#include <iostream>
 
struct CopyOnly
{
    CopyOnly() = default;
    CopyOnly(const CopyOnly&) = default;
    CopyOnly(CopyOnly&&) = delete;
};
 
struct Verbose
{
    Verbose() { std::cout << "default constructor" << std::endl; }
    Verbose(const Verbose&) { std::cout << "copy constructor" << std::endl; }
    Verbose(Verbose&&) { std::cout << "move constructor" << std::endl; }
};
 
struct A : CopyOnly, Verbose {};
 
void  foo(A &&x){ std::cout<<"&&" <<std::endl; A a(std::move(x));}
 
void  foo(A &x){ std::cout<<"&" <<std::endl; A a(x);}
 
int main() {
    foo(A()); // prints &&
    A a;
    foo(a); // prints &
    return 0;
}
 

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