}
  }

  /** An {@code Iterator} over distinct keys in key head order. */
  private final class DistinctKeyIterator implements Iterator<K> {
    final Set<K> seenKeys = Sets.newHashSetWithExpectedSize(keySet().size());
    @Nullable Node<K, V> next = head;
    @Nullable Node<K, V> current;
    int expectedModCount = modCount;

    private void checkForConcurrentModification() {

   * collision rate looks sane.
   */
  static void assertInvariants(HashFunction hashFunction) {
    int objects = 100;
    Set<HashCode> hashcodes = Sets.newHashSetWithExpectedSize(objects);
    Random random = new Random(314159);
    for (int i = 0; i < objects; i++) {
      int value = random.nextInt();
      HashCode hashcode1 = hashFunction.hashInt(value);

    private final Set<Object> delegate;

    JdkBackedSetBuilderImpl(SetBuilderImpl<E> toCopy) {
      super(toCopy); // initializes dedupedElements and distinct
      delegate = Sets.newHashSetWithExpectedSize(distinct);
      for (int i = 0; i < distinct; i++) {
        /*
         * requireNonNull is safe because we ensure that the first `distinct` elements have been
         * populated.
         */

   */
  @SuppressWarnings("NonApiType") // acts as a direct substitute for a constructor call
  public static <E extends @Nullable Object> HashSet<E> newHashSet(E... elements) {
    HashSet<E> set = newHashSetWithExpectedSize(elements.length);
    Collections.addAll(set, elements);
    return set;
  }

  /**
   * Creates a <i>mutable</i> {@code HashSet} instance containing the given elements. A very thin

      try {
        return super.retainAll(checkNotNull(c));
      } catch (UnsupportedOperationException e) {
        // if the iterators don't support remove
        Set<@Nullable Object> keys = Sets.newHashSetWithExpectedSize(c.size());
        for (Object o : c) {
          /*
           * `o instanceof Entry` is guaranteed by `contains`, but we check it here to satisfy our
           * nullness checker.
           */

      try {
        return super.retainAll(checkNotNull(c));
      } catch (UnsupportedOperationException e) {
        // if the iterators don't support remove
        Set<@Nullable Object> keys = Sets.newHashSetWithExpectedSize(c.size());
        for (Object o : c) {
          /*
           * `o instanceof Entry` is guaranteed by `contains`, but we check it here to satisfy our
           * nullness checker.
           */