add pimp for Future.pipeTo(Channel), closes #1235

cherry-picked from release-1.3

The ticket contains more methods around this issue, both on Actor and
Future itself, but I think it is better to provide the basic primitive
in a way which does not further couple Future and Actor. Will need to be
revisited for 2.0.

akka-actor-tests/src/test/scala/akka/dataflow/Future2Actor.scala

@@ -0,0 +1,34 @@
+/**
+ *  Copyright (C) 2009-2011 Typesafe Inc. <http://www.typesafe.com>
+ */
+package akka.dataflow
+
+import akka.actor.{ Actor, Props }
+import akka.dispatch.Future
+import akka.actor.future2actor
+import akka.util.duration._
+import akka.testkit.AkkaSpec
+
+class Future2ActorSpec extends AkkaSpec {
+
+  "The Future2Actor bridge" must {
+
+    "support convenient sending to multiple destinations" in {
+      Future(42) pipeTo testActor pipeTo testActor
+      expectMsgAllOf(1 second, 42, 42)
+    }
+
+    "support reply via channel" in {
+      val actor = app.actorOf(Props(new Actor {
+        def receive = {
+          case "do" ⇒ Future(31) pipeTo context.channel
+          case "ex" ⇒ Future(throw new AssertionError) pipeTo context.channel
+        }
+      }))
+      (actor ? "do").as[Int] must be(Some(31))
+      intercept[AssertionError] {
+        (actor ? "ex").get
+      }
+    }
+  }
+}

akka-actor/src/main/scala/akka/actor/package.scala

@@ -22,4 +22,15 @@ package object actor {
     n.substring(i + 1).replaceAll("\\$+", ".")
   }
 
+  implicit def future2actor[T](f: akka.dispatch.Future[T]) = new {
+    def pipeTo(channel: Channel[T]): this.type = {
+      if (f.isCompleted) {
+        f.value.get.fold(channel.sendException(_), channel.tryTell(_))
+      } else {
+        f onComplete { _.value.get.fold(channel.sendException(_), channel.tryTell(_)) }
+      }
+      this
+    }
+  }
+
 }