Why is move constructor not picked when returning a local object of type derived from the function's return type?

Question

The following code is rejected by both Clang and GCC (trunk versions):

#include 

struct Base 
{
    Base() = default; 
    Base(Base const&         


        

Answer 1

[class.copy]/32 continues:

[...] if the type of the first parameter of the selected constructor is not an rvalue reference to the object's type (possibly cv-qualified), overload resolution is performed again, considering the object as an lvalue.

The first overload resolution, treating d as an rvalue, selects Base::Base(Base&&). The type of the first parameter of the selected constructor is, however, not Derived&& but Base&&, so the result of that overload resolution is discarded and you perform overload resolution again, treating d as an lvalue. That second overload resolution selects the deleted copy constructor.