title: Non-empty iterator over regex groups becomes empty array
body: <p>I have this strange situation - when I print regex groups to a console, they show up. When I convert this iterator to array - it's empty. Following code doesnt print anything:</p>
  
  <pre><code>val str = "buy--751-rates.data"
  
  val expr = "--(.+)-rates.data".r
  
  val target = Array[String]()
  expr.findAllIn(str).matchData map(m =&gt; m group 1) copyToArray(target, 0, 4)
  target foreach { println }
  </code></pre>
  
  <p>But this snippet works:</p>
  
  <pre><code>val str = "buy--751-rates.data"
  
  val expr = "--(.+)-rates.data".r
  println("Scala matches:")
  expr.findAllIn(str).matchData foreach {
     m =&gt; println(m group 1)
  }
  </code></pre>
  
  <p>I guess I missed something simple</p>