When does another language then become a case of premature optimization? I'm serious. If performance is an issue, you can profile Objective-C code and then either deal with the runtime directly, or rewrite critical portions in C. But I would think that there is a lot of Objective-C code out there that runs just fine without any fancy tricks like what I'm describing.
Sure, but that doesn't mesh with Swift's goals, as I understand them. The team seems to be positioning Swift as a language that will scale down to low-level performance-critical pieces in a way that Objective-C can't (though I may be wrong here since I'm not involved in that community very much).
Well, they say they want that. But this is at best aspirational, it isn't true. Certainly not so far and as far as I can tell not in the foreseeable future. Quite frankly, I doubt it will ever be true, because in essence their claim is that they are building the Sufficiently Smart Compiler and despite all the problems now it will be totally awesome when they're done.
Swift currently can't hold a candle to Objective-C on the performance front, which is why all the heavy lifting is done in Objective-C. As a small example, see how many articles there are on "Swift JSON parsing", then check what percentage of those call into the NSJSONSerialization Objective-C class to the actual, you know, parsing.
No, I think you are right. My understanding is that Swift is supposed to scale down, as you say, and performance there is critical. I was considering things from the point of view of higher level programming. Thanks.