in
checkValidTheta InstThetaCtxt theta `thenM_`
checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_`
- checkValidInstHead tau `thenM` \ (clas,inst_tys) ->
+ checkValidInstHead tau `thenM` \ (clas,inst_tys) ->
checkTc (checkInstFDs theta clas inst_tys)
(instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
newDFunName clas inst_tys src_loc `thenM` \ dfun_name ->