On Sat, Apr 9, 2011 at 12:13 PM, Michael Snoyman <michael@snoyman.com> wrote:

I definitely don't want to deal with cabal flags for this, it would mean that some packages wouldn't install on your system depending on how you build Persistent. For your case, it might be acceptable to just use standalone deriving declarations, ie:

deriving instance Data SpeciesId

deriving instance Data Animal

...

  I read the user's guide on how this works, but I think there might be something going on with the quasiquoter that is preventing it from working.  Or, more probable, I'm doing it wrong.

{-# LANGUAGE StandaloneDeriving #-}

Species

 name String Eq

 deriving Data Typeable

Animal

 species SpeciesId Eq

 name String Eq

 deriving Data Typeable

 deriving instance Data SpeciesId

Any combination that I've tried of 'deriving instance' throws an illegal type constructor error.  Do you happen to have an example of this?