import Maybes
import Util
import FastString
-
-import Maybe
\end{code}
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)
%* *
%************************************************************************
-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
-- 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)
:: 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
-- 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"
| 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
-> [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
--------------
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
| 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
---------------
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
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
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}
projects / ghc-hetmet.git / blobdiff