@CheckForNull
  transient ImmutableSortedSet<E> descendingSet;

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  public ImmutableSortedSet<E> descendingSet() {
    // racy single-check idiom
    ImmutableSortedSet<E> result = descendingSet;
    if (result == null) {
      result = descendingSet = createDescendingSet();
      result.descendingSet = this;
    }
    return result;
  }

              @Override
              public Set<E> create(Object... elements) {
                NavigableSet<E> navigableSet = (NavigableSet<E>) delegate.create(elements);
                return navigableSet.descendingSet();
              }
            })
        .named(parentBuilder.getName() + " descending")
        .withFeatures(features)
        .suppressing(parentBuilder.getSuppressedTests())
        .createTestSuite();

              @Override
              public Set<E> create(Object... elements) {
                NavigableSet<E> navigableSet = (NavigableSet<E>) delegate.create(elements);
                return navigableSet.descendingSet();
              }
            })
        .named(parentBuilder.getName() + " descending")
        .withFeatures(features)
        .suppressing(parentBuilder.getSuppressedTests())
        .createTestSuite();

  @CheckForNull
  transient ImmutableSortedSet<E> descendingSet;

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  public ImmutableSortedSet<E> descendingSet() {
    // racy single-check idiom
    ImmutableSortedSet<E> result = descendingSet;
    if (result == null) {
      result = descendingSet = createDescendingSet();
      result.descendingSet = this;
    }
    return result;
  }

    @CheckForNull transient NavigableSet<E> descendingSet;

    @Override
    public NavigableSet<E> descendingSet() {
      synchronized (mutex) {
        if (descendingSet == null) {
          NavigableSet<E> dS = Synchronized.navigableSet(delegate().descendingSet(), mutex);
          descendingSet = dS;
          return dS;
        }
        return descendingSet;
      }
    }

    @Override

    @CheckForNull transient NavigableSet<E> descendingSet;

    @Override
    public NavigableSet<E> descendingSet() {
      synchronized (mutex) {
        if (descendingSet == null) {
          NavigableSet<E> dS = Synchronized.navigableSet(delegate().descendingSet(), mutex);
          descendingSet = dS;
          return dS;
        }
        return descendingSet;
      }
    }

    @Override

    NavigableSet<E> empty = navigableSet.subSet(e0(), false, e0(), false);
    assertEquals(new TreeSet<E>(), empty);
  }

  /*
   * TODO(cpovirk): more testing of subSet/headSet/tailSet/descendingSet? and/or generate derived
   * suites?
   */

  /**
   * Returns the {@link Method} instances for the test methods in this class that create a set with

    /* Unmodifiable is a view. */
    mod.add(4);
    assertTrue(unmod.contains(4));
    assertTrue(unmod.descendingSet().contains(4));

    ensureNotDirectlyModifiable(unmod);
    ensureNotDirectlyModifiable(unmod.descendingSet());
    ensureNotDirectlyModifiable(unmod.headSet(2));
    ensureNotDirectlyModifiable(unmod.headSet(2, true));

    NavigableSet<E> empty = navigableSet.subSet(e0(), false, e0(), false);
    assertEquals(new TreeSet<E>(), empty);
  }

  /*
   * TODO(cpovirk): more testing of subSet/headSet/tailSet/descendingSet? and/or generate derived
   * suites?
   */

  /**
   * Returns the {@link Method} instances for the test methods in this class that create a set with

              .createTestSuite());

      suite.addTest(
          NavigableSetTestSuiteBuilder.using(new ContiguousSetDescendingGenerator())
              .named("Range.asSet.descendingSet")
              .withFeatures(
                  CollectionSize.ANY,
                  KNOWN_ORDER,
                  ALLOWS_NULL_QUERIES,
                  NON_STANDARD_TOSTRING,