X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcGadt.lhs;h=3761c68fada484fa600e215005bb306fbcaf7f36;hp=e0725fb66ce6c102185af7c88975540829f1ec3e;hb=84923cc7de2a93c22a2f72daf9ac863959efae13;hpb=143f4381d242e4a1c3174e8a0732a1e48f00a1aa diff --git a/compiler/typecheck/TcGadt.lhs b/compiler/typecheck/TcGadt.lhs index e0725fb..3761c68 100644 --- a/compiler/typecheck/TcGadt.lhs +++ b/compiler/typecheck/TcGadt.lhs @@ -1,4 +1,5 @@ % +% (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % @@ -10,33 +11,34 @@ \begin{code} module TcGadt ( - Refinement, emptyRefinement, gadtRefine, - refineType, refineResType, + Refinement, emptyRefinement, isEmptyRefinement, + gadtRefine, + refineType, refinePred, refineResType, dataConCanMatch, tcUnifyTys, BindFlag(..) ) where -import HsSyn ( ExprCoFn(..), idCoercion, isIdCoercion ) -import Coercion ( Coercion, mkSymCoercion, mkTransCoercion, mkUnsafeCoercion, - mkLeftCoercion, mkRightCoercion, - splitCoercionKind, decomposeCo ) -import TcType ( TvSubst(..), TvSubstEnv, substTy, mkTvSubst, - substTyVar, zipTopTvSubst, typeKind, - eqKind, isSubKind, repSplitAppTy_maybe, - tcView - ) -import Type ( Type, tyVarsOfType, tyVarsOfTypes ) -import TypeRep ( Type(..), PredType(..) ) -import DataCon ( DataCon, dataConUnivTyVars, dataConEqSpec ) -import Var ( CoVar, TyVar, tyVarKind ) +#include "HsVersions.h" + +import HsSyn +import Coercion +import Type + +import TypeRep +import DataCon +import Var import VarEnv import VarSet -import ErrUtils ( Message ) -import Maybes ( MaybeErr(..), isJust ) -import Control.Monad ( foldM ) +import ErrUtils +import Maybes +import Control.Monad import Outputable +import TcType -#include "HsVersions.h" +#ifdef DEBUG +import Unique +import UniqFM +#endif \end{code} @@ -47,42 +49,58 @@ import Outputable %************************************************************************ \begin{code} -data Refinement = Reft InScopeSet TvSubstEnv CoSubstEnv -type CoSubstEnv = TvSubstEnv -- Maps type variables to *coercions* --- INVARIANT: in the refinement (tsub, csub) --- forall a. (csub(a) :: a:=:tsub(a)) +data Refinement = Reft InScopeSet InternalReft + +type InternalReft = TyVarEnv (Coercion, Type) +-- INVARIANT: a->(co,ty) then co :: (a:=:ty) +-- Not necessarily idemopotent instance Outputable Refinement where - ppr (Reft in_scope tv_env co_env) - = ptext SLIT("Refinment") <+> - braces (ppr tv_env $$ ppr co_env) + ppr (Reft in_scope env) + = ptext SLIT("Refinement") <+> + braces (ppr env) emptyRefinement :: Refinement -emptyRefinement = Reft emptyInScopeSet emptyVarEnv emptyVarEnv +emptyRefinement = (Reft emptyInScopeSet emptyVarEnv) + +isEmptyRefinement :: Refinement -> Bool +isEmptyRefinement (Reft _ env) = isEmptyVarEnv env -refineType :: Refinement -> Type -> (ExprCoFn, Type) +refineType :: Refinement -> Type -> Maybe (Coercion, Type) -- Apply the refinement to the type. -- If (refineType r ty) = (co, ty') -- Then co :: ty:=:ty' -refineType (Reft in_scope tv_env co_env) ty - | not (isEmptyVarEnv tv_env), -- Common case - any (`elemVarEnv` tv_env) (varSetElems (tyVarsOfType ty)) - = (ExprCoFn (substTy co_subst ty), substTy tv_subst ty) +-- Nothing => the refinement does nothing to this type +refineType (Reft in_scope env) ty + | not (isEmptyVarEnv env), -- Common case + any (`elemVarEnv` env) (varSetElems (tyVarsOfType ty)) + = Just (substTy co_subst ty, substTy tv_subst ty) | otherwise - = (idCoercion, ty) -- The type doesn't mention any refined type variables + = Nothing -- The type doesn't mention any refined type variables where - tv_subst = mkTvSubst in_scope tv_env - co_subst = mkTvSubst in_scope co_env + tv_subst = mkTvSubst in_scope (mapVarEnv snd env) + co_subst = mkTvSubst in_scope (mapVarEnv fst env) -refineResType :: Refinement -> Type -> (ExprCoFn, Type) +refinePred :: Refinement -> PredType -> Maybe (Coercion, PredType) +refinePred (Reft in_scope env) pred + | not (isEmptyVarEnv env), -- Common case + any (`elemVarEnv` env) (varSetElems (tyVarsOfPred pred)) + = Just (mkPredTy (substPred co_subst pred), substPred tv_subst pred) + | otherwise + = Nothing -- The type doesn't mention any refined type variables + where + tv_subst = mkTvSubst in_scope (mapVarEnv snd env) + co_subst = mkTvSubst in_scope (mapVarEnv fst env) + +refineResType :: Refinement -> Type -> (HsWrapper, Type) -- Like refineType, but returns the 'sym' coercion -- If (refineResType r ty) = (co, ty') -- Then co :: ty':=:ty +-- It's convenient to return a HsWrapper here refineResType reft ty = case refineType reft ty of - (ExprCoFn co, ty1) -> (ExprCoFn (mkSymCoercion co), ty1) - (id_co, ty1) -> ASSERT( isIdCoercion id_co ) - (idCoercion, ty1) + Just (co, ty1) -> (WpCo (mkSymCoercion co), ty1) + Nothing -> (idHsWrapper, ty) \end{code} @@ -135,34 +153,38 @@ Two refinements: -- The result is idempotent: the \begin{code} -gadtRefine (Reft in_scope tv_env1 co_env1) +gadtRefine (Reft in_scope env1) ex_tvs co_vars --- Precondition: fvs( co_vars ) # tv_env1 +-- Precondition: fvs( co_vars ) # env1 -- That is, the kinds of the co_vars are a --- fixed point of the incoming refinement +-- fixed point of the incoming refinement - = initUM (tryToBind tv_set) $ + = ASSERT2( not $ any (`elemVarEnv` env1) (varSetElems $ tyVarsOfTypes $ map tyVarKind co_vars), + ppr env1 $$ ppr co_vars $$ ppr (map tyVarKind co_vars) ) + initUM (tryToBind tv_set) $ do { -- Run the unifier, starting with an empty env ; env2 <- foldM do_one emptyInternalReft co_vars -- Find the fixed point of the resulting -- non-idempotent substitution - ; let tv_env2 = tv_env1 `plusVarEnv` mapVarEnv snd env2 - co_env2 = co_env1 `plusVarEnv` mapVarEnv fst env2 - - ; return (Reft in_scope' (fixTvSubstEnv in_scope' tv_env2) - (fixTvSubstEnv in_scope' co_env2)) } + ; let tmp_env = env1 `plusVarEnv` env2 + out_env = fixTvCoEnv in_scope' tmp_env + ; WARN( not (null (badReftElts tmp_env)), ppr (badReftElts tmp_env) $$ ppr tmp_env ) + WARN( not (null (badReftElts out_env)), ppr (badReftElts out_env) $$ ppr out_env ) + return (Reft in_scope' out_env) } where tv_set = mkVarSet ex_tvs in_scope' = foldr extend in_scope co_vars + + -- For each co_var, add it *and* the tyvars it mentions, to in_scope extend co_var in_scope - = extendInScopeSetSet (extendInScopeSet in_scope co_var) - (tyVarsOfType (tyVarKind co_var)) + = extendInScopeSetSet in_scope $ + extendVarSet (tyVarsOfType (tyVarKind co_var)) co_var do_one reft co_var = unify reft (TyVarTy co_var) ty1 ty2 where (ty1,ty2) = splitCoercionKind (tyVarKind co_var) -\end{code} +\end{code} %************************************************************************ %* * @@ -196,21 +218,39 @@ tcUnifyTys bind_fn tys1 tys2 ---------------------------- -fixTvSubstEnv :: InScopeSet -> TvSubstEnv -> TvSubstEnv - -- Find the fixed point of a TvSubstEnv +fixTvCoEnv :: InScopeSet -> InternalReft -> InternalReft + -- Find the fixed point of a Refinement -- (assuming it has no loops!) +fixTvCoEnv in_scope env + = fixpt + where + fixpt = mapVarEnv step env + + step (co, ty) = case refineType (Reft in_scope fixpt) ty of + Nothing -> (co, ty) + Just (co', ty') -> (mkTransCoercion co co', ty') + -- Apply fixpt one step: + -- Use refineType to get a substituted type, ty', and a coercion, co_fn, + -- which justifies the substitution. If the coercion is not the identity + -- then use transitivity with the original coercion + +----------------------------- +fixTvSubstEnv :: InScopeSet -> TvSubstEnv -> TvSubstEnv fixTvSubstEnv in_scope env = fixpt where fixpt = mapVarEnv (substTy (mkTvSubst in_scope fixpt)) env ---------------------------- -dataConCanMatch :: DataCon -> [Type] -> Bool +dataConCanMatch :: [Type] -> DataCon -> Bool -- Returns True iff the data con can match a scrutinee of type (T tys) -- where T is the type constructor for the data con -- -- Instantiate the equations and try to unify them -dataConCanMatch con tys +dataConCanMatch tys con + | null eq_spec = True -- Common + | all isTyVarTy tys = True -- Also common + | otherwise = isJust (tcUnifyTys (\tv -> BindMe) (map (substTyVar subst . fst) eq_spec) (map snd eq_spec)) @@ -223,6 +263,8 @@ dataConCanMatch con tys tryToBind :: TyVarSet -> TyVar -> BindFlag tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe | otherwise = AvoidMe + + \end{code} @@ -233,10 +275,20 @@ tryToBind tv_set tv | tv `elemVarSet` tv_set = BindMe %************************************************************************ \begin{code} -type InternalReft = TyVarEnv (Coercion, Type) - --- INVARIANT: a->(co,ty) then co :: (a:=:ty) --- Not necessarily idemopotent +#ifdef DEBUG +badReftElts :: InternalReft -> [(Unique, (Coercion,Type))] +-- Return the BAD elements of the refinement +-- Should be empty; used in asserions only +badReftElts env + = filter (not . ok) (ufmToList env) + where + ok :: (Unique, (Coercion, Type)) -> Bool + ok (u, (co, ty)) | Just tv <- tcGetTyVar_maybe ty1 + = varUnique tv == u && ty `tcEqType` ty2 + | otherwise = False + where + (ty1,ty2) = coercionKind co +#endif emptyInternalReft :: InternalReft emptyInternalReft = emptyVarEnv @@ -338,11 +390,12 @@ uVar swap subst co tv1 ty -> unify subst (mkTransCoercion (mkSymCoercion co') co) ty' ty -- No, continue - Nothing -> uUnrefined subst (if swap then mkSymCoercion co else co) + Nothing -> uUnrefined swap subst co tv1 ty ty -uUnrefined :: InternalReft -- An existing substitution to extend +uUnrefined :: Bool -- Whether the input is swapped + -> InternalReft -- An existing substitution to extend -> Coercion -> TyVar -- Type variable to be unified -> Type -- with this type @@ -350,60 +403,62 @@ uUnrefined :: InternalReft -- An existing substitution to extend -> UM InternalReft -- We know that tv1 isn't refined --- PRE-CONDITION: in the call (uUnrefined r co tv ty ty'), we know that --- co :: tv:=:ty +-- PRE-CONDITION: in the call (uUnrefined False r co tv1 ty2 ty2'), we know that +-- co :: tv1:=:ty2 +-- and if the first argument is True instead, we know +-- co :: ty2:=:tv1 -uUnrefined subst co tv1 ty2 ty2' +uUnrefined swap subst co tv1 ty2 ty2' | Just ty2'' <- tcView ty2' - = uUnrefined subst co tv1 ty2 ty2'' -- Unwrap synonyms + = uUnrefined swap subst co tv1 ty2 ty2'' -- Unwrap synonyms -- This is essential, in case we have -- type Foo a = a -- and then unify a :=: Foo a -uUnrefined subst co tv1 ty2 (TyVarTy tv2) +uUnrefined swap subst co tv1 ty2 (TyVarTy tv2) | tv1 == tv2 -- Same type variable = return subst -- Check to see whether tv2 is refined - | Just (co',ty') <- lookupVarEnv subst tv2 - = uUnrefined subst (mkTransCoercion co co') tv1 ty' ty' + | Just (co',ty') <- lookupVarEnv subst tv2 -- co' :: tv2:=:ty' + = uUnrefined False subst (mkTransCoercion (doSwap swap co) co') tv1 ty' ty' -- So both are unrefined; next, see if the kinds force the direction | eqKind k1 k2 -- Can update either; so check the bind-flags = do { b1 <- tvBindFlag tv1 ; b2 <- tvBindFlag tv2 ; case (b1,b2) of - (BindMe, _) -> bind tv1 ty2 + (BindMe, _) -> bind swap tv1 ty2 - (AvoidMe, BindMe) -> bind tv2 ty1 - (AvoidMe, _) -> bind tv1 ty2 + (AvoidMe, BindMe) -> bind (not swap) tv2 ty1 + (AvoidMe, _) -> bind swap tv1 ty2 (WildCard, WildCard) -> return subst (WildCard, Skolem) -> return subst - (WildCard, _) -> bind tv2 ty1 + (WildCard, _) -> bind (not swap) tv2 ty1 (Skolem, WildCard) -> return subst (Skolem, Skolem) -> failWith (misMatch ty1 ty2) - (Skolem, _) -> bind tv2 ty1 + (Skolem, _) -> bind (not swap) tv2 ty1 } - | k1 `isSubKind` k2 = bindTv subst co tv2 ty1 -- Must update tv2 - | k2 `isSubKind` k1 = bindTv subst co tv1 ty2 -- Must update tv1 + | k1 `isSubKind` k2 = bindTv (not swap) subst co tv2 ty1 -- Must update tv2 + | k2 `isSubKind` k1 = bindTv swap subst co tv1 ty2 -- Must update tv1 | otherwise = failWith (kindMisMatch tv1 ty2) where ty1 = TyVarTy tv1 k1 = tyVarKind tv1 k2 = tyVarKind tv2 - bind tv ty = return (extendVarEnv subst tv (co,ty)) + bind swap tv ty = extendReft swap subst tv co ty -uUnrefined subst co tv1 ty2 ty2' -- ty2 is not a type variable +uUnrefined swap subst co tv1 ty2 ty2' -- ty2 is not a type variable | tv1 `elemVarSet` substTvSet subst (tyVarsOfType ty2') = failWith (occursCheck tv1 ty2) -- Occurs check | not (k2 `isSubKind` k1) = failWith (kindMisMatch tv1 ty2) -- Kind check | otherwise - = bindTv subst co tv1 ty2 -- Bind tyvar to the synonym if poss + = bindTv swap subst co tv1 ty2 -- Bind tyvar to the synonym if poss where k1 = tyVarKind tv1 k2 = typeKind ty2' @@ -418,13 +473,30 @@ substTvSet subst tvs Nothing -> unitVarSet tv Just (_,ty) -> substTvSet subst (tyVarsOfType ty) -bindTv subst co tv ty -- ty is not a type variable - = do { b <- tvBindFlag tv +bindTv swap subst co tv ty -- ty is not a type variable + = do { b <- tvBindFlag tv ; case b of Skolem -> failWith (misMatch (TyVarTy tv) ty) WildCard -> return subst - other -> return (extendVarEnv subst tv (co,ty)) + other -> extendReft swap subst tv co ty } + +doSwap :: Bool -> Coercion -> Coercion +doSwap swap co = if swap then mkSymCoercion co else co + +extendReft :: Bool + -> InternalReft + -> TyVar + -> Coercion + -> Type + -> UM InternalReft +extendReft swap subst tv co ty + = ASSERT2( (coercionKindPredTy co1 `tcEqType` mkCoKind (mkTyVarTy tv) ty), + (text "Refinement invariant failure: co = " <+> ppr co1 <+> ppr (coercionKindPredTy co1) $$ text "subst = " <+> ppr tv <+> ppr (mkCoKind (mkTyVarTy tv) ty)) ) + return (extendVarEnv subst tv (co1, ty)) + where + co1 = doSwap swap co + \end{code} %************************************************************************ @@ -496,4 +568,4 @@ kindMisMatch tv1 t2 occursCheck tv ty = hang (ptext SLIT("Can't construct the infinite type")) 2 (ppr tv <+> equals <+> ppr ty) -\end{code} \ No newline at end of file +\end{code}