panic at applyTypeToArgs

[Robert Ennals]

Just came across an interesting little bug.


The compiler is essentially HEAD (last cvs updated yesterday - no obvious 
recent commits that would affect this).


The panic goes away if I do one of the following:
	change "Double" to "Int"  
	change "Double" to "[Double"]
	remove "deriving Show"
	compile without optimisation 


Hoping that this isn't just me doing something stupid when updating my source 
tree...


Here comes a log:


bash$ cat Bug.hs

module Bug
where

data Bla = Blob Double
        deriving Show
bash$ ghc --make -O Bug.hs
ghc-5.03: chasing modules from: Bug.hs
Compiling Bug              ( Bug.hs, ./Bug.o )
ghc-5.03: panic! (the `impossible' happened, GHC version 5.03):
        applyTypeToArgs
    PrelFloat.zdwshowsPrec1{-roY-}
      lvl_s1ae
      w_a19o
      ww_a19q
      (let {
         lvl46{-s1a7-} L :: [PrelBase.Char{-3o-}]
         Arity 0 Just DmdType
         lvl46{-s1a7-} =
           PrelBase.zdwZC{-65-}
             @ PrelBase.Char{-3o-} PrelShow.lvl37{-rhQ-} s{-rvo-} } in
       __letrec {
         showl{-s1a9-} _Kx L :: ([Bug.Bla{-r4-}] -> [PrelBase.Char{-3o-}])
         Arity 1 Just DmdType V
         showl{-s1a9-}
           = \ ds2{-rvx-} V :: [Bug.Bla{-r4-}] ->
               case ds2{-rvx-} of wild1{-rvt-} A {
                 PrelBase.ZC{-64-} y{-rvw-} U*(S*(L)) ys{-rvv-} L ->
                   let {
                     a_s1al L :: PrelBase.String{-r8R-}
                     Arity 0 Just DmdType {rvw->U(S*(L))}
                     a_s1al
                       = case y{-rvw-} of wild_XQ A { Bug.Blob{-r3-} 
b1{-X12K-} S*(L) ->
                         PrelBase.append{-r8U-}
                           @ PrelBase.Char{-3o-}
                           zz_s1a0
                           (case b1{-X12K-} of w_X1ad L { PrelFloat.Dzh{-66-} 
ww_X1ah L ->
                            PrelFloat.zdwshowsPrec1{-roY-}
                              lvl_s1ae w_X1ad ww_X1ah (showl{-s1a9-} ys{-rvv-})
                            })
                         }
                   } in
                     PrelBase.zdwZC{-65-}
                       @ PrelBase.Char{-3o-} PrelShow.lvl13{-ri0-} a_s1al;
                 PrelBase.ZMZN{-6m-} -> lvl46{-s1a7-}
               };
       } in  showl{-s1a9-} xs{-rvq-})

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


bash$ ghc --make Bug.hs
ghc-5.03: chasing modules from: Bug.hs
Compiling Bug              ( Bug.hs, ./Bug.o )     
bash$


-Rob