Template class works fine in Visual Studio but gets errors in Linux

Question

//my template class
#include "shape.h"
#include <iostream>
using namespace std;
template <typename T>
//error : shadows template parm????
class CCircle : public CShape {
private:
    T Radius;
public:
    CCircle() {}
    CCircle(int a, int b, T r) {
        x = a;
        y = b;
        Radius = r;
    }
    double GetArea() {
        return Radius * Radius * 3.14;
    }
    void Print() {
        cout << GetArea() << endl;
    }
    template <typename T>
    friend ostream& operator << (ostream& out, CCircle<T>& Po);

    template <typename T>
    CCircle operator+(const CCircle<T>& p) {
        return CCircle(x, y, Radius + p.Radius);
    }


};

template <typename T>
ostream& operator << (ostream& out, CCircle<T>& Po) {
    out << "Area: " << Po.GetArea() << endl;
    return out;
}