id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
3964	Impossible happened when using ViewPattern in Arrows	uzytkownik	simonpj	"When I try to load file in ghci impossible happened:
{{{
ghc: panic! (the 'impossible' happened)
  (GHC version 6.12.1 for x86_64-unknown-linux):
	collectl/go
    ((=={v aOp} [lid]
      u{v avw} [lid]) -> {229:56-59}{229:56-59}ghc-prim:GHC.Bool.True{(w) d 6u})

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
}}}
Problematic function:
{{{
isOn :: ArrowChoice a => DSignal a c -> SF a b (Maybe c)                        
isOn (DSignal _ f u) = let sf = SF $! \_ -> proc (_, s, e) ->                   
                             case fromDynamic (_payload e) of                   
                                 Just (Event ((== u) -> True) v) ->             
                                     returnA -< (Just (f v), s, sf)             
                                 Nothing -> returnA -< (Nothing, s, sf)         
                       in sf
}}}
(Full sources will be attached. As it was found in-development so style may not be perfect)"	bug	closed	high	6.12.3	Compiler	6.12.1	fixed		uzytkownik2@…	Linux	x86_64 (amd64)	Compile-time crash		arrows/should_compile/T3964