message: make-vector: Prefer `if constexpr`.
diff: @@ -106,21 +106,18 @@ namespace elle
  {
  using std::begin;
  using std::end;
  - using Res = decltype(make_vector<R, Cont>(std::forward<Cont>(c)));
  - return elle::meta::static_if<
  - std::is_same<std::remove_reference_t<Cont>, Cont>::value &&
  - detail::make_vector_move<std::remove_reference_t<Cont>>::value >(
  - [] (auto&& c) -> Res
  + if constexpr(std::is_same<std::remove_reference_t<Cont>, Cont>::value &&
  + detail::make_vector_move<std::remove_reference_t<Cont>>::value)
  {
  return {
  std::make_move_iterator(c.begin()),
  std::make_move_iterator(c.end()),
  };
  - },
  - [] (auto const& c) -> Res
  + }
  + else
  {
  return {begin(c), end(c)};
  - })(std::forward<Cont>(c));
  + }
  }
  /// This is really the `filter` function in functional languages:
  