PolymorphicCloneOwner.cpp

struct Interface1
{
    virtual owner<Interface1*> clone() const = 0;
    //...
};
 
struct Interface2
{
    virtual owner<Interface2*> clone() const = 0;
    //...
};
 
class Implementation : public Interface1, public Interface2
{
public:
    virtual owner<Implementation*> clone() const override
    {
        return new Implementation(*this);
    }
    //...
};