anchor.diff:   ;
   
   break_statement
  - : BREAK
  + : Mark=BREAK
    ;
   
   return_statement
  - : RETURN expression?
  + : Mark=RETURN Value=expression?
    ;
   
   compound_statement
  
positive.code:  ;           
  
  pass_statement
   : PASS
   ;
  
  flow_statement
  
negative.code:  ;
  
  if_statement
   : Mark=IF Condition=expression ':' IfSuite=suite ( ELSE ':' ElseSuite=suite )?
   ;
  
  for_statement
   : Mark=FOR Variable=NAME IN Object=expression ':' ForSuite=suite ( ELSE ':' ElseSuite=suite )?
   ;
  
  function_definition
   : Mark=DEF Name=NAME ('(' Parameter=parameter? ')')? ':' FunctionSuite=suite
   ;
  
  parameter
  