[Voted into the WP at the March, 2011 meeting as part of paper N3262.]

It was intended for empty pack expansions to be useful in contexts like base-specifiers, e.g.,

    template<class... T> struct A : T... {};
    A<> x; // ok?

However, the current wording provides no description of how that might work. (More generally, the problem arises in any context where the pack expansion follows a token that should only be present when the pack expansion is non-empty: following another argument in a function call, etc.)