Don't allow two different actors (different types) to share the same work stealing dispatcher. Added unit test.

akka-core/src/main/scala/dispatch/ExecutorBasedEventDrivenWorkStealingDispatcher.scala

@@ -161,6 +161,7 @@ class ExecutorBasedEventDrivenWorkStealingDispatcher(_name: String) extends Mess
   private[akka] def init = withNewThreadPoolWithLinkedBlockingQueueWithUnboundedCapacity.buildThreadPool
 
   override def register(actor: Actor) = {
+    verifyActorsAreOfSameType(actor)
     super.register(actor)
   }
 
@@ -170,8 +171,10 @@ class ExecutorBasedEventDrivenWorkStealingDispatcher(_name: String) extends Mess
         actorType = Some(newActor.getClass)
       }
       case Some(aType) => {
-        if (aType != newActor.getClass) // TODO: is assignable from ?!
-          throw new IllegalStateException(String.format("Can't register actor %s in a work stealing dispatcher which already knows actors of type %s", newActor, aType))
+        if (aType != newActor.getClass)
+          throw new IllegalStateException(
+            String.format("Can't register actor %s in a work stealing dispatcher which already knows actors of type %s",
+              newActor, aType))
       }
     }
 

akka-core/src/test/scala/ExecutorBasedEventDrivenWorkStealingDispatcherTest.scala

@@ -58,4 +58,42 @@ class ExecutorBasedEventDrivenWorkStealingDispatcherTest extends JUnitSuite with
     }
   })
 
+  @Test def canNotUseActorsOfDifferentTypesInSameDispatcher:Unit = {
+    val first = new FirstActor
+    val second = new SecondActor
+
+    first.start
+    intercept[IllegalStateException] {
+      second.start
+    }
+  }
+
+  class FirstActor extends Actor {
+    messageDispatcher = poolDispatcher
+    def receive = {case _ => {}}
+  }
+
+  class SecondActor extends Actor {
+    messageDispatcher = poolDispatcher
+    def receive = {case _ => {}}
+  }
+
+  @Test def canNotUseActorsOfDifferentSubTypesInSameDispatcher:Unit = {
+    val parent = new ParentActor
+    val child = new ChildActor
+
+    parent.start
+    intercept[IllegalStateException] {
+      child.start
+    }
+  }
+
+  class ParentActor extends Actor {
+    messageDispatcher = poolDispatcher
+    def receive = {case _ => {}}
+  }
+
+  class ChildActor extends ParentActor {
+  }
+
 }