fork download

#include <type_traits>
 
template <typename T, typename TMethod>
class has_bar_method
{
private:
	struct yes { char _; };
	struct no { char _[2]; };
	template <typename U, TMethod = &U::Bar>
	static yes impl(U*);
	static no impl(...);
 
public:
	enum { value = sizeof(impl(static_cast<T*>(nullptr))) == sizeof(yes) };
};
 
template <class T>
class A
{
private:
 
public:
   void Foo(T& b)
   {
   	   static_assert(has_bar_method<T, void (T::*)(float)>::value, "T has method void Bar(float)");
 
       b.Bar(0.5);
   }
};
 
class B
{
public:
    //void Bar(float) {}
    void Bar(double) {}
    void Bar(int) {}
};
 
int main() {
	A<B> a;
	B b;
 
	a.Foo(b);
 
	return 0;
}

prog.cpp: In instantiation of ‘void A<T>::Foo(T&) [with T = B]’:
prog.cpp:43:9:   required from here
prog.cpp:25:8: error: static assertion failed: T has method void Bar(float)
        static_assert(has_bar_method<T, void (T::*)(float)>::value, "T has method void Bar(float)");
        ^

Standard output is empty