export default function <T, E extends T>(
  it: Iterable<T>,
  pred: (val: T) => val is E
): it is Iterable<E>;
export default function <T, E extends T>(
  it: Set<T>,
  pred: (val: T) => val is E
): it is Set<E>;
export default function <T, E extends T>(
  it: T[],
  pred: (val: T) => val is E
): it is E[];
export default function <T>(
  it: Iterable<T>,
  pred: (val: T) => boolean
): boolean;
export default function <T>(
  it: Iterable<T>,
  pred: (val: T) => boolean
): boolean {
  for (const val of it) {
    if (!pred(val)) {
      return false;
    }
  }
  return true;
}