public ContiguousSet<C> tailSet(C fromElement, boolean inclusive) {
    return tailSetImpl(checkNotNull(fromElement), inclusive);
  }

  /*
   * These methods perform most headSet, subSet, and tailSet logic, besides parameter validation.
   */
  @SuppressWarnings("MissingOverride") // Supermethod does not exist under GWT.
  abstract ContiguousSet<C> headSetImpl(C toElement, boolean inclusive);

  public ContiguousSet<C> tailSet(C fromElement, boolean inclusive) {
    return tailSetImpl(checkNotNull(fromElement), inclusive);
  }

  /*
   * These methods perform most headSet, subSet, and tailSet logic, besides parameter validation.
   */
  @SuppressWarnings("MissingOverride") // Supermethod does not exist under GWT.
  abstract ContiguousSet<C> headSetImpl(C toElement, boolean inclusive);

      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.NO_BOUND));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.INCLUSIVE));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    return derivedSuites;

      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.NO_BOUND));
      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubMultisetSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    return derivedSuites;
  }

  private TestSuite createSubMultisetSuite(

      E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
    return tailSetImpl(fromElement, fromInclusive).headSetImpl(toElement, toInclusive);
  }

  @Override
  ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive) {
    return getSubSet(tailIndex(fromElement, inclusive), size());
  }

  int tailIndex(E fromElement, boolean inclusive) {

    }

    @Override
    public NavigableSet<E> tailSet(@ParametricNullness E fromElement, boolean inclusive) {
      return new NavigableElementSet<>(
          multiset().tailMultiset(fromElement, BoundType.forBoolean(inclusive)));
    }
  }

  private static <E extends @Nullable Object> E getElementOrThrow(@Nullable Entry<E> entry) {
    if (entry == null) {

      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.NO_BOUND));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.EXCLUSIVE));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.EXCLUSIVE, Bound.INCLUSIVE));
      derivedSuites.add(createSubmapSuite(parentBuilder, Bound.INCLUSIVE, Bound.INCLUSIVE));
    }

    return derivedSuites;

      for (List<Integer> contents : SAMPLE_INPUTS) {
        for (int i = 0; i < 10; i++) {
          for (boolean inclusive : ImmutableList.of(true, false)) {
            assertEquals(
                filter(createUnfiltered(contents).headSet(i, inclusive), EVEN),
                filter(createUnfiltered(contents), EVEN).headSet(i, inclusive));
          }
        }
      }
    }

    public void testNavigableTailSet() {

  @Override
  ContiguousSet<C> headSetImpl(C toElement, boolean inclusive) {
    return intersectionInCurrentDomain(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
  }

  @Override
  @SuppressWarnings("unchecked") // TODO(cpovirk): Use a shared unsafeCompare method.
  ContiguousSet<C> subSetImpl(
      C fromElement, boolean fromInclusive, C toElement, boolean toInclusive) {

      for (boolean inclusive : new boolean[] {false, true}) {
        assertThat(navigableMap.headMap(key, inclusive).entrySet())
            .containsExactlyElementsIn(expected.headMap(key, inclusive).entrySet())
            .inOrder();
        assertThat(navigableMap.tailMap(key, inclusive).entrySet())
            .containsExactlyElementsIn(expected.tailMap(key, inclusive).entrySet())
            .inOrder();