return result;
    } else {
      return new RegularImmutableSortedSet<>(ImmutableList.of(), comparator);
    }
  }

  /**
   * Returns the empty immutable sorted set.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings("unchecked") // The natural-ordered empty set supports all types.
  public static <E> ImmutableSortedSet<E> of() {

      return result;
    } else {
      return new RegularImmutableSortedSet<>(ImmutableList.of(), comparator);
    }
  }

  /**
   * Returns the empty immutable sorted set.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings("unchecked") // The natural-ordered empty set supports all types.
  public static <E> ImmutableSortedSet<E> of() {