Sendable enums with @Sendable case constructors

Using Swift
1

I couldn't find any information on this in the structured concurrency proposal, but has there been any discussion of making the cases of a Sendable enum act as a @Sendable function? Currently the following produces a warning:

enum Foo: Sendable {
  case bar(Int)
}

let f: @Sendable (Int) -> Foo = Foo.bar

…saying that Foo.bar is not @Sendable. As far as I can tell it seems @Sendable to me.

Is this theoretically possible at some point, or was it specifically disallowed for a particular reason?

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2

I've run into something similar to this before, but in that situation it was a func rather than an enum case. This solution worked for me then; does it work here, too?

let f: @Sendable (Int) -> Foo = { .bar($0) }

Regardless, I think it is odd that this doesn't work.

3

Yeah that's right and I should have mentioned. Using { Foo.bar($0) } does get around the problem. However, it can make call sites of APIs look really bad, so I was hoping Foo.bar would work.

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4

Just came across this, and we have many many warnings across our project. Is there anything that can be done about it other than changing all the code?

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5

It seems that it's just a matter of making the enum Sendable, right? so probably using the long syntax just misses the warning, and it actually doesn't fix anything.

6

The issue presented in this thread was fixed by SE-0418.

This code will compile diagnostic-free with Swift 6 mode. For 5 mode, you'll have to enable InferSendableFromCaptures explicitly.

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