strict map and filter types

types.ts

interface Array<T> {
  map<U>(
      callbackfn: (value: T, index: number, array: T[]) => U,
      thisArg?: unknown
  ): { [K in keyof this]: U };
  filter<S extends T>(
    callbackfn: (value: T, index: number, array: T[]) => value is S,
    thisArg?: unknown
  ): { [K in keyof this]-?: this[K] extends S ? S : never }
}