}

  // This declaration is needed to make Set.iterator() and
  // ImmutableCollection.iterator() consistent.
  @Override
  public abstract UnmodifiableIterator<E> iterator();

  abstract static class CachingAsList<E> extends ImmutableSet<E> {
    @LazyInit @RetainedWith private transient @Nullable ImmutableList<E> asList;

    @Override
    public ImmutableList<E> asList() {
      ImmutableList<E> result = asList;

// TODO(benyu): benchmark and optimize all creation paths, which are a mess now
@GwtCompatible
@SuppressWarnings("serial") // we're overriding default serialization
public abstract class ImmutableSortedSet<E> extends ImmutableSet.CachingAsList<E>
    implements NavigableSet<E>, SortedIterable<E> {
  static final int SPLITERATOR_CHARACTERISTICS =
      ImmutableSet.SPLITERATOR_CHARACTERISTICS | Spliterator.SORTED;

  /**