Typescript Union To Intersection 永远不会返回值 [英] Typescript Union To Intersection returns values as never
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问题描述
我的问题是参考这篇文章
My question is with reference to this post
每当我将联合转换为交集时,我都会失去联合类型,这是我为解决此问题而编写的一些代码
Whenever i convert a union To Intersection i loose the union type, here is some code i wrote to get around the issue
type SomeUnion = 'A' | 'B';
type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends ((k: infer I) => void) ? I : never
type UnionToInterSectionWoNever<T> = {
[K in keyof UnionToIntersection<T>]: UnionToIntersection<T>[K] extends never ? T[K] : UnionToIntersection<T>[K]
};
type UnionDistribution<T> = T extends SomeUnion ?
{ unionType: T } & (
T extends 'A' ? { aProp1: string, aProp2: number } :
T extends 'B' ? { bProp1: string } : never) :
never;
type ABUnion = UnionDistribution<SomeUnion>;
type ABInterSection = UnionToIntersection<ABUnion>;
type ABInterSectionWoNever = UnionToInterSectionWoNever<ABUnion>;
// This in infered as never;
type ABInterSectionUnionType = ABInterSection['unionType'];
// This in inferred as 'A' | 'B'
type ABInterSectionWoNeverUnionType = ABInterSectionWoNever['unionType'];
所以我对代码不是 100% 有信心,再考虑一下会很有帮助.当这样的事情会失败以及如何解决同样的问题时,我很好奇.
So i am not 100% confident of the code, it would be really helpful to have a second thought on the same. I'm curios when something like this will fail and how to resolve the same.
提前致谢.
推荐答案
你得到 never
因为 TypeScript 不能将类型表示为 'A' &'B'
.
You get never
because TypeScript can not represent type as 'A' & 'B'
.
看看这个:
type test = {
foo: 'bar',
} & {
foo: 'baz',
} // never
type test2 = 'A' & 'B' // never
发现于 TS 挑战问题 偶尔.
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