[Bug c++/57401] New: 'Conflicting declaration' involving using declaration and dependent name

[lucdanton at free dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57401

            Bug ID: 57401
           Summary: 'Conflicting declaration' involving using declaration
                    and dependent name
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lucdanton at free dot fr

Using 4.9.0 20130509 (experimental) [trunk revision 198734] with flags
-std=c++11:

$ cat main.cpp 
struct base {
    using base_type = base;
    using type = int;
};

template<typename T>
struct derived: T {
    using typename derived::base_type::type;

    // Uses of once dependent type, explicitly introduced
    // into scope by using declaration above -- no complaints
    type foo(type);

    // No complaints as well
    static type t;
};

// Error: conflicting declaration
template<typename T>
typename derived<T>::type derived<T>::t = 0;

int main()
{}

//-------------------

$ g++-snapshot -std=c++11 main.cpp 
main.cpp:20:39: error: conflicting declaration 'typename derived<T>::type
derived<T>::t'
 typename derived<T>::type derived<T>::t = 0;
                                       ^
main.cpp:15:17: error: 'derived<T>::t' has a previous declaration as 'typename
derived<T>::base_type::type derived<T>::t'
     static type t;
                 ^
main.cpp:20:39: error: declaration of 'typename derived<T>::base_type::type
derived<T>::t' outside of class is not definition [-fpermissive]
 typename derived<T>::type derived<T>::t = 0;
                                       ^

I suspect the code is wrongly rejected, as demonstrated by the other uses of
type as if it weren't a dependent type anymore. (Admittedly writing a
definition of foo that matches the declaration can be troublesome, but I assume
this is the same issue in another form.) If it is any indication, Clang accepts
the code.