title: xtext: Statements in different order
body: <p>I'm trying to write a xtext rule, where I can write statements in different random orders but all statements have to be saved as a list. </p>
  
  <p>I tried:</p>
  
  <pre><code>Root:
   ( (entity += Entity)? &amp; (component += Component)? )*
  ;
  </code></pre>
  
  <p>But it doesn’t work. 
  Can someone help me?</p>