* the first are ignored.
   */
  public static <E> ImmutableSet<E> of(E e1, E e2) {
    return new RegularSetBuilderImpl<E>(2).add(e1).add(e2).review().build();
  }

  /**
   * Returns an immutable set containing the given elements, minus duplicates, in the order each was

   * would declare a return type of `@Nullable T[]`. However, we've decided not to think too hard
   * about arrays for now, as they're a mess. (We previously discussed this in the review of
   * ObjectArrays, which is the main caller of this method.)
   */
  static <T extends @Nullable Object> T[] newArray(T[] reference, int length) {

   * would declare a return type of `@Nullable T[]`. However, we've decided not to think too hard
   * about arrays for now, as they're a mess. (We previously discussed this in the review of
   * ObjectArrays, which is the main caller of this method.)
   */
  static <T extends @Nullable Object> T[] newArray(T[] reference, int length) {