akka-cluster-tools compiler warnings as fatal errors (#26647)

akka-cluster-tools/src/multi-jvm/scala/akka/cluster/client/ClusterClientSpec.scala

@@ -28,6 +28,7 @@ import akka.testkit._
 import akka.cluster.pubsub._
 import akka.remote.transport.ThrottlerTransportAdapter.Direction
 import akka.util.Timeout
+import akka.util.unused
 
 import scala.concurrent.Await
 
@@ -64,7 +65,7 @@ object ClusterClientSpec extends MultiNodeConfig {
         context.system.terminate()
       case msg =>
         testActor.forward(msg)
-        sender() ! Reply(msg + "-ack", Cluster(context.system).selfAddress)
+        sender() ! Reply(s"$msg-ack", Cluster(context.system).selfAddress)
     }
   }
 
@@ -189,6 +190,19 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
     node(r) / "system" / "receptionist"
   }
 
+  @unused
+  def docOnly = { //not used, only demo
+    //#initialContacts
+    val initialContacts = Set(
+      ActorPath.fromString("akka.tcp://OtherSys@host1:2552/system/receptionist"),
+      ActorPath.fromString("akka.tcp://OtherSys@host2:2552/system/receptionist"))
+    val settings = ClusterClientSettings(system).withInitialContacts(initialContacts)
+    //#initialContacts
+
+    // make the compiler happy and thinking we use it
+    settings.acceptableHeartbeatPause
+  }
+
   "A ClusterClient" must {
 
     "startup cluster" in within(30 seconds) {
@@ -278,15 +292,6 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
         receiveN(3).toSet should ===(Set("hello", "hi"))
       }
 
-      lazy val docOnly = { //not used, only demo
-        //#initialContacts
-        val initialContacts = Set(
-          ActorPath.fromString("akka.tcp://OtherSys@host1:2552/system/receptionist"),
-          ActorPath.fromString("akka.tcp://OtherSys@host2:2552/system/receptionist"))
-        val settings = ClusterClientSettings(system).withInitialContacts(initialContacts)
-        //#initialContacts
-      }
-
       // strange, barriers fail without this sleep
       Thread.sleep(1000)
       enterBarrier("after-4")
@@ -436,7 +441,7 @@ class ClusterClientSpec extends MultiNodeSpec(ClusterClientSpec) with STMultiNod
         c ! ClusterClient.Send("/user/service2", "ping", localAffinity = true)
         // if we would use remote watch the failure detector would trigger and
         // connection quarantined
-        expectNoMsg(5 seconds)
+        expectNoMessage(5 seconds)
 
         testConductor.passThrough(client, receptionistRoleName, Direction.Both).await