X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FCoercion.lhs;h=83a5af341cacc4c33acb5a8a390b2852b47ee2b8;hb=bcadca676448e38427b910bad5d7063f948a99c8;hp=eda45a3efb99b57655c1f3fb6aaf946bcf78dbff;hpb=a17d329568660592dad5c7668fb09f31ab77cd69;p=ghc-hetmet.git diff --git a/compiler/types/Coercion.lhs b/compiler/types/Coercion.lhs index eda45a3..83a5af3 100644 --- a/compiler/types/Coercion.lhs +++ b/compiler/types/Coercion.lhs @@ -1,4 +1,4 @@ -% +T% % (c) The University of Glasgow 2006 % @@ -21,8 +21,8 @@ module Coercion ( -- * Main data type Coercion, - mkCoKind, mkReflCoKind, splitCoercionKind_maybe, splitCoercionKind, - coercionKind, coercionKinds, coercionKindPredTy, isIdentityCoercion, + mkCoKind, mkReflCoKind, coVarKind, + coercionKind, coercionKinds, isIdentityCoercion, -- ** Equality predicates isEqPred, mkEqPred, getEqPredTys, isEqPredTy, @@ -31,15 +31,20 @@ module Coercion ( mkCoercion, mkSymCoercion, mkTransCoercion, mkLeftCoercion, mkRightCoercion, mkRightCoercions, - mkInstCoercion, mkAppCoercion, - mkForAllCoercion, mkFunCoercion, mkInstsCoercion, mkUnsafeCoercion, + mkInstCoercion, mkAppCoercion, mkTyConCoercion, mkFunCoercion, + mkForAllCoercion, mkInstsCoercion, mkUnsafeCoercion, mkNewTypeCoercion, mkFamInstCoercion, mkAppsCoercion, + mkCsel1Coercion, mkCsel2Coercion, mkCselRCoercion, splitNewTypeRepCo_maybe, instNewTyCon_maybe, decomposeCo, unsafeCoercionTyCon, symCoercionTyCon, transCoercionTyCon, leftCoercionTyCon, rightCoercionTyCon, instCoercionTyCon, -- needed by TysWiredIn + csel1CoercionTyCon, csel2CoercionTyCon, cselRCoercionTyCon, + + -- ** Optimisation + optCoercion, -- ** Comparison coreEqCoercion, @@ -63,10 +68,8 @@ import TyCon import Class import Var import Name -import OccName import PrelNames import Util -import Unique import BasicTypes import Outputable import FastString @@ -97,6 +100,24 @@ decomposeCo n co ------------------------------------------------------- -- and some coercion kind stuff +coVarKind :: CoVar -> (Type,Type) +-- c :: t1 ~ t2 +coVarKind cv = splitCoVarKind (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) + +-- | 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) + +-- | (mkCoPredTy s t r) produces the type: (s~t) => r +mkCoPredTy :: Type -> Type -> Type -> Type +mkCoPredTy s t r = ForAllTy (mkWildCoVar (mkCoKind s t)) r + -- | Tests whether a type is just a type equality predicate isEqPredTy :: Type -> Bool isEqPredTy (PredTy pred) = isEqPred pred @@ -112,34 +133,17 @@ getEqPredTys :: PredType -> (Type,Type) getEqPredTys (EqPred ty1 ty2) = (ty1, ty2) getEqPredTys other = pprPanic "getEqPredTys" (ppr other) --- | 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) - -- | Create a reflexive 'CoercionKind' that asserts that a type can be coerced to itself mkReflCoKind :: Type -> CoercionKind mkReflCoKind ty = mkCoKind ty ty --- | Take a 'CoercionKind' apart into the two types it relates: see also 'mkCoKind'. --- Panics if the argument is not a valid 'CoercionKind' -splitCoercionKind :: CoercionKind -> (Type, Type) -splitCoercionKind co | Just co' <- kindView co = splitCoercionKind co' -splitCoercionKind (PredTy (EqPred ty1 ty2)) = (ty1, ty2) - --- | Take a 'CoercionKind' apart into the two types it relates, if possible. See also 'splitCoercionKind' -splitCoercionKind_maybe :: Kind -> Maybe (Type, Type) -splitCoercionKind_maybe co | Just co' <- kindView co = splitCoercionKind_maybe co' -splitCoercionKind_maybe (PredTy (EqPred ty1 ty2)) = Just (ty1, ty2) -splitCoercionKind_maybe _ = Nothing - -- | If it is the case that -- -- > c :: (t1 ~ t2) -- -- i.e. the kind of @c@ is a 'CoercionKind' relating @t1@ and @t2@, then @coercionKind c = (t1, t2)@. --- See also 'coercionKindPredTy' coercionKind :: Coercion -> (Type, Type) -coercionKind ty@(TyVarTy a) | isCoVar a = splitCoercionKind (tyVarKind a) +coercionKind ty@(TyVarTy a) | isCoVar a = coVarKind a | otherwise = (ty, ty) coercionKind (AppTy ty1 ty2) = let (t1, t2) = coercionKind ty1 @@ -160,13 +164,40 @@ coercionKind (FunTy ty1 ty2) = let (t1, t2) = coercionKind ty1 (s1, s2) = coercionKind ty2 in (mkFunTy t1 s1, mkFunTy t2 s2) -coercionKind (ForAllTy tv ty) + +coercionKind (ForAllTy tv ty) + | isCoVar tv +-- c1 :: s1~s2 c2 :: t1~t2 c3 :: r1~r2 +-- ---------------------------------------------- +-- c1~c2 => c3 :: (s1~t1) => r1 ~ (s2~t2) => r2 +-- or +-- forall (_:c1~c2) + = let (c1,c2) = coVarKind tv + (s1,s2) = coercionKind c1 + (t1,t2) = coercionKind c2 + (r1,r2) = coercionKind ty + in + (mkCoPredTy s1 t1 r1, mkCoPredTy s2 t2 r2) + + | otherwise +-- c1 :: s1~s2 c2 :: t1~t2 c3 :: r1~r2 +-- ---------------------------------------------- +-- forall a:k. c :: forall a:k. t1 ~ forall a:k. t2 = let (ty1, ty2) = coercionKind ty in (ForAllTy tv ty1, ForAllTy tv ty2) + coercionKind (PredTy (EqPred c1 c2)) - = let k1 = coercionKindPredTy c1 + = pprTrace "coercionKind" (pprEqPred (c1,c2)) $ + let k1 = coercionKindPredTy c1 k2 = coercionKindPredTy c2 in (k1,k2) + -- These should not show up in coercions at all + -- becuase they are in the form of for-alls + where + coercionKindPredTy c = let (t1, t2) = coercionKind c in mkCoKind t1 t2 + + + coercionKind (PredTy (ClassP cl args)) = let (lArgs, rArgs) = coercionKinds args in (PredTy (ClassP cl lArgs), PredTy (ClassP cl rArgs)) @@ -174,11 +205,6 @@ coercionKind (PredTy (IParam name ty)) = let (ty1, ty2) = coercionKind ty in (PredTy (IParam name ty1), PredTy (IParam name ty2)) --- | Recover the 'CoercionKind' corresponding to a particular 'Coerceion'. See also 'coercionKind' --- and 'mkCoKind' -coercionKindPredTy :: Coercion -> CoercionKind -coercionKindPredTy c = let (t1, t2) = coercionKind c in mkCoKind t1 t2 - -- | Apply 'coercionKind' to multiple 'Coercion's coercionKinds :: [Coercion] -> ([Type], [Type]) coercionKinds tys = unzip $ map coercionKind tys @@ -188,11 +214,17 @@ isIdentityCoercion :: Coercion -> Bool isIdentityCoercion co = case coercionKind co of (t1,t2) -> t1 `coreEqType` t2 +\end{code} -------------------------------------- --- Coercion kind and type mk's --- (make saturated TyConApp CoercionTyCon{...} args) +%************************************************************************ +%* * + Building coercions +%* * +%************************************************************************ + +Coercion kind and type mk's (make saturated TyConApp CoercionTyCon{...} args) +\begin{code} -- | Make a coercion from the specified coercion 'TyCon' and the 'Type' arguments to -- that coercion. Try to use the @mk*Coercion@ family of functions instead of using this function -- if possible @@ -200,36 +232,40 @@ mkCoercion :: TyCon -> [Type] -> Coercion mkCoercion coCon args = ASSERT( tyConArity coCon == length args ) TyConApp coCon args --- | Apply a 'Coercion' to another 'Coercion', which is presumably a 'Coercion' constructor of some --- kind +-- | Apply a 'Coercion' to another 'Coercion', which is presumably a +-- 'Coercion' constructor of some kind mkAppCoercion :: Coercion -> Coercion -> Coercion -mkAppCoercion co1 co2 = mkAppTy co1 co2 +mkAppCoercion co1 co2 = mkAppTy co1 co2 -- | Applies multiple 'Coercion's to another 'Coercion', from left to right. -- See also 'mkAppCoercion' mkAppsCoercion :: Coercion -> [Coercion] -> Coercion -mkAppsCoercion co1 tys = foldl mkAppTy co1 tys +mkAppsCoercion co1 tys = foldl mkAppTy co1 tys + +-- | Apply a type constructor to a list of coercions. +mkTyConCoercion :: TyCon -> [Coercion] -> Coercion +mkTyConCoercion con cos = mkTyConApp con cos + +-- | Make a function 'Coercion' between two other 'Coercion's +mkFunCoercion :: Coercion -> Coercion -> Coercion +mkFunCoercion co1 co2 = mkFunTy co1 co2 -- | Make a 'Coercion' which binds a variable within an inner 'Coercion' mkForAllCoercion :: Var -> Coercion -> Coercion -- note that a TyVar should be used here, not a CoVar (nor a TcTyVar) mkForAllCoercion tv co = ASSERT ( isTyVar tv ) mkForAllTy tv co --- | Make a function 'Coercion' between two other 'Coercion's -mkFunCoercion :: Coercion -> Coercion -> Coercion -mkFunCoercion co1 co2 = mkFunTy co1 co2 - ------------------------------- 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@. +-- ^ 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@. +-- 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' @@ -318,6 +354,12 @@ mkRightCoercions n co = acc +mkCsel1Coercion, mkCsel2Coercion, mkCselRCoercion :: Coercion -> Coercion +mkCsel1Coercion co = mkCoercion csel1CoercionTyCon [co] +mkCsel2Coercion co = mkCoercion csel2CoercionTyCon [co] +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. @@ -427,24 +469,34 @@ mkFamInstCoercion name tvs family instTys rep_tycon rule args = (substTyWith tvs args $ -- with sigma = [tys/tvs], TyConApp family instTys, -- sigma (F ts) TyConApp rep_tycon args) -- ~ R tys +\end{code} --------------------------------------- --- Coercion Type Constructors... - --- Example. The coercion ((sym c) (sym d) (sym e)) --- will be represented by (TyConApp sym [c, sym d, sym e]) --- If sym c :: p1=q1 --- sym d :: p2=q2 --- sym e :: p3=q3 --- then ((sym c) (sym d) (sym e)) :: (p1 p2 p3)=(q1 q2 q3) - --- | Coercion type constructors: avoid using these directly and instead use the @mk*Coercion@ and @split*Coercion@ family --- of functions if possible. -symCoercionTyCon, transCoercionTyCon, leftCoercionTyCon, rightCoercionTyCon, instCoercionTyCon, unsafeCoercionTyCon :: TyCon + +%************************************************************************ +%* * + Coercion Type Constructors +%* * +%************************************************************************ + +Example. The coercion ((sym c) (sym d) (sym e)) +will be represented by (TyConApp sym [c, sym d, sym e]) +If sym c :: p1=q1 + sym d :: p2=q2 + sym e :: p3=q3 +then ((sym c) (sym d) (sym e)) :: (p1 p2 p3)=(q1 q2 q3) + +\begin{code} +-- | Coercion type constructors: avoid using these directly and instead use +-- the @mk*Coercion@ and @split*Coercion@ family of functions if possible. +-- -- Each coercion TyCon is built with the special CoercionTyCon record and -- carries its own kinding rule. Such CoercionTyCons must be fully applied -- by any TyConApp in which they are applied, however they may also be over -- applied (see example above) and the kinding function must deal with this. +symCoercionTyCon, transCoercionTyCon, leftCoercionTyCon, + rightCoercionTyCon, instCoercionTyCon, unsafeCoercionTyCon, + csel1CoercionTyCon, csel2CoercionTyCon, cselRCoercionTyCon :: TyCon + symCoercionTyCon = mkCoercionTyCon symCoercionTyConName 1 flipCoercionKindOf where @@ -457,43 +509,42 @@ transCoercionTyCon = where composeCoercionKindsOf (co1:co2:rest) = ASSERT( null rest ) - WARN( not (r1 `coreEqType` a2), + WARN( not (r1 `coreEqType` a2), text "Strange! Type mismatch in trans coercion, probably a bug" $$ - ppr r1 <+> text "=/=" <+> ppr a2) + _err_stuff ) (a1, r2) where (a1, r1) = coercionKind co1 (a2, r2) = coercionKind co2 -leftCoercionTyCon = - mkCoercionTyCon leftCoercionTyConName 1 leftProjectCoercionKindOf - where - leftProjectCoercionKindOf (co:rest) = ASSERT( null rest ) (ty1, ty2) - where - (ty1,ty2) = fst (splitCoercionKindOf co) + _err_stuff = vcat [ text "co1:" <+> ppr co1 + , text "co1 kind left:" <+> ppr a1 + , text "co1 kind right:" <+> ppr r1 + , text "co2:" <+> ppr co2 + , text "co2 kind left:" <+> ppr a2 + , text "co2 kind right:" <+> ppr r2 ] -rightCoercionTyCon = - mkCoercionTyCon rightCoercionTyConName 1 rightProjectCoercionKindOf - where - rightProjectCoercionKindOf (co:rest) = ASSERT( null rest ) (ty1, ty2) - where - (ty1,ty2) = snd (splitCoercionKindOf co) +--------------------------------------------------- +leftCoercionTyCon = mkCoercionTyCon leftCoercionTyConName 1 (fst . decompLR) +rightCoercionTyCon = mkCoercionTyCon rightCoercionTyConName 1 (snd . decompLR) -splitCoercionKindOf :: Type -> ((Type,Type), (Type,Type)) +decompLR :: [Type] -> ((Type,Type), (Type,Type)) -- Helper for left and right. Finds coercion kind of its input and -- returns the left and right projections of the coercion... -- -- if c :: t1 s1 ~ t2 s2 then splitCoercionKindOf c = ((t1, t2), (s1, s2)) -splitCoercionKindOf co - | Just (ty1, ty2) <- splitCoercionKind_maybe (coercionKindPredTy co) +decompLR (co : rest) + | (ty1, ty2) <- coercionKind co , Just (ty_fun1, ty_arg1) <- splitAppTy_maybe ty1 , Just (ty_fun2, ty_arg2) <- splitAppTy_maybe ty2 - = ((ty_fun1, ty_fun2),(ty_arg1, ty_arg2)) -splitCoercionKindOf co - = pprPanic "Coercion.splitCoercionKindOf" - (ppr co $$ ppr (coercionKindPredTy co)) + = ASSERT( null rest) + ((ty_fun1, ty_fun2),(ty_arg1, ty_arg2)) +decompLR cos + = pprPanic "Coercion.decompLR" + (ppr cos $$ vcat (map (pprEqPred .coercionKind) cos)) +--------------------------------------------------- instCoercionTyCon = mkCoercionTyCon instCoercionTyConName 2 instCoercionKind where @@ -505,29 +556,71 @@ instCoercionTyCon (instantiateCo t1 ty, instantiateCo t2 ty) where (t1, t2) = coercionKind co1 +--------------------------------------------------- unsafeCoercionTyCon = mkCoercionTyCon unsafeCoercionTyConName 2 unsafeCoercionKind where unsafeCoercionKind (ty1:ty2:rest) = ASSERT( null rest ) (ty1,ty2) +--------------------------------------------------- +-- The csel* family +-- 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) + +fstOf3 :: (a,b,c) -> a +sndOf3 :: (a,b,c) -> b +thirdOf3 :: (a,b,c) -> c +fstOf3 (a,_,_) = a +sndOf3 (_,b,_) = b +thirdOf3 (_,_,c) = c + -------------------------------------- --- ...and their names +-- Their Names + +transCoercionTyConName, symCoercionTyConName, leftCoercionTyConName, + rightCoercionTyConName, instCoercionTyConName, unsafeCoercionTyConName, + csel1CoercionTyConName, csel2CoercionTyConName, cselRCoercionTyConName :: Name + +transCoercionTyConName = mkCoConName (fsLit "trans") transCoercionTyConKey transCoercionTyCon +symCoercionTyConName = mkCoConName (fsLit "sym") symCoercionTyConKey symCoercionTyCon +leftCoercionTyConName = mkCoConName (fsLit "left") leftCoercionTyConKey leftCoercionTyCon +rightCoercionTyConName = mkCoConName (fsLit "right") rightCoercionTyConKey rightCoercionTyCon +instCoercionTyConName = mkCoConName (fsLit "inst") instCoercionTyConKey instCoercionTyCon +csel1CoercionTyConName = mkCoConName (fsLit "csel1") csel1CoercionTyConKey csel1CoercionTyCon +csel2CoercionTyConName = mkCoConName (fsLit "csel2") csel2CoercionTyConKey csel2CoercionTyCon +cselRCoercionTyConName = mkCoConName (fsLit "cselR") cselRCoercionTyConKey cselRCoercionTyCon +unsafeCoercionTyConName = mkCoConName (fsLit "CoUnsafe") unsafeCoercionTyConKey unsafeCoercionTyCon mkCoConName :: FastString -> Unique -> TyCon -> Name mkCoConName occ key coCon = mkWiredInName gHC_PRIM (mkTcOccFS occ) key (ATyCon coCon) BuiltInSyntax - -transCoercionTyConName, symCoercionTyConName, leftCoercionTyConName, rightCoercionTyConName, instCoercionTyConName, unsafeCoercionTyConName :: Name - -transCoercionTyConName = mkCoConName (fsLit "trans") transCoercionTyConKey transCoercionTyCon -symCoercionTyConName = mkCoConName (fsLit "sym") symCoercionTyConKey symCoercionTyCon -leftCoercionTyConName = mkCoConName (fsLit "left") leftCoercionTyConKey leftCoercionTyCon -rightCoercionTyConName = mkCoConName (fsLit "right") rightCoercionTyConKey rightCoercionTyCon -instCoercionTyConName = mkCoConName (fsLit "inst") instCoercionTyConKey instCoercionTyCon -unsafeCoercionTyConName = mkCoConName (fsLit "CoUnsafe") unsafeCoercionTyConKey unsafeCoercionTyCon +\end{code} +%************************************************************************ +%* * + Newtypes +%* * +%************************************************************************ +\begin{code} instNewTyCon_maybe :: TyCon -> [Type] -> Maybe (Type, CoercionI) -- ^ If @co :: T ts ~ rep_ty@ then: -- @@ -569,6 +662,12 @@ coreEqCoercion = coreEqType \end{code} +%************************************************************************ +%* * + CoercionI and its constructors +%* * +%************************************************************************ + -------------------------------------- -- CoercionI smart constructors -- lifted smart constructors of ordinary coercions @@ -665,3 +764,107 @@ mkEqPredCoI _ IdCo _ IdCo = IdCo mkEqPredCoI ty1 IdCo _ (ACo co2) = ACo $ PredTy $ EqPred ty1 co2 mkEqPredCoI _ (ACo co1) ty2 coi2 = ACo $ PredTy $ EqPred co1 (fromCoI coi2 ty2) \end{code} + +%************************************************************************ +%* * + Optimising coercions +%* * +%************************************************************************ + +\begin{code} +optCoercion :: Coercion -> Coercion +optCoercion co + = ASSERT2( coercionKind co `eq` coercionKind result, + ppr co $$ ppr result $$ ppr (coercionKind co) $$ ppr (coercionKind result) ) + result + 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 + -- + 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] <- args + = case go ty1 of + (ty1', _ , True) -> (ty1', True, True) + (ty1', True, _ ) -> (TyConApp tc [ty1'], True, False) + (_ , _ , _ ) -> (ty, False, False) + | tc == transCoercionTyCon, [ty1,ty2] <- args + = let (ty1', chan1, id1) = go ty1 + (ty2', chan2, id2) = go ty2 + in if id1 + then (ty2', True, id2) + else if id2 + then (ty1', True, False) + else if chan1 || chan2 + then (TyConApp tc [ty1',ty2'], True , False) + else (ty , False, False) + | tc == leftCoercionTyCon, [ty1] <- args + = let (ty1', chan1, id1) = go ty1 + in if chan1 + then (TyConApp tc [ty1'], True , id1) + else (ty , False, id1) + | tc == rightCoercionTyCon, [ty1] <- args + = let (ty1', chan1, id1) = go ty1 + in if chan1 + then (TyConApp tc [ty1'], True , id1) + else (ty , False, id1) + | 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) +\end{code}