/**
 * {@code keySet()} implementation for {@link ImmutableMap}.
 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 */
@GwtCompatible
final class ImmutableMapKeySet<K, V> extends IndexedImmutableSet<K> {
  private final ImmutableMap<K, V> map;

  ImmutableMapKeySet(ImmutableMap<K, V> map) {
    this.map = map;
  }

  @Override
  public int size() {
    return map.size();
  }

  @Override

/**
 * {@code keySet()} implementation for {@link ImmutableMap}.
 *
 * @author Jesse Wilson
 * @author Kevin Bourrillion
 */
@GwtCompatible
final class ImmutableMapKeySet<K, V> extends IndexedImmutableSet<K> {
  private final ImmutableMap<K, V> map;

  ImmutableMapKeySet(ImmutableMap<K, V> map) {
    this.map = map;
  }

  @Override
  public int size() {
    return map.size();
  }

  @Override

  public ImmutableSet<E> elementSet() {
    ImmutableSet<E> result = elementSet;
    return (result == null) ? elementSet = new ElementSet() : result;
  }

  @WeakOuter
  private final class ElementSet extends IndexedImmutableSet<E> {

    @Override
    E get(int index) {
      return contents.getKey(index);
    }

    @Override
    public boolean contains(@Nullable Object object) {

  }

  @Override
  ImmutableSet<K> createKeySet() {
    return new KeySet<>(this);
  }

  private static final class KeySet<K> extends IndexedImmutableSet<K> {
    private final RegularImmutableMap<K, ?> map;

    KeySet(RegularImmutableMap<K, ?> map) {
      this.map = map;
    }

    @Override
    K get(int index) {

    return isEmpty() ? ImmutableSet.<Entry<E>>of() : new EntrySet();
  }

  abstract Entry<E> getEntry(int index);

  @WeakOuter
  private final class EntrySet extends IndexedImmutableSet<Entry<E>> {
    @Override
    boolean isPartialView() {
      return ImmutableMultiset.this.isPartialView();
    }

    @Override
    Entry<E> get(int index) {
      return getEntry(index);