[roop]

For the kind of applications that Swift is intended for now (i.e. iOS / Mac apps), debug-mode runtime doesn't affect productivity very much as long as runtimes are fast enough to respond to UI events. It might affect automated testing times, but not productivity directly.

So, for that particular use-case, debug-mode being within 2x of release-mode build is not a valid concern.

What would affect productivity for this kind of use-case is build times. (Swift isn't great here either.)