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January 26, 2024 10:13
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type UnionToIntersection<U> = | |
(U extends U ? (arg: U) => unknown : never) extends | |
((arg: infer I) => unknown) ? I : never | |
type LastOfUnion<U> = | |
UnionToIntersection< | |
(U extends unknown ? (arg: U) => unknown : never) | |
> extends (arg: infer I) => unknown ? I : never | |
type IsAny<T> = [T] extends [never] ? | |
false : | |
T extends (1 & T) ? | |
true : unknown extends T ? | |
true : false | |
type IsUnion<T, Copy = T> = | |
[T] extends [never] ? | |
false : | |
T extends T ? | |
[Copy] extends [T] ? | |
// using isAny here because of | |
// specific type-cases | |
IsAny<T> extends true ? | |
true : | |
false : | |
true : | |
false | |
type UnionToTupleImpl<U, R extends unknown[] = []> = | |
[U] extends [never] ? | |
R : | |
UnionToTupleImpl<Exclude<U, LastOfUnion<U>>, [...R, LastOfUnion<U>]> | |
type UnionToTuple<U> = | |
[U] extends [never] ? | |
never : | |
IsUnion<U> extends false ? | |
U : | |
UnionToTupleImpl<U> | |
/* _____________ Test Cases _____________ */ | |
import type { Equal, Expect } from '@type-challenges/utils' | |
type ExtractValuesOfTuple<T extends any[]> = T[keyof T & number] | |
type cases = [ | |
Expect<Equal<UnionToTuple<'a' | 'b'>['length'], 2>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<'a' | 'b'>>, 'a' | 'b'>>, | |
// Expect<Equal<ExtractValuesOfTuple<UnionToTuple<'a'>>, 'a'>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<any>>, any>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<undefined | void | 1>>, void | 1>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<any | 1>>, any | 1>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<any | 1>>, any>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<'d' | 'f' | 1 | never>>, 'f' | 'd' | 1>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<[{ a: 1 }] | 1>>, [{ a: 1 }] | 1>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<never>>, never>>, | |
Expect<Equal<ExtractValuesOfTuple<UnionToTuple<'a' | 'b' | 'c' | 1 | 2 | 'd' | 'e' | 'f' | 'g'>>, 'f' | 'e' | 1 | 2 | 'g' | 'c' | 'd' | 'a' | 'b'>>, | |
] |
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