id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
3886	Standalone deriving of NFData causes panic	blarsen		"Using the -XStandaloneDeriving option, I tried to generate an NFData instance for the CNF type from the funsat 0.60 package on Hackage.


{{{
{-# LANGUAGE StandaloneDeriving #-}
module Broken where

import Funsat.Types
import Control.Parallel.Strategies

deriving instance NFData AST
}}}


With ghc 6.12.1 on 32-bit Ubuntu, the above causes a panic:

ghc: panic! (the 'impossible' happened)
  (GHC version 6.12.1 for i386-unknown-linux):
	genDerivBinds: bad derived class
    deepseq-1.1.0.0:Control.DeepSeq.NFData{tc rou}

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
"	bug	closed	normal		Compiler	6.12.1	duplicate			Unknown/Multiple	Unknown/Multiple	Compile-time crash