GCC raises issues with `-Werror=non-template-friend`

Bắt đầu với subprojects/wg21_p2300_std_execution/include/execution.hpp tại các dòng 969-986 và tái hiện bản build Meson bằng GCC cùng -Werror=non-template-friend. Kiểm tra các khai báo friend được báo cáo và xác minh rằng dự án vẫn build thành công khi cảnh báo này được xử lý như một lỗi.

By default, repositories compiled using the meson build enable -Werror=non-template-friend and this causes the following errors:

../subprojects/wg21_p2300_std_execution/include/execution.hpp:969:66: error: friend declaration ‘void std::execution::__connect::tag_invoke(_Tag, std::execution::__connect::__completion<_Tag(_Args ...)>&&, _Args&& ...)’ declares a non-template function [-Werror=non-template-friend]
  969 |         friend void tag_invoke(_Tag, __completion&&, _Args&&...) noexcept;
      |                                                                  ^~~~~~~~
../subprojects/wg21_p2300_std_execution/include/execution.hpp:969:66: note: (if this is not what you intended, make sure the function template has already been declared and add ‘<>’ after the function name here)
../subprojects/wg21_p2300_std_execution/include/execution.hpp:978:76: error: friend declaration ‘std::execution::__connect::__debug_env_t<_Env> std::execution::__connect::tag_invoke(std::execution::__env::get_env_t, std::execution::__connect::__debug_receiver<_Env, std::execution::completion_signatures<_Sigs ...> >)’ declares a non-template function [-Werror=non-template-friend]
  978 |         friend __debug_env_t<_Env> tag_invoke(get_env_t, __debug_receiver) noexcept;
      |                                                                            ^~~~~~~~
../subprojects/wg21_p2300_std_execution/include/execution.hpp:985:71: error: friend declaration ‘void std::execution::__connect::tag_invoke(std::execution::__receivers::set_stopped_t, std::execution::__connect::__any_debug_receiver<_Env>&&)’ declares a non-template function [-Werror=non-template-friend]
  985 |         friend void tag_invoke(set_stopped_t, __any_debug_receiver&&) noexcept;
      |                                                                       ^~~~~~~~
../subprojects/wg21_p2300_std_execution/include/execution.hpp:986:80: error: friend declaration ‘std::execution::__connect::__debug_env_t<_Env> std::execution::__connect::tag_invoke(std::execution::__env::get_env_t, std::execution::__connect::__any_debug_receiver<_Env>)’ declares a non-template function [-Werror=non-template-friend]
  986 |         friend __debug_env_t<_Env> tag_invoke(get_env_t, __any_debug_receiver) noexcept;