`@isolated(any)` function types

[hborla (Holly Borla)]

@cal

Could it make sense to also use the @isolated annotation to support applying an explicit isolation to a closure? That could let us simplify this example to:

func delay(operation: @isolated(any) () -> ()) {
  Task { @isolated(operation) in  // seems very elegant!
    // ...
  }
}

I find this spelling really appealing because it's more similar to the syntax for isolating a closure to a global actor (both would use an @ annotation: @MainActor in and @isolated(myActor) in).

e.g. in this example from earlier, I'd find @isolated(counter) to be more intuitive and appealing:

@cal

Task { [isolation counter] in
  counter.incrementAndAssertCountEquals(iteration)
}

vs

Task { @isolated(counter) in
  counter.incrementAndAssertCountEquals(iteration)
}

This syntax is specified in a separate proposal, which has been pitched over in

Closure isolation control

Greetings Swift evolvers. For your consideration, I have drafted a proposal allowing for more explicit control over the isolation of closures. You can read the proposal at nnnn-closure-isolation.md Please share thoughts and feedback here or as comments on the pull request. Thank you.

I think your feedback would be valuable to post in that pitch thread!