union-to-tuple.ts

import {expectAssignable, expectType} from 'tsd';
import type {UnionToTuple} from '../index.d.ts';

type Options = UnionToTuple<'a' | 'b' | 'c'>;
// Results unordered
expectAssignable<['a', 'b', 'c'] | ['a', 'c', 'b'] | ['b', 'a', 'c'] | ['b', 'c', 'a'] | ['c', 'a', 'b'] | ['c', 'b', 'a']>({} as Options);
expectType<Options[number]>({} as ('a' | 'b' | 'c'));

type Options1 = UnionToTuple<1 | 2 | 3>;
expectType<Options1[number]>({} as (1 | 2 | 3));

type Options2 = UnionToTuple<boolean | 1>;
expectType<Options2[number]>({} as (1 | false | true));

// Different modifiers cases.
type DifferentModifiers = {a: 0} | {readonly a: 0} | {a?: 0} | {readonly a?: 0};
expectType<UnionToTuple<DifferentModifiers>[number]>({} as DifferentModifiers);

// Super type cases.
type UnionSuperType0 = {a: string; b: string} | {a: string};
expectType<UnionSuperType0>({} as UnionToTuple<UnionSuperType0>[number]);

type UnionSuperType1 = {a: 1} | {b: 1} | {[x: string]: number};
expectType<UnionSuperType1>({} as UnionToTuple<UnionSuperType1>[number]);