I can’t believe it’s already August! This means we are only one or two months away from a final release of Xcode 9, Swift 4, and all of the Apple OSes. We usually see a GM around late August or September. There are still a number of proposals that have not been implemented and I think it’s safe to say they will not be included in Swift 4. Anyway, this week there were some changes to SourceKit that will make SwiftLint users happy and an initial implementation of Swift bindings to libSyntax. On the mailing list, Jordan Rose discussed his 99 problems — spoiler, all of them are inheritance and initializers.

Swift Unwrapped

In Episode 22: ABI Stability — The Big Picture, we clear up some of the misconceptions around what ABI stability means, how we’ll get there and why it’s important.

Commits and pull requests

Marcelo Fabri merged changes to SourceKit to address SR-2487. The issue here was that Swift 2.3 removed the “source.decl.attribute.__raw_doc_comment” attribute from structures returned by SourceKit. This was used by SwiftLint (everyone’s favorite Swift linter 😄) to implement ValidDocsRule and MissingDocsRule. Marcelo’s pull request not only restores the functionality, but takes it a step further and adds the range of a doc comment for each declaration. This would make possible to add back those rules (and their implementation could possibly even be simpler now). Nice work Mercelo! 🙌

Harlan Haskins opened a pull request with an initial implementation of the Swift libSyntax API, which aims to provide all features of the C++ API but exposed to Swift — that is, Swift bindings to libSyntax. libSyntax is a library in the Swift compiler that provides a full source-preserving Syntax tree that can be easily transformed and re-printed as a file. Why is this exciting? Let JP Simard explain: “this should eventually make it easier to write Swift tools in Swift.” 😱

Roman Levenstein implemented a more robust way to avoid infinite generic specialization loops.

Nate Cook merged documentation revisions for the stdlib.

Proposals

Some proposal statuses were updated this week, which means the Status Page should be accurate now. Currently it looks like there are 12 accepted but unimplemented proposals and one still in review.

Kelvin Ma completed and merged the first draft of SE-0184: Improved pointers which was pitched on the mailing lists last week. It is not yet scheduled for a review and I am highly skeptical it will even be reviewed in the Swift 4 time frame, much less implemented if it gets accepted.

Mailing lists

Jordan Rose sent out a great explanation on Decodable and required initializers in response to a discussion on twitter. He outlines the intricacies of Swift initializers and eventually refers readers to this doc on Initializer Problems. The TL;DR is that there’s not really a great answer and initializers are hard, but there are a few potential directions to explore in the future. Or, as Alexis Beingessner‏ put it, it’s “a great piece on why inheritance continues to be a nightmare when you try to mix it with traits/protocols/typeclasses.” 😄

Why you can’t make someone else’s class Decodable: a long-winded explanation of required initializers

David Hart recently asked on Twitter if there was a good way to add Decodable support to somebody else’s class. The short answer is “no, because you don’t control all the subclasses”, but David already understood that and wanted to know if there was anything working to mitigate the problem. So I decided to write up a long email about it instead. (Well, actually I decided to write a short email and then failed at doing so.)

Continue reading…

Nicole Jacque announced some planned downtown for Swift.org:

We will have some downtime for swift.org resources over the weekend as we upgrade our infrastructure.

The outage schedule will be as follows:

• bugs.swift.org will become unavailable starting at 9 PM Thursday, Aug 3 (Pacific) until the upgrade is completed on Saturday, Aug 5
• swift.org mailing lists (including this list) will become unavailable starting at 3 PM Friday, Aug 4 until the upgrade is completed on Saturday
• ci.swift.org and all CI infrastructure will become unavailable starting at 3 PM Friday, Aug 4 until the upgrade is completed on Saturday. We will also be locking the repos at this time until CI is back up.
• The swift.org website will be unavailable for a short time on Saturday afternoon.

We expect the upgrade to be complete on Saturday afternoon or evening. We will send out email when the upgrade is complete.

Finally

And finally — I got two words for you.