"P.S.: I'm unsure why anyone would think that this has anything to do with the Objective-C runtime. I guess it may if you pass any kind of ARC objects."
Because the comment on the commit that adds this to the swift source states that "It relies on ObjC interop".
Because the comment on the commit that adds this to the swift source states that "It relies on ObjC interop".
https://github.com/apple/swift/commit/013aad13d4245a012cfb76...
So maybe not the runtime, per se, but haven't looked into what it's actually generating.