How to check if given type of template function was created?

I would like to detect cycles in class dependency by trying to check if given function was create.

template < class PA, class CH>
void dependsOn( PA* , CH* )
{
    #pragma message("COMPILE: " __FUNCSIG__)
    static_assert(!std::is_function< decltype(dependsOn<PA, CH>) >::value,"Cycle in dependencies");
}

Each class will call that template function class B();

class A{
    B b;
public:
    A(){ dependsOn(this, &b);}
}

However this check is not working as is_function returns always true, no matter if such template function was created or not.