Polymorphic Trex fields

Hi! Hugs does not seem to support polymorphic fields for Trex records. What I want is to have types like: Rec ( id :: forall a . a -> a ) or Rec (bind :: (forall a b . M a -> (a -> M b) -> M b), return :: (forall a . a -> M a)) Is there a good reasong for not supporting this? (I suppose there is but I just want to make sure.) It would be great if this restriction could be lifted. Cheers, /Josef