X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FCoercion.lhs;h=49ae740c7009ce6a7a09101099b086aec8dfa808;hb=71d2bf9206b94d45570dc20de1a5ded12d493708;hp=c9de505c2a631647e4e4a6b69796ddfc205fc209;hpb=67ee8a93fc96a38c3f73468cb86d8421a11d2911;p=ghc-hetmet.git diff --git a/compiler/types/Coercion.lhs b/compiler/types/Coercion.lhs index c9de505..49ae740 100644 --- a/compiler/types/Coercion.lhs +++ b/compiler/types/Coercion.lhs @@ -1,5 +1,8 @@ +% +% (c) The University of Glasgow 2006 +% - Module for type coercions, as in System FC. +Module for type coercions, as in System FC. Coercions are represented as types, and their kinds tell what types the coercion works on. @@ -22,7 +25,7 @@ module Coercion ( mkSymCoercion, mkTransCoercion, mkLeftCoercion, mkRightCoercion, mkInstCoercion, mkAppCoercion, mkForAllCoercion, mkFunCoercion, mkInstsCoercion, mkUnsafeCoercion, - mkNewTypeCoercion, mkAppsCoercion, + mkNewTypeCoercion, mkFamInstCoercion, mkAppsCoercion, splitNewTypeRepCo_maybe, decomposeCo, @@ -34,29 +37,18 @@ module Coercion ( #include "HsVersions.h" import TypeRep -import Type ( Type, Kind, PredType, substTyWith, mkAppTy, mkForAllTy, - mkFunTy, splitAppTy_maybe, splitForAllTy_maybe, coreView, - kindView, mkTyConApp, isCoercionKind, isEqPred, mkAppTys, - coreEqType - ) -import TyCon ( TyCon, tyConArity, mkCoercionTyCon, isNewTyCon, - newTyConRhs, newTyConCo, - isCoercionTyCon, isCoercionTyCon_maybe ) -import Var ( Var, TyVar, isTyVar, tyVarKind ) -import Name ( BuiltInSyntax(..), Name, mkWiredInName, tcName ) -import OccName ( mkOccNameFS ) -import PrelNames ( symCoercionTyConKey, - transCoercionTyConKey, leftCoercionTyConKey, - rightCoercionTyConKey, instCoercionTyConKey, - unsafeCoercionTyConKey, gHC_PRIM - ) -import Util ( lengthIs, snocView ) -import Unique ( hasKey ) -import BasicTypes ( Arity ) +import Type +import TyCon +import Var +import Name +import OccName +import PrelNames +import Util +import Unique +import BasicTypes import Outputable - ------------------------------ decomposeCo :: Arity -> Coercion -> [Coercion] -- (decomposeCo 3 c) = [right (left (left c)), right (left c), right c] @@ -99,17 +91,14 @@ splitCoercionKind_maybe co | Just co' <- kindView co = splitCoercionKind_maybe c splitCoercionKind_maybe (PredTy (EqPred ty1 ty2)) = Just (ty1, ty2) splitCoercionKind_maybe other = Nothing -isCoVar :: Var -> Bool -isCoVar tv = isTyVar tv && isCoercionKind (tyVarKind tv) - type Coercion = Type type CoercionKind = Kind -- A CoercionKind is always of form (ty1 :=: ty2) coercionKind :: Coercion -> (Type, Type) -- c :: (t1 :=: t2) -- Then (coercionKind c) = (t1,t2) -coercionKind (TyVarTy a) | isCoVar a = splitCoercionKind (tyVarKind a) - | otherwise = let t = (TyVarTy a) in (t, t) +coercionKind ty@(TyVarTy a) | isCoVar a = splitCoercionKind (tyVarKind a) + | otherwise = (ty, ty) coercionKind (AppTy ty1 ty2) = let (t1, t2) = coercionKind ty1 (s1, s2) = coercionKind ty2 in @@ -117,10 +106,11 @@ coercionKind (AppTy ty1 ty2) coercionKind (TyConApp tc args) | Just (ar, rule) <- isCoercionTyCon_maybe tc -- CoercionTyCons carry their kinding rule, so we use it here - = if length args >= ar - then splitCoercionKind (rule args) - else pprPanic ("arity/arguments mismatch in coercionKind:") - (ppr ar $$ ppr tc <+> ppr args) + = 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) + | otherwise = let (lArgs, rArgs) = coercionKinds args in (TyConApp tc lArgs, TyConApp tc rArgs) @@ -165,40 +155,72 @@ mkAppsCoercion co1 tys = foldl mkAppTy co1 tys mkForAllCoercion tv co = ASSERT ( isTyVar tv ) mkForAllTy tv co mkFunCoercion co1 co2 = mkFunTy co1 co2 + +------------------------------- +-- This smart constructor creates a sym'ed version its argument, +-- but tries to push the sym's down to the leaves. If we come to +-- sym tv or sym tycon then we can drop the sym because tv and tycon +-- are reflexive coercions mkSymCoercion co - | Just co2 <- splitSymCoercion_maybe co = co2 - | Just (co1, co2) <- splitAppCoercion_maybe co - -- should make this case better - = mkAppCoercion (mkSymCoercion co1) (mkSymCoercion co2) - | Just (co1, co2) <- splitTransCoercion_maybe 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) - | Just (co, ty) <- splitInstCoercion_maybe co - = mkInstCoercion (mkSymCoercion co) ty - | Just co <- splitLeftCoercion_maybe co - = mkLeftCoercion (mkSymCoercion co) - | Just co <- splitRightCoercion_maybe co - = mkRightCoercion (mkSymCoercion co) -mkSymCoercion (ForAllTy tv ty) = ForAllTy tv (mkSymCoercion ty) --- for atomic types and constructors, we can just ignore sym since these --- are reflexive coercions + + | 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 -mkSymCoercion co = mkCoercion symCoercionTyCon [co] - -- this should not happen but does + | otherwise = TyVarTy tv -- Reflexive + +------------------------------- +-- ToDo: we should be cleverer about transitivity +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 mkLeftCoercion co | Just (co', _) <- splitAppCoercion_maybe co = co' - | otherwise = mkCoercion leftCoercionTyCon [co] + | otherwise = mkCoercion leftCoercionTyCon [co] mkRightCoercion co | Just (co1, co2) <- splitAppCoercion_maybe co = co2 | otherwise = mkCoercion rightCoercionTyCon [co] -mkTransCoercion co1 co2 = mkCoercion transCoercionTyCon [co1, co2] - -mkInstCoercion co ty = mkCoercion instCoercionTyCon [co, ty] +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] mkInstsCoercion co tys = foldl mkInstCoercion co tys @@ -255,27 +277,41 @@ splitRightCoercion_maybe (TyConApp tc [co]) splitRightCoercion_maybe other = Nothing -- Unsafe coercion is not safe, it is used when we know we are dealing with --- bottom, which is the one case in which it is safe. It is also used to +-- bottom, which is one case in which it is safe. It is also used to -- implement the unsafeCoerce# primitive. mkUnsafeCoercion :: Type -> Type -> Coercion mkUnsafeCoercion ty1 ty2 = mkCoercion unsafeCoercionTyCon [ty1, ty2] --- Make the coercion associated with a newtype. If we have --- --- newtype T a b = MkT (Int, a, b) --- --- Then (mkNewTypeCoercion CoT T [a,b] (Int, a, b)) creates the coercion --- CoT, such kinding rule such that --- --- CoT S U :: (Int, S, U) :=: T S U +-- See note [Newtype coercions] in TyCon mkNewTypeCoercion :: Name -> TyCon -> [TyVar] -> Type -> TyCon -mkNewTypeCoercion name tycon tvs rhs_ty - = ASSERT (length tvs == tyConArity tycon) - mkCoercionTyCon name (tyConArity tycon) rule +mkNewTypeCoercion name tycon tvs rhs_ty + = mkCoercionTyCon name co_con_arity rule where - rule args = mkCoKind (substTyWith tvs args rhs_ty) (TyConApp tycon args) + co_con_arity = length tvs + + rule args = ASSERT( co_con_arity == length args ) + (TyConApp tycon args, substTyWith tvs args rhs_ty) + +-- Coercion identifying a data/newtype/synonym representation type and its +-- family instance. It has the form `Co tvs :: F ts :=: R tvs', where `Co' is +-- the coercion tycon built here, `F' the family tycon and `R' the (derived) +-- representation tycon. +-- +mkFamInstCoercion :: Name -- unique name for the coercion tycon + -> [TyVar] -- type parameters of the coercion (`tvs') + -> TyCon -- family tycon (`F') + -> [Type] -- type instance (`ts') + -> TyCon -- representation tycon (`R') + -> TyCon -- => coercion tycon (`Co') +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 -------------------------------------- -- Coercion Type Constructors... @@ -286,14 +322,6 @@ mkNewTypeCoercion name tycon tvs rhs_ty -- sym d :: p2=q2 -- sym e :: p3=q3 -- then ((sym c) (sym d) (sym e)) :: (p1 p2 p3)=(q1 q2 q3) --- --- (mkKindingFun f) is given the args [c, sym d, sym e] -mkKindingFun :: ([Type] -> (Type, Type, [Type])) -> [Type] -> Kind -mkKindingFun f args = - let (ty1, ty2, rest) = f args in - let (argtys1, argtys2) = unzip (map coercionKind rest) in - mkCoKind (mkAppTys ty1 argtys1) (mkAppTys ty2 argtys2) - symCoercionTyCon, transCoercionTyCon, leftCoercionTyCon, rightCoercionTyCon, instCoercionTyCon :: TyCon -- Each coercion TyCon is built with the special CoercionTyCon record and @@ -301,33 +329,34 @@ symCoercionTyCon, transCoercionTyCon, leftCoercionTyCon, rightCoercionTyCon, ins -- 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 = - mkCoercionTyCon symCoercionTyConName 1 (mkKindingFun flipCoercionKindOf) + mkCoercionTyCon symCoercionTyConName 1 flipCoercionKindOf where - flipCoercionKindOf (co:rest) = (ty2, ty1, rest) + flipCoercionKindOf (co:rest) = ASSERT( null rest ) (ty2, ty1) where (ty1, ty2) = coercionKind co transCoercionTyCon = - mkCoercionTyCon transCoercionTyConName 2 (mkKindingFun composeCoercionKindsOf) + mkCoercionTyCon transCoercionTyConName 2 composeCoercionKindsOf where - composeCoercionKindsOf (co1:co2:rest) = + composeCoercionKindsOf (co1:co2:rest) + = ASSERT( null rest ) WARN( not (r1 `coreEqType` a2), text "Strange! Type mismatch in trans coercion, probably a bug") - (a1, r2, rest) + (a1, r2) where (a1, r1) = coercionKind co1 (a2, r2) = coercionKind co2 leftCoercionTyCon = - mkCoercionTyCon leftCoercionTyConName 1 (mkKindingFun leftProjectCoercionKindOf) + mkCoercionTyCon leftCoercionTyConName 1 leftProjectCoercionKindOf where - leftProjectCoercionKindOf (co:rest) = (ty1, ty2, rest) + leftProjectCoercionKindOf (co:rest) = ASSERT( null rest ) (ty1, ty2) where (ty1,ty2) = fst (splitCoercionKindOf co) rightCoercionTyCon = - mkCoercionTyCon rightCoercionTyConName 1 (mkKindingFun rightProjectCoercionKindOf) + mkCoercionTyCon rightCoercionTyConName 1 rightProjectCoercionKindOf where - rightProjectCoercionKindOf (co:rest) = (ty1, ty2, rest) + rightProjectCoercionKindOf (co:rest) = ASSERT( null rest ) (ty1, ty2) where (ty1,ty2) = snd (splitCoercionKindOf co) @@ -343,25 +372,26 @@ splitCoercionKindOf co = ((ty_fun1, ty_fun2),(ty_arg1, ty_arg2)) instCoercionTyCon - = mkCoercionTyCon instCoercionTyConName 2 (mkKindingFun instCoercionKind) + = mkCoercionTyCon instCoercionTyConName 2 instCoercionKind where instantiateCo t s = let Just (tv, ty) = splitForAllTy_maybe t in substTyWith [tv] [s] ty - instCoercionKind (co1:ty:rest) = (instantiateCo t1 ty, instantiateCo t2 ty, rest) + instCoercionKind (co1:ty:rest) = ASSERT( null rest ) + (instantiateCo t1 ty, instantiateCo t2 ty) where (t1, t2) = coercionKind co1 unsafeCoercionTyCon - = mkCoercionTyCon unsafeCoercionTyConName 2 (mkKindingFun unsafeCoercionKind) + = mkCoercionTyCon unsafeCoercionTyConName 2 unsafeCoercionKind where - unsafeCoercionKind (ty1:ty2:rest) = (ty1,ty2,rest) + unsafeCoercionKind (ty1:ty2:rest) = ASSERT( null rest ) (ty1,ty2) -------------------------------------- -- ...and their names mkCoConName occ key coCon = mkWiredInName gHC_PRIM (mkOccNameFS tcName occ) - key Nothing (ATyCon coCon) BuiltInSyntax + key (ATyCon coCon) BuiltInSyntax transCoercionTyConName = mkCoConName FSLIT("trans") transCoercionTyConKey transCoercionTyCon symCoercionTyConName = mkCoConName FSLIT("sym") symCoercionTyConKey symCoercionTyCon @@ -380,7 +410,7 @@ splitNewTypeRepCo_maybe :: Type -> Maybe (Type, Coercion) splitNewTypeRepCo_maybe ty | Just ty' <- coreView ty = splitNewTypeRepCo_maybe ty' splitNewTypeRepCo_maybe (TyConApp tc tys) - | isNewTyCon tc + | isClosedNewTyCon tc = ASSERT( tys `lengthIs` tyConArity tc ) -- splitNewTypeRepCo_maybe only be applied -- to *types* (of kind *) case newTyConRhs tc of @@ -388,6 +418,6 @@ splitNewTypeRepCo_maybe (TyConApp tc tys) ASSERT( length tvs == length tys ) Just (substTyWith tvs tys rep_ty, mkTyConApp co_con tys) where - co_con = maybe (pprPanic "splitNewTypeRepCo_maybe" (ppr tc)) id (newTyConCo tc) + co_con = maybe (pprPanic "splitNewTypeRepCo_maybe" (ppr tc)) id (newTyConCo_maybe tc) splitNewTypeRepCo_maybe other = Nothing \end{code}