18142-medium-all.ts

// ============= Test Cases =============
import type { Equal, Expect } from "./test-utils";

type cases = [
  Expect<Equal<All<[1, 1, 1], 1>, true>>,
  Expect<Equal<All<[1, 1, 2], 1>, false>>,
  Expect<Equal<All<["1", "1", "1"], "1">, true>>,
  Expect<Equal<All<["1", "1", "1"], 1>, false>>,
  Expect<Equal<All<[number, number, number], number>, true>>,
  Expect<Equal<All<[number, number, string], number>, false>>,
  Expect<Equal<All<[null, null, null], null>, true>>,
  Expect<Equal<All<[[1], [1], [1]], [1]>, true>>,
  Expect<Equal<All<[{}, {}, {}], {}>, true>>,
  Expect<Equal<All<[never], never>, true>>,
  Expect<Equal<All<[any], any>, true>>,
  Expect<Equal<All<[unknown], unknown>, true>>,
  Expect<Equal<All<[any], unknown>, false>>,
  Expect<Equal<All<[unknown], any>, false>>,
  Expect<Equal<All<[1, 1, 2], 1 | 2>, false>>
];

// ============= Your Code Here =============
type All<T, E> = T extends [infer F, ...infer R]
  ? Equal<F, E> extends true
    ? All<R, E>
    : false
  : true;