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union-member.d.ts
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39 lines (30 loc) · 750 Bytes
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import type {UnionToIntersection} from './union-to-intersection.d.ts';
import type {IsNever} from './is-never.d.ts';
/**
Returns an arbitrary member of a union type.
Returns `never` when the input is `never`.
@example
```
import type {UnionMember} from 'type-fest';
type Last = UnionMember<1 | 2 | 3>;
//=> 3
type LastNever = UnionMember<never>;
//=> never
```
@example
```
import type {UnionMember, IsNever} from 'type-fest';
type UnionToTuple<T, L = UnionMember<T>> =
IsNever<T> extends false
? [...UnionToTuple<Exclude<T, L>>, L]
: [];
```
@category Type
*/
export type UnionMember<T> =
IsNever<T> extends true
? never
: UnionToIntersection<T extends any ? () => T : never> extends () => (infer R)
? R
: never;
export {};