title: Why this _._1 shorthand isn't working?
body: <p>I am trying to flatten a map. Not sure why 1) is working but 2) isn't.</p>
  
  <pre><code>   scala&gt; val m = Map(1-&gt;2, 2-&gt;4, 3-&gt;6)
      m: scala.collection.immutable.Map[Int,Int] = Map(1 -&gt; 2, 2 -&gt; 4, 3 -&gt; 6)
  </code></pre>
  
  <p>1)    </p>
  
  <pre><code>scala&gt; m.flatMap(e =&gt; List(e._1, e._2)
       | )
  res11: scala.collection.immutable.Iterable[Int] = List(1, 2, 2, 4, 3, 6)
  </code></pre>
  
  <p>2)    </p>
  
  <pre><code> scala&gt; m.flatMap(List(_._1,_._2))
      &lt;console&gt;:12: error: missing parameter type for expanded function ((x$1) =&gt; x$1._1)
             m.flatMap(List(_._1,_._2))
                            ^
      &lt;
  </code></pre>