#include <iostream>
#include <type_traits>
using namespace std;
 
template<class T>
struct Base {
    string name = "Base";
    void print() const {
        cout << name << endl;
        cout << static_cast<const T&>(*this).name << endl;
    }
};
 
struct Derived1 : public Base<Derived1> {
    string name = "Derived1";
};
 
struct Derived2 { // こいつを弾く仕組みが欲しい
    string name = "Derived2";
};
 
// 関数テンプレートは部分特殊化できないためこんぱいるえらー
template <class T, bool b = is_base_of<Base<T>, T>::value>
ostream& operator << (ostream& os, const Base<T>& base) {
    static_assert(b, "T is not derived from Base<T>");
}
 
template <class T>
ostream& operator << <T, true> (ostream& os, const Base<T>& base) {
    base.print();
    return os;
}
 
int main(){
    // Derived1 d1;
    // Derived2 d2;
    // f(d1);
    // f(d2);
    return 0;
}
 

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