title: Nil for maps as like for Lists
body: <p>Is it possible to create <code>Nil</code> for maps?</p>
  
  <p>I mean somethin similar to that:</p>
  
  <pre><code>List() match {
      case Nil =&gt; true
  }
  </code></pre>
  
  <p>but with map:</p>
  
  <pre><code>Map() match {
      case NilMap =&gt; true
  }
  </code></pre>
  
  <p>I tried to implement it, but I'm stuck:</p>
  
  <pre><code>object NilMap extends Map[Nothing, Nothin] {
      def unapply[K,V](map: Map[K,V]): Option[Map[K,V]] = 
         if(map.isEmpty) Some(map) else None
  
  }
  </code></pre>
  
  <p>but id doesn't compile...</p>