type-challenges/easy-includes.ts at master · ballsona/type-challenges · GitHub

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/* _____________ Your Code Here _____________ */

type isEqual<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y
  ? 1
  : 2
  ? true
  : false;

type Includes<T extends readonly any[], U> = T extends [infer A, ...infer B]
  ? isEqual<A, U> extends true
    ? true
    : Includes<B, U>
  : false;

/* _____________ Test Cases _____________ */
import type { Equal, Expect } from '@type-challenges/utils';

type cases = [
  Expect<
    Equal<Includes<['Kars', 'Esidisi', 'Wamuu', 'Santana'], 'Kars'>, true>
  >,
  Expect<
    Equal<Includes<['Kars', 'Esidisi', 'Wamuu', 'Santana'], 'Dio'>, false>
  >,
  Expect<Equal<Includes<[1, 2, 3, 5, 6, 7], 7>, true>>,
  Expect<Equal<Includes<[1, 2, 3, 5, 6, 7], 4>, false>>,
  Expect<Equal<Includes<[1, 2, 3], 2>, true>>,
  Expect<Equal<Includes<[1, 2, 3], 1>, true>>,
  Expect<Equal<Includes<[{}], { a: 'A' }>, false>>,
  Expect<Equal<Includes<[boolean, 2, 3, 5, 6, 7], false>, false>>,
  Expect<Equal<Includes<[true, 2, 3, 5, 6, 7], boolean>, false>>,
  Expect<Equal<Includes<[false, 2, 3, 5, 6, 7], false>, true>>,
  Expect<Equal<Includes<[{ a: 'A' }], { readonly a: 'A' }>, false>>,
  Expect<Equal<Includes<[{ readonly a: 'A' }], { a: 'A' }>, false>>,
  Expect<Equal<Includes<[1], 1 | 2>, false>>,
  Expect<Equal<Includes<[1 | 2], 1>, false>>,
  Expect<Equal<Includes<[null], undefined>, false>>,
  Expect<Equal<Includes<[undefined], null>, false>>,
];

/* _____________ Further Steps _____________ */
/*
  > Share your solutions: https://tsch.js.org/898/answer
  > View solutions: https://tsch.js.org/898/solutions
  > More Challenges: https://tsch.js.org
*/