Refined actor initialization and deinitialization

Paul Hudson      @twostraws

SE-0327 adds some clarifications about how state inside actors is created and destroyed, and also relaxes some rules that were overly restrictive.

This proposal contains a number of small, specific changes to actors. For example, Swift will now automatically make actors with an async initializer move to the actor's executor when all its properties are initialized.

In code, it means the two print() calls shown below might execute on entirely different threads:

actor Actor {
    var name: String

    init(name: String) async {
        print(name)
        self.name = name
        print(name)
    }
}

let actor = await Actor(name: "Margot")

This means the code has a potential suspension directly after the name property is set.

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Other changes in Swift 5.10…

• Data races are now clearly diagnosed
• Allow Protocols to be Nested in Non-Generic Contexts
• Deprecate @UIApplicationMain and @NSApplicationMain

Download all Swift 5.10 changes as a playground Link to Swift 5.10 changes

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