<type_traits>: some traits are aliases and fail when used with parameter packs

[jonathanpoelen]

In an alias, a pack parameter cannot be used with a non-pack parameter and some traits fail in this case:

#include <type_traits>

template<class... xs>
using test = std::is_nothrow_convertible<xs...>; // error: pack expansion used as argument
                                                 // for non-pack parameter of alias template

std::is_nothrow_convertible<int,int> a; // ok
test<int,int> b; // fail

(https://godbolt.org/z/dTbWTYd4s)

From what I understand of cppreference and https://www.eel.is/c++draft/meta.type.synop, is_nothrow_convertible should be a class (who don't have this problem).

Expected behavior

The code above should compile.

STL version

msvc 19.37.32826.1 (sorry if this is not enough, I base this on what my github CI displays, but the main branch also uses aliases).

[frederick-vs-ja]

Thanks for noting this. I think there're no other type trait class templates that are misimplemented as alias templates...