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Use nominal checks in union type subtype reduction

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This commit is contained in:
Anders Hejlsberg 2017-10-30 15:35:51 -07:00
parent d669771462
commit 3d89837cfa
1 changed files with 15 additions and 10 deletions
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25
src/compiler/checker.ts
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@ -7431,9 +7431,12 @@ namespace ts {
return false;
}
function isSubtypeOfAny(candidate: Type, types: Type[]): boolean {
for (const type of types) {
if (candidate !== type && isTypeSubtypeOf(candidate, type)) {
function isSubtypeOfAny(source: Type, targets: Type[]): boolean {
for (const target of targets) {
if (source !== target && isTypeSubtypeOf(source, target) && (
!(getObjectFlags(source) & (ObjectFlags.ClassOrInterface | ObjectFlags.Reference)) ||
!(getObjectFlags(target) & (ObjectFlags.ClassOrInterface | ObjectFlags.Reference)) ||
isTypeDerivedFrom(source, target))) {
return true;
}
}
@ -8556,13 +8559,15 @@ namespace ts {
return isTypeRelatedTo(source, target, assignableRelation);
}
// 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
// An object type S is considered to be derived from an object type T if
// S is a union type and every constituent of S is derived from T,
// T is a union type and S is derived from 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 source.flags & TypeFlags.Union ? every((<UnionType>source).types, t => isTypeInstanceOf(t, target)) :
target.flags & TypeFlags.Union ? some((<UnionType>target).types, t => isTypeInstanceOf(source, t)) :
// Note that this check ignores type parameters and only considers the
// inheritance hierarchy.
function isTypeDerivedFrom(source: Type, target: Type): boolean {
return source.flags & TypeFlags.Union ? every((<UnionType>source).types, t => isTypeDerivedFrom(t, target)) :
target.flags & TypeFlags.Union ? some((<UnionType>target).types, t => isTypeDerivedFrom(source, t)) :
hasBaseType(source, getTargetType(target));
}
@ -12411,7 +12416,7 @@ namespace ts {
}
if (targetType) {
return getNarrowedType(type, targetType, assumeTrue, isTypeInstanceOf);
return getNarrowedType(type, targetType, assumeTrue, isTypeDerivedFrom);
}
return type;