[Bug c++/56452] New: [C++11] Using declaration for inheriting constructors taints template parameter

["lucdanton at free dot fr" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56452

             Bug #: 56452
           Summary: [C++11] Using declaration for inheriting constructors
                    taints template parameter
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: lucdanton@free.fr


Created attachment 29537
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29537
Minimal reproducible testcase

$ g++-snapshot --version
g++-snapshot (Debian 20130222-1) 4.8.0 20130223 (experimental) [trunk revision
196236]

$ cat main.cpp 
struct foo {
    explicit foo(int) {}
};

template<typename T>
struct bar: T {
    using T::T;

    // Bad
    explicit bar(): T(0) {}

    void baz()
    {
        // Also bad
        using qux = T;
    }
};

int main()
{}

$ g++-snapshot -std=c++11 -pthread main.cpp 
main.cpp: In constructor 'bar<T>::bar()':
main.cpp:10:21: error: 'using T::T' is not a non-static data member of 'bar<T>'
     explicit bar(): T(0) {}
                     ^
main.cpp: In member function 'void bar<T>::baz()':
main.cpp:15:21: error: expected type-specifier before 'T'
         using qux = T;
                     ^

---

If the using declaration is commented out, then things proceed as usual. It is
also possible to alias the template parameter before the using declaration
(e.g. using base_type = T;) to substitute for uses of T after the declaration.
Because this doesn't happen if bar is not a template, I don't think it is
intended.