-refineTidyEnv :: TidyEnv -> DataCon -> [TyVar] -> Type -> TidyEnv
--- Refine the TidyEnv in the light of the type refinement from coreRefineTys
-refineTidyEnv tidy_env@(occ_env, var_env) con tvs scrut_ty
- = case coreRefineTys con tvs scrut_ty of
- Nothing -> tidy_env
- Just (tv_subst, all_bound_here)
- | all_bound_here -- Local type refinement only
- -> tidy_env
- | otherwise -- Apply the refining subst to the tidy env
- -- This ensures that occurences have the most refined type
- -- And that means that exprType will work right everywhere
- -> (occ_env, mapVarEnv (refine subst) var_env)
- where
- subst = mkOpenTvSubst tv_subst
- where
- refine subst var | isId var = setIdType var (substTy subst (idType var))
- | otherwise = var
-