Pattern matching with implicit par. bug

There it goes,
J.A.


type CTPar = ([Double],Int,Int)
us :: (?ctPar :: CTPar) => [Double]
us = let (us',_,_) = ?ctPar in us'


ghc-5.04: panic! (the `impossible' happened, GHC version 5.04):
        tcSplitTyConApp
    {?ctPar{-r2kd-} :: ([GHCziFloat.Double{-3u-}],
                        GHCziBase.Int{-3J-},
                        GHCziBase.Int{-3J-})}

Please report it as a compiler bug to glasgow-haskell-bugs@xxxxxxxxxxx,
or http://sourceforge.net/projects/ghc/.