Forwarding references for non-reference types

Question

 template
 void F(T&& x) {}

If we call it with argument of type int& everything is clear - reference collapsing takes pla

Answer 1

Forwarding references deduce lvalue reference for lvalues and rvalue reference for rvalues. For example, even for lvalue of type int&& it will still deduce int& (as it would for lvalue of type int), likewise, for rvalues of type int or int&& it will deduce int&&:

template
class show;

template
void F(T&& x) 
{ show();}

int main() {
    int&& x = 5;
    F(x);
}

main.cpp:6:3: error: implicit instantiation of undefined template 'show'

int main() {
    F(5);
}

main.cpp:6:3: error: implicit instantiation of undefined template 'show'

int main() {
    int x = 5;
    F(x);
}

main.cpp:6:3: error: implicit instantiation of undefined template 'show'

int main() {
    F([]()->int{return 5;}());
}

main.cpp:6:3: error: implicit instantiation of undefined template 'show'