/**
   * swap
   */
  void swap(Expected& that) noexcept(
      expected_detail::StrictAllOf<IsNothrowSwappable, Value, Error>::value) {
    if (this->uninitializedByException() || that.uninitializedByException())
      throw BadExpectedAccess();
    using std::swap;
    if (*this) {
      if (that) {
        swap(this->value_, that.value_);
      } else {
        Error e(std::move(that.error_));
        that.assignValue(std::move(this->value_));
        this->assignError(std::move(e));
      }
    } else {
      if (!that) {
        swap(this->error_, that.error_);
      } else {
        Error e(std::move(this->error_));
        this->assignValue(std::move(that.value_));
        that.assignError(std::move(e));
      }
    }
  }