https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103081
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed on the GCC 11 branch head and trunk. clang complains:
> clang++-11 -S t.C -std=c++20
t.C:4:9: error: expected unqualified-id
using enum Pig;
^
t.C:10:18: error: no member named 'OINK' in 'Hog'
(void)Hog(Hog::OINK);
~~~~~^
2 errors generated.
