Variadic alias template to non-variadic class template - c++

Question

In trying to write a simple example for currying of metafunction classes, I wrote the following:
#include <type_traits>
struct first {
template <typename T, typename U>
using apply = T;
};
template <typename C, typename... Args>
struct curry {
struct type {
template <typename... OtherArgs>
using apply = typename C::template apply<Args..., OtherArgs...>;
};
};
int main() {
static_assert(std::is_same<first::apply<int, char>, int>::value, ""); // OK
using AlwaysInt = curry<first, int>::type;
static_assert(std::is_same<AlwaysInt::apply<char>, int>::value, ""); // error
}
The second static_assert fails to compile on both gcc 5.1:
main.cpp:17:72: error: pack expansion argument for non-pack parameter 'U' of alias template 'template<class T, class U> using apply = T'
using apply = typename C::template apply<Args..., OtherArgs...>;
^
and clang 3.6:
main.cpp:17:59: error: pack expansion used as argument for non-pack parameter of alias template
using apply = typename C::template apply<Args..., OtherArgs...>;
^~~~~~~~~~~~
Same error in both cases. However, if I outsource the application in curry to a separate metafunction:
template <typename C, typename... Args>
struct eval {
using type = typename C::template apply<Args...>;
};
template <typename C, typename... Args>
struct curry {
struct type {
template <typename... OtherArgs>
using apply = typename eval<C, Args..., OtherArgs...>::type;
};
};
Both compilers compile just fine. Is there something wrong with the original example or is this just a bug in both compilers?