Swift Concurrency for Older OS Versions
You can now use Swift Concurrency in applications that deploy to macOS 10.15, iOS 13, tvOS 13, and watchOS 6 or newer. This support includes async/await, actors, global actors, structured concurrency, and the task APIs.
See also: Swift concurrency back deployment. The memory corruption issues are apparently fixed, too.
Previously:
Update (2021-10-29): John Sundell:
Although Swift 5.5’s new concurrency system is becoming backward compatible in Xcode 13.2, some of the built-in system APIs that make use of these new concurrency features are still only available on iOS 15, macOS Monterey, and the rest of Apple’s 2021 operating systems.
[…]
Thankfully, the above problem is something that we can fix ourselves, since Swift’s new concurrency system ships with a continuation mechanism that lets us retrofit existing code with async/await support.
Here’s how we could use that mechanism to replicate the above async/await-powered
URLSessionAPI in order to make it available all the way back to iOS 13[…]
Update (2021-12-16): Dimitri Bouniol:
Now that Swift’s concurrency system is backwards compatible with iOS 13/Catalina, here are a few packages you might want to check out!
Update (2022-01-31): Doug Gregor:
For folks using #SwiftLang concurrency on older Apple platforms, Xcode 13.3 beta addresses launch-time crashes reported on earlier OS versions (eg iOS 12, macOS 10.14).
Update (2022-04-27): Ole Begemann:
Boy, this back-deployment of Swift features is complicated.
tl;dr: Critical concurrency bug fixes that shipped in iOS 15.4/macOS 12.3 don’t magically make it into the concurrency runtime used on iOS 13/14.
