panic parsing a stmt in ghc 7 (possible regression?)

[Simon Peyton-Jones]

A panic is always a bug. Thanks for the test case.  I've created a ticket http://hackage.haskell.org/trac/ghc/ticket/4939

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-haskell-
| users-bounces at haskell.org] On Behalf Of Daniel Gorín
| Sent: 31 January 2011 21:56
| To: glasgow-haskell-users
| Subject: panic parsing a stmt in ghc 7 (possible regression?)
| 
| Hi
| 
| 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
| 
| 
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