C++运算符重载的问题...

class Integer
{
private:
    int data;
public:
    Integer(int a):data(a){}
    Integer operator-(Integer &another)
    {
        Integer tmp(0);
        tmp.data= this->data-another.data;
        return tmp;
    }
    void show()
    {
        cout<<data<<endl;
    }
};

tmp= this->data-another.data;这样不写成tmp.data编译器也没报错，执行结果也正确，C++是会自动匹配吗