[Bug c++/93809] bogus error class tag used in naming union on typedef typename ::U U2

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93809

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 51939
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51939&action=edit
untested patch