBaseType(source, getTargetType(target));
}
/**