title: Why do I get a "missing parameter for expanded function" in one case and not the other?
body: <p>Case this works:</p>
  
  <pre><code>Seq(fromDir, toDir) find (!_.isDirectory) foreach (println(_))
  </code></pre>
  
  <p>Whereas this doesn't:</p>
  
  <pre><code>Seq(fromDir, toDir) find (!_.isDirectory) foreach (throw new Exception(_.toString))
  </code></pre>
  
  <p>Compilation ends with this error:</p>
  
  <pre><code>error: missing parameter type for expanded function ((x$4) =&gt; x$4.toString)
  </code></pre>
  
  <p>Now if I write it this way it compiles again:</p>
  
  <pre><code>Seq(fromDir, toDir) find (!_.isDirectory) foreach (s =&gt; throw new Exception(s.toString))
  </code></pre>
  
  <p>I am sure there is a reasonable explanation ;)</p>