Array.prototype.match overload that works for tuples

mapping-over-tuples.ts

// 1. Let's define a tuple of country codes.
const countries: [string, string] = ["es", "ko"];

// 2. Good! We know the returned tuple will only have two elements.
const [spanish, korean, valyrian] =
  countries.map(country => new Intl.DateTimeFormat(country));

// 3. We know `valyrian` doesn't exist!
valyrian.format(new Date());

declare global {
  interface Array<T> {
    map<U>(this: T[] | [T], callbackfn: (value: T, index: number, array: this) => U, thisArg?: any): {
      [index in keyof this]: U
    };
  }
}