genericcast.swift

import Foundation

func doStuff<T:CollectionType where T.Generator.Element: Equatable, T.Index.Distance == Int>(collection:T) {
    //Do Stuff
}

var list: [Any] = [1,2,2,3,4,5] //This HAS to be saved as [Any]. Or is there another way to specify all kinds of collections that would work with doStuff()?

doStuff(list) //This fails: cannot invoke 'doStuff' with an argument list of type '([Any])'

You can use a custom protocol like
protocol MyEquatable {
func isEqual(object: Any) -> Bool
}