X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FFamInstEnv.lhs;h=eed3bf57cb5b254c4c724dec7d16bf83769f123d;hb=ca9e79e1c70a26b12ea4b63f3a1c5a804462c1a5;hp=50c827f2223f73368c28aede19c1f39ac6f59e91;hpb=027e6be20af2e59e2ec720042d23ef06d9a7d4c1;p=ghc-hetmet.git diff --git a/compiler/types/FamInstEnv.lhs b/compiler/types/FamInstEnv.lhs index 50c827f..eed3bf5 100644 --- a/compiler/types/FamInstEnv.lhs +++ b/compiler/types/FamInstEnv.lhs @@ -36,8 +36,6 @@ import Outputable import Maybes import Util import FastString - -import Maybe \end{code} @@ -90,14 +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") - | 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) @@ -148,13 +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 @@ -226,9 +251,10 @@ 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 + = lookup_fam_inst_env match True where match _ tpl_tvs tpl_tys tys = tcMatchTys tpl_tvs tpl_tys tys @@ -243,9 +269,11 @@ 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 envs fam tys' + = lookup_fam_inst_env my_unify False envs fam tys' where inst_tycon = famInstTyCon fam_inst (fam, tys) = expectJust "FamInstEnv.lookuFamInstEnvConflicts" @@ -275,12 +303,13 @@ lookupFamInstEnvConflicts envs fam_inst skol_tvs | otherwise = not (old_rhs `tcEqType` new_rhs) where old_tycon = famInstTyCon old_fam_inst - old_rhs = mkTyConApp old_tycon (substTyVars subst (tyConTyVars old_tycon)) + old_tvs = tyConTyVars old_tycon + old_rhs = mkTyConApp old_tycon (substTyVars subst old_tvs) new_rhs = mkTyConApp inst_tycon (substTyVars subst skol_tvs) \end{code} While @lookupFamInstEnv@ uses a one-way match, the next function -@lookupFamInstEnvUnify@ uses two-way matching (ie, unification). This is +@lookupFamInstEnvConflicts@ uses two-way matching (ie, unification). This is needed to check for overlapping instances. For class instances, these two variants of lookup are combined into one @@ -297,16 +326,23 @@ type MatchFun = FamInst -- The FamInst template -> [Type] -- Target to match against -> Maybe TvSubst +type OneSidedMatch = Bool -- Are optimisations that are only valid for + -- one sided matches allowed? + lookup_fam_inst_env -- The worker, local to this module :: MatchFun + -> OneSidedMatch -> FamInstEnvs -> TyCon -> [Type] -- What we are looking for -> [FamInstMatch] -- Successful matches -lookup_fam_inst_env match_fun (pkg_ie, home_ie) fam tys - | not (isOpenTyCon fam) + +-- 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 @@ -323,7 +359,7 @@ lookup_fam_inst_env match_fun (pkg_ie, home_ie) fam tys -------------- rough_tcs = roughMatchTcs match_tys - all_tvs = all isNothing rough_tcs + all_tvs = all isNothing rough_tcs && one_sided -------------- lookup env = case lookupUFM env fam of @@ -412,7 +448,7 @@ topNormaliseType env ty | otherwise = rec_nts go rec_nts (TyConApp tc tys) -- Expand open tycons - | isOpenTyCon tc + | isFamilyTyCon tc , (ACo co, ty) <- normaliseTcApp env tc tys = -- The ACo says "something happened" -- Note that normaliseType fully normalises, but it has do to so @@ -430,25 +466,28 @@ 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 ntys 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 @@ -464,16 +503,16 @@ normaliseType env (TyConApp tc tys) normaliseType env (AppTy ty1 ty2) = let (coi1,nty1) = normaliseType env ty1 (coi2,nty2) = normaliseType env ty2 - in (mkAppTyCoI nty1 coi1 nty2 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 nty1 coi1 nty2 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) + in (mkForAllTyCoI tyvar coi, ForAllTy tyvar nty1) normaliseType _ ty@(TyVarTy _) - = (IdCo,ty) + = (IdCo ty,ty) normaliseType env (PredTy predty) = normalisePred env predty @@ -481,12 +520,12 @@ normaliseType env (PredTy predty) normalisePred :: FamInstEnvs -> PredType -> (CoercionI,Type) normalisePred env (ClassP cls tys) = let (cois,tys') = mapAndUnzip (normaliseType env) tys - in (mkClassPPredCoI cls tys' cois, PredTy $ ClassP cls tys') + in (mkClassPPredCoI cls cois, PredTy $ ClassP cls tys') normalisePred env (IParam ipn ty) = let (coi,ty') = normaliseType env ty in (mkIParamPredCoI ipn coi, PredTy $ IParam ipn ty') normalisePred env (EqPred ty1 ty2) = let (coi1,ty1') = normaliseType env ty1 (coi2,ty2') = normaliseType env ty2 - in (mkEqPredCoI ty1' coi1 ty2' coi2, PredTy $ EqPred ty1' ty2') + in (mkEqPredCoI coi1 coi2, PredTy $ EqPred ty1' ty2') \end{code}