I/O流操作符和前/后递增/递减操作符重载错误

这是我在网站上发现的代码，我正在学习c++。我不知道如何调试程序，所以我不知道问题出在哪里。

#include <iostream>
using namespace std;
class Complex
{
int real;
int img;
public:
Complex()
{
    real = 0;
    img = 0;
}
Complex(int r, int i)
{
    real = r;
    img = i;
}
Complex& operator++();
Complex operator++(int);
friend Complex operator+(Complex &a, Complex &b);
friend ostream& operator<<(ostream &out, Complex &a);
friend istream& operator>>(istream &in, Complex &a);
void display()
{
    using namespace std;
    cout << real << " + " << img << endl;
}
};
Complex& Complex::operator++()
{
    ++real;
    ++img;
    return *this;
}
Complex Complex::operator++(int)
{
    Complex temp(*this);
    ++(*this);
    return temp;
}
Complex operator+(Complex &a, Complex &b)
{
    int x = a.real + b.real;
    int y = a.img + b.img;
    return Complex(x, y);
}
ostream& operator<<(ostream &out, Complex &a)
{
    using namespace std;
    out << a.real << " + " << a.img << endl;
    return out;
}
istream& operator>>(istream &in, Complex &a)
{
    using namespace std;
    cout << "Enter the real part" << endl;
    in >> a.real;
    cout << "Enter the imaginary part" << endl;
    in >> a.img;
    return in;
}
int main()
{
    Complex a;
    cin >> a;
    Complex b(11,8);
    cout << "a is :" << a << endl;
    cout << "b is :" << b << endl;
    Complex c = Complex(a + b);
    cout << "c is :" << c << endl;
    cout << c;
    cout << c++;
    cout << c;
    cout << ++c;
    cout << c;
}

当我试图在main()中增加Complex的实例时，编译器给出了错误。在我看来，一切都是正确的，但是Code::Blocks给出了这些错误:

1. error: cannot bind 'std::ostream {aka std::basic_ostream<char>}' lvalue to 'std::basic_ostream<char>&&'|

2. error: initializing argument 1 of 'std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&&, const _Tp&) [with _CharT = char; _Traits = std::char_traits<char>; _Tp = Complex]|

现在这让我相信(重载)I/O操作符有一些特殊的规则，为了使用(重载)自增/自减操作符，应该遵循这些规则。

问题:

1. 这是真的，还是我没有捕捉到的代码中有问题?我是这个领域的初学者。

2. 是否重载输出/输入操作符和自增(post,pre)/自减操作符有一些额外的规则来一起使用它们?

注:如:请原谅我的英语很差谢谢