[Bug c++/60894] [4.8/4.9/5 Regression] Use of redundant struct keyword in function prototype combined with using statement causes compilation error

[fabien at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60894

--- Comment #9 from fabien at gcc dot gnu.org ---
(In reply to Jason Merrill from comment #8)
> (In reply to fabien from comment #6)
> > I looked into it but did not manage to get it fixed. I will have another try
> > this week. Thanks for the reminder.
> 
> Ping?

I have a patch for it, but not perfect as it triggers a minor diagnostic
regression about class-type redefinition in presence of using decl at class
scope. The using decl is no longer mentioned in the diagnostic... I'll try to
make it work, otherwise I would ask you some help...