#include <cassert>
#include <memory>

class Base {
    int observed_;
public:
    Base() : observed_(kind()) {}
    virtual int kind() const { return 1; }
    int observed_during_construction() const { return observed_; }
    virtual std::unique_ptr<Base> clone() const = 0;
    virtual ~Base() = default;
};

class Derived final : public Base {
public:
    int kind() const override { return 2; }
    std::unique_ptr<Base> clone() const override {
        return std::make_unique<Derived>(*this);
    }
};

std::unique_ptr<Base> make_object() {
    return std::make_unique<Derived>();
}

int main() {
    auto object = make_object();
    assert(object->observed_during_construction() == 1);
    assert(object->kind() == 2);
    auto copy = object->clone();
    assert(copy.get() != object.get());
    assert(copy->kind() == 2);
}