[Bug c++/91826] [8/9/10 Regression] Unexpected behavior when class defined with namespace alias

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91826

--- Comment #4 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
Fixed master feaa1640b3543c7c3a1f3a788bc449a3638cb780, will backport