anchor.diff:  arguments 
       : positionalArguments | namedArguments
       ;
  -      
  +    
   namedArgument
       : parameterName specifier /*(',' assignable)**/ ';'
       ;
  
positive.code: 
  assignable 
      : (functorStart) => functor
      | expression
      ;
  
  
negative.code: 
  classDeclaration
      :
          'class'?
          typeName
          typeParameters?
          formalParameters?
  