ghc5.04.1 deriving Read/Show broken

[Simon Marlow]

> > The bug was also in 5.04.
> [snipped]
> No it wasn't.  This is what happens with ghc5.04 on Linux
> ----- cut here ------------------------
> # ghci --interactive
>    ___         ___ _
>   / _ \ /\  /\/ __(_)
>  / /_\// /_/ / /  | |      GHC Interactive, version 5.04, for 
> Haskell 98.
> / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
> \____/\/ /_/\____/|_|      Type :? for help.
> 
> Loading package base ... linking ... done.
> Loading package haskell98 ... linking ... done.
> Prelude> :load GHCBug
> Compiling GHCBug           ( GHCBug.hs, interpreted )
> Ok, modules loaded: GHCBug.
> *GHCBug> show (read (show (Commit 1 "1" Nothing)) :: Command)
> "Commit 1 \"1\" Nothing"
> ----- cut here -----------------------------

Sorry, it seems 5.04 didn't have this bug.  It had a different bug,
however; try

	> read "Just Nothing" :: Maybe (Maybe ())

we're currently looking into exactly what's changed.

Cheers,	
	Simon