Is substitution performed on a variadic parameter pack type if the pack is empty?

Question

Consider the following program:

#include 

enum class dummy {};
template 
using EnableIf = typename std::enable_if

        

Answer 1

I believe I have found the relevant piece of standardese. §14.8.2p7 says:

The substitution occurs in all types and expressions that are used in the function type and in template parameter declarations.

Since EnableIf<dependent_true_type<T>> is used in a template parameter declaration, substitution should occur and this is a bug in clang.