*
   * @since 10.0 (previously, subclasses would override hash())
   */
  @ForOverride
  protected abstract int doHash(T t);

  /**
   * Returns a new equivalence relation for {@code F} which evaluates equivalence by first applying
   * {@code function} to the argument, then evaluating using {@code this}. That is, for any pair of
   * non-null objects {@code x} and {@code y}, {@code equivalence.onResultOf(function).equivalent(a,

   *
   * @since 10.0 (previously, subclasses would override hash())
   */
  @ForOverride
  protected abstract int doHash(T t);

  /**
   * Returns a new equivalence relation for {@code F} which evaluates equivalence by first applying
   * {@code function} to the argument, then evaluating using {@code this}. That is, for any pair of
   * non-null objects {@code x} and {@code y}, {@code equivalence.onResultOf(function).equivalent(a,