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struct B {};
struct D : B {};
 
template<typename T>
class MyPtr
{
public:
    MyPtr(T* t) : t(t) {}
 
    template <typename U>
    MyPtr(U*) = delete;
 
    MyPtr operator = (T* t) { this->t = t; }
 
    template <typename U>
    MyPtr operator = (U* t) = delete;
 
    operator T* () const { return t; }
 
private:
    T* t;
};
 
int main()
{
    D d;
    B* bd = &d;
    MyPtr<B> pd = &d;
    MyPtr<B> n = nullptr;
}
 

prog.cpp: In function 'int main()':
prog.cpp:28:20: error: use of deleted function 'MyPtr<T>::MyPtr(U*) [with U = D; T = B]'
     MyPtr<B> pd = &d;
                    ^
prog.cpp:11:5: note: declared here
     MyPtr(U*) = delete;
     ^

Standard output is empty