- ([], _) -> returnNF_Tc ([], ty) -- Nothing to do
- (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) ->
- returnNF_Tc (tyvars', substTy tenv rho)
+ ([], _) -> returnNF_Tc ([], [], ty) -- Nothing to do
+ (tyvars, rho) -> tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', _, tenv) ->
+ tcSplitRhoTy (substTy tenv rho) `thenNF_Tc` \ (theta, tau) ->
+ returnNF_Tc (tyvars', theta, tau)