@swift-ci create

With Xcode 14.1 beta 3 with SWIFT_STRICT_CONCURRENCY = "targeted", I'm seeing a lot of warnings as below.

Cannot form key path that captures non-sendable type 'KeyPath<AttributeScopes.SwiftUIAttributes, AttributeScopes.SwiftUIAttributes.FontAttribute>
Generic class 'KeyPath' does not conform to the 'Sendable' protocol

and I can't even tell where it's happening.

@nh7a did you by any chance find out how to solve or at least suppress those warnings?
Normally I'd think I can just suppress the warning with an @preconcurrency import, but as KeyPath lives in the swift standard library, I think I can't do that?

I'm facing the same issue. Lot's of warnings for KeyPath non-sendable conformance in various files where there are no KeyPath what so ever...

"Generic class 'KeyPath' does not conform to the 'Sendable' protocol"

This is a significant pain point when using SWIFT_STRICT_CONCURRENCY=complete with Swift 5.8/5.9 as well.

In particular the AttributedString APIs that use dynamic member lookup completely break:

var string = AttributedString("Hello")
string.accessibilitySpeechSpellsOutCharacters = true

Produces this error:

<unknown>:0: error: cannot form key path that captures non-sendable type 'KeyPath<AttributeScopes.AccessibilityAttributes, AttributeScopes.AccessibilityAttributes.SpellOutAttribute>'
Swift.KeyPath:1:14: note: generic class 'KeyPath' does not conform to the 'Sendable' protocol
public class KeyPath<Root, Value> : PartialKeyPath<Root> {
             ^
error: fatalError

As mentioned by others in this issue, the diagnostics have no line/column information so it can be hard to pinpoint what line is causing the issue.

Changing -strict-concurrency=targeted works around the problem. I've filed FB13085158 to track the bug on the Foundation side of things.

For AttributedString in particular, I've been able to work around it by using more verbose APIs:

var attributes = AttributeContainer()
attributes[AttributeScopes.AccessibilityAttributes.SpellOutAttribute.self] = true
let string = AttributedString("Hello", attributes: attributes)

But that's very non-obvious that you can even do this.

This will be resolved with SE-0418. You can test it out using a main development snapshot and enabling -enable-experimental-feature InferSendableFromCaptures.

Thanks for the good news @hborla will it be included in 5.10? If not, is it possible for it to be cherry-picked?

Hello everyone,

I wanted to share a workaround specifically for suppressing the non-Sendable warning for KeyPaths in concurrent Swift code:

extension KeyPath: @unchecked Sendable {}

This approach is targeted solely at the Sendable conformance warning for KeyPaths and should be used cautiously as a temporary solution. It allows continued development without the immediate need to refactor large codebases, awaiting a more permanent resolution.

Looking forward to any input or better alternatives from the community.

Best,
Stefan