// ImmutableCollection.iterator() appear consistent to javac's type inference.
  @Override
  public abstract UnmodifiableIterator<E> iterator();

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

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

  }

  // 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;

import java.util.Spliterator;
import java.util.function.Consumer;
import org.jspecify.annotations.Nullable;

@GwtCompatible
abstract class IndexedImmutableSet<E> extends ImmutableSet.CachingAsList<E> {
  abstract E get(int index);

  @Override
  public UnmodifiableIterator<E> iterator() {
    return asList().iterator();
  }

  @Override
  public Spliterator<E> spliterator() {

 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
final class RegularImmutableSet<E> extends ImmutableSet.CachingAsList<E> {
  private static final Object[] EMPTY_ARRAY = new Object[0];
  static final RegularImmutableSet<Object> EMPTY =
      new RegularImmutableSet<>(EMPTY_ARRAY, 0, EMPTY_ARRAY, 0);

/**
 * {@code entrySet()} implementation for {@link ImmutableMap}.
 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 */
@GwtCompatible
abstract class ImmutableMapEntrySet<K, V> extends ImmutableSet.CachingAsList<Entry<K, V>> {
  private static final int SPLITERATOR_CHARACTERISTICS =
      Spliterator.ORDERED | Spliterator.DISTINCT | Spliterator.NONNULL | Spliterator.IMMUTABLE;

// 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;

  /**