#include <iostream>
#include <functional>
#include <string>
using namespace std;
class Msg {
public:
    void parse(const std::string &s) {
        x = int(s[0]);
    }
    int x = 0;
};
class C {
public:
    C(function<void(const std::string &)> cb)
        : cb_(cb)
    {}
    template<typename TMsg>
    C(function<void(const TMsg &)> cb)
        : C([&, cb](const std::string &s) {
                TMsg m;
                m.parse(s);
                cb(m);
          })
    {}
    void test() {
        cb_("foo");
    }
    function<void(const std::string &)> cb_;
};
void cb1(const string &s) {
    cout << "cb1: " << s << endl;
}
void cb2(const Msg &msg) {
    cout << "cb2: Msg{x=" << msg.x << "}" << endl;
}
int main() {
    C c1(&cb1), c2(&cb2);
    c1.test();
    c2.test();
    return 0;
}

test_func_arg_overload.cpp:39:17: error: no matching constructor for initialization of 'C'
    C c1(&cb1), c2(&cb2);
                ^  ~~~~
test_func_arg_overload.cpp:12:7: note: candidate constructor (the implicit move constructor) not
      viable: no known conversion from 'void (*)(const Msg &)' to 'C' for 1st argument
class C {
      ^
test_func_arg_overload.cpp:12:7: note: candidate constructor (the implicit copy constructor) not
      viable: no known conversion from 'void (*)(const Msg &)' to 'const C' for 1st argument
class C {
      ^
test_func_arg_overload.cpp:14:5: note: candidate constructor not viable: no known conversion from
      'void (*)(const Msg &)' to 'function<void (const std::string &)>' (aka 'function<void (const
      basic_string<char, char_traits<char>, allocator<char> > &)>') for 1st argument
    C(function<void(const std::string &)> cb)
    ^
test_func_arg_overload.cpp:19:5: note: candidate template ignored: could not match 'function<void
      (const type-parameter-0-0 &)>' against 'void (*)(const Msg &)'
    C(function<void(const TMsg &)> cb)
    ^
1 error generated.