Crashes on gcc trunk.

See https://gcc.godbolt.org/z/EErMqe44o

```
template <template <typename> typename T>
struct K {};

template <typename U, int...N>
class Foo {};

template <template<typename> typename TTP,
          int...N>
using Bar = Foo<K<TTP>, N...>; 

template <class T>
class Container {};
Bar t = Foo<K<Container>, 1>();

```