https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125230
--- Comment #3 from Drea Pinski <pinskia at gcc dot gnu.org> --- https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Modules.html Has part of this documented for gcc. But this is exactly how c++20 modules are supposed to work.
