[Bug c++/124214] New: Templated class with static constexpr method compiles without warning about non C++11 compliant body

[giovanni.gaio at proton dot me via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124214

            Bug ID: 124214
           Summary: Templated class with static constexpr method compiles
                    without warning about non C++11 compliant body
           Product: gcc
           Version: 15.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: giovanni.gaio at proton dot me
  Target Milestone: ---

Consider the following:

template< typename T = int >
class foo {

    public:
    static constexpr int bar(T x){
        (void) x;
        return 42;
    }
};

int f(int x){
    return foo<>::bar( x );
}

This is NOT valid C++11 as the constexpr function contains a return statement
and a non-null statement. So compiling with -std=c++11 should raise an error
but doesn't.

Live demonstration: https://godbolt.org/z/8n6PPvoP8

An error is correctly raised with GCC11.5, but not later versions