Hi all, H98 and H2010 allow a context to be given for datatypes, e.g. the "Eq a" in data Eq a => Foo a = Constr a I have made a proposal to remove support for that context (ticket #139). More details are on the proposal wiki page: http://hackage.haskell.org/trac/haskell-prime/wiki/NoDatatypeContexts Thanks Ian