How to detect if a method is virtual?

Question

I tried to make a traits to find if a method is virtual: (https://ideone.com/9pfaCZ)

// Several structs which should fail depending if T::f is v         


        

Answer 1

The code isn't perfect but it basically passes the tests (at least in all clangs available on wandbox and gcc since 7.):

#include 

template 
using void_t = void;

template >
struct can_be_compaired: std::false_type { };

template 
struct can_be_compaired>: std::true_type { };

template 
struct has_virtual_f: std::false_type { };

template 
struct has_virtual_f>{
    constexpr static auto value = !can_be_compaired::value;
};

struct V  { virtual void f() { }      };
struct NV {         void f() { }      };
struct E  {                           };
struct F  { virtual void f() final{ } }; // Bonus (unspecified expected output)

int main() {
   static_assert( has_virtual_f< V>::value, "");
   static_assert(!has_virtual_f::value, "");
   static_assert(!has_virtual_f< E>::value, "");
   static_assert( has_virtual_f< F>::value, "");
}

[live demo]

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The relevant standard parts that theoretically let the trait fly: [expr.eq]/4.3, [expr.const]/4.23