bind class member funtion to std::function not need check parameters? - c++

Question

why gcc 9.4 not check parameters when bind a class member funtion to a std::function viriable, but check when bind a global function? here is example code, CreateRpcFun has a parameter, but Test member function print doesn't have any other parameters except this, bind print to CreateRpcFun works well, but global funtion print2 cannot, can anybody explain why?
#include <functional>
#include <iostream>
#include <string>
using namespace std;
using CreateRpcFun = std::function<void(const string &)>;
class Test {
public:
Test() : str_("nihao!") {}
// bind print to CreateRpcFun passed compile
void print() { cout << str_ << endl; }
private:
string str_;
};
class Holder {
public:
CreateRpcFun CreateRpc;
};
class Other {
public:
Other(Holder h, string str) : h_(h), str_(str) {}
void run() { h_.CreateRpc("world!"); }
private:
Holder h_;
string str_;
};
void print1(const string &str) { cout << str << endl; }
void print2() { cout << "magic" << endl; }
int main() {
Test t;
Holder h;
h.CreateRpc = std::bind(&Test::print, &t);
Other o(h, "hhhh");
o.run();
h.CreateRpc = &print1;
h.CreateRpc("test");
// h.CreateRpc = &print2; // compile error
// h.CreateRpc("test");
}