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