pekko/akka-docs/rst/additional/code/docs/faq/Faq.scala

package docs.faq

import akka.actor.Actor

//#exhaustiveness-check
object MyActor {
  // these are the messages we accept
  sealed abstract trait Message
  final case class FooMessage(foo: String) extends Message
  final case class BarMessage(bar: Int) extends Message

  // these are the replies we send
  sealed abstract trait Reply
  final case class BazMessage(baz: String) extends Reply
}

class MyActor extends Actor {
  import MyActor._
  def receive = {
    case message: Message => message match {
      case BarMessage(bar) => sender() ! BazMessage("Got " + bar)
      // warning here: 
      // "match may not be exhaustive. It would fail on the following input: FooMessage(_)"
      //#exhaustiveness-check
      case FooMessage(_)   => // avoid the warning in our build logs
      //#exhaustiveness-check
    }
  }
}
//#exhaustiveness-check