X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypes%2FFamInstEnv.lhs;h=4cf33fc4d748ab65edfcf84674caa21b63f3538c;hp=60b55d10ce08c6c7b90b814062b3c9f6d51f0cff;hb=d2ce0f52d42edf32bb9f13796e6ba6edba8bd516;hpb=cd290fc88d35d5a32c994664baa56a5eae250e9e diff --git a/compiler/types/FamInstEnv.lhs b/compiler/types/FamInstEnv.lhs index 60b55d1..4cf33fc 100644 --- a/compiler/types/FamInstEnv.lhs +++ b/compiler/types/FamInstEnv.lhs @@ -10,30 +10,32 @@ module FamInstEnv ( pprFamInst, pprFamInstHdr, pprFamInsts, famInstHead, mkLocalFamInst, mkImportedFamInst, - FamInstEnvs, FamInstEnv, emptyFamInstEnv, + FamInstEnvs, FamInstEnv, emptyFamInstEnv, emptyFamInstEnvs, extendFamInstEnv, extendFamInstEnvList, famInstEnvElts, familyInstances, - lookupFamInstEnv, lookupFamInstEnvUnify + lookupFamInstEnv, lookupFamInstEnvConflicts, + + -- Normalisation + topNormaliseType ) where #include "HsVersions.h" import InstEnv import Unify -import TcGadt -import TcType import Type +import TypeRep import TyCon +import Coercion import VarSet import Var import Name -import OccName -import SrcLoc import UniqFM import Outputable - -import Maybe +import Maybes +import Util +import FastString \end{code} @@ -51,7 +53,7 @@ data FamInst -- Used for "rough matching"; same idea as for class instances , fi_tcs :: [Maybe Name] -- Top of type args - -- INVARIANT: fi_tcs = roughMatchTcs is_tys + -- INVARIANT: fi_tcs = roughMatchTcs fi_tys -- Used for "proper matching"; ditto , fi_tvs :: TyVarSet -- Template tyvars for full match @@ -68,6 +70,7 @@ data FamInst famInstTyCon :: FamInst -> TyCon famInstTyCon = fi_tycon +famInstTyVars :: FamInst -> TyVarSet famInstTyVars = fi_tvs \end{code} @@ -82,17 +85,18 @@ instance Outputable FamInst where pprFamInst :: FamInst -> SDoc pprFamInst famInst = hang (pprFamInstHdr famInst) - 2 (ptext SLIT("--") <+> (pprDefnLoc (getSrcLoc famInst))) + 2 (ptext (sLit "--") <+> pprNameLoc (getName famInst)) pprFamInstHdr :: FamInst -> SDoc pprFamInstHdr (FamInst {fi_fam = fam, fi_tys = tys, fi_tycon = tycon}) = pprTyConSort <+> pprHead where - pprHead = pprTypeApp (parenSymOcc (getOccName fam) (ppr 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" + 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" pprFamInsts :: [FamInst] -> SDoc pprFamInsts finsts = vcat (map pprFamInst finsts) @@ -161,6 +165,9 @@ data FamilyInstEnv -- * The fs_tvs are distinct in each FamInst -- of a range value of the map (so we can safely unify them) +emptyFamInstEnvs :: (FamInstEnv, FamInstEnv) +emptyFamInstEnvs = (emptyFamInstEnv, emptyFamInstEnv) + emptyFamInstEnv :: FamInstEnv emptyFamInstEnv = emptyUFM @@ -189,7 +196,7 @@ extendFamInstEnv inst_env ins_item@(FamInst {fi_fam = cls_nm, fi_tcs = mb_tcs}) %************************************************************************ %* * -\subsection{Looking up a family instance} + Looking up a family instance %* * %************************************************************************ @@ -198,48 +205,82 @@ Multiple matches are only possible in case of type families (not data families), and then, it doesn't matter which match we choose (as the instances are guaranteed confluent). -\begin{code} -lookupFamInstEnv :: FamInstEnvs - -> TyCon -> [Type] -- What we are looking for - -> [(TvSubst, FamInst)] -- Successful matches -lookupFamInstEnv (pkg_ie, home_ie) fam tys - = home_matches ++ pkg_matches - where - rough_tcs = roughMatchTcs tys - all_tvs = all isNothing rough_tcs - home_matches = lookup home_ie - pkg_matches = lookup pkg_ie +We return the matching family instances and the type instance at which it +matches. For example, if we lookup 'T [Int]' and have a family instance - -------------- - lookup env = case lookupUFM env fam of - Nothing -> [] -- No instances for this class - Just (FamIE insts has_tv_insts) - -- Short cut for common case: - -- The thing we are looking up is of form (C a - -- b c), and the FamIE has no instances of - -- that form, so don't bother to search - | all_tvs && not has_tv_insts -> [] - | otherwise -> find insts + data instance T [a] = .. - -------------- - find [] = [] - find (item@(FamInst { fi_tcs = mb_tcs, fi_tvs = tpl_tvs, - fi_tys = tpl_tys, fi_tycon = tycon }) : rest) - -- Fast check for no match, uses the "rough match" fields - | instanceCantMatch rough_tcs mb_tcs - = find rest +desugared to - -- Proper check - | Just subst <- tcMatchTys tpl_tvs tpl_tys tys - = (subst, item) : find rest + data :R42T a = .. + coe :Co:R42T a :: T [a] ~ :R42T a - -- No match => try next - | otherwise - = find rest +we return the matching instance '(FamInst{.., fi_tycon = :R42T}, Int)'. + +\begin{code} +type FamInstMatch = (FamInst, [Type]) -- Matching type instance + -- See Note [Over-saturated matches] + +lookupFamInstEnv + :: FamInstEnvs + -> TyCon -> [Type] -- What we are looking for + -> [FamInstMatch] -- Successful matches + +lookupFamInstEnv + = lookup_fam_inst_env match True + where + match _ tpl_tvs tpl_tys tys = tcMatchTys tpl_tvs tpl_tys tys + +lookupFamInstEnvConflicts + :: FamInstEnvs + -> FamInst -- Putative new instance + -> [TyVar] -- Unique tyvars, matching arity of FamInst + -> [FamInstMatch] -- Conflicting matches +-- E.g. when we are about to add +-- f : type instance F [a] = a->a +-- we do (lookupFamInstConflicts f [b]) +-- to find conflicting matches +-- The skolem tyvars are needed because we don't have a +-- unique supply to hand + +lookupFamInstEnvConflicts envs fam_inst skol_tvs + = lookup_fam_inst_env my_unify False envs fam tys' + where + inst_tycon = famInstTyCon fam_inst + (fam, tys) = expectJust "FamInstEnv.lookuFamInstEnvConflicts" + (tyConFamInst_maybe inst_tycon) + skol_tys = mkTyVarTys skol_tvs + tys' = substTys (zipTopTvSubst (tyConTyVars inst_tycon) skol_tys) tys + -- In example above, fam tys' = F [b] + + my_unify old_fam_inst tpl_tvs tpl_tys match_tys + = ASSERT2( tyVarsOfTypes tys `disjointVarSet` tpl_tvs, + (ppr fam <+> ppr tys) $$ + (ppr tpl_tvs <+> ppr tpl_tys) ) + -- Unification will break badly if the variables overlap + -- They shouldn't because we allocate separate uniques for them + case tcUnifyTys instanceBindFun tpl_tys match_tys of + Just subst | conflicting old_fam_inst subst -> Just subst + _other -> Nothing + + -- - In the case of data family instances, any overlap is fundamentally a + -- conflict (as these instances imply injective type mappings). + -- - In the case of type family instances, overlap is admitted as long as + -- the right-hand sides of the overlapping rules coincide under the + -- overlap substitution. We require that they are syntactically equal; + -- anything else would be difficult to test for at this stage. + conflicting old_fam_inst subst + | isAlgTyCon fam = True + | otherwise = not (old_rhs `tcEqType` new_rhs) + where + old_tycon = famInstTyCon old_fam_inst + 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 @@ -249,16 +290,45 @@ Moreover, matching is the wildly more frequently used operation in the case of indexed synonyms and we don't want to slow that down by needless unification. \begin{code} -lookupFamInstEnvUnify :: (FamInstEnv, FamInstEnv) -> TyCon -> [Type] - -> [(TvSubst, FamInst)] -lookupFamInstEnvUnify (pkg_ie, home_ie) fam tys - = home_matches ++ pkg_matches +------------------------------------------------------------ +-- Might be a one-way match or a unifier +type MatchFun = FamInst -- The FamInst template + -> TyVarSet -> [Type] -- fi_tvs, fi_tys of that FamInst + -> [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 one_sided (pkg_ie, home_ie) fam tys + | not (isFamilyTyCon fam) + = [] + | otherwise + = ASSERT( n_tys >= arity ) -- Family type applications must be saturated + home_matches ++ pkg_matches where - rough_tcs = roughMatchTcs tys - all_tvs = all isNothing rough_tcs home_matches = lookup home_ie pkg_matches = lookup pkg_ie + -- See Note [Over-saturated matches] + arity = tyConArity fam + n_tys = length tys + extra_tys = drop arity tys + (match_tys, add_extra_tys) + | arity > n_tys = (take arity tys, \res_tys -> res_tys ++ extra_tys) + | otherwise = (tys, \res_tys -> res_tys) + -- The second case is the common one, hence functional representation + + -------------- + rough_tcs = roughMatchTcs match_tys + all_tvs = all isNothing rough_tcs && one_sided + -------------- lookup env = case lookupUFM env fam of Nothing -> [] -- No instances for this class @@ -278,19 +348,149 @@ lookupFamInstEnvUnify (pkg_ie, home_ie) fam tys | instanceCantMatch rough_tcs mb_tcs = find rest + -- Proper check + | Just subst <- match_fun item tpl_tvs tpl_tys match_tys + = (item, add_extra_tys $ substTyVars subst (tyConTyVars tycon)) : find rest + + -- No match => try next | otherwise - = ASSERT2( tyVarsOfTypes tys `disjointVarSet` tpl_tvs, - (ppr fam <+> ppr tys <+> ppr all_tvs) $$ - (ppr tycon <+> ppr tpl_tvs <+> ppr tpl_tys) - ) - -- Unification will break badly if the variables overlap - -- They shouldn't because we allocate separate uniques for them - case tcUnifyTys bind_fn tpl_tys tys of - Just subst -> (subst, item) : find rest - Nothing -> find rest + = find rest +\end{code} --- See explanation at @InstEnv.bind_fn@. --- -bind_fn tv | isTcTyVar tv && isExistentialTyVar tv = Skolem - | otherwise = BindMe +Note [Over-saturated matches] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +It's ok to look up an over-saturated type constructor. E.g. + type family F a :: * -> * + type instance F (a,b) = Either (a->b) + +The type instance gives rise to a newtype TyCon (at a higher kind +which you can't do in Haskell!): + newtype FPair a b = FP (Either (a->b)) + +Then looking up (F (Int,Bool) Char) will return a FamInstMatch + (FPair, [Int,Bool,Char]) + +The "extra" type argument [Char] just stays on the end. + + + + +%************************************************************************ +%* * + Looking up a family instance +%* * +%************************************************************************ + +\begin{code} +topNormaliseType :: FamInstEnvs + -> Type + -> Maybe (Coercion, Type) + +-- Get rid of *outermost* (or toplevel) +-- * type functions +-- * newtypes +-- using appropriate coercions. +-- By "outer" we mean that toplevelNormaliseType guarantees to return +-- a type that does not have a reducible redex (F ty1 .. tyn) as its +-- outermost form. It *can* return something like (Maybe (F ty)), where +-- (F ty) is a redex. + +-- Its a bit like Type.repType, but handles type families too + +topNormaliseType env ty + = go [] ty + where + go :: [TyCon] -> Type -> Maybe (Coercion, Type) + go rec_nts ty | Just ty' <- coreView ty -- Expand synonyms + = go rec_nts ty' + + go rec_nts (TyConApp tc tys) -- Expand newtypes + | Just co_con <- newTyConCo_maybe tc -- See Note [Expanding newtypes] + = if tc `elem` rec_nts -- in Type.lhs + then Nothing + else let nt_co = mkTyConApp co_con tys + in add_co nt_co rec_nts' nt_rhs + where + nt_rhs = newTyConInstRhs tc tys + rec_nts' | isRecursiveTyCon tc = tc:rec_nts + | otherwise = rec_nts + + go rec_nts (TyConApp tc tys) -- Expand open tycons + | 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 + -- to be sure that + add_co co rec_nts ty + + go _ _ = Nothing + + add_co co rec_nts ty + = case go rec_nts ty of + Nothing -> Just (co, ty) + Just (co', ty') -> Just (mkTransCoercion co co', ty') + + +--------------- +normaliseTcApp :: FamInstEnvs -> TyCon -> [Type] -> (CoercionI, Type) +normaliseTcApp env tc tys + = let -- First 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) +--------------- +normaliseType :: FamInstEnvs -- environment with family instances + -> Type -- old type + -> (CoercionI, Type) -- (coercion,new type), where + -- co :: old-type ~ new_type +-- Normalise the input type, by eliminating *all* type-function redexes +-- Returns with IdCo if nothing happens + +normaliseType env ty + | Just ty' <- coreView ty = normaliseType env ty' +normaliseType env (TyConApp tc tys) + = normaliseTcApp env 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) +normaliseType env (FunTy ty1 ty2) + = let (coi1,nty1) = normaliseType env ty1 + (coi2,nty2) = normaliseType env ty2 + in (mkFunTyCoI coi1 coi2, FunTy nty1 nty2) +normaliseType env (ForAllTy tyvar ty1) + = let (coi,nty1) = normaliseType env ty1 + in (mkForAllTyCoI tyvar coi, ForAllTy tyvar nty1) +normaliseType _ ty@(TyVarTy _) + = (IdCo ty,ty) +normaliseType env (PredTy predty) + = normalisePred env predty + +--------------- +normalisePred :: FamInstEnvs -> PredType -> (CoercionI,Type) +normalisePred env (ClassP cls tys) + = let (cois,tys') = mapAndUnzip (normaliseType env) 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 coi1 coi2, PredTy $ EqPred ty1' ty2') \end{code}