[Bug c++/63139] New: Class-scope typedef overwrites typedef of previously defined class

[david.d.kretzmer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63139

            Bug ID: 63139
           Summary: Class-scope typedef overwrites typedef of previously
                    defined class
           Product: gcc
           Version: 4.9.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.d.kretzmer at gmail dot com

In GCC 4.8 and 4.9 (4.7 seems to work correctly) a type alias inside a class
seems to overwrite under certain conditions a type alias of the same name in a
previously defined class.
Code to reproduce this bug:

------------------------------------------------------------
#include <type_traits>

template<typename ...T>
struct type_list {};

template<typename ...T>
struct make_type_list
{
    using type = type_list<T...>;
};

// The bug disappears if you use make_type_list directly.
template<typename ...T>
using make_type_list_t = typename make_type_list<T...>::type;


struct ContainerEndA {};

template<typename ...Ts>
struct ContainerA
{
    using type = make_type_list_t<Ts..., ContainerEndA>;
};


struct ContainerEndB {};

//template<typename Head, typename ...Lists>    // If you use this line instead
of the next a Internal compiler error is generated.
template<typename ...Ts>
struct ContainerB
{
    using type = make_type_list_t<Ts..., ContainerEndB>;
};


int main()
{
    // To see the types in ContainerA<>::type uncomment the following line.
    //
    //ContainerA<>::type::doesnt_exist; 
    //
    // GCC error: ‘doesnt_exist’ is not a member of ‘ContainerA<>::type {aka
type_list<ContainerEndB>}’.
    // So according to GCC ContainerA<>::type contains ContainerEndB, but it
clearly contains only ContainerEndB!


    static_assert(
        // It doesn't matter which types you use to instantiate ContainerA and
ContainerB
        std::is_same<ContainerA<int>::type, ContainerB<int>::type>::value,
        "This assert doesn't fail but it clearly should!"
    );
}
------------------------------------------------------------

I have tried to minimize the code further but any time I remove something the
bug disappears.