C++11 特性：成员函数引用限定 （Reference qualifier）

#include <iostream>

struct Test {
    void workLvalue() & {
        std::cout << " work only if object was a lvalue\n";
    }
    void workRvalue() && {
        std::cout << " work only if object was a rvalue\n";
    }
};

int main() {
    Test t;
    t.workLvalue();     //ok
    
    t.workRvalue();     //不能编译

    Test{}.workRvalue();//ok
    Test{}.workLvalue();//不能编译
    return 0;
}