This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

1982. Deduction extending parameter pack

According to 13.10.2 [temp.arg.explicit] paragraph 9,

Template argument deduction can extend the sequence of template arguments corresponding to a template parameter pack, even when the sequence contains explicitly specified template arguments.

However, it is not clear how to handle an example like:

  template<class...> struct Z {
    Z (int);
  };

  template<class... Ts> void f (Z<Ts...>);

  int main () {
    f<void, void> (0);
  }

Rationale (November, 2014):

CWG was not convinced that such cases are sufficiently useful to warrant the additional complexity in the rules required to support them.