template <class Ptr, class Class, class Res, class... ArgTypes>
Function<Res (ArgTypes...)> MemFn(Ptr object, Res (Class::*method)(ArgTypes...))
{
	return [=](ArgTypes... args) { return (object->*method)(args...); };
}

#define THISFN(x)   MemFn(this, &CLASSNAME::x)

#define THISFN(memfun) std::bind_front(&std::remove_cvref_t<decltype(*this)>::memfun, this)

class MyClass
{
    typedef MyClass CLASSNAME;
//....
}

	menu.Set( THISFN(MenuMain) );

	menu.Set ( [=, this] ( Bar & bar )
		{
			MenuMain ( bar );
		}
	);

#ifdef THISFN
#    undef THISFN
#    define THISFN(memfun) ....
#endif