[Bug c++/67190] New: gcc allows extra template <> on explicit template specializations

["vanyacpp at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67190

            Bug ID: 67190
           Summary: gcc allows extra template <> on explicit template
                    specializations
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vanyacpp at gmail dot com
  Target Milestone: ---

GCC accepts this code:

template <typename T>
struct vector
{};

template <typename T>
struct z
{};

template <>
template <> // extra
struct z<vector<int> >
{};

After reading [temp.expl.spec] I can not find anything that forbids or allows
extra 'template<>'. MSVC rejects this code and I find this reasonable.

1>main.cpp(44): error C2910: 'z<vector<T>>' : cannot be explicitly specialized

Clang accepts this code, but it gives a warning: "extraneous template parameter
list in template specialization".