[Bug c++/51507] New: [C++0x] Function parameter pack doesn't use in template-argument-list

["digital-ghost_tsundere at hotmail dot co.jp" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51507

             Bug #: 51507
           Summary: [C++0x] Function parameter pack doesn't use in
                    template-argument-list
    Classification: Unclassified
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: digital-ghost_tsundere@hotmail.co.jp


Following code cannot compile with gcc:

  template<typename ...>
  struct foo { typedef void type; };
  template<typename ...Ts>
  auto g(Ts ...ts)->
      typename foo<decltype(ts)...>::type
  {}
  int main() {
      g(42);
  }

Error:

  test1.cpp: In function 'int main()':
  test1.cpp:8:9: error: expansion pattern 'int' contains no argument packs
  test1.cpp:8:9: error: no matching function for call to 'g(int)'
  test1.cpp:8:9: note: candidate is:
  test1.cpp:4:6: note: template<class ... Ts> typename foo<decltype
(ts)...>::type g(Ts ...)

I think decltype(fs()) is a valid template-argument pattern for foo.