[Bug c++/102175] New: Error comparing the pointers on static class fields in static_assert

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102175

            Bug ID: 102175
           Summary: Error comparing the pointers on static class fields in
                    static_assert
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

This code:
```
template<int N> struct C { 
    static int x; 
};

template<int N> int C<N>::x = 0;

int main() { 
    static_assert(&C<0>::x != &C<1>::x); 
}
```
produces an error in GCC: "non-constant condition for static assertion", but
accepted in other compilers. Demo: https://gcc.godbolt.org/z/o6dE3GaMK

A similar code without templates is accepted by GCC:
```
struct C { static int x; };
int C::x = 0;
struct D { static int x; };
int D::x = 0;
int main() { static_assert( &D::x != &C::x ); }
```