This program

#include <iostream>
template <typename ...Bases>
struct S : Bases...
{
    using Bases::Bases...;
};
int main()
{
}
does not compile using gcc HEAD 10.0.0 20190 .

The error message is

rog.cc:6:23: error: parameter packs not expanded with '...':
    6 | using Bases::Bases...;
      | ^~~
prog.cc:6:23: note: 'Bases'
 However it compiles using Clang HEAD 9.0.0.

So the question is Is it a valid using declaration or is there a gcc bug?
  With best regards,
Vlad from Moscow

You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or http://ru.stackoverflow.com