CWG 2024-06-28

CWG opined that, contrary to the assertion in the issue, the treatment of non-templated class definitions should be changed to more closely resemble templated ones. This direction is covered by issue 2335.

The Standard should make clear that a constexpr member function cannot be used in a constant expression until its class is complete. For example:

  template<typename T> struct C {
    template<typename T2> static constexpr bool _S_chk() {
      return false;
    }
    static const bool __value = _S_chk<int>();
  };

  C<double> c;

Current implementations accept this, although they reject the corresponding non-template case:

  struct C {
    static constexpr bool _S_chk() { return false; }
    static const bool __value = _S_chk();
  };

  C c;

Presumably the template case should be handled consistently with the non-template case.