return emptySet(comparator());
    }
    return tailSet(fromElement, fromInclusive).headSet(toElement, toInclusive);
  }

  public ImmutableSortedSet<E> tailSet(E fromElement) {
    checkNotNull(fromElement);
    try {
      return unsafeDelegateSortedSet(sortedDelegate.tailSet(fromElement), true);
    } catch (IllegalArgumentException e) {
      return emptySet(comparator());

    }

    @Override
    public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
      synchronized (mutex) {
        return Synchronized.navigableSet(delegate().tailSet(fromElement, inclusive), mutex);
      }
    }

    @Override
    public SortedSet<E> tailSet(E fromElement) {
      return tailSet(fromElement, true);
    }

      return standardPollLast();
    }

    @Override
    public SortedSet<T> headSet(T toElement) {
      return standardHeadSet(toElement);
    }

    @Override
    public SortedSet<T> tailSet(T fromElement) {
      return standardTailSet(fromElement);
    }
  }

  public static Test suite() {
    TestSuite suite = new TestSuite();

    suite.addTestSuite(ForwardingNavigableSetTest.class);

    return subSetImpl(fromElement, fromInclusive, toElement, toInclusive);
  }

  @Override
  public ContiguousSet<C> tailSet(C fromElement) {
    return tailSetImpl(checkNotNull(fromElement), true);
  }

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  public ContiguousSet<C> tailSet(C fromElement, boolean inclusive) {
    return tailSetImpl(checkNotNull(fromElement), inclusive);
  }

  /*

      for (List<Integer> contents : SAMPLE_INPUTS) {
        for (int i = 0; i < 10; i++) {
          assertEquals(
              filter((C) createUnfiltered(contents).tailSet(i), EVEN),
              filter(createUnfiltered(contents), EVEN).tailSet(i));
        }
      }
    }

    @SuppressWarnings("unchecked")
    public void testSubSet() {
      for (List<Integer> contents : SAMPLE_INPUTS) {

    ImmutableSortedSet<Integer> asSet = RANGE_SET_ONE.asSet(DiscreteDomain.integers());

    for (int i = 0; i <= 20; i++) {
      assertEquals(asSet.tailSet(i, false), expectedSet.tailSet(i, false));
      assertEquals(asSet.tailSet(i, true), expectedSet.tailSet(i, true));
    }
  }

  public void testAsSetSubSet() {
    ImmutableSortedSet<Integer> expectedSet = ImmutableSortedSet.of(2, 3, 4, 8, 9, 16, 17);

      return new FilteredSortedSet<>(((SortedSet<E>) unfiltered).headSet(toElement), predicate);
    }

    @Override
    public SortedSet<E> tailSet(@ParametricNullness E fromElement) {
      return new FilteredSortedSet<>(((SortedSet<E>) unfiltered).tailSet(fromElement), predicate);
    }

    @Override
    @ParametricNullness
    public E first() {

    assertEquals(StringLength.COMPARATOR, keySet.comparator());
    assertEquals(Sets.<@Nullable String>newHashSet(null, "tree"), keySet.headSet("yahoo"));
    assertEquals(Sets.newHashSet("google"), keySet.tailSet("yahoo"));
    assertEquals(Sets.newHashSet("tree"), keySet.subSet("ask", "yahoo"));
  }

  @GwtIncompatible // SerializableTester
  public void testExplicitComparatorSerialization() {

    return subSetImpl(fromElement, fromInclusive, toElement, toInclusive);
  }

  @Override
  public ContiguousSet<C> tailSet(C fromElement) {
    return tailSetImpl(checkNotNull(fromElement), true);
  }

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  public ContiguousSet<C> tailSet(C fromElement, boolean inclusive) {
    return tailSetImpl(checkNotNull(fromElement), inclusive);
  }

  /*

   *
   * <p>The {@link SortedSet#tailSet} documentation states that a subset of a subset throws an
   * {@link IllegalArgumentException} if passed a {@code fromElement} smaller than an earlier {@code
   * fromElement}. However, this method doesn't throw an exception in that situation, but instead
   * keeps the original {@code fromElement}.
   */
  @Override
  public ImmutableSortedSet<E> tailSet(E fromElement) {