operator ->重载是怎么做到的?

https://stackoverflow.com/questions/8777845/overloading-member-access-operators-c

struct client
    { int a; };

struct proxy {
    client *target;
    client *operator->() const
        { return target; }
};

struct proxy2 {
    proxy *target;
    proxy &operator->() const
        { return * target; }
};

void f() {
    client x = { 3 };
    proxy y = { & x };
    proxy2 z = { & y };

    std

并非如普通操作符一样在class内部定义一个函数做重载,而是通过一个代理类.