title: Scala compile warning with pattern matching
body: <p>I have an Akka Actor that has the following case pattern match check in its receive method as below:</p>
  
  <pre><code>def receive = {
    case x: (String, ListBuffer[String]) if(x._2.size &gt;= 0) =&gt; {
    .....
    .....
  }
  </code></pre>
  
  <p>When I compile, I get to see the following compiler warnings:</p>
  
  <pre><code>warning: non-variable type argument String in type pattern (String, scala.collection.mutable.ListBuffer[String]) 
  is unchecked since it is eliminated by erasure)
  </code></pre>
  
  <p>Any clues as to how I could get rid of them? I do not want to set the compiler settings to ignore these warnings, but I do not see a reason why the compiler issues a warning?</p>