anchor.diff:  
   directive
       : 'return' assignable? 
  -    //| 'produce' assignable
       | 'throw' expression? 
       | 'break' expression?
  +    | 'retry'
       ;
   
   abstractMemberDeclaration
  
positive.code: //assignable can be an assignment
  statement 
      : expressionStatement
      | controlStructure
      ;
  
  
negative.code:     : SIMPLESTRINGLITERAL
      | LEFTSTRINGLITERAL expression (MIDDLESTRINGLITERAL expression)* RIGHTSTRINGLITERAL 
      ;
  
  /*eventListener
      : 'on' '(' expression ')' 
        'assign'? memberName formalParameters?
        block
      ;*/
  
  assignable 
      : reflectedLiteral
  