https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110936
--- Comment #2 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> --- FWIW, it seems that you can use <https://quuxplusone.github.io/blog/2022/01/04/test-constexpr-friendliness/> to test the validity during constant evaluation. It seems that an invalid constant expression implies a `false` result. So I guard the check with a validity check: <https://compiler-explorer.com/z/had59d6nv>. ```C++ #include <type_traits> template<auto F> concept is_constant = requires { typename std::integral_constant<int, (F(), 0)>; }; template<auto l, auto r> constexpr bool implements() { using R = decltype(r); if constexpr (requires { static_cast<R>(l); }) #if !defined(__GNUC__) || defined(__clang__) return static_cast<R>(l) != r; #else // Workaround <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71962>. return !is_constant<[]() { return static_cast<R>(l) != r; }> || static_cast<R>(l) != r; #endif return false; } struct B { void f(); }; struct D0 : B { }; struct D1 : B { void f(); }; struct D2 : B { void f() const; }; // struct D3 : B { int f(); void f() const; }; static_assert(!implements<&D0::f, &B::f>()); static_assert(implements<&D1::f, &B::f>()); static_assert(!implements<&D2::f, &B::f>()); // static_assert(!implements<&D3::f, &B::f>()); ```
