"impossible happened" with "class XML a where toXML :: a -> XML"

[Shae Matijs Erisson]

Breaking code is:
"class XML a where toXML :: a -> XML"

result is:
Compiling Main ( /home/shae/src/haskell/ProtoWebPublish.hs, interpreted )
ghc-6.4.20050303: panic! (the `impossible' happened, GHC version 6.4.20050303):
	ds_app_type Main.XML{tc r1BX} []

Not sure if this is already a known bug.
-- 
Shae Matijs Erisson - http://www.ScannedInAvian.com/ - Sockmonster once said:
You could switch out the unicycles for badgers, and the game would be the same.