27958 - CheckRepeatedTuple

[jiaowoxiaobala]

type IsEqual<A, B> = (<X>() => X extends A ? 1 : 2) extends <X>() => X extends B
  ? 1
  : 2
  ? true
  : false;

type Includes<T extends unknown[], U> = T extends [infer F, ...infer Rest]
  ? IsEqual<F, U> extends true
    ? true
    : Includes<Rest, U>
  : false;

// number extends T['length']排除非元组类型，因为T有可能是string[]
// type arr1 = string[] -> arr1['length'] -> number
// type arr2 = [string] -> arr2['length'] -> 1
type CheckRepeatedTuple<T extends unknown[]> = number extends T["length"]
  ? false
  : // 递归遍历T，每次取出第一项
  T extends [infer F, ...infer Rest]
  ? // 判断后面的所有成员中是否有与第一项相等的
    Includes<Rest, F> extends true
    ? true
    : // 如果没有，继续递归后面的所有成员，此时第一项可以排除了
      CheckRepeatedTuple<Rest>
  : false;