(ImmutableList<K>) new KeysOrValuesAsList(alternatingKeysAndValues, 0, size);
    return new KeySet<K>(this, keyList);
  }

  static final class KeysOrValuesAsList extends ImmutableList<Object> {
    private final transient @Nullable Object[] alternatingKeysAndValues;
    private final transient int offset;
    private final transient int size;