final boolean isSubset;

  RegularImmutableSortedSet(SortedSet<E> delegate, boolean isSubset) {
    super(delegate);
    this.isSubset = isSubset;
  }

  @Override
  ImmutableList<E> createAsList() {
    return new ImmutableSortedAsList<>(this, ImmutableList.asImmutableList(toArray()));
  }

    @Override
    public ImmutableList<E> asList() {
      ImmutableList<E> result = asList;
      if (result == null) {
        return asList = createAsList();
      } else {
        return result;
      }
    }

    @Override
    ImmutableList<E> createAsList() {
      return new RegularImmutableAsList<E>(this, toArray());
    }
  }

  abstract static class Indexed<E> extends ImmutableSet<E> {

    // requireNonNull is safe because we checked the range is not empty in ContiguousSet.create.
    return requireNonNull(range.upperBound.greatestValueBelow(domain));
  }

  @Override
  ImmutableList<C> createAsList() {
    if (domain.supportsFastOffset) {
      return new ImmutableAsList<C>() {
        @Override
        ImmutableSortedSet<C> delegateCollection() {
          return RegularContiguousSet.this;
        }

  }

  private transient @Nullable ImmutableList<E> asList;

  public ImmutableList<E> asList() {
    ImmutableList<E> list = asList;
    return (list == null) ? (asList = createAsList()) : list;
  }

  ImmutableList<E> createAsList() {
    switch (size()) {
      case 0:
        return ImmutableList.of();
      case 1:
        return ImmutableList.of(iterator().next());
      default: