I am trying to work out empirically whether empty statement lists are allowed in a stmtlist, and one of the points these are used in Parser.y is for recursive do. If I try to load the following ---------------- {-# LANGUAGE RecursiveDo #-} bar :: IO () bar = do rec {} return () ----------------------- into GHCI, I get a "Prelude.head: empty list" panic. I think this is related to `rnRecStmtsAndThen` If I try --------------------- bar :: IO () bar = do do {} return () ----------------------- I get a warning about empty do statements not being allowed. Hence the question as to wether recursive do should be allowed to have an empty statement list. I am trying to manage the API annotations for semicolons in statement lists, and the current way it is being parsed makes this difficult, I would prefer to simplify it to something like how import decls are parsed, which can also have multiple semicolons in between. Alan