}, w)
			}

			// fallback only when set.
			for {
				fd := fallback(werr)
				if fd == nil {
					break
				}
				// This fallback is only set when
				// askDisks is less than total
				// number of disks per set.
				werr = fd.WalkDir(ctx, WalkDirOptions{
					Limit:          opts.perDiskLimit,
					Bucket:         opts.bucket,
					BaseDir:        opts.path,

 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0 (implements {@code NavigableSet} since 12.0)
 */
// TODO(benyu): benchmark and optimize all creation paths, which are a mess now
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
public abstract class ImmutableSortedSet<E> extends ImmutableSet<E>