[patch] c++/58051 Implement Core 1579

[Marc Glisse]

On Tue, 1 Jul 2014, Markus Trippelsdorf wrote:

> This patch cause yet another LLVM build error:
[...]
> Reduced:
>
> markus@x4 llvm_build % cat CompilerInvocation.ii
> template <typename T> class A
> {
>  T Obj;
>
> public:
>  T element_type;
>  A (T *);
>  template <class X> A (A<X> &&p1) { p1.Obj; }
>  template <class X> A (A<X> &);
> };
>
> class B
> {
> public:
>  B (A<int>);
> };
> A<int> fn1 ()
> {
>  A<B> a (new B (0));
>  return a;
> }
>
> markus@x4 llvm_build % /var/tmp/gcc_test/usr/local/bin/g++ -c -std=c++11 CompilerInvocation.ii
> CompilerInvocation.ii: In instantiation of Β‘A<T>::A(A<X>&&) [with X = B; T = int]Β’:
> CompilerInvocation.ii:20:10:   required from here
> CompilerInvocation.ii:3:5: error: Β‘B A<B>::ObjΒ’ is private
>   T Obj;
>     ^
> CompilerInvocation.ii:8:38: error: within this context
>   template <class X> A (A<X> &&p1) { p1.Obj; }
>                                      ^

This looks invalid. As the core issue says, the return statement looks up 
a as an rvalue, so it uses that constructor for A<int>, and that uses a 
private member of a different specialization of A, which is illegal.

-- 
Marc Glisse