[Bug c++/72756] New: Using an enum as a constant expression via dot operator should not compile.

[claas.bontus at web dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72756

            Bug ID: 72756
           Summary: Using an enum as a constant expression via dot
                    operator should not compile.
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: claas.bontus at web dot de
  Target Milestone: ---

This is a follow up from discussion at
http://stackoverflow.com/q/38398475/3876684

The following should not compile, since enum m is accessed via dot operator at
//1. Compiler should at least emit a warning.

template<size_t n> struct A{};

template<size_t n>
struct tst
{   enum : size_t { m= n % 15 };

    template<size_t p>
    void
    call( tst<p> const &t2 ) {
        A<t2.m>  a; // 1
    }
};