Keeping up with Swift and preparing for Swift 6

For a while now (a couple of years) Swift has been in a transitional phase towards Swift 6. There are major changes that the Swift team wants to introduce into the language while they’re also continuing to make new features available and doing some preliminary work to ease developers into breaking changes.

I think the biggest example where the team is doing this is Swift Concurrency.

We’ve had concurrency for about two years now and overall I’m enjoying Swift Concurrency a lot. Especially when use cases are simple and you’re not building intricate systems you’ll find that Swift Concurrency works well. On the other hand, if you are building someting complex, large, or highly performance sensitive things can get tricky. It’s at the edges of what’s available that it becomes clear that Swift Concurrency is still under construction. The fundamentals are mostly there but it’s definitely still under construction.

One of the ways in which Apple is helping us to ease into Swift 6 is by having a more relaxed set of constraints for sendability in Swift for the time being. We can opt-in to Swift 6’s strict checking which for many folks will mean getting lots of new warnings and errors that demonstrate that there’s still a lot of work that developers need to do to be fully Swift 6 compliant.

At the moment, Apple is still actively working on implementing new features and tools that can both help us transition into strict checking by having ways to essentially “force unwrap” our sendability through things like unchecked sendable, unchecked(unsafe) for global mutable state and @preconcurrency imports. None of these features provide us the kind of safetry that Swift Concurrency aims to provide but instead they provide us means to silence warnings for the time being.

We’re also still getting new features that will help us write safe code that doesn’t require us to jump through hoops when the compiler can proof that our code is safe. For example, that’s what the recently accepted region based isolation proposal provides.

All in all there’s a lot to keep up with these days, and it’s even harder to know exactly what is or will be available at what time.

These are exciting times in my opinion, but I can certainly see why Swift Concurrency can be a somewhat daunting topic for some. Especially if you factor in that Swift 6 will be a pretty big release that will require your attention either way I can see why folks would want to hold off on going too deep into concurrency at the moment.

I guess it’s a good thing that Swift 6 will come with a Swift 5.10 compiler mode…

Cheers!
Donny

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