Template arity trait

I'm making a template arity trait, but cannot make it work on MSVC. The basic idea is to specialize the template below. It works fine on clang and g++, but MSVC fails to specialize the argument list (cf. https://godbolt.org/z/h9rGddzvz ). Any Idea how to achieve this ?

template <template <typename...> class C>
struct templatearity;

template <template <typename> class C>
struct templatearity<C> : std::integralconstant<std::sizet, 1> {};

I intended to use it in some static_asserts but can live without it.

https://redd.it/1ok81tr
@r_cpp