[Bug c++/65221] New: typedef-name identifier not resolved in static member instantiation

["pit at shgn dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65221

            Bug ID: 65221
           Summary: typedef-name identifier not resolved in static member
                    instantiation
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pit at shgn dot de

Consider the following minimal example:

template< typename A >
struct X
{
  using this_type = X<A>;
//  typedef X<A> this_type;
  static this_type inst;
};

template< typename A >
X<A> X<A>::inst;

g++ 4.9.1 (Debian 4.9.1-19) produces the following error:

$ g++ --std=c++11 -c test.cpp

test.cpp:10:12: error: conflicting declaration âX<A> X<A>::instâ
 X<A> X<A>::inst;
            ^
test.cpp:6:20: note: previous declaration as âX<A>::this_type X<A>::instâ
   static this_type inst;
                    ^
test.cpp:10:12: error: declaration of âX<A>::this_type X<A>::instâ
outside of class is not definition [-fpermissive]
 X<A> X<A>::inst;

I expected the compiler to resolve the typedef-name from the
alias-declaration when instantiating the static member.  If we
use this_type instead of the type directly:

template< typename A >
const typename X<A>::this_type X<A>::inst;

the code compiles again. I assume that gcc is unable to map X<A> to the
alias-declaration this_type.  Commenting out the alias declaration and
using the typedef line solves the problem.  The standard however states
in Â7.1.3 (2):

A typedef-name can also be introduced by an alias-declaration. The
identifier following the using keyword becomes a typedef-name and the
optional attribute-specifier-seq following the identifier appertains to
that typedef-name. It has the same semantics as if it were introduced by
the typedef specifier. In particular, it does not define a new type and
it shall not appear in the type-id.