anchor.diff:  
   expression
   	:   or_test
  -        -> or_test
       ;
   
   or_test
  
positive.code: not_test
  	:   OP_LOGICAL_NOT^ not_test
  	|   comparison
          -> comparison
  	;
  
  comparison
  
negative.code: 
  attr_constant_name
      :   NAME_NAME ATTR_EQ ATTR_VALUE_START t=NAME ATTR_VALUE_END
          -> CONSTANTNAME[$t, ($t.text)->chars]
      ;
  
  attr_expression_value
      :   NAME_VALUE! ATTR_EQ! ATTR_VALUE_START! expression ATTR_VALUE_END!
  