title: What does Cannot create delegate without target for instance method or closure mean
body: <p>I am using vala.
  This is the source code that gives that compile time bug :</p>
  
  <pre><code>private Gee.HashMap&lt;string,VoidFunc&gt; fill_actions()
  {
      var actions = new Gee.HashMap&lt;string,VoidFunc&gt;();
      MainWindow win = window;
      actions["t"] = () =&gt; _puts(win.title);
      return actions;
  }
  </code></pre>
  
  <p>First I tried to access this.window directly but that gave another error so I tried this with a local scope variable.</p>
  
  <p>Error when doing directly this.window :</p>
  
  <pre><code>This access invalid outside of instance methods
  </code></pre>