[Pitch] Parameter Packs

[Slava_Pestov]

@Jumhyn

A priori, I don't necessarily consider "it's the same way C++ does it!" to be an argument for or against this spelling . C++ didn't have all the same existing baggage around ... that Swift has, and given that the fundamental model for generics is already quite different between Swift and C++ I'm not too concerned that experienced C++ programmers would also have to learn a slightly different syntax for variadic generics.

I also don't think the ... syntax is ideal due to ambiguities with operators and non-generic variadics, but it's worth mentioning it's not just C++ that uses .... I've also seen this syntax in ML dialects with row polymorphism, and even more obscurely, Factor used it for row polymorphic stack effects.

@Jumhyn

But there's some space between "bare keyword" and "operator" that I'd be curious about, such as #pack(T) and #expand(t).

I think pack T or many T or something could work as a declaration for the pack type parameter in a generic parameter list. Not sure how I feel about #expand(T) for a pack expansion type or expression, though.