https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109181
Bug ID: 109181 Summary: requires expression type requirement rejects valid type when it is a nested member template Product: gcc Version: 10.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: waffl3x at protonmail dot com Target Milestone: --- https://godbolt.org/z/5hG9Eqhc9 struct A { template<typename> using B = int; }; inline constexpr bool go = requires{typename A::template B<int>;}; error: 'typename A::B' names 'template<class> using B = int', which is not a type I believe this is not a regression as the bug exists all the way back to 10.1 (assuming I understand what regression means) Clang and MSVC accept this code, I assume GCC is incorrect since I couldn't find anything specifying that a member template is not allowed, however I also haven't found anything that specifies that it is allowed so I am not certain. The behavior exists in all versions I checked since GCC 10.1