https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102345
Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2021-09-15 Status|UNCONFIRMED |NEW Ever confirmed|0 |1 --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- The first problem is demonstrated by: export module newdel; namespace std { using size_t = decltype(sizeof(0)); enum class align_val_t : size_t; } new.cc:5:28: error: cannot define ‘enum class std::align_val_t’ in different module 5 | enum class align_val_t : size_t; | ^~~~~~ <built-in>: note: declared here new.cc:5: confused by earlier errors, bailing out Preprocessed source stored into /tmp/cc4qIyxE.out file, please attach this to your bugreport. This is fixed by Jason's patch in PR 48396 comment 4.