checkState(set.size() == size);
    return set;
  }

  /**
   * Returns a {@link SetView} with a {@link SetView#minSize()} of {@code min} and a {@link
   * SetView#maxSize()} of {@code max}.
   */
  private static SetView<Integer> setSizeRange(int min, int max) {
    checkArgument(min >= 0 && max >= min);
    SetView<Integer> set = difference(setSize(max), setSize(max - min));

   * you either use it as a plain {@link Set}, or immediately invoke {@link #immutableCopy} or
   * {@link #copyInto} and forget the {@code SetView} itself.
   *
   * @since 2.0
   */
  public abstract static class SetView<E extends @Nullable Object> extends AbstractSet<E> {
    private SetView() {} // no subclasses but our own

    /**