title: Antlr grammar, implicit token definition in parser rule
body: <p>A weird thing is going on. I defined the grammar and this is an excerpt.</p>
  
  <pre><code>name  
     : Letter                 
     | Digit name              
     | Letter name          
     ;
  
  numeral  
     : Digit                
     | Digit numeral         
     ;
  
  fragment  
  Digit  
     : [0-9]  
     ;  
  
  fragment  
  Letter  
     : [a-zA-Z]  
     ;
  </code></pre>
  
  <p>So why does it show warnings for just two lines (Letter and Digit name) where i referenced a fragment and others below are completely fine...</p>