[Bug c++/86301] g++ does not mark declarations used in non-dependent types as referenced

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86301

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to zhonghao from comment #2)
> (In reply to Jonathan Wakely from comment #1)
> > (In reply to zhonghao from comment #0)
> > > A previous version of clang++ produces similar error message for this code,
> > > but was fixed.
> > 
> > No it didn't, the error shown in the Clang bug comes from GCC!
> > 
> > Please make more effort to understand what you are doing, OR I WILL BAN YOUR
> > ACCOUNT.
> 
> Did you try the latest g++ and clang++.

Yes.

> They produce different results when
> they compile the code. My clang is 7.0.0. It does not produce any error
> messages for this code.

That doesn't mean the code is valid.

> Do the difference indicate bugs in g++?

No. See https://gcc.gnu.org/gcc-7/porting_to.html#hypothetical-instantiation