Wow, it’s been quite the week! There has been a lot going on this week, and quite a few swift-evolution proposals have landed. And not the smallest ones either: what about Automatic Equatable and Hashable conformance for example? Swift 4.1 is shaping up to be a great release that will make our lives even easier. 🏎💨

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Starter tasks

Submit a task by sending a pull request or opening an issue.

Swift Unwrapped

Episode 32: Migrating to Swift 4: JP and Jesse share their thoughts on the transition to Swift 4.

News and community

Kubra Mracek improved the display of fatal errors and wrote a blog post on describing the changes. Now, you will see where and why a failure occurred, which is a big improvement to the previous ambiguous errors in the main function.

Commits and pull requests

Tony Allevato’s SE-0185: Synthesizing Equatable and Hashable conformance was merged! This is huge — it provides automatic Equatable and Hashable conformance for types for whose members are all Equatable or Hashable. 😱🎉

Greg Spiers implemented SE-0186: Remove ownership keyword support in protocols.

Robert Widmann opened a pull request that implements SE-0155: Normalize Enum Case Representation.

Javi Soto opened a pull request to make +new unavailable when -init is too.

Doug Gregor made some more improvements for type checking in the standard library. Another 16% speedup!

David Ungar opened a pull request to speed up compilation for full rebuilds in non-WMO (Whole Module Optimization) mode. And there’s more to come!

Chris Lattner opened a pull request with some small improvements to the optimizer.

Recursive protocol constraints are now available on the master toolchain!

Accepted proposals

SE-0184: Unsafe[Mutable][Raw][Buffer]Pointer: add missing methods, adjust existing labels for clarity, and remove deallocation size was accepted with revisions.

It was a large proposal for which most parts received a lot of support, while other parts were contentious. The proposal is accepted with revisions:

  • Partial initialization/assignment will be removed from this proposal and discussed separately
  • Some argument labels will be changed for clarity (bytes -> byteCount, alignedTo -> alignment)
  • The count argument to deallocate() will be removed entirely

SE-0186: Remove ownership keyword support in protocols was accepted.

The proposal has been accepted.

Feedback for the proposal — which many interpreted as being mostly a compiler bug fix — was limited but unanimously positive. The consensus was that removing the support for these ownership keywords in protocols removes false expectations on their behavior, which could be a source of bugs.

Mailing lists

Jordan Rose pitched a proposal to restrict cross-module struct initializers.

While working on the non-exhaustive enums proposal I had it pointed out to me that structs actually currently leak implementation details across module boundaries, specifically their full set of stored properties. This only comes up in one place: when making an initializer for the struct in an extension in another module. We really want people to be able to change the stored properties in their structs between releases without it being a source break—that’s half the point of computed properties—and it’s also important for a struct author to be able to enforce invariants across the struct’s properties.

There’s already a proposal and an initial implementation.


Chris Lattner is back to square one.