Hi,
In attempting to use the lexer to see whether we are within an alternative
layout context:
ALR: True means that we are "Alternative Layout Mode" which happens when we
run the lexer. The False instances are from when the parser runs (after we
have done our checking).
Prelude Control.Monad.State> flip evalStateT 10 $ do
ALR: True
ALR: True
ALR: True
ALR: True
ALR: True
ALR: True
ALR: True
ALR: True
ALR: False
ALR: False
ALR: False
ALR: False
ALR: False
ALR: False
ALR: False
<interactive>:1:22: Empty 'do' construct
I have a function which tells us if there is layout going on:
activeContext :: P Bool
activeContext = do
ctxt <- getALRContext
expc <- getAlrExpectingOCurly
impt <- implicitTokenPending
case (ctxt,expc) of
([],Nothing) -> return $ False || impt
_other -> return $ True
and in InteractiveUI.hs:
we check the lexer state before we get the next token, since we want the
state immediately prior to encountering EOF.
-- #4316
-- lex the input. If there is an unclosed layout context, request input
checkInputForLayout :: String -> InputT GHCi (Maybe String)
-> InputT GHCi (Maybe String)
checkInputForLayout stmt getStmt = do
dflags' <- getDynFlags
let dflags = flattenExtensionFlags $
xopt_set dflags' Opt_AlternativeLayoutRule
buf <- liftIO $ stringToStringBuffer stmt
let loc = mkSrcLoc (fsLit "<interactive>") 1 1
pstate = Lexer.mkPState dflags buf loc
case Lexer.unP (goToEnd check) pstate of
(Lexer.POk _ False) -> return $ Just stmt
_other -> do
st <- lift getGHCiState
let p = prompt st
lift $ setGHCiState st{ prompt = "%s| " }
mb_stmt <- ghciHandle (\ex -> case fromException ex of
Just UserInterrupt -> return Nothing
_ -> case fromException ex of
Just ghc_e ->
do liftIO (print (ghc_e :: GhcException))
return Nothing
_other -> liftIO (Exception.throwIO ex))
getStmt
lift $ getGHCiState >>= \st->setGHCiState st{ prompt = p }
-- the recursive call does not recycle parser state
-- as we use a new string buffer
case mb_stmt of
Nothing -> return Nothing
Just str -> if str == ""
then return $ Just stmt
else checkInputForLayout (stmt++"\n"++str) getStmt
where lexFinished (L _ Lexer.ITeof) = return True
lexFinished _ = return False
check = do
actx <- Lexer.activeContext
eof <- Lexer.lexer lexFinished
return (actx,eof)
goToEnd m = do
(actx,eof) <- m
if eof then return actx else goToEnd m
Unfortunately, my "activeContext" is not firing on the input at the top of
the post. SimonM, any pointers?
Vivian
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