Conditions on deriving Typeable
Wed, 11 Jun 2003 14:07:04 +0200
Please satisfy my curiosity, what is it about
data WrappedDisplayType = forall displayType .
DisplayType displayType => WrappedDisplayType displayType
that causes GHC 6.0 to utter
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?