[Bug c++/88252] New: Deduction guide assume the constructor parameter is a forwarding reference if constructor defined outside class

[okannen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88252

            Bug ID: 88252
           Summary: Deduction guide assume the constructor parameter is a
                    forwarding reference if constructor defined outside
                    class
           Product: gcc
           Version: 8.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: okannen at gmail dot com
  Target Milestone: ---

Constructor parameter that have the forms of a forwarding reference (T&&)
inside a constructor are not forwarding reference if T is a parameter of the
class template. But gcc assumes it is a forwarding reference if the constructor
is defined outside the class:


template<typename T>
struct B1 {
    B1(T&& x){}
};

template<typename T>
struct B2 {
    B2(T&& x) ;
};
template<typename T>
B2<T>::B2(T&& x){}

int i;
B1 a{i};//Expect: compilation error, class template argument deduction failed
B2 b{i};//Unexpected: no compilation error.