title: missing parameter type error by calling toSet
body: <p>Why this code doesn't work:</p>
  
  <pre><code>scala&gt; List('a', 'b', 'c').toSet.subsets.foreach(e =&gt; println(e))
  
  &lt;console&gt;:8: error: missing parameter type
                List('a', 'b', 'c').toSet.subsets.foreach(e =&gt; println(e))
                                                          ^
  </code></pre>
  
  <p>But when I split it then it works fine:</p>
  
  <pre><code>scala&gt; val itr=List('a', 'b', 'c').toSet.subsets
  itr: Iterator[scala.collection.immutable.Set[Char]] = non-empty iterator
  
  scala&gt; itr.foreach(e =&gt; println(e))
  Set()
  Set(a)
  Set(b)
  Set(c)
  Set(a, b)
  Set(a, c)
  Set(b, c)
  Set(a, b, c)
  </code></pre>
  
  <p>And this code is OK as well:</p>
  
  <pre><code>Set('a', 'b', 'c').subsets.foreach(e =&gt; println(e))
  </code></pre>