Method store_error

include/exec/sequence/merge_each.hpp:199–223

      template <class _Error>
        requires(!__std::same_as<_Error, _ErrorStorage>)
      void store_error(_Error&& __error)
        noexcept(__nothrow_callable<decltype(&_ErrorStorage::template emplace<_Error>),
                                    _ErrorStorage&,
                                    _Error>)
      {
        if (this->nested_value_fail())
        {
          // We are the first child to complete with an error, so we must save the error. (Any
          // subsequent errors are ignored.)
          if constexpr (noexcept(__error_storage_->template emplace<_Error>(
                          static_cast<_Error&&>(__error))))
          {
            __error_storage_->template emplace<_Error>(static_cast<_Error&&>(__error));
          }
          else
          {
            STDEXEC_TRY
            {
              __error_storage_->template emplace<_Error>(static_cast<_Error&&>(__error));
            }
            STDEXEC_CATCH_ALL
            {
              __error_storage_->template emplace<std::exception_ptr>(std::current_exception());
            }
          }
        }
      }
    };