anchor.diff:     ;
   
   fieldList
  -   : (fixedPart (SEMI variantPart | SEMI)? | variantPart)
  +   : fixedPart (SEMI variantPart)? 
  +   | variantPart
      ;
   
   fixedPart
  
positive.code:    ;
  
  typeDefinitionPart
     : TYPE typeDefinition (SEMI typeDefinition)* SEMI
     ;
  
  typeDefinition
  
negative.code:    ;
  
  constantDefinitionPart
     : CONST (constantDefinition SEMI)+
     ;
  
  constantDefinition
  