standalone binary deriving

[Simon Peyton-Jones]

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 at haskell.org [mailto:glasgow-haskell-
| users-bounces at haskell.org] On Behalf Of Ben
| Sent: 04 May 2010 06:55
| To: glasgow-haskell-users at 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
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