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
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