*
     * <p>Since the last element of the array is actually in the middle of the sorted structure, a
     * childless aunt node could be smaller, which would corrupt the invariant if this element
     * becomes the new parent of the aunt node. In that case, we first switch the last element with
     * its aunt node, before returning.
     */
    int swapWithConceptuallyLastElement(E actualLastElement) {

   * Foo<Enum<?>>} according to JLS. See testRecursiveWildcardSubtypeBug() for a real example.
   *
   * <p>It appears that properly handling recursive type bounds in the presence of implicit type
   * bounds is not easy. For now we punt, hoping that this defect should rarely cause issues in real
   * code.
   *
   * @param formalType is {@code Foo<formalType>} a supertype of {@code Foo<T>}?