X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypes%2FFamInstEnv.lhs;h=93a67a7eddc17417e9ed7fb1fed3c0c8039d5cc5;hp=4cf33fc4d748ab65edfcf84674caa21b63f3538c;hb=1e3348f855578fc60ed52fa62bb4846798a5cd3e;hpb=d2ce0f52d42edf32bb9f13796e6ba6edba8bd516 diff --git a/compiler/types/FamInstEnv.lhs b/compiler/types/FamInstEnv.lhs index 4cf33fc..93a67a7 100644 --- a/compiler/types/FamInstEnv.lhs +++ b/compiler/types/FamInstEnv.lhs @@ -88,15 +88,23 @@ pprFamInst famInst 2 (ptext (sLit "--") <+> pprNameLoc (getName famInst)) pprFamInstHdr :: FamInst -> SDoc -pprFamInstHdr (FamInst {fi_fam = fam, fi_tys = tys, fi_tycon = tycon}) - = pprTyConSort <+> pprHead +pprFamInstHdr (FamInst {fi_tycon = rep_tc}) + = pprTyConSort <+> pp_instance <+> pprHead where - pprHead = pprTypeApp fam tys - pprTyConSort | isDataTyCon tycon = ptext (sLit "data instance") - | isNewTyCon tycon = ptext (sLit "newtype instance") - | isSynTyCon tycon = ptext (sLit "type instance") - | isAbstractTyCon tycon = ptext (sLit "data instance") - | otherwise = panic "FamInstEnv.pprFamInstHdr" + Just (fam_tc, tys) = tyConFamInst_maybe rep_tc + + -- For *associated* types, say "type T Int = blah" + -- For *top level* type instances, say "type instance T Int = blah" + pp_instance + | isTyConAssoc fam_tc = empty + | otherwise = ptext (sLit "instance") + + pprHead = pprTypeApp fam_tc tys + pprTyConSort | isDataTyCon rep_tc = ptext (sLit "data") + | isNewTyCon rep_tc = ptext (sLit "newtype") + | isSynTyCon rep_tc = ptext (sLit "type") + | isAbstractTyCon rep_tc = ptext (sLit "data") + | otherwise = panic "FamInstEnv.pprFamInstHdr" pprFamInsts :: [FamInst] -> SDoc pprFamInsts finsts = vcat (map pprFamInst finsts) @@ -147,13 +155,31 @@ mkImportedFamInst fam mb_tcs tycon %* * %************************************************************************ -InstEnv maps a family name to the list of known instances for that family. +Note [FamInstEnv] +~~~~~~~~~~~~~~~~~~~~~ +A FamInstEnv maps a family name to the list of known instances for that family. + +The same FamInstEnv includes both 'data family' and 'type family' instances. +Type families are reduced during type inference, but not data families; +the user explains when to use a data family instance by using contructors +and pattern matching. + +Neverthless it is still useful to have data families in the FamInstEnv: + + - For finding overlaps and conflicts + + - For finding the representation type...see FamInstEnv.topNormaliseType + and its call site in Simplify + + - In standalone deriving instance Eq (T [Int]) we need to find the + representation type for T [Int] \begin{code} type FamInstEnv = UniqFM FamilyInstEnv -- Maps a family to its instances + -- See Note [FamInstEnv] type FamInstEnvs = (FamInstEnv, FamInstEnv) - -- External package inst-env, Home-package inst-env + -- External package inst-env, Home-package inst-env data FamilyInstEnv = FamIE [FamInst] -- The instances for a particular family, in any order @@ -161,6 +187,9 @@ data FamilyInstEnv -- If *not* then the common case of looking up -- (T a b c) can fail immediately +instance Outputable FamilyInstEnv where + ppr (FamIE fs b) = ptext (sLit "FamIE") <+> ppr b <+> vcat (map ppr fs) + -- INVARIANTS: -- * The fs_tvs are distinct in each FamInst -- of a range value of the map (so we can safely unify them) @@ -225,6 +254,7 @@ lookupFamInstEnv :: FamInstEnvs -> TyCon -> [Type] -- What we are looking for -> [FamInstMatch] -- Successful matches +-- Precondition: the tycon is saturated (or over-saturated) lookupFamInstEnv = lookup_fam_inst_env match True @@ -242,6 +272,8 @@ lookupFamInstEnvConflicts -- to find conflicting matches -- The skolem tyvars are needed because we don't have a -- unique supply to hand +-- +-- Precondition: the tycon is saturated (or over-saturated) lookupFamInstEnvConflicts envs fam_inst skol_tvs = lookup_fam_inst_env my_unify False envs fam tys' @@ -306,11 +338,14 @@ lookup_fam_inst_env -- The worker, local to this module -> FamInstEnvs -> TyCon -> [Type] -- What we are looking for -> [FamInstMatch] -- Successful matches + +-- Precondition: the tycon is saturated (or over-saturated) + lookup_fam_inst_env match_fun one_sided (pkg_ie, home_ie) fam tys | not (isFamilyTyCon fam) = [] | otherwise - = ASSERT( n_tys >= arity ) -- Family type applications must be saturated + = ASSERT2( n_tys >= arity, ppr fam <+> ppr tys ) -- Family type applications must be saturated home_matches ++ pkg_matches where home_matches = lookup home_ie @@ -434,25 +469,28 @@ topNormaliseType env ty --------------- normaliseTcApp :: FamInstEnvs -> TyCon -> [Type] -> (CoercionI, Type) normaliseTcApp env tc tys - = let -- First normalise the arg types so that they'll match + | isFamilyTyCon tc + , tyConArity tc <= length tys -- Unsaturated data families are possible + , [(fam_inst, inst_tys)] <- lookupFamInstEnv env tc ntys + = let -- A matching family instance exists + rep_tc = famInstTyCon fam_inst + co_tycon = expectJust "lookupFamInst" (tyConFamilyCoercion_maybe rep_tc) + co = mkTyConApp co_tycon inst_tys + first_coi = mkTransCoI tycon_coi (ACo co) + (rest_coi, nty) = normaliseType env (mkTyConApp rep_tc inst_tys) + fix_coi = mkTransCoI first_coi rest_coi + in + (fix_coi, nty) + + | otherwise + = (tycon_coi, TyConApp tc ntys) + + where + -- Normalise the arg types so that they'll match -- when we lookup in in the instance envt - (cois, ntys) = mapAndUnzip (normaliseType env) tys - tycon_coi = mkTyConAppCoI tc cois - in -- Now try the top-level redex - case lookupFamInstEnv env tc ntys of - -- A matching family instance exists - [(fam_inst, tys)] -> (fix_coi, nty) - where - rep_tc = famInstTyCon fam_inst - co_tycon = expectJust "lookupFamInst" (tyConFamilyCoercion_maybe rep_tc) - co = mkTyConApp co_tycon tys - first_coi = mkTransCoI tycon_coi (ACo co) - (rest_coi,nty) = normaliseType env (mkTyConApp rep_tc tys) - fix_coi = mkTransCoI first_coi rest_coi - - -- No unique matching family instance exists; - -- we do not do anything - _ -> (tycon_coi, TyConApp tc ntys) + (cois, ntys) = mapAndUnzip (normaliseType env) tys + tycon_coi = mkTyConAppCoI tc cois + --------------- normaliseType :: FamInstEnvs -- environment with family instances -> Type -- old type @@ -468,11 +506,11 @@ normaliseType env (TyConApp tc tys) normaliseType env (AppTy ty1 ty2) = let (coi1,nty1) = normaliseType env ty1 (coi2,nty2) = normaliseType env ty2 - in (mkAppTyCoI coi1 coi2, AppTy nty1 nty2) + in (mkAppTyCoI coi1 coi2, mkAppTy nty1 nty2) normaliseType env (FunTy ty1 ty2) = let (coi1,nty1) = normaliseType env ty1 (coi2,nty2) = normaliseType env ty2 - in (mkFunTyCoI coi1 coi2, FunTy nty1 nty2) + in (mkFunTyCoI coi1 coi2, mkFunTy nty1 nty2) normaliseType env (ForAllTy tyvar ty1) = let (coi,nty1) = normaliseType env ty1 in (mkForAllTyCoI tyvar coi, ForAllTy tyvar nty1)