title: Boolean extension function
body: <p>When I try to create <strong>Extension Function</strong> to set Boolean true or false like the below.</p>
  
  <pre><code>Boolean.setTrue(){
   this = true
  }
  
  Boolean.setFalse(){
   this = false
  }
  </code></pre>
  
  <p>It says <strong>variable expected</strong>. How to achieve this.</p>