I have added some of the required deriving clauses, however I now get lots of warnings about: Bad eta expand __coerce () (CmmParse.zgzg {- v rnrp -} @ () @ () (__coerce CmmParse.ExtCode {- tc rB2 -} happyzuxzu1 {- v a1B9 -}) (__coerce CmmParse.ExtCode {- tc rB2 -} happyzuxzu2 {- v a1B8 -}) (__coerce CmmParse.Env {- tc rB6 -} eta {- v skLC -})) () Is this something I should worry about? Keean.