=act #3572 Add parens to sender

* because it is not referentially transparent; normally we reserved parens for
  side-effecting code but given how people thoughtlessly close over it we revised
  that that decision for sender
* caller can still omit parens

akka-docs/rst/scala/code/docs/actor/ActorDocSpec.scala

@@ -40,7 +40,7 @@ class FirstActor extends Actor {
   val child = context.actorOf(Props[MyActor], name = "myChild")
   //#plus-some-behavior
   def receive = {
-    case x => sender ! x
+    case x => sender() ! x
   }
   //#plus-some-behavior
 }
@@ -64,7 +64,7 @@ class DemoActorWrapper extends Actor {
 
   class DemoActor(magicNumber: Int) extends Actor {
     def receive = {
-      case x: Int => sender ! (x + magicNumber)
+      case x: Int => sender() ! (x + magicNumber)
     }
   }
 
@@ -91,7 +91,7 @@ class AnonymousActor extends Actor {
         def receive = {
           case DoIt(msg) =>
             val replyMsg = doSomeDangerousWork(msg)
-            sender ! replyMsg
+            sender() ! replyMsg
             context.stop(self)
         }
         def doSomeDangerousWork(msg: ImmutableMessage): String = { "done" }
@@ -123,10 +123,10 @@ class ReplyException extends Actor {
       //#reply-exception
       try {
         val result = operation()
-        sender ! result
+        sender() ! result
       } catch {
         case e: Exception =>
-          sender ! akka.actor.Status.Failure(e)
+          sender() ! akka.actor.Status.Failure(e)
           throw e
       }
     //#reply-exception
@@ -271,7 +271,7 @@ class ActorDocSpec extends AkkaSpec(Map("akka.loglevel" -> "INFO")) {
   "creating actor with IndirectActorProducer" in {
     class Echo(name: String) extends Actor {
       def receive = {
-        case n: Int => sender ! name
+        case n: Int => sender() ! name
         case message =>
           val target = testActor
           //#forward
@@ -365,12 +365,12 @@ class ActorDocSpec extends AkkaSpec(Map("akka.loglevel" -> "INFO")) {
   class HotSwapActor extends Actor {
     import context._
     def angry: Receive = {
-      case "foo" => sender ! "I am already angry?"
+      case "foo" => sender() ! "I am already angry?"
       case "bar" => become(happy)
     }
 
     def happy: Receive = {
-      case "bar" => sender ! "I am already happy :-)"
+      case "bar" => sender() ! "I am already happy :-)"
       case "foo" => become(angry)
     }
 
@@ -417,7 +417,7 @@ class ActorDocSpec extends AkkaSpec(Map("akka.loglevel" -> "INFO")) {
 
         def receive = {
           case "kill" =>
-            context.stop(child); lastSender = sender
+            context.stop(child); lastSender = sender()
           case Terminated(`child`) => lastSender ! "finished"
         }
       }
@@ -522,12 +522,12 @@ class ActorDocSpec extends AkkaSpec(Map("akka.loglevel" -> "INFO")) {
     def receive = {
       case ref: ActorRef =>
         //#reply-with-sender
-        sender.tell("reply", context.parent) // replies will go back to parent
-        sender.!("reply")(context.parent) // alternative syntax (beware of the parens!)
+        sender().tell("reply", context.parent) // replies will go back to parent
+        sender().!("reply")(context.parent) // alternative syntax (beware of the parens!)
       //#reply-with-sender
       case x =>
         //#reply-without-sender
-        sender ! x // replies will go to this actor
+        sender() ! x // replies will go to this actor
       //#reply-without-sender
     }
   }
@@ -585,13 +585,13 @@ class ActorDocSpec extends AkkaSpec(Map("akka.loglevel" -> "INFO")) {
 
   trait TheirComposableActor extends ComposableActor {
     receiveBuilder += {
-      case "foo" => sender ! "foo received"
+      case "foo" => sender() ! "foo received"
     }
   }
 
   class MyComposableActor extends TheirComposableActor {
     receiveBuilder += {
-      case "bar" => sender ! "bar received"
+      case "bar" => sender() ! "bar received"
     }
   }
   //#receive-orElse2

akka-docs/rst/scala/code/docs/actor/FaultHandlingDocSample.scala

@@ -204,7 +204,7 @@ class CounterService extends Actor {
         if (backlog.size >= MaxBacklog)
           throw new ServiceUnavailable(
             "CounterService not available, lack of initial value")
-        backlog :+= (sender -> msg)
+        backlog :+= (sender() -> msg)
     }
   }
 
@@ -239,7 +239,7 @@ class Counter(key: String, initialValue: Long) extends Actor {
       storeCount()
 
     case GetCurrentCount =>
-      sender ! CurrentCount(key, count)
+      sender() ! CurrentCount(key, count)
 
   }
 
@@ -272,7 +272,7 @@ class Storage extends Actor {
 
   def receive = LoggingReceive {
     case Store(Entry(key, count)) => db.save(key, count)
-    case Get(key)                 => sender ! Entry(key, db.load(key).getOrElse(0L))
+    case Get(key)                 => sender() ! Entry(key, db.load(key).getOrElse(0L))
   }
 }
 

akka-docs/rst/scala/code/docs/actor/FaultHandlingDocSpec.scala

@@ -34,7 +34,7 @@ object FaultHandlingDocSpec {
     //#strategy
 
     def receive = {
-      case p: Props => sender ! context.actorOf(p)
+      case p: Props => sender() ! context.actorOf(p)
     }
   }
   //#supervisor
@@ -56,7 +56,7 @@ object FaultHandlingDocSpec {
     //#strategy2
 
     def receive = {
-      case p: Props => sender ! context.actorOf(p)
+      case p: Props => sender() ! context.actorOf(p)
     }
     // override default to kill all children during restart
     override def preRestart(cause: Throwable, msg: Option[Any]) {}
@@ -87,7 +87,7 @@ object FaultHandlingDocSpec {
     def receive = {
       case ex: Exception => throw ex
       case x: Int        => state = x
-      case "get"         => sender ! state
+      case "get"         => sender() ! state
     }
   }
   //#child

akka-docs/rst/scala/code/docs/actor/InitializationDocSpec.scala

@@ -44,7 +44,7 @@ object InitializationDocSpec {
     }
 
     def initialized: Receive = {
-      case "U OK?" => initializeMe foreach { sender ! _ }
+      case "U OK?" => initializeMe foreach { sender() ! _ }
     }
     //#messageInit