ghc puzzling behaviour

Hi, When compiling with -funbox-strict-fields, the supplied code doesn't seem to compile, requiring 'Ord Foo' to derive 'Ord Zot', even if 'Ord Bar' is explicitly declared. Without the flag, it works as expected. Is this intentional? I'll get by by dropping -funbox, or explicitly declaring the instance, so it's no big deal -- just slightly surprising. --T1.hs--

module T1 where

data Foo = Foo Int String data Bar = Bar Int Foo

instance Ord Bar where compare (Bar i _) (Bar j _) = compare i j

instance Eq Bar where (Bar i _) == (Bar j _) = i == j

--T2.hs--

module Main where

import T1

data Zot = Zot !Bar !String deriving (Ord,Eq)

main = putStrLn "Success"

-kzm -- If I haven't seen further, it is by standing in the footprints of giants