Ошибка E0349 отсутствует оператор "="

#include <math.h>
#include <iostream>
#include<string>
#define Pi 3.1415
 
using namespace std;
 
class Figure
{
public:
 
    Figure(void) { mRadius = mCoord.x = mCoord = 0.0; }
    Figure(double _x, double _y, double _r) { mRadius = _r; mCoord.x = _x; mCoord.y = _y; }
 
    void move(double _x, double _y) { mCoord.x = _x, mCoord.y = _y; }
 
    virtual double area(void) const = 0;
    virtual double volume(void) const { return 0.0; }
    virtual void print(void) const = 0;
 
protected:
    struct { double x, y; } mCoord;
    double mRadius;
 
    void prPrint(void) const {
        std::cout << "\tCoordinates (x, y): " << mCoord.x << ", " << mCoord.y << std::endl
            << "\tRadius: " << mRadius << std::endl;
    }
};
 
class Circle : public Figure
{
public:
    Circle(void) : Figure() {}
    Circle(double _x, double _y, double _r) : Figure(_x, _y, _r) {}
 
    virtual double area(void) const override { return mRadius * mRadius * Pi; }
    virtual void print(void) const override {
        std::cout << "Figure type: Circle" << std::endl
            << "{" << std::endl;
        prPrint();
        std::cout << "\tArea: " << area() << std::endl
            << "}" << std::endl;
    }
};
 
class Sphere : public Figure
{
public:
    Sphere(void) : Figure() {}
    Sphere(double _x, double _y, double _r) : Figure(_x, _y, _r) {}
 
    virtual double area(void) const override { return 4 * Pi * mRadius * mRadius; }
    virtual double volume(void) const override { return 4 / 3 * Pi * mRadius * mRadius * mRadius; }
    virtual void print(void) const override {
        std::cout << "Figure type: Sphere" << std::endl
            << "{" << std::endl;
        prPrint();
        std::cout << "\tSurface area: " << area() << std::endl
            << "\tVolume: " << volume() << std::endl
            << "}" << std::endl;
    }
};