[Bug c++/107126] GCC accepts invalid out of class definition for destructor with C++17

["jlame646 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107126

--- Comment #5 from Jason Liam <jlame646 at gmail dot com> ---
(In reply to Jakub Jelinek from comment #4)
> (In reply to Jason Liam from comment #2)
> > Second, i'm already aware that this is rejected by gcc with c++20 as i
> > provided a demo link https://godbolt.org/z/TYjEzss6q at the first line of my
> > bug report.
> 
> One thing is to know that some versions of g++ do that, but the above
> provides details on what change actually changed the behavior, which is
> useful information for any further changes.
> Then it is https://cplusplus.github.io/CWG/issues/1435.html which we perhaps
> don't implement or don't implement fully.

Note that the program shown in this bug is ill-formed in all c++ versions
including c++17. That is, it is different from
https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2237 because that
cwg defect report only talks about declarations that are in the member
specification of the class and not in the namespace scope.

This means that the program shown in that cwg defect report is ill-formed only
from c++20 and onwards. But the program shown in my bug is ill-formed with all
modern c++ version including c++17. So this is a different bug.