#4953: panic: urk! lookup local fingerprint main:B.throwErr{v rR3}
---------------------------------+------------------------------------------
Reporter: igloo | Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.0.2
Component: Compiler | Version: 7.0.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
---------------------------------+------------------------------------------
7.0.1 and HEAD accept the following pair of modules, but the 7.0 branch
panics (cut down from iteratee; iteratee-mtl and uni-htk have similar
panics):
{{{
{-# LANGUAGE Rank2Types, DeriveDataTypeable #-}
module A where
import Control.Exception (SomeException)
class NullPoint c where
empty :: c
class NullPoint c => Nullable c where
nullC :: c -> Bool
data Stream c = EOF | Chunk c
deriving (Show)
newtype Iteratee s m a = Iteratee{ runIter :: forall r.
(a -> Stream s -> m r) ->
((Stream s -> Iteratee s m a) -> Maybe SomeException -> m r) ->
m r}
icont :: (Stream s -> Iteratee s m a) -> Maybe SomeException -> Iteratee s
m a
icont k e = Iteratee $ \_ onCont -> onCont k e
instance (Monad m, Nullable s) => Monad (Iteratee s m) where
{-# INLINE return #-}
return x = Iteratee $ \onDone _ -> onDone x (Chunk empty)
{-# INLINE (>>=) #-}
m >>= f = Iteratee $ \onDone onCont ->
let m_done a (Chunk s)
| nullC s = runIter (f a) onDone onCont
m_done a stream = runIter (f a) (const . flip onDone stream)
f_cont
where f_cont k Nothing = runIter (k stream) onDone onCont
f_cont k e = onCont k e
in runIter m m_done (onCont . ((>>= f) .))
}}}
{{{
module B (throwErr, joinI) where
import A
import Control.Exception
import Data.Maybe
excDivergent :: SomeException
excDivergent = undefined
throwErr :: (Monad m) => SomeException -> Iteratee s m a
throwErr e = icont (const (throwErr e)) (Just e)
joinI ::
(Monad m, Nullable s) =>
Iteratee s m (Iteratee s' m a)
-> Iteratee s m a
joinI = (>>=
\inner -> Iteratee $ \od oc ->
let on_done x _ = od x (Chunk empty)
on_cont k Nothing = runIter (k EOF) on_done on_cont'
on_cont _ (Just e) = runIter (throwErr e) od oc
on_cont' _ e = runIter (throwErr (fromMaybe excDivergent e))
od oc
in runIter inner on_done on_cont)
}}}
{{{
$ ghc --make -O B
[1 of 2] Compiling A ( A.hs, A.o )
[2 of 2] Compiling B ( B.hs, B.o )
ghc-stage2: panic! (the 'impossible' happened)
(GHC version 7.0.1.20110203 for x86_64-unknown-linux):
urk! lookup local fingerprint main:B.throwErr{v rR3}
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4953>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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