It's a bug, but it's been fixed http://hackage.haskell.org/trac/ghc/ticket/3833 Thakns Simon | -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell- | users-bounces@haskell.org] On Behalf Of Ben | Sent: 04 May 2010 06:55 | To: glasgow-haskell-users@haskell.org | Subject: standalone binary deriving | | compiling the following fragment in ghci | | {-# LANGUAGE StandaloneDeriving #-} | | import Data.Binary (Binary) | | newtype Pair a b = Pair (a,b) | deriving instance (Binary a, Binary b) => Binary (Pair a b) | | results in the following message: | | Prelude> :load "/Users/catbee/Documents/dev/haskell/savestream/foo.hs" | [1 of 1] Compiling Main ( | /Users/catbee/Documents/dev/haskell/savestream/foo.hs, interpreted ) | ghc: panic! (the 'impossible' happened) | (GHC version 6.12.1 for i386-apple-darwin): | genDerivBinds: bad derived class | binary-0.5.0.2:Data.Binary.Binary{tc rkt} | | Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug | | should i file a bug report? | | b | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users