mkSymCoercion, mkTransCoercion,
mkLeftCoercion, mkRightCoercion, mkInstCoercion, mkAppCoercion,
mkForAllCoercion, mkFunCoercion, mkInstsCoercion, mkUnsafeCoercion,
- mkNewTypeCoercion, mkDataInstCoercion, mkAppsCoercion,
+ mkNewTypeCoercion, mkFamInstCoercion, mkAppsCoercion,
splitNewTypeRepCo_maybe, decomposeCo,
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
- -- sym (sym co) --> co
- | Just (co1, arg_tys) <- splitTyConApp_maybe co
- , not (isCoercionTyCon co1) = mkTyConApp co1 (map mkSymCoercion arg_tys)
- -- we can drop the sym for a TyCon
- -- sym (ty [t1, ..., tn]) --> ty [sym t1, ..., sym tn]
- | (co1, arg_tys) <- splitAppTys co
- , isTyVarTy co1 = mkAppTys (maybe_drop co1) (map mkSymCoercion arg_tys)
- -- sym (tv [t1, ..., tn]) --> tv [sym t1, ..., sym tn]
- -- if tv type variable
- -- sym (cv [t1, ..., tn]) --> (sym cv) [sym t1, ..., sym tn]
- -- if cv is a coercion variable
- -- fall through if head is a CoercionTyCon
- | 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
+
+ | tc `hasKey` instCoercionTyConKey
-- sym (co @ ty) --> (sym co) @ ty
- = mkInstCoercion (mkSymCoercion co) ty
- | Just co <- splitLeftCoercion_maybe co
- -- sym (left co) --> left (sym co)
- = mkLeftCoercion (mkSymCoercion co)
- | Just co <- splitRightCoercion_maybe co
- -- sym (right co) --> right (sym co)
- = mkRightCoercion (mkSymCoercion co)
- where
- maybe_drop (TyVarTy tv)
- | isCoVar tv = mkCoercion symCoercionTyCon [TyVarTy tv]
- | otherwise = TyVarTy tv
- maybe_drop other = other
-mkSymCoercion (ForAllTy tv ty) = ForAllTy tv (mkSymCoercion ty)
--- for atomic types and constructors, we can just ignore sym since these
--- are reflexive coercions
+ -- 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]
+ | 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
rule args = ASSERT( co_con_arity == length args )
(TyConApp tycon args, substTyWith tvs args rhs_ty)
--- Coercion identifying a data/newtype 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)
+-- 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.
--
-mkDataInstCoercion :: 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')
-mkDataInstCoercion name tvs family instTys rep_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
projects / ghc-hetmet.git / blobdiff