X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FCoercion.lhs;h=08f593e9bd0c984e49ca56070162151c7dc350f9;hb=0e73a9fbdc8555ffb948cfd72401a700b122c395;hp=1996e704c3193a4cfe4c8698eaa94fd1fb169457;hpb=9e7dd142eeddc99ccfa9eada236371b267cfbdbb;p=ghc-hetmet.git diff --git a/compiler/types/Coercion.lhs b/compiler/types/Coercion.lhs index 1996e70..08f593e 100644 --- a/compiler/types/Coercion.lhs +++ b/compiler/types/Coercion.lhs @@ -1,9 +1,8 @@ -T% +% % (c) The University of Glasgow 2006 % \begin{code} -{-# OPTIONS -fno-warn-incomplete-patterns #-} -- The above warning supression flag is a temporary kludge. -- While working on this module you are encouraged to remove it and fix -- any warnings in the module. See @@ -21,7 +20,7 @@ module Coercion ( -- * Main data type Coercion, - mkCoKind, mkReflCoKind, coVarKind, + mkCoKind, mkCoPredTy, coVarKind, coVarKind_maybe, coercionKind, coercionKinds, isIdentityCoercion, -- ** Equality predicates @@ -30,7 +29,7 @@ module Coercion ( -- ** Coercion transformations mkCoercion, mkSymCoercion, mkTransCoercion, - mkLeftCoercion, mkRightCoercion, mkRightCoercions, + mkLeftCoercion, mkRightCoercion, mkInstCoercion, mkAppCoercion, mkTyConCoercion, mkFunCoercion, mkForAllCoercion, mkInstsCoercion, mkUnsafeCoercion, mkNewTypeCoercion, mkFamInstCoercion, mkAppsCoercion, @@ -43,11 +42,14 @@ module Coercion ( rightCoercionTyCon, instCoercionTyCon, -- needed by TysWiredIn csel1CoercionTyCon, csel2CoercionTyCon, cselRCoercionTyCon, + -- ** Decomposition + decompLR_maybe, decompCsel_maybe, decompInst_maybe, + -- ** Optimisation optCoercion, -- ** Comparison - coreEqCoercion, + coreEqCoercion, coreEqCoercion2, -- * CoercionI CoercionI(..), @@ -67,10 +69,13 @@ import Type import TyCon import Class import Var +import VarEnv import Name import PrelNames import Util +import Control.Monad import BasicTypes +import MonadUtils import Outputable import FastString @@ -102,15 +107,22 @@ decomposeCo n co coVarKind :: CoVar -> (Type,Type) -- c :: t1 ~ t2 -coVarKind cv = splitCoVarKind (tyVarKind cv) +coVarKind cv = case coVarKind_maybe cv of + Just ts -> ts + Nothing -> pprPanic "coVarKind" (ppr cv $$ ppr (tyVarKind cv)) + +coVarKind_maybe :: CoVar -> Maybe (Type,Type) +coVarKind_maybe cv = splitCoKind_maybe (tyVarKind cv) -- | Take a 'CoercionKind' apart into the two types it relates: see also 'mkCoKind'. -- Panics if the argument is not a valid 'CoercionKind' -splitCoVarKind :: Kind -> (Type, Type) -splitCoVarKind co | Just co' <- kindView co = splitCoVarKind co' -splitCoVarKind (PredTy (EqPred ty1 ty2)) = (ty1, ty2) +splitCoKind_maybe :: Kind -> Maybe (Type, Type) +splitCoKind_maybe co | Just co' <- kindView co = splitCoKind_maybe co' +splitCoKind_maybe (PredTy (EqPred ty1 ty2)) = Just (ty1, ty2) +splitCoKind_maybe _ = Nothing --- | Makes a 'CoercionKind' from two types: the types whose equality is proven by the relevant 'Coercion' +-- | Makes a 'CoercionKind' from two types: the types whose equality +-- is proven by the relevant 'Coercion' mkCoKind :: Type -> Type -> CoercionKind mkCoKind ty1 ty2 = PredTy (EqPred ty1 ty2) @@ -118,6 +130,15 @@ mkCoKind ty1 ty2 = PredTy (EqPred ty1 ty2) mkCoPredTy :: Type -> Type -> Type -> Type mkCoPredTy s t r = ForAllTy (mkWildCoVar (mkCoKind s t)) r +splitCoPredTy_maybe :: Type -> Maybe (Type, Type, Type) +splitCoPredTy_maybe ty + | Just (cv,r) <- splitForAllTy_maybe ty + , isCoVar cv + , Just (s,t) <- coVarKind_maybe cv + = Just (s,t,r) + | otherwise + = Nothing + -- | Tests whether a type is just a type equality predicate isEqPredTy :: Type -> Bool isEqPredTy (PredTy pred) = isEqPred pred @@ -133,10 +154,6 @@ getEqPredTys :: PredType -> (Type,Type) getEqPredTys (EqPred ty1 ty2) = (ty1, ty2) getEqPredTys other = pprPanic "getEqPredTys" (ppr other) --- | Create a reflexive 'CoercionKind' that asserts that a type can be coerced to itself -mkReflCoKind :: Type -> CoercionKind -mkReflCoKind ty = mkCoKind ty ty - -- | If it is the case that -- -- > c :: (t1 ~ t2) @@ -146,16 +163,20 @@ coercionKind :: Coercion -> (Type, Type) coercionKind ty@(TyVarTy a) | isCoVar a = coVarKind a | otherwise = (ty, ty) coercionKind (AppTy ty1 ty2) - = let (t1, t2) = coercionKind ty1 - (s1, s2) = coercionKind ty2 in - (mkAppTy t1 s1, mkAppTy t2 s2) -coercionKind (TyConApp tc args) + = let (s1, t1) = coercionKind ty1 + (s2, t2) = coercionKind ty2 in + (mkAppTy s1 s2, mkAppTy t1 t2) +coercionKind co@(TyConApp tc args) | Just (ar, rule) <- isCoercionTyCon_maybe tc -- CoercionTyCons carry their kinding rule, so we use it here - = ASSERT( length args >= ar ) -- Always saturated - let (ty1,ty2) = rule (take ar args) -- Apply the rule to the right number of args - (tys1, tys2) = coercionKinds (drop ar args) - in (mkAppTys ty1 tys1, mkAppTys ty2 tys2) + = WARN( not (length args >= ar), ppr co ) -- Always saturated + (let (ty1,ty2) = runID (rule (return . typeKind) + (return . coercionKind) + False (take ar args)) + -- Apply the rule to the right number of args + -- Always succeeds (if term is well-kinded!) + (tys1, tys2) = coercionKinds (drop ar args) + in (mkAppTys ty1 tys1, mkAppTys ty2 tys2)) | otherwise = let (lArgs, rArgs) = coercionKinds args in @@ -262,97 +283,25 @@ mkSymCoercion :: Coercion -> Coercion -- ^ Create a symmetric version of the given 'Coercion' that asserts equality -- between the same types but in the other "direction", so a kind of @t1 ~ t2@ -- becomes the kind @t2 ~ t1@. --- --- This function attempts to simplify the generated 'Coercion' by removing --- redundant applications of @sym@. This is done by pushing this new @sym@ --- down into the 'Coercion' and exploiting the fact that @sym (sym co) = co@. -mkSymCoercion co - | Just co' <- coreView co = mkSymCoercion co' - -mkSymCoercion (ForAllTy tv ty) = ForAllTy tv (mkSymCoercion ty) -mkSymCoercion (AppTy co1 co2) = AppTy (mkSymCoercion co1) (mkSymCoercion co2) -mkSymCoercion (FunTy co1 co2) = FunTy (mkSymCoercion co1) (mkSymCoercion co2) - -mkSymCoercion (TyConApp tc cos) - | not (isCoercionTyCon tc) = mkTyConApp tc (map mkSymCoercion cos) - -mkSymCoercion (TyConApp tc [co]) - | tc `hasKey` symCoercionTyConKey = co -- sym (sym co) --> co - | tc `hasKey` leftCoercionTyConKey = mkLeftCoercion (mkSymCoercion co) - | tc `hasKey` rightCoercionTyConKey = mkRightCoercion (mkSymCoercion co) - -mkSymCoercion (TyConApp tc [co1,co2]) - | tc `hasKey` transCoercionTyConKey - -- sym (co1 `trans` co2) --> (sym co2) `trans (sym co2) - -- Note reversal of arguments! - = mkTransCoercion (mkSymCoercion co2) (mkSymCoercion co1) - - | tc `hasKey` instCoercionTyConKey - -- sym (co @ ty) --> (sym co) @ ty - -- Note: sym is not applied to 'ty' - = mkInstCoercion (mkSymCoercion co1) co2 - -mkSymCoercion (TyConApp tc cos) -- Other coercion tycons, such as those - = mkCoercion symCoercionTyCon [TyConApp tc cos] -- arising from newtypes - -mkSymCoercion (TyVarTy tv) - | isCoVar tv = mkCoercion symCoercionTyCon [TyVarTy tv] - | otherwise = TyVarTy tv -- Reflexive - -------------------------------- --- ToDo: we should be cleverer about transitivity +mkSymCoercion g = mkCoercion symCoercionTyCon [g] mkTransCoercion :: Coercion -> Coercion -> Coercion -- ^ Create a new 'Coercion' by exploiting transitivity on the two given 'Coercion's. --- --- This function attempts to simplify the generated 'Coercion' by exploiting the fact that --- @sym g `trans` g = id@. -mkTransCoercion g1 g2 -- sym g `trans` g = id - | (t1,_) <- coercionKind g1 - , (_,t2) <- coercionKind g2 - , t1 `coreEqType` t2 - = t1 - - | otherwise - = mkCoercion transCoercionTyCon [g1, g2] - - -------------------------------- --- Smart constructors for left and right +mkTransCoercion g1 g2 = mkCoercion transCoercionTyCon [g1, g2] mkLeftCoercion :: Coercion -> Coercion -- ^ From an application 'Coercion' build a 'Coercion' that asserts the equality of -- the "functions" on either side of the type equality. So if @c@ has kind @f x ~ g y@ then: -- -- > mkLeftCoercion c :: f ~ g -mkLeftCoercion co - | Just (co', _) <- splitAppCoercion_maybe co = co' - | otherwise = mkCoercion leftCoercionTyCon [co] +mkLeftCoercion co = mkCoercion leftCoercionTyCon [co] mkRightCoercion :: Coercion -> Coercion -- ^ From an application 'Coercion' build a 'Coercion' that asserts the equality of -- the "arguments" on either side of the type equality. So if @c@ has kind @f x ~ g y@ then: -- -- > mkLeftCoercion c :: x ~ y -mkRightCoercion co - | Just (_, co2) <- splitAppCoercion_maybe co = co2 - | otherwise = mkCoercion rightCoercionTyCon [co] - -mkRightCoercions :: Int -> Coercion -> [Coercion] --- ^ As 'mkRightCoercion', but finds the 'Coercion's available on the right side of @n@ --- nested application 'Coercion's, manufacturing new left or right cooercions as necessary --- if suffficiently many are not directly available. -mkRightCoercions n co - = go n co [] - where - go n co acc - | n > 0 - = case splitAppCoercion_maybe co of - Just (co1,co2) -> go (n-1) co1 (co2:acc) - Nothing -> go (n-1) (mkCoercion leftCoercionTyCon [co]) (mkCoercion rightCoercionTyCon [co]:acc) - | otherwise - = acc - +mkRightCoercion co = mkCoercion rightCoercionTyCon [co] mkCsel1Coercion, mkCsel2Coercion, mkCselRCoercion :: Coercion -> Coercion mkCsel1Coercion co = mkCoercion csel1CoercionTyCon [co] @@ -363,72 +312,12 @@ mkCselRCoercion co = mkCoercion cselRCoercionTyCon [co] mkInstCoercion :: Coercion -> Type -> Coercion -- ^ Instantiates a 'Coercion' with a 'Type' argument. If possible, it immediately performs -- the resulting beta-reduction, otherwise it creates a suspended instantiation. -mkInstCoercion co ty - | Just (tv,co') <- splitForAllTy_maybe co - = substTyWith [tv] [ty] co' -- (forall a.co) @ ty --> co[ty/a] - | otherwise - = mkCoercion instCoercionTyCon [co, ty] +mkInstCoercion co ty = mkCoercion instCoercionTyCon [co, ty] mkInstsCoercion :: Coercion -> [Type] -> Coercion -- ^ As 'mkInstCoercion', but instantiates the coercion with a number of type arguments, left-to-right mkInstsCoercion co tys = foldl mkInstCoercion co tys -{- -splitSymCoercion_maybe :: Coercion -> Maybe Coercion -splitSymCoercion_maybe (TyConApp tc [co]) = - if tc `hasKey` symCoercionTyConKey - then Just co - else Nothing -splitSymCoercion_maybe co = Nothing --} - -splitAppCoercion_maybe :: Coercion -> Maybe (Coercion, Coercion) --- ^ Splits a coercion application, being careful *not* to split @left c@ etc. --- This is because those are really syntactic constructs, not applications -splitAppCoercion_maybe co | Just co' <- coreView co = splitAppCoercion_maybe co' -splitAppCoercion_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2) -splitAppCoercion_maybe (AppTy ty1 ty2) = Just (ty1, ty2) -splitAppCoercion_maybe (TyConApp tc tys) - | not (isCoercionTyCon tc) - = case snocView tys of - Just (tys', ty') -> Just (TyConApp tc tys', ty') - Nothing -> Nothing -splitAppCoercion_maybe _ = Nothing - -{- -splitTransCoercion_maybe :: Coercion -> Maybe (Coercion, Coercion) -splitTransCoercion_maybe (TyConApp tc [ty1, ty2]) - = if tc `hasKey` transCoercionTyConKey then - Just (ty1, ty2) - else - Nothing -splitTransCoercion_maybe other = Nothing - -splitInstCoercion_maybe :: Coercion -> Maybe (Coercion, Type) -splitInstCoercion_maybe (TyConApp tc [ty1, ty2]) - = if tc `hasKey` instCoercionTyConKey then - Just (ty1, ty2) - else - Nothing -splitInstCoercion_maybe other = Nothing - -splitLeftCoercion_maybe :: Coercion -> Maybe Coercion -splitLeftCoercion_maybe (TyConApp tc [co]) - = if tc `hasKey` leftCoercionTyConKey then - Just co - else - Nothing -splitLeftCoercion_maybe other = Nothing - -splitRightCoercion_maybe :: Coercion -> Maybe Coercion -splitRightCoercion_maybe (TyConApp tc [co]) - = if tc `hasKey` rightCoercionTyConKey then - Just co - else - Nothing -splitRightCoercion_maybe other = Nothing --} - -- | Manufacture a coercion from this air. Needless to say, this is not usually safe, -- but it is used when we know we are dealing with bottom, which is one case in which -- it is safe. This is also used implement the @unsafeCoerce#@ primitive. @@ -449,8 +338,12 @@ mkNewTypeCoercion name tycon tvs rhs_ty where co_con_arity = length tvs - rule args = ASSERT( co_con_arity == length args ) - (TyConApp tycon args, substTyWith tvs args rhs_ty) + rule :: CoTyConKindChecker + rule kc_ty _kc_co checking args + = do { ks <- mapM kc_ty args + ; unless (not checking || kindAppOk (tyConKind tycon) ks) + (fail "Argument kind mis-match") + ; return (TyConApp tycon args, substTyWith tvs args rhs_ty) } -- | Create a coercion identifying a @data@, @newtype@ or @type@ representation type -- and its family instance. It has the form @Co tvs :: F ts ~ R tvs@, where @Co@ is @@ -466,9 +359,22 @@ mkFamInstCoercion name tvs family instTys rep_tycon = mkCoercionTyCon name coArity rule where coArity = length tvs - rule args = (substTyWith tvs args $ -- with sigma = [tys/tvs], - TyConApp family instTys, -- sigma (F ts) - TyConApp rep_tycon args) -- ~ R tys + + rule :: CoTyConKindChecker + rule kc_ty _kc_co checking args + = do { ks <- mapM kc_ty args + ; unless (not checking || kindAppOk (tyConKind rep_tycon) ks) + (fail "Argument kind mis-match") + ; return (substTyWith tvs args $ -- with sigma = [tys/tvs], + TyConApp family instTys -- sigma (F ts) + , TyConApp rep_tycon args) } -- ~ R tys + +kindAppOk :: Kind -> [Kind] -> Bool +kindAppOk _ [] = True +kindAppOk kfn (k:ks) + = case splitKindFunTy_maybe kfn of + Just (kfa, kfb) | k `isSubKind` kfa -> kindAppOk kfb ks + _other -> False \end{code} @@ -497,92 +403,109 @@ symCoercionTyCon, transCoercionTyCon, leftCoercionTyCon, rightCoercionTyCon, instCoercionTyCon, unsafeCoercionTyCon, csel1CoercionTyCon, csel2CoercionTyCon, cselRCoercionTyCon :: TyCon -symCoercionTyCon = - mkCoercionTyCon symCoercionTyConName 1 flipCoercionKindOf +symCoercionTyCon + = mkCoercionTyCon symCoercionTyConName 1 kc_sym where - flipCoercionKindOf (co:rest) = ASSERT( null rest ) (ty2, ty1) - where - (ty1, ty2) = coercionKind co - -transCoercionTyCon = - mkCoercionTyCon transCoercionTyConName 2 composeCoercionKindsOf + kc_sym :: CoTyConKindChecker + kc_sym _kc_ty kc_co _ (co:_) + = do { (ty1,ty2) <- kc_co co + ; return (ty2,ty1) } + kc_sym _ _ _ _ = panic "kc_sym" + +transCoercionTyCon + = mkCoercionTyCon transCoercionTyConName 2 kc_trans where - composeCoercionKindsOf (co1:co2:rest) - = ASSERT( null rest ) - WARN( not (r1 `coreEqType` a2), - text "Strange! Type mismatch in trans coercion, probably a bug" - $$ - _err_stuff ) - (a1, r2) - where - (a1, r1) = coercionKind co1 - (a2, r2) = coercionKind co2 - - _err_stuff = vcat [ text "co1:" <+> ppr co1 - , text "co1 kind left:" <+> ppr a1 - , text "co1 kind right:" <+> ppr r1 - , text "co2:" <+> ppr co2 - , text "co2 kind left:" <+> ppr a2 - , text "co2 kind right:" <+> ppr r2 ] + kc_trans :: CoTyConKindChecker + kc_trans _kc_ty kc_co checking (co1:co2:_) + = do { (a1, r1) <- kc_co co1 + ; (a2, r2) <- kc_co co2 + ; unless (not checking || (r1 `coreEqType` a2)) + (fail "Trans coercion mis-match") + ; return (a1, r2) } + kc_trans _ _ _ _ = panic "kc_sym" --------------------------------------------------- -leftCoercionTyCon = mkCoercionTyCon leftCoercionTyConName 1 (fst . decompLR) -rightCoercionTyCon = mkCoercionTyCon rightCoercionTyConName 1 (snd . decompLR) - -decompLR :: [Type] -> ((Type,Type), (Type,Type)) +leftCoercionTyCon = mkCoercionTyCon leftCoercionTyConName 1 (kcLR_help fst) +rightCoercionTyCon = mkCoercionTyCon rightCoercionTyConName 1 (kcLR_help snd) + +kcLR_help :: (forall a. (a,a)->a) -> CoTyConKindChecker +kcLR_help select _kc_ty kc_co _checking (co : _) + = do { (ty1, ty2) <- kc_co co + ; case decompLR_maybe ty1 ty2 of + Nothing -> fail "decompLR" + Just res -> return (select res) } +kcLR_help _ _ _ _ _ = panic "kcLR_help" + +decompLR_maybe :: Type -> Type -> Maybe ((Type,Type), (Type,Type)) -- Helper for left and right. Finds coercion kind of its input and -- returns the left and right projections of the coercion... -- -- if c :: t1 s1 ~ t2 s2 then splitCoercionKindOf c = ((t1, t2), (s1, s2)) -decompLR (co : rest) - | (ty1, ty2) <- coercionKind co - , Just (ty_fun1, ty_arg1) <- splitAppTy_maybe ty1 +decompLR_maybe ty1 ty2 + | Just (ty_fun1, ty_arg1) <- splitAppTy_maybe ty1 , Just (ty_fun2, ty_arg2) <- splitAppTy_maybe ty2 - = ASSERT( null rest) - ((ty_fun1, ty_fun2),(ty_arg1, ty_arg2)) -decompLR cos - = pprPanic "Coercion.decompLR" - (ppr cos $$ vcat (map (pprEqPred .coercionKind) cos)) + = Just ((ty_fun1, ty_fun2),(ty_arg1, ty_arg2)) +decompLR_maybe _ _ = Nothing --------------------------------------------------- instCoercionTyCon - = mkCoercionTyCon instCoercionTyConName 2 instCoercionKind + = mkCoercionTyCon instCoercionTyConName 2 kcInst_help where - instantiateCo t s = - let Just (tv, ty) = splitForAllTy_maybe t in - substTyWith [tv] [s] ty - - instCoercionKind (co1:ty:rest) = ASSERT( null rest ) - (instantiateCo t1 ty, instantiateCo t2 ty) - where (t1, t2) = coercionKind co1 + kcInst_help :: CoTyConKindChecker + kcInst_help kc_ty kc_co checking (co : ty : _) + = do { (t1,t2) <- kc_co co + ; k <- kc_ty ty + ; case decompInst_maybe t1 t2 of + Nothing -> fail "decompInst" + Just ((tv1,tv2), (ty1,ty2)) -> do + { unless (not checking || (k `isSubKind` tyVarKind tv1)) + (fail "Coercion instantation kind mis-match") + ; return (substTyWith [tv1] [ty] ty1, + substTyWith [tv2] [ty] ty2) } } + kcInst_help _ _ _ _ = panic "kcInst_help" + +decompInst_maybe :: Type -> Type -> Maybe ((TyVar,TyVar), (Type,Type)) +decompInst_maybe ty1 ty2 + | Just (tv1,r1) <- splitForAllTy_maybe ty1 + , Just (tv2,r2) <- splitForAllTy_maybe ty2 + = Just ((tv1,tv2), (r1,r2)) +decompInst_maybe _ _ = Nothing --------------------------------------------------- unsafeCoercionTyCon - = mkCoercionTyCon unsafeCoercionTyConName 2 unsafeCoercionKind + = mkCoercionTyCon unsafeCoercionTyConName 2 kc_unsafe where - unsafeCoercionKind (ty1:ty2:rest) = ASSERT( null rest ) (ty1,ty2) + kc_unsafe kc_ty _kc_co _checking (ty1:ty2:_) + = do { _ <- kc_ty ty1 + ; _ <- kc_ty ty2 + ; return (ty1,ty2) } + kc_unsafe _ _ _ _ = panic "kc_unsafe" --------------------------------------------------- -- The csel* family + +csel1CoercionTyCon = mkCoercionTyCon csel1CoercionTyConName 1 (kcCsel_help fstOf3) +csel2CoercionTyCon = mkCoercionTyCon csel2CoercionTyConName 1 (kcCsel_help sndOf3) +cselRCoercionTyCon = mkCoercionTyCon cselRCoercionTyConName 1 (kcCsel_help thirdOf3) + +kcCsel_help :: (forall a. (a,a,a) -> a) -> CoTyConKindChecker +kcCsel_help select _kc_ty kc_co _checking (co : _) + = do { (ty1,ty2) <- kc_co co + ; case decompCsel_maybe ty1 ty2 of + Nothing -> fail "decompCsel" + Just res -> return (select res) } +kcCsel_help _ _ _ _ _ = panic "kcCsel_help" + +decompCsel_maybe :: Type -> Type -> Maybe ((Type,Type), (Type,Type), (Type,Type)) -- If co :: (s1~t1 => r1) ~ (s2~t2 => r2) --- Then csel1 co :: s1 ~ s2 --- csel2 co :: t1 ~ t2 --- cselR co :: r1 ~ r2 - -csel1CoercionTyCon = mkCoercionTyCon csel1CoercionTyConName 1 (fstOf3 . decompCsel) -csel2CoercionTyCon = mkCoercionTyCon csel2CoercionTyConName 1 (sndOf3 . decompCsel) -cselRCoercionTyCon = mkCoercionTyCon cselRCoercionTyConName 1 (thirdOf3 . decompCsel) - -decompCsel :: [Coercion] -> ((Type,Type), (Type,Type), (Type,Type)) -decompCsel (co : rest) - | (ty1,ty2) <- coercionKind co - , Just (cv1, r1) <- splitForAllTy_maybe ty1 - , Just (cv2, r2) <- splitForAllTy_maybe ty2 - , (s1,t1) <- ASSERT( isCoVar cv1) coVarKind cv1 - , (s2,t2) <- ASSERT( isCoVar cv1) coVarKind cv2 - = ASSERT( null rest ) - ((s1,s2), (t1,t2), (r1,r2)) -decompCsel other = pprPanic "decompCsel" (ppr other) +-- Then csel1 co :: s1 ~ s2 +-- csel2 co :: t1 ~ t2 +-- cselR co :: r1 ~ r2 +decompCsel_maybe ty1 ty2 + | Just (s1, t1, r1) <- splitCoPredTy_maybe ty1 + , Just (s2, t2, r2) <- splitCoPredTy_maybe ty2 + = Just ((s1,s2), (t1,t2), (r1,r2)) +decompCsel_maybe _ _ = Nothing fstOf3 :: (a,b,c) -> a sndOf3 :: (a,b,c) -> b @@ -659,6 +582,9 @@ splitNewTypeRepCo_maybe _ -- | Determines syntactic equality of coercions coreEqCoercion :: Coercion -> Coercion -> Bool coreEqCoercion = coreEqType + +coreEqCoercion2 :: RnEnv2 -> Coercion -> Coercion -> Bool +coreEqCoercion2 = coreEqType2 \end{code} @@ -729,7 +655,7 @@ mkAppTyCoI _ IdCo _ IdCo = IdCo mkAppTyCoI ty1 coi1 ty2 coi2 = ACo $ AppTy (fromCoI coi1 ty1) (fromCoI coi2 ty2) --- | Smart constructor for function-'Coercion's on 'CoercionI', see also 'mkFunCoercion' + mkFunTyCoI :: Type -> CoercionI -> Type -> CoercionI -> CoercionI mkFunTyCoI _ IdCo _ IdCo = IdCo mkFunTyCoI ty1 coi1 ty2 coi2 = @@ -743,7 +669,8 @@ mkForAllTyCoI tv (ACo co) = ACo $ ForAllTy tv co -- | Extract a 'Coercion' from a 'CoercionI' if it represents one. If it is the identity coercion, -- panic fromACo :: CoercionI -> Coercion -fromACo (ACo co) = co +fromACo (ACo co) = co +fromACo (IdCo {}) = panic "fromACo" -- | Smart constructor for class 'Coercion's on 'CoercionI'. Satisfies: -- @@ -772,182 +699,209 @@ mkEqPredCoI _ (ACo co1) ty2 coi2 = ACo $ PredTy $ EqPred co1 (fromCoI coi %************************************************************************ \begin{code} -optCoercion :: Coercion -> Coercion -optCoercion co - = ASSERT2( coercionKind co `eq` coercionKind result, - ppr co $$ ppr result $$ ppr (coercionKind co) $$ ppr (coercionKind result) ) - result +type NormalCo = Coercion + -- Invariants: + -- * For trans coercions (co1 `trans` co2) + -- co1 is not a trans, and neither co1 nor co2 is identity + -- * If the coercion is the identity, it has no CoVars of CoTyCons in it (just types) + +type NormalNonIdCo = NormalCo -- Extra invariant: not the identity + +optCoercion :: Coercion -> NormalCo +optCoercion co = opt_co False co + +opt_co :: Bool -- True <=> return (sym co) + -> Coercion + -> NormalCo +opt_co = opt_co' +-- opt_co sym co = pprTrace "opt_co {" (ppr sym <+> ppr co) $ +-- co1 `seq` +-- pprTrace "opt_co done }" (ppr co1) +-- WARN( not same_co_kind, ppr co <+> dcolon <+> pprEqPred (s1,t1) +-- $$ ppr co1 <+> dcolon <+> pprEqPred (s2,t2) ) +-- co1 +-- where +-- co1 = opt_co' sym co +-- same_co_kind = s1 `coreEqType` s2 && t1 `coreEqType` t2 +-- (s,t) = coercionKind co +-- (s1,t1) | sym = (t,s) +-- | otherwise = (s,t) +-- (s2,t2) = coercionKind co1 + +opt_co' sym (AppTy ty1 ty2) = mkAppTy (opt_co sym ty1) (opt_co sym ty2) +opt_co' sym (FunTy ty1 ty2) = FunTy (opt_co sym ty1) (opt_co sym ty2) +opt_co' sym (PredTy (ClassP cls tys)) = PredTy (ClassP cls (map (opt_co sym) tys)) +opt_co' sym (PredTy (IParam n ty)) = PredTy (IParam n (opt_co sym ty)) + +opt_co' sym co@(TyVarTy tv) + | not (isCoVar tv) = co -- Identity; does not mention a CoVar + | ty1 `coreEqType` ty2 = ty1 -- Identity; ..ditto.. + | not sym = co + | otherwise = mkSymCoercion co + where + (ty1,ty2) = coVarKind tv + +opt_co' sym (ForAllTy tv cor) + | isCoVar tv = mkCoPredTy (opt_co sym co1) (opt_co sym co2) (opt_co sym cor) + | otherwise = ForAllTy tv (opt_co sym cor) + where + (co1,co2) = coVarKind tv + +opt_co' sym (TyConApp tc cos) + | isCoercionTyCon tc + = foldl mkAppTy opt_co_tc + (map (opt_co sym) (drop arity cos)) + | otherwise + = TyConApp tc (map (opt_co sym) cos) + where + arity = tyConArity tc + opt_co_tc :: NormalCo + opt_co_tc = opt_co_tc_app sym tc (take arity cos) + +-------- +opt_co_tc_app :: Bool -> TyCon -> [Type] -> NormalCo +-- Used for CoercionTyCons only +opt_co_tc_app sym tc cos + | tc `hasKey` symCoercionTyConKey + = opt_co (not sym) co1 + + | tc `hasKey` transCoercionTyConKey + = if sym then opt_trans opt_co2 opt_co1 + else opt_trans opt_co1 opt_co2 + + | tc `hasKey` leftCoercionTyConKey + , Just (co1, _) <- splitAppTy_maybe opt_co1 + = co1 + + | tc `hasKey` rightCoercionTyConKey + , Just (_, co2) <- splitAppTy_maybe opt_co1 + = co2 + + | tc `hasKey` csel1CoercionTyConKey + , Just (s1,_,_) <- splitCoPredTy_maybe opt_co1 + = s1 + + | tc `hasKey` csel2CoercionTyConKey + , Just (_,s2,_) <- splitCoPredTy_maybe opt_co1 + = s2 + + | tc `hasKey` cselRCoercionTyConKey + , Just (_,_,r) <- splitCoPredTy_maybe opt_co1 + = r + + | tc `hasKey` instCoercionTyConKey + , Just (tv, co'') <- splitForAllTy_maybe opt_co1 + , let ty = co2 + = substTyWith [tv] [ty] co'' + + | otherwise -- Do not push sym inside top-level axioms + -- e.g. if g is a top-level axiom + -- g a : F a ~ a + -- Then (sym (g ty)) /= g (sym ty) !! + = if sym then mkSymCoercion the_co + else the_co + where + the_co = TyConApp tc cos + (co1 : cos1) = cos + (co2 : _) = cos1 + opt_co1 = opt_co sym co1 + opt_co2 = opt_co sym co2 + +------------- +opt_trans :: NormalCo -> NormalCo -> NormalCo +opt_trans co1 co2 + | isIdNormCo co1 = co2 + | otherwise = opt_trans1 co1 co2 + +opt_trans1 :: NormalNonIdCo -> NormalCo -> NormalCo +-- First arg is not the identity +opt_trans1 co1 co2 + | isIdNormCo co2 = co1 + | otherwise = opt_trans2 co1 co2 + +opt_trans2 :: NormalNonIdCo -> NormalNonIdCo -> NormalCo +-- Neither arg is the identity +opt_trans2 (TyConApp tc [co1a,co1b]) co2 + | tc `hasKey` transCoercionTyConKey + = opt_trans1 co1a (opt_trans2 co1b co2) + +opt_trans2 co1 co2 + | Just co <- opt_trans_rule co1 co2 + = co + +opt_trans2 co1 (TyConApp tc [co2a,co2b]) + | tc `hasKey` transCoercionTyConKey + , Just co1_2a <- opt_trans_rule co1 co2a + = if isIdNormCo co1_2a + then co2b + else opt_trans2 co1_2a co2b + +opt_trans2 co1 co2 + = mkTransCoercion co1 co2 + +------ +opt_trans_rule :: NormalNonIdCo -> NormalNonIdCo -> Maybe NormalCo +opt_trans_rule (TyConApp tc [co1]) co2 + | tc `hasKey` symCoercionTyConKey + , co1 `coreEqType` co2 + , (_,ty2) <- coercionKind co2 + = Just ty2 + +opt_trans_rule co1 (TyConApp tc [co2]) + | tc `hasKey` symCoercionTyConKey + , co1 `coreEqType` co2 + , (ty1,_) <- coercionKind co1 + = Just ty1 + +opt_trans_rule (TyConApp tc1 [co1,ty1]) (TyConApp tc2 [co2,ty2]) + | tc1 `hasKey` instCoercionTyConKey + , tc1 == tc2 + , ty1 `coreEqType` ty2 + = Just (mkInstCoercion (opt_trans2 co1 co2) ty1) + +opt_trans_rule (TyConApp tc1 cos1) (TyConApp tc2 cos2) + | not (isCoercionTyCon tc1) || + getUnique tc1 `elem` [ leftCoercionTyConKey, rightCoercionTyConKey + , csel1CoercionTyConKey, csel2CoercionTyConKey + , cselRCoercionTyConKey ] --Yuk! + , tc1 == tc2 -- Works for left,right, and csel* family + -- BUT NOT equality axioms + -- E.g. (g Int) `trans` (g Bool) + -- /= g (Int . Bool) + = Just (TyConApp tc1 (zipWith opt_trans cos1 cos2)) + +opt_trans_rule co1 co2 + | Just (co1a, co1b) <- splitAppTy_maybe co1 + , Just (co2a, co2b) <- splitAppTy_maybe co2 + = Just (mkAppTy (opt_trans co1a co2a) (opt_trans co1b co2b)) + + | Just (s1,t1,r1) <- splitCoPredTy_maybe co1 + , Just (s2,t2,r2) <- splitCoPredTy_maybe co1 + = Just (mkCoPredTy (opt_trans s1 s2) + (opt_trans t1 t2) + (opt_trans r1 r2)) + + | Just (tv1,r1) <- splitForAllTy_maybe co1 + , Just (tv2,r2) <- splitForAllTy_maybe co2 + , not (isCoVar tv1) -- Both have same kind + , let r2' = substTyWith [tv2] [TyVarTy tv1] r2 + = Just (ForAllTy tv1 (opt_trans2 r1 r2')) + +opt_trans_rule _ _ = Nothing + + +------------- +isIdNormCo :: NormalCo -> Bool +-- Cheap identity test: look for coercions with no coercion variables at all +-- So it'll return False for (sym g `trans` g) +isIdNormCo ty = go ty where - (s1,t1) `eq` (s2,t2) = s1 `coreEqType` s2 && t1 `coreEqType` t2 - - (result,_,_) = go co - -- optimized, changed?, identity? - go :: Coercion -> ( Coercion, Bool, Bool ) - -- traverse coercion term bottom up and return - -- - -- 1) equivalent coercion, in optimized form - -- - -- 2) whether the output coercion differs from - -- the input coercion - -- - -- 3) whether the coercion is an identity coercion - -- - -- Performs the following optimizations: - -- - -- sym id >-> id - -- trans id co >-> co - -- trans co id >-> co - -- sym (sym co) >-> co - -- trans g (sym g) >-> id - -- trans (sym g) g >-> id - -- - go ty@(TyVarTy a) | isCoVar a = let (ty1,ty2) = coercionKind ty - in (ty, False, ty1 `coreEqType` ty2) - | otherwise = (ty, False, True) - go ty@(AppTy ty1 ty2) - = let (ty1', chan1, id1) = go ty1 - (ty2', chan2, id2) = go ty2 - in if chan1 || chan2 - then (AppTy ty1' ty2', True, id1 && id2) - else (ty , False, id1 && id2) - go ty@(TyConApp tc args) - | tc == symCoercionTyCon, (ty1:tys) <- args - = goSym ty ty1 tys - | tc == transCoercionTyCon, [ty1,ty2] <- args - = goTrans ty ty1 ty2 - | tc == leftCoercionTyCon, [ty1] <- args - = goLeft ty ty1 - | tc == rightCoercionTyCon, [ty1] <- args - = goRight ty ty1 - | tc == instCoercionTyCon, [ty1,ty2] <- args - = goInst ty ty1 ty2 - | not (isCoercionTyCon tc) - = let (args', chans, ids) = mapAndUnzip3 go args - in if or chans - then (TyConApp tc args', True , and ids) - else (ty , False, and ids) - | otherwise - = (ty, False, False) - go ty@(FunTy ty1 ty2) - = let (ty1',chan1,id1) = go ty1 - (ty2',chan2,id2) = go ty2 - in if chan1 || chan2 - then (FunTy ty1' ty2', True , id1 && id2) - else (ty , False, id1 && id2) - go ty@(ForAllTy tv ty1) - = let (ty1', chan1, id1) = go ty1 - in if chan1 - then (ForAllTy tv ty1', True , id1) - else (ty , False, id1) - go ty@(PredTy (EqPred ty1 ty2)) - = let (ty1', chan1, id1) = go ty1 - (ty2', chan2, id2) = go ty2 - in if chan1 || chan2 - then (PredTy (EqPred ty1' ty2'), True , id1 && id2) - else (ty , False, id1 && id2) - go ty@(PredTy (ClassP cl args)) - = let (args', chans, ids) = mapAndUnzip3 go args - in if or chans - then (PredTy (ClassP cl args'), True , and ids) - else (ty , False, and ids) - go ty@(PredTy (IParam name ty1)) - = let (ty1', chan1, id1) = go ty1 - in if chan1 - then (PredTy (IParam name ty1'), True , id1) - else (ty , False, id1) - - goSym :: Coercion -> Coercion -> [Coercion] -> ( Coercion, Bool, Bool ) - -- - -- pushes the sym constructor inwards, if possible - -- - -- takes original coercion term - -- first argument - -- rest of arguments - goSym ty ty1 tys - = case mkSymCoercion ty1 of - (TyConApp tc _ ) | tc == symCoercionTyCon - -> let (tys',chans',ids) = mapAndUnzip3 go (ty1:tys) - in if or chans' - then (TyConApp symCoercionTyCon tys', True , and ids) - else (ty , False, and ids) - ty1' -> let (ty',_ ,id') = go (mkAppsCoercion ty1' tys) - in (ty',True,id') - - - goRight :: Coercion -> Coercion -> ( Coercion, Bool, Bool ) - -- - -- reduces the right constructor, if possible - -- - -- takes original coercion term - -- argument - -- - goRight ty ty1 - = case mkRightCoercion ty1 of - (TyConApp tc _ ) | tc == rightCoercionTyCon - -> let (ty1',chan1,id1) = go ty1 - in if chan1 - then (TyConApp rightCoercionTyCon [ty1'], True , id1) - else (ty , False, id1) - ty1' -> let (ty',_ ,id') = go ty1' - in (ty',True,id') - - goLeft :: Coercion -> Coercion -> ( Coercion, Bool, Bool ) - -- - -- reduces the left constructor, if possible - -- - -- takes original coercion term - -- argument - -- - goLeft ty ty1 - = case mkLeftCoercion ty1 of - (TyConApp tc _ ) | tc == leftCoercionTyCon - -> let (ty1',chan1,id1) = go ty1 - in if chan1 - then (TyConApp leftCoercionTyCon [ty1'], True , id1) - else (ty , False, id1) - ty1' -> let (ty',_ ,id') = go ty1' - in (ty',True,id') - - goInst :: Coercion -> Coercion -> Coercion -> ( Coercion, Bool, Bool ) - -- - -- reduces the inst constructor, if possible - -- - -- takes original coercion term - -- coercion argument - -- type argument - -- - goInst ty ty1 ty2 - = case mkInstCoercion ty1 ty2 of - (TyConApp tc _ ) | tc == instCoercionTyCon - -> let (ty1',chan1,id1) = go ty1 - in if chan1 - then (TyConApp instCoercionTyCon [ty1',ty2], True , id1) - else (ty , False, id1) - ty1' -> let (ty',_ ,id') = go ty1' - in (ty',True,id') - - goTrans :: Coercion -> Coercion -> Coercion -> ( Coercion, Bool, Bool ) - -- - -- trans id co >-> co - -- trans co id >-> co - -- trans g (sym g) >-> id - -- trans (sym g) g >-> id - -- - goTrans ty ty1 ty2 - | id1 - = (ty2', True, id2) - | id2 - = (ty1', True, False) - | chan1 || chan2 - = (TyConApp transCoercionTyCon [ty1',ty2'], True , False) - | Just ty' <- mty' - = (ty', True, True) - | otherwise - = (ty, False, False) - where (ty1', chan1, id1) = go ty1 - (ty2', chan2, id2) = go ty2 - mty' = case mkTransCoercion ty1' ty2' - of (TyConApp tc _) | tc == transCoercionTyCon - -> Nothing - ty' -> Just ty' + go (TyVarTy tv) = not (isCoVar tv) + go (AppTy t1 t2) = go t1 && go t2 + go (FunTy t1 t2) = go t1 && go t2 + go (ForAllTy tv ty) = go (tyVarKind tv) && go ty + go (TyConApp tc tys) = not (isCoercionTyCon tc) && all go tys + go (PredTy (IParam _ ty)) = go ty + go (PredTy (ClassP _ tys)) = all go tys + go (PredTy (EqPred t1 t2)) = go t1 && go t2 \end{code}