c++ 函数重载中 fatal error C1001: INTERNAL COMPILER ERROR 是什么原因？谢谢

#include<iostream>
using namespace std;

class Complex
{public:
Complex(){real=0;imag=0;}
Complex(double r,double i) {real=r;imag=i;}
friend Complex operator+(Complex &c1,Complex &c2);
void display();
private:
double real;
double imag;
};


Complex operator+(Complex &c1,Complex &c2)
{return Complex(c1.real+c2.real,c1.imag+c2.imag);}

void Complex::display()
{cout<<"("<<real<<","<<imag<<"i)"<<endl;}

int main()
{
Complex c1(3,4),c2(5,-10),c3;
c3=c1+c2;
cout<<"c1=";c1.display();
cout<<"c2=";c2.display();
cout<<"c1+c2=";c3.display();
return 0;
}

缺少Complex(Complex & c) {real=c.r;imag=c.i;}