this.range = GeneralRange.all(comparator);
    this.header = new AvlNode<>();
    successor(header, header);
    this.rootReference = new Reference<>();
  }

  /** A function which can be summed across a subtree. */
  private enum Aggregate {
    SIZE {
      @Override
      int nodeAggregate(AvlNode<?> node) {
        return node.elemCount;
      }

      @Override

   * being a real directory to being a symlink to another directory. It then calls
   * deleteDirectoryContents thousands of times on a directory whose subtree contains the file
   * that's switching between directory and symlink to try to ensure that under no circumstance does
   * deleteDirectoryContents follow the symlink to the other directory and delete that directory's

   * @throws NullPointerException if any of {@code elements} is null
   */
  public static <E> ImmutableSortedSet<E> copyOf(Iterable<? extends E> elements) {
    // Hack around E not being a subtype of Comparable.
    // Unsafe, see ImmutableSortedSetFauxverideShim.
    @SuppressWarnings("unchecked")
    Ordering<E> naturalOrder = (Ordering<E>) Ordering.<Comparable<?>>natural();
    return copyOf(naturalOrder, elements);

        List<RecursiveTypeBoundBugExample<? extends RecursiveTypeBoundBugExample<T>>> arg) {
      return notSubtype(arg); // isSubtype() currently incorrectly considers it a subtype.
    }
  }

  private static class WildcardSubtypingTests extends SubtypeTester {
    @TestSubtype(suppressGetSupertype = true, suppressGetSubtype = true)
    public Iterable<?> noBounds(List<?> list) {

      void visitClass(Class<?> t) {
        result.set(t.getComponentType());
      }
    }.visit(type);
    return result.get();
  }

  /**
   * Returns {@code ? extends X} if any of {@code bounds} is a subtype of {@code X[]}; or null
   * otherwise.
   */
  @CheckForNull
  private static Type subtypeOfComponentType(Type[] bounds) {
    for (Type bound : bounds) {
      Type componentType = getComponentType(bound);

          // subtyping between declared type bound and actual type bound. So it's possible that we
          // may generate something like <capture#1-of ? extends Foo&SubFoo>.
          // Checking subtype between declared and actual type bounds
          // adds recursive isSubtypeOf() call and feels complicated.
          // There is no contract one way or another as long as isSubtypeOf() works as expected.

   * @throws IllegalArgumentException if any two keys are equal according to their natural ordering
   */
  public static <K, V> ImmutableSortedMap<K, V> copyOf(Map<? extends K, ? extends V> map) {
    // Hack around K not being a subtype of Comparable.
    // Unsafe, see ImmutableSortedSetFauxverideShim.
    @SuppressWarnings("unchecked")
    Ordering<K> naturalOrder = (Ordering<K>) NATURAL_ORDER;
    return copyOfInternal(map, naturalOrder);
  }

   * String#equalsIgnoreCase}). However in almost all cases that ASCII strings are used, the author
   * probably wanted the behavior provided by this method rather than the subtle and sometimes
   * surprising behavior of {@code toUpperCase()} and {@code toLowerCase()}.
   *
   * @since 16.0
   */
  public static boolean equalsIgnoreCase(CharSequence s1, CharSequence s2) {

   * includes exceptional exits, so all control paths involving signalling must be protected by a
   * finally block.
   *
   * Further optimizations of this algorithm become increasingly subtle. A wait that terminates
   * without the guard being satisfied (due to timeout, but not interrupt) can then immediately exit
   * the monitor without signalling. If it timed out without being signalled, it does not need to

  /** Call this in a {@link TestSubtype} public method asserting subtype relationship. */
  final <T> T isSubtype(T sub) {
    Type returnType = method.getGenericReturnType();
    Type paramType = getOnlyParameterType();
    TestSubtype spec = method.getAnnotation(TestSubtype.class);
    assertWithMessage("%s is subtype of %s", paramType, returnType)
        .that(TypeToken.of(paramType).isSubtypeOf(returnType))