[jarpadat]

Concurrent memory safety is definitely a goal. Try the new ‘-warn-concurrency’ flag to see what I mean, it is comparable to rust and quite different than thread sanitizer. There’s also a new runtime sanitizer this year with swift intrinsics, not best effort like tsan was.

That said. Swift is in the tough position of trying to be a lot of things at once to users with competing needs. Applications, systems, performance, education, prototyping, etc. While there’s broad agreement concurrency safety is important, not everybody thinks it is important enough to bury your working build under a thousand errors (though that view is represented)

Ultimately swift’s philosophy is that safety is practice and not theory. Some people do turn on ‘-warn-concurrency’ and fix their errors, others would want to ignore them and find some escape hatch to squash them which doesn’t appreciably improve safety, still others might not upgrade if that was required and maybe the ecosystem as a whole becomes less safe for it. Swift feels responsible for these kinds of outcomes.

It’s a tough problem but it does lead to interesting ideas that make safety more practical and productive. Remains to be seen how much of both worlds you can have, but swift/clang/llvm have a long history of doing stuff like that better than you expect.