Variadic alias template rejected without instantiation

[llvmbot]

Bugzilla Link	32905
Version	trunk
OS	Linux
Reporter	LLVM Bugzilla Contributor

Extended Description

template <typename... Ts> 
struct X {
    template <typename... Us>
    using Y = X<void(Ts, Us)...>;
};

template<typename... T>
using any_pairs_list = X<int, int>::Y<T...>;

---

Diagnostic: error: pack expansion contains parameter pack 'Us' that has a different length (2 vs. 1) from outer parameter packs

[llvmbot]

Make that

template<typename... T>
using any_pairs_list = typename X<int, int>::template Y<T...>;

Same problem, still.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[opensdh]

Make that

template<typename... T>
using any_pairs_list = typename X<int, int>::template Y<T...>;

X<int, int> isn't dependent, so of course typename and ::template shouldn't do anything here.

[opensdh]

This seems to be a duplicate of #17042 (complete with the circular-looking reproducer, though that can be avoided).