ts-essentials/dist/union-to-tuple.d.ts

All essential TypeScript types in one place

import { UnionToIntersection } from "./union-to-intersection";
type LastOfUnion<UnionType> = UnionToIntersection<
  UnionType extends unknown ? (arg: UnionType) => unknown : never
> extends (arg: infer LastUnionElement) => unknown
  ? LastUnionElement
  : never;
/**
 * A solution to 730. UnionToTuple (hard).
 *
 * Please avoid when possible, the `LastOfUnion` logic may break at any TS
 * version. However, it's acceptable to use `UnionToTuple`, when the logic
 * doesn't rely on the tuple order. For example, `Exact` or `DeepMarkRequired`.
 *
 * @see https://github.com/type-challenges/type-challenges/blob/main/questions/00730-hard-union-to-tuple/README.md
 */
export type UnionToTuple<UnionType, Accumulator extends string[] = []> = [UnionType] extends [never]
  ? Accumulator
  : LastOfUnion<UnionType> extends infer LastUnionElement
  ? LastUnionElement extends string
    ? UnionToTuple<Exclude<UnionType, LastUnionElement>, [...Accumulator, LastUnionElement]>
    : never
  : never;
export {};