ghc-5.04: panic! ... tySplitTyConApp ...

compiling the below program with
   ghc -fglasgow-exts Main.hs

gives the following error:

ghc-5.04: panic! (the `impossible' happened, GHC
version 5.04):
        tcSplitTyConApp forall x{-r6S-} :: *.
Main.L{-rr-} x{-r6S-}


-----------------------------------------------------
-- Main.hs

module Main where

newtype FA c = FA (forall x . c x)
newtype L x = L [x]

my_nil = FA (L []) :: FA L

sample :: String
sample = case my_nil of FA (L x) -> "foo"++x 

-- -- but this works fine
-- sample = case my_nil of FA x -> case x of L y ->
"foo"++y 

main = print sample

Trac metadata

Trac field	Value
Version	5.04.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedFixed
Component	Compiler
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