MyActor Phase#1

MyActor+phase1.swift

actor class MyActor {
  let immutable: String = "42"
  var mutableArray: [String] = []

  func synchronousFunction() {
    mutableArray += ["syncFunction called"]
  }
}

extension MyActor {

  func asyncFunction(other: MyActor) async {
    // allowed: an actor can access its internal state, even in an extension
    self.mutableArray += ["asyncFunction called"]
  
    // allowed: immutable memory can be accessed from outside the actor
    print(other.immutable)

    // error: an actor cannot access another's mutable state
    otherActor.mutableArray += ["not allowed"]

    // error: either reading or writing
    print(other.mutableArray.first)
    
    // allowed: async functions can call async functions on other actors
    await other.asyncFunction(otherActor: self)
    
    // error: only asynchronous functions can be called from outside the actor
    other.synchronousFunction()    
  }
}