return new Converter<F, T>() {
      @Override
      protected T doForward(F a) {
        return doConvert(convertToType);
      }

      @Override
      protected F doBackward(T b) {
        return doConvert(convertFromType);
      }

      private /*static*/ <S> S doConvert(TypeToken<S> type) {
        return checkNotNull(getDefaultValue(type));
      }
    };
  }