[Bug c++/96330] New: Constexpr variables cannot be used in the template context.

[steve_green at qq dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96330

            Bug ID: 96330
           Summary: Constexpr variables cannot be used in the template
                    context.
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: steve_green at qq dot com
  Target Milestone: ---

demo code:
struct foo_t {
    template<class T>
        static constexpr bool bar = true;
};
inline constexpr foo_t foo{};

template<class T>
    struct baz {
        static_assert(foo.bar<T>); // bug in clang (before instantiation) and
gcc (during instantiation)
        static_assert(foo_t::bar<T>); // OK
    };

int main()
{
    static_assert(foo.bar<void>, ""); // OK
    static_assert(foo_t::bar<void>, ""); // OK
    static_cast<void>(baz<void>{});
}