title: flutter auto_route, error on generated file
body: <p>this is the piece of code of generated file by flutter auto_route plugin:</p>
  <pre><code>  @override
    final Map&lt;String, _i1.PageFactory&gt; pagesMap = {
      MainRoute.name: (routeData) =&gt; _i1.MaterialPageX&lt;dynamic&gt;(
          routeData: routeData,
          builder: (_) {
            return _i3.MainPage();
          })
    };
  </code></pre>
  <p>I have 2 errors:
  The named parameter 'child' is required, but there's no corresponding argument.
  Try adding the required argument.
  The named parameter 'builder' isn't defined.
  Try correcting the name to an existing named parameter's name, or defining a named parameter with the name 'builder'.</p>
  <p>I follow the guide step by step and I can't understand where is the problem.
  I'm using auto_route 2.2.2.</p>
  <p>Thank you</p>