title: Flutter: How to handle "The default value of an optional parameter must be constant"
body: <p>I have a simple class like this:</p>
  <pre><code>class Restaurant{
    final String id;
    final String name;
    List&lt;Serving&gt; servingList;
  
    Restaurant({
      required this.id,
      required this.name,
      this.servingList = [], // ERROR
    });
  }
  </code></pre>
  <p>By default I want an empty List for <code>servingList</code> and add Objects to this List later. But I get the error <code>The default value of an optional parameter must be constant.</code>
  What do I need to do?</p>
  <p>I appreciate every help, thanks!</p>