Variadic template aliases as template arguments (part 2)

Question

This is a follow-up of another question. It refers to the same problem (I hope) but uses an entirely different example to illustrate it. The reason is that in the previous examp

Answer 1

I think the situation is pretty well standardized; C++11 14.3.3/1 says:

A template-argument for a template template-parameter shall be the name of a class template or an alias template, expressed as id-expression.