anchor.diff:  
   statement
       :   namespace
  -    |   block
  +    |   enum_block
       |   if_block
  +    |   foreach_block
       |   while_block
       |   dowhile_block
       |   RETURN expression?
  
positive.code:     |   expression
      ;
  
  if_block
      :   IF expression block (ELSIF expression block)* (ELSE block)?
      ;
  
  while_block
  
negative.code:     ;
  
  func
      :   '(' params ')' flow_block
      |   '(' params ')' '->' inline_block
      ;
  
  call
  