type-challenges-solutions/en/medium-unique about type-challenges-solutions HOT 1 OPEN

Expect<Equal<Unique<[string, number, 1, 'a', 1, string, 2, 'b', 2, number]>, [string, number, 1, 'a', 2, 'b']>>,
Expect<Equal<Unique<[unknown, unknown, any, any, never, never]>, [unknown, any, never]>>,

type IsElemInSet<E, S extends unknown[]> = 
  S extends [infer Head, ...infer Rest extends unknown[]]
    ? Equal<E, Head> extends true
      ? true
      : IsElemInSet<E, Rest>
    : false

type Unique<T extends unknown[], Acc extends unknown[] = []> =
  T extends [infer First, ...infer Rest extends unknown[]]
    ? IsElemInSet<First, Acc> extends true
      ? Unique<Rest, Acc>
      : Unique<Rest, [...Acc, First]>
    : Acc