message: Type Traits/`void_t`: Add missing default for the first type parameter.
  Bug
diff: @@ -41,7 +41,7 @@ template <typename... Ts> using void_t = typename voider<Ts...>::type;
  #else // Older than C++11.
  template <
  - typename T
  + typename = void
  , typename = void
  , typename = void
  , typename = void
  