id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
7094,Irrefutable pattern failed for pattern Data.Maybe.Just,pganelin,,"The following invalid program causes ghc panic
{{{
-----------------------
--State-Monad.hs
data Term =  Con Int
     | Div Term Term
     deriving (Show)

type M a =  State -> (a,State)
type State =Int

instance Monad Int -> (a,Int) where
    g >>= f = undefined
    return = undefined
-------------------------------
}}}

{{{
D:\>""C:\Free\Haskell Platform\2012.2.0.0\bin\ghc.exe"" D:\State-Monad.hs
[1 of 1] Compiling Main             ( D:\State-Monad.hs, D:\State-Monad.o )
ghc.exe: panic! (the 'impossible' happened)
  (GHC version 7.4.1 for i386-unknown-mingw32):
        compiler\rename\RnSource.lhs:429:14-81: Irrefutable pattern failed for pattern Data.Maybe.Just (inst_tyvars,
                                                        _,
                                                        SrcLoc.L _ cls,
                                                        _)


Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
}}}",bug,closed,normal,7.6.1,Compiler (Parser),7.4.1,fixed,,,Windows,Unknown/Multiple,Compile-time crash,Unknown,,,,