Panic in parsing a stmt

Daniel Gorin (dgorin@dc.uba.ar) reports: I'm trying to make the hint library work also with ghc 7 and I'm having problems with some test-cases that are now raising exceptions. I've been able to reduce the problem to a small example. The program below runs ghc in interpreter-mode and attempts to parse an statement using ghc's parseStmt function; the particular statement is a let-expression with a \n in the middle. The observed behaviour is:

$ ghc-6.12.1 -fforce-recomp --make -package ghc -cpp -Wall d.hs && ./d 
[1 of 1] Compiling Main             ( d.hs, d.o )
Linking d ...
let {e = let x = ()
in x ;} in e
Ok
$ ghc-7.0.1 -fforce-recomp --make -package ghc -cpp -Wall d.hs && ./d 
[1 of 1] Compiling Main             ( d.hs, d.o )
Linking d ...
let {e = let x = ()
in x ;} in e
d: d: panic! (the 'impossible' happened)
  (GHC version 7.0.1 for i386-apple-darwin):
	srcLocCol <no location info>

Please report this as a GHC bug:  
http://www.haskell.org/ghc/reportabug

Is it a regression or should I be doing this some other way?

Thanks, Daniel

-- d.hs
import qualified GHC
import qualified MonadUtils as GHC ( liftIO ) import qualified StringBuffer as GHC import qualified Lexer as GHC import qualified Parser as GHC import qualified GHC.Paths

main :: IO ()
main = GHC.runGhcT (Just GHC.Paths.libdir) $ do
       -- initialize
       df0 <- GHC.getSessionDynFlags
       _ <- GHC.setSessionDynFlags df0{GHC.ghcMode    = GHC.CompManager,
                                       GHC.hscTarget  = GHC.HscInterpreted,
                                       GHC.ghcLink    = GHC.LinkInMemory,
                                       GHC.verbosity  = 0}
       df1 <- GHC.getSessionDynFlags
      -- runParser
       let expr = "let {e = let x = ()\nin x ;} in e"
       GHC.liftIO $ putStrLn expr
       buf <- GHC.liftIO $ GHC.stringToStringBuffer expr
       let p_res = GHC.unP GHC.parseStmt (mkPState df1 buf GHC.noSrcLoc)
       case  p_res of
         GHC.POk{} -> GHC.liftIO $ putStrLn "Ok"
         GHC.PFailed{} -> GHC.liftIO $ putStrLn "Failed"
    where
#if __GLASGOW_HASKELL__ >= 700
          mkPState = GHC.mkPState
#else
          mkPState = \a b c -> GHC.mkPState b c a #endif

Trac metadata

Trac field	Value
Version	7.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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