Will Swift Concurrency deploy back to older OSs?

[Douglas_Gregor]

@wbrian

Is the implication here that supporting older versions of macOS/iOS would, at the very least, require updating the runtime and all apps on the device?

No. It requires bundling some code in apps and back-patching older Swift runtimes to cope with the new model.

@GuyB

Perhaps this discussion could move to a more practical theme of what, if anything, the Swift community can do to support backporting to earlier macOS/iOS versions.

Back-porting requires work deep in the runtime and compiler. Much of that work is understood. I don’t think this discussion will produce new insight into that work; the insight will come from doing it.

The best thing the Swift community can do for the concurrency effort is to try out the features on their own code. Even if you can’t ship it. Find the rough spots so we can smooth over them. Find the latent bugs, the design oversights, the ideas that are hard to communicate. Write the tutorials that make all of this more accessible to more people. We have time to make the model even better.

@GuyB

I assume the plan is that the concurrency features of swift 5.5 will be ported to other platforms such as Linux or Windows

Concurrency is already supported on these platforms as part of 5.5. They don’t benefit from OS integration, so their performance characteristics aren’t as well understood.

@GuyB

should backporting pre macOS12/iOS15 be considered as a port to another platform too ?

Not really. The tricky part of back-porting is the back-patching. It’s a different set of concerns than bringing up an implementation on a new platform.

Doug