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

    @SuppressWarnings("unchecked") // guarded by the isAssignableFrom() statement above
    TypeToken<? extends T> subtype = (TypeToken<? extends T>) of(resolvedTypeArgs);
    checkArgument(
        subtype.isSubtypeOf(this), "%s does not appear to be a subtype of %s", subtype, this);
    return subtype;
  }

  /**
   * Returns true if this type is a supertype of the given {@code type}. "Supertype" is defined

  /** 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))

   * Returns the value the specified class is mapped to, or {@code null} if no entry for this class
   * is present. This will only return a value that was bound to this specific class, not a value
   * that may have been bound to a subtype.
   */
  @CheckForNull
  <T extends @NonNull B> T getInstance(Class<T> type);

  /**
   * Maps the specified class to the specified value. Does <i>not</i> associate this value with any
   * of the class's supertypes.

        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) {

 *     "Unexpected bill status: %s", bill.status());
 * }</pre>
 *
 * <h3>Comparison to alternatives</h3>
 *
 * <p><b>Note:</b> In some cases the differences explained below can be subtle. When it's unclear
 * which approach to use, <b>don't worry</b> too much about it; just pick something that seems
 * reasonable and it will be fine.
 *
 * <ul>

    Type subtype = new TypeCapture<TypedKeyMap<T>>() {}.capture();
    assertEquals(
        new TypeCapture<TypedKeyMap<String>>() {}.capture(),
        new TypeResolver()
            .where(
                new TypeCapture<Map<Integer, T>>() {}.capture(),
                new TypeCapture<Map<?, String>>() {}.capture())
            .resolveType(subtype));
  }

  public abstract Iterable<T> children(T root);

  /**
   * Returns an unmodifiable iterable over the nodes in a tree structure, using pre-order traversal.
   * That is, each node's subtrees are traversed after the node itself is returned.
   *
   * <p>No guarantees are made about the behavior of the traversal when nodes change while iteration

   *       Serializable}.
   *   <li>Serialization test is not performed on method return values unless the method is a
   *       visible static factory method whose return type is {@code C} or {@code C}'s subtype.
   * </ul>
   *
   * <p>In all cases, if {@code C} needs custom logic for testing serialization, you can add an
   * explicit {@code testSerializable()} test in the corresponding {@code CTest} class, and {@code