Add a proposal to allow nonisolated to prevent global actor inference.

[simanerush]

This proposal allows annotating a set of declarations with nonisolated to prevent global actor inference.

Read full proposal...

[Jumhyn]

I had a hard time understanding rules 3 and 4 because they don't really seem to be related to global actor isolation at all even though that's the framing of the document. I also don't really see those rules discussed in the motivation section nor mentioned in the proposed solution section, unless I'm totally missing something?

[simanerush]

@Jumhyn good point! I can restructure the proposal a bit to make it clear that while these rules are not strictly related to global actor cut-off, they still enable nonisolated to be written in more places than today.

[Jumhyn]

@simanerush Thanks, I think that restructuring reads a lot better!! I might even argue for dropping any mention of global actors from the document title as well, since I think that sets the stage wrong. But also I see how perhaps the global actor bits are the 'primary' focus and the other parts are more ancillary.

[allevato]

Is this simply introducing a new explicit spelling of existing default behavior? In other words, is this snippet exactly equivalent to the following?

class MyClass {
  var x: NonSendable = NonSendable()
}

It might be helpful to show the two snippets side-by-side to emphasize that this isn't adding new functionality, but merely making it possible to write it explicitly.

Do you have any motivating use cases for when someone would want to spell it explicitly that you could add here?

[simanerush]

Yes, I think the main goal here is to allow expressing the default behavior for consistency. I don't think I have a motivating use case here, since it's more about a personal preference of the programmer.

[allevato]

Thanks for the recent changes! I'll be scheduling the review shortly.