[Bug libstdc++/47380] New: concept checking and incomplete types

["marc.glisse at normalesup dot org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47380

           Summary: concept checking and incomplete types
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: marc.glisse@normalesup.org


The following code compiles fine in normal mode, but not with
-D_GLIBCXX_CONCEPT_CHECKS, which basically thinks the types are incomplete. Is
this a known limitation?
(by the way, the relevant doc still says C++0x will have concepts)

#include <map>

template<typename T, typename U> struct A;

template< typename T> struct B {
        typedef A<T,B> Handle;
        std::map<int,Handle> y;
};

template<typename T, typename U = B< T> >
struct A : U { };

int main(){
        A<int> x;
}