bind binded function as argument

I have a class foo with a method bar which takes something callable (function-pointer/ functor). this callable something should be passed to another method doit as an binded element with a third method bar_cb method.

#include <functional>
#include <iostream>

class foo {
public:
    template<typename T>
    void bar(T&& t) {
        std::cout << "bar\n";
        doit(std::bind(&foo::template bar_cb<T>, this, std::forward<T>(t)));
    }

    template<typename T>
    void doit(T&& t) {
        std::cout << "doit\n";
        t();
    }

    template<typename T>
    void bar_cb(T&& t) {
        std::cout << "bar_cb\n";
        t();
    }
};


void lala() {
    std::cout << "lala\n";
}

class functor {
public:
    void operator()() {
        std::cout << "functor::operator()\n";
    }
};


int main() {
    foo f;
    functor fn;
    f.bar(fn);
    f.bar(std::bind(lala));  // error

    return 0;
}

This works fine for functors but not for binded functions as argument for foo::bar (lala in my example). Is it possible to pass an unknowable type to a method and bind it in this method as an argument to another (and if so how)?

I know I could wrap a functor (std::function for example) around the function but since I can call an unknowable type I think there is a way to also bind it (I think I'm just missing something simple).

Here an link to an example.