[Bug c++/91405] [concepts] internal compiler error: in synthesize_implicit_template_parm, at cp/parser.c:41206

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91405

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Or simpler:

template<typename T>
concept DatabaseTransaction = requires(T a) {
  a.commit();
};

template<typename T>
concept UserRepository = requires(T a, DatabaseTransaction auto transaction) {
  a.insert_user_if_not_exists(transaction);
};