[Bug c++/68396] New: bug with parameter pack expansion

[ryan.burn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68396

            Bug ID: 68396
           Summary: bug with parameter pack expansion
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ryan.burn at gmail dot com
  Target Milestone: ---

This valid code below worked until recently with gcc-6. The latest version of
gcc-6 gives the incorrect error:

bug2.cpp: In function ‘auto make_dimensionality_impl()’:
bug2.cpp:7:17: error: parameter packs not expanded with ‘...’:
   return get<2>();
                 ^

bug2.cpp:7:17: note:         ‘auto’


////////////////////////////////////////////////////////////////////
template <unsigned> auto get() {                                                
  return 2;                                                                     
};                                                                              
template <class> class Dimensionality {};                                       
template <int... Indexes> auto make_dimensionality_impl() {                     
  Dimensionality<decltype(get<Indexes>())...>();                                
  return get<2>();                                                              
}                                                                               

int main() { return 0; }
////////////////////////////////////////////////////////////////////