anchor.diff:      | base
       ;
   
  -getterSetterMethodReference
  -    : 'set' prim -> ^(SET_EXPR prim)
  -    | 'get' prim -> ^(GET_EXPR prim)
  -    ;
  -
   postfixOperator
       : '--' | '++'
       ;	
  
positive.code:     | specialValue 
      | nonstringLiteral
      | prefixOperator
      | 'get'
      | 'set'
      ;
  
  expression
  
negative.code: 
  NONEMPTY
      :   'nonempty'
      ;
  
  RETURN
  