SE-0523: Hashable conformance for UnownedTaskExecutor

Evolution Proposal Reviews
1

Hello, Swift community.

The review of SE-0523: Hashable conformance for UnownedTaskExecutor begins now and runs through April 6th, 2026.

Reviews are an important part of the Swift evolution process. All review feedback should be either on this forum thread or, if you would like to keep your feedback private, directly to me as the review manager by DM or [email:mailto:rjmccall@apple.com). When contacting me directly as the review manager, please put "[SE-0523]" at the start of the subject line.

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John McCall
Review Manager

2 Likes
Pitch: `Hashable` conformance for `UnownedTaskExecutor`
[Accepted] SE-0523: Hashable conformance for UnownedTaskExecutor
2

+1

I've only done a quick reading of the proposal, but it seems like a useful and warranted change for the use cases described in the proposal.

One question I have is that the Detailed Design section includes the declaration:

@available(SwiftStdlib 6.0, *)
extension UnownedTaskExecutor: Hashable {}

But later the Implications on adoption says:

This feature requires a minimum deployment target matching the Swift standard library version in which it ships.

Is this intended to be available back to version 6.0 as in the code? Or will be it '6.x' as implied by the Implications on adoption section?

2 Likes
3

Oh, I don’t think we can back-deploy conformances easily so this probably snuck through from when we first thought about it… it would be 6.4 in this case.

I posted a mini pr to remove this to avoid confusion Proposal should not assume swift version in impl by ktoso · Pull Request #3214 · swiftlang/swift-evolution · GitHub thank you for noticing // fyi @fabianfett

2 Likes
4

+1 - The value for highly concurrent software designs is huge, and the impact extremely minimal. I wish it could be back ported, but I'd be happy to have it forward regardless.

1 Like
5

The conformance can't back-deploy, but we should be able to make the implementation back-deploy, if someone wants to use it in their own conformance.

1 Like
6

Sounds good, can do that!

2 Likes
7

SE-0523 has been accepted. If there's any further discussion to be had, please continue it in the new thread.

John McCall
Review Manager