@ParametricNullness
  public E getLast() {
    return delegate().getLast();
  }

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  public boolean offerFirst(@ParametricNullness E e) {
    return delegate().offerFirst(e);
  }

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  public boolean offerLast(@ParametricNullness E e) {
    return delegate().offerLast(e);

  public synchronized void clear() {
    list.clear();
  }

  /** Returns a snapshot of the logged records. */
  /*
   * TODO(cpovirk): consider higher-level APIs here (say, assertNoRecordsLogged(),
   * getOnlyRecordLogged(), getAndClearLogRecords()...)
   *
   * TODO(cpovirk): consider renaming this method to reflect that it takes a snapshot (and/or return
   * an ImmutableList)
   */

  public synchronized void clear() {
    list.clear();
  }

  /** Returns a snapshot of the logged records. */
  /*
   * TODO(cpovirk): consider higher-level APIs here (say, assertNoRecordsLogged(),
   * getOnlyRecordLogged(), getAndClearLogRecords()...)
   *
   * TODO(cpovirk): consider renaming this method to reflect that it takes a snapshot (and/or return
   * an ImmutableList)
   */

    resetWithHole();
    assertEquals(c, navigableSet.higher(a));
    assertEquals(c, navigableSet.higher(b));
    assertEquals(null, navigableSet.higher(c));
  }

  /*
   * TODO(cpovirk): make "too small" and "too large" elements available for better navigation
   * testing. At that point, we may be able to eliminate the "hole" tests, which would mean that

@SuppressWarnings("serial") // Serialization only done in GWT.
public abstract class ForwardingImmutableSet<E> extends ImmutableSet<E> {
  private final transient Set<E> delegate;

  ForwardingImmutableSet(Set<E> delegate) {
    // TODO(cpovirk): are we over-wrapping?
    this.delegate = Collections.unmodifiableSet(delegate);
  }

  @Override
  public UnmodifiableIterator<E> iterator() {
    return Iterators.unmodifiableIterator(delegate.iterator());
  }

    return delegateCollection().comparator();
  }

  // Override indexOf() and lastIndexOf() to be O(log N) instead of O(N).

  @GwtIncompatible // ImmutableSortedSet.indexOf
  // TODO(cpovirk): consider manual binary search under GWT to preserve O(log N) lookup
  @Override
  public int indexOf(@CheckForNull Object target) {
    int index = delegateCollection().indexOf(target);

  static final ImmutableList<Object> EMPTY = new RegularImmutableList<Object>(emptyList());

  private final List<E> delegate;
  @Nullable E forSerialization;

  RegularImmutableList(List<E> delegate) {
    // TODO(cpovirk): avoid redundant unmodifiableList wrapping
    this.delegate = unmodifiableList(delegate);
  }

  @Override
  List<E> delegateList() {
    return delegate;
  }

    resetWithHole();
    assertEquals(c, navigableSet.higher(a));
    assertEquals(c, navigableSet.higher(b));
    assertEquals(null, navigableSet.higher(c));
  }

  /*
   * TODO(cpovirk): make "too small" and "too large" elements available for better navigation
   * testing. At that point, we may be able to eliminate the "hole" tests, which would mean that

  protected ForwardingQueue() {}

  @Override
  protected abstract Queue<E> delegate();

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  public boolean offer(@ParametricNullness E o) {
    return delegate().offer(o);
  }

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  @CheckForNull
  public E poll() {
    return delegate().poll();
  }

  protected ForwardingQueue() {}

  @Override
  protected abstract Queue<E> delegate();

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  public boolean offer(@ParametricNullness E o) {
    return delegate().offer(o);
  }

  @CanIgnoreReturnValue // TODO(cpovirk): Consider removing this?
  @Override
  @CheckForNull
  public E poll() {
    return delegate().poll();
  }