It's a bug. Thank you Simon | -----Original Message----- | From: glasgow-haskell-users-admin@haskell.org [mailto:glasgow-haskell-users-admin@haskell.org] | On Behalf Of George Russell | Sent: 11 June 2003 13:07 | To: glasgow-haskell-users@haskell.org | Subject: Conditions on deriving Typeable | | Please satisfy my curiosity, what is it about | | data WrappedDisplayType = forall displayType . | DisplayType displayType => WrappedDisplayType displayType | deriving (Typeable) | | that causes GHC 6.0 to utter | | DisplayTypes.hs:135: | Can't make a derived instance of `Typeable WrappedDisplayType' | (`WrappedDisplayType' has existentially-quantified constructor(s)) | When deriving instances for type `WrappedDisplayType' | | Obviously it doesn't like the existential quantifier, but why should | that be a problem for Typeable? | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users