std::bind 是否丢弃 C++11 中参数的类型信息?

Please consider the following c++ code:

#include <functional>
#include <iostream>
#include <string>

// Superclass
class A {
    public:
    virtual std::string get() const {
        return "A";
    }
};

// Subclass
class B : public A {
    public:
    virtual std::string get() const {
        return "B";
    }
};

// Simple function that prints the object type
void print(const A &instance) {
    std::cout << "It's " << instance.get() << std::endl;
}

// Class that holds a reference to an instance of A
class State {
    A &instance;
    public:
    State(A &instance) : instance(instance) { }
    void run() {

        // Invokes print on the instance directly
        print(instance);

        // Creates a new function by binding the instance
        // to the first parameter of the print function, 
        // then calls the function. 
        auto func = std::bind(&print, instance);    
        func();
    }    
};

int main() {
    B instance;
    State state(instance);

    state.run();
}

在这个例子中，我们有两个类 A 和 B.B 继承自类 A.这两个类都实现了一个返回类型名称的简单虚方法.

auto func = std::bind(&print, std::ref(instance));
//                            ^^^^^^^^