}

    @Override
    protected A doBackward(C c) {
      throw new AssertionError();
    }

    @Override
    @CheckForNull
    C correctedDoForward(@CheckForNull A a) {
      return second.correctedDoForward(first.correctedDoForward(a));
    }

    @Override
    @CheckForNull
    A correctedDoBackward(@CheckForNull C c) {
      return first.correctedDoBackward(second.correctedDoBackward(c));