X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FUnify.lhs;h=7195e5b2f54a425e3b54ae6db71d29309af66cd2;hb=0e73a9fbdc8555ffb948cfd72401a700b122c395;hp=d301b7659134d76b8e2e9603f77c9a0f99636d58;hpb=17b297d97d327620ed6bfab942f8992b2446f1bf;p=ghc-hetmet.git diff --git a/compiler/types/Unify.lhs b/compiler/types/Unify.lhs index d301b76..7195e5b 100644 --- a/compiler/types/Unify.lhs +++ b/compiler/types/Unify.lhs @@ -3,13 +3,6 @@ % \begin{code} -{-# OPTIONS_GHC -w #-} --- 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 --- http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings --- for details - module Unify ( -- Matching of types: -- the "tc" prefix indicates that matching always @@ -17,7 +10,15 @@ module Unify ( tcMatchTy, tcMatchTys, tcMatchTyX, ruleMatchTyX, tcMatchPreds, MatchEnv(..), - dataConCannotMatch + dataConCannotMatch, + + -- GADT type refinement + Refinement, emptyRefinement, isEmptyRefinement, + matchRefine, refineType, refinePred, refineResType, + + -- side-effect free unification + tcUnifyTys, BindFlag(..) + ) where #include "HsVersions.h" @@ -26,12 +27,16 @@ import Var import VarEnv import VarSet import Type +import Coercion import TyCon import DataCon import TypeRep import Outputable +import ErrUtils import Util import Maybes +import UniqFM +import FastString \end{code} @@ -145,35 +150,32 @@ match :: MatchEnv -- For the most part this is pushed downwards -- in-scope set of the RnEnv2 -> Type -> Type -- Template and target respectively -> Maybe TvSubstEnv --- This matcher works on source types; that is, --- it respects NewTypes and PredType +-- This matcher works on core types; that is, it ignores PredTypes +-- Watch out if newtypes become transparent agin! +-- this matcher must respect newtypes -match menv subst ty1 ty2 | Just ty1' <- tcView ty1 = match menv subst ty1' ty2 - | Just ty2' <- tcView ty2 = match menv subst ty1 ty2' +match menv subst ty1 ty2 | Just ty1' <- coreView ty1 = match menv subst ty1' ty2 + | Just ty2' <- coreView ty2 = match menv subst ty1 ty2' match menv subst (TyVarTy tv1) ty2 + | Just ty1' <- lookupVarEnv subst tv1' -- tv1' is already bound + = if tcEqTypeX (nukeRnEnvL rn_env) ty1' ty2 + -- ty1 has no locally-bound variables, hence nukeRnEnvL + -- Note tcEqType...we are doing source-type matching here + then Just subst + else Nothing -- ty2 doesn't match + | tv1' `elemVarSet` me_tmpls menv - = case lookupVarEnv subst tv1' of - Nothing -- No existing binding - | any (inRnEnvR rn_env) (varSetElems (tyVarsOfType ty2)) - -> Nothing -- Occurs check - | not (typeKind ty2 `isSubKind` tyVarKind tv1) - -> Nothing -- Kind mis-match - | otherwise - -> Just (extendVarEnv subst tv1' ty2) - - Just ty1' -- There is an existing binding; check whether ty2 matches it - | tcEqTypeX (nukeRnEnvL rn_env) ty1' ty2 - -- ty1 has no locally-bound variables, hence nukeRnEnvL - -- Note tcEqType...we are doing source-type matching here - -> Just subst - | otherwise -> Nothing -- ty2 doesn't match - + = if any (inRnEnvR rn_env) (varSetElems (tyVarsOfType ty2)) + then Nothing -- Occurs check + else do { subst1 <- match_kind menv subst tv1 ty2 + -- Note [Matching kinds] + ; return (extendVarEnv subst1 tv1' ty2) } | otherwise -- tv1 is not a template tyvar = case ty2 of TyVarTy tv2 | tv1' == rnOccR rn_env tv2 -> Just subst - other -> Nothing + _ -> Nothing where rn_env = me_env menv tv1' = rnOccL rn_env tv1 @@ -196,26 +198,55 @@ match menv subst (AppTy ty1a ty1b) ty2 = do { subst' <- match menv subst ty1a ty2a ; match menv subst' ty1b ty2b } -match menv subst ty1 ty2 +match _ _ _ _ = Nothing -------------- +match_kind :: MatchEnv -> TvSubstEnv -> TyVar -> Type -> Maybe TvSubstEnv +-- Match the kind of the template tyvar with the kind of Type +-- Note [Matching kinds] +match_kind menv subst tv ty + | isCoVar tv = do { let (ty1,ty2) = coVarKind tv + (ty3,ty4) = coercionKind ty + ; subst1 <- match menv subst ty1 ty3 + ; match menv subst1 ty2 ty4 } + | otherwise = if typeKind ty `isSubKind` tyVarKind tv + then Just subst + else Nothing + +-- Note [Matching kinds] +-- ~~~~~~~~~~~~~~~~~~~~~ +-- For ordinary type variables, we don't want (m a) to match (n b) +-- if say (a::*) and (b::*->*). This is just a yes/no issue. +-- +-- For coercion kinds matters are more complicated. If we have a +-- coercion template variable co::a~[b], where a,b are presumably also +-- template type variables, then we must match co's kind against the +-- kind of the actual argument, so as to give bindings to a,b. +-- +-- In fact I have no example in mind that *requires* this kind-matching +-- to instantiate template type variables, but it seems like the right +-- thing to do. C.f. Note [Matching variable types] in Rules.lhs + +-------------- +match_tys :: MatchEnv -> TvSubstEnv -> [Type] -> [Type] -> Maybe TvSubstEnv match_tys menv subst tys1 tys2 = match_list (match menv) subst tys1 tys2 -------------- match_list :: (TvSubstEnv -> a -> a -> Maybe TvSubstEnv) -> TvSubstEnv -> [a] -> [a] -> Maybe TvSubstEnv -match_list fn subst [] [] = Just subst +match_list _ subst [] [] = Just subst match_list fn subst (ty1:tys1) (ty2:tys2) = do { subst' <- fn subst ty1 ty2 ; match_list fn subst' tys1 tys2 } -match_list fn subst tys1 tys2 = Nothing +match_list _ _ _ _ = Nothing -------------- +match_pred :: MatchEnv -> TvSubstEnv -> PredType -> PredType -> Maybe TvSubstEnv match_pred menv subst (ClassP c1 tys1) (ClassP c2 tys2) | c1 == c2 = match_tys menv subst tys1 tys2 match_pred menv subst (IParam n1 t1) (IParam n2 t2) | n1 == n2 = match menv subst t1 t2 -match_pred menv subst p1 p2 = Nothing +match_pred _ _ _ _ = Nothing \end{code} @@ -334,10 +365,417 @@ dataConCannotMatch tys con | Just (f1, a1) <- repSplitAppTy_maybe ty1 = cant_match f1 f2 || cant_match a1 a2 - cant_match ty1 ty2 = False -- Safe! + cant_match _ _ = False -- Safe! -- Things we could add; -- foralls -- look through newtypes -- take account of tyvar bindings (EQ example above) -\end{code} \ No newline at end of file +\end{code} + + +%************************************************************************ +%* * + What a refinement is +%* * +%************************************************************************ + +\begin{code} +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 env) + = ptext (sLit "Refinement") <+> + braces (ppr env) + +emptyRefinement :: Refinement +emptyRefinement = (Reft emptyInScopeSet emptyVarEnv) + +isEmptyRefinement :: Refinement -> Bool +isEmptyRefinement (Reft _ env) = isEmptyVarEnv env + +refineType :: Refinement -> Type -> Maybe (Coercion, Type) +-- Apply the refinement to the type. +-- If (refineType r ty) = (co, ty') +-- Then co :: ty~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 + = 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) + +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 -> Maybe (Coercion, Type) +-- Like refineType, but returns the 'sym' coercion +-- If (refineResType r ty) = (co, ty') +-- Then co :: ty'~ty +refineResType reft ty + = case refineType reft ty of + Just (co, ty1) -> Just (mkSymCoercion co, ty1) + Nothing -> Nothing +\end{code} + + +%************************************************************************ +%* * + Simple generation of a type refinement +%* * +%************************************************************************ + +\begin{code} +matchRefine :: [TyVar] -> [Coercion] -> Refinement +\end{code} + +Given a list of coercions, where for each coercion c::(ty1~ty2), the type ty2 +is a specialisation of ty1, produce a type refinement that maps the variables +of ty1 to the corresponding sub-terms of ty2 using appropriate coercions; eg, + + matchRefine (co :: [(a, b)] ~ [(c, Maybe d)]) + = { right (left (right co)) :: a ~ c + , right (right co) :: b ~ Maybe d + } + +Precondition: The rhs types must indeed be a specialisation of the lhs types; + i.e., some free variables of the lhs are replaced with either distinct free + variables or proper type terms to obtain the rhs. (We don't perform full + unification or type matching here!) + +NB: matchRefine does *not* expand the type synonyms. + +\begin{code} +matchRefine in_scope_tvs cos + = Reft in_scope (foldr plusVarEnv emptyVarEnv (map refineOne cos)) + where + in_scope = mkInScopeSet (mkVarSet in_scope_tvs) + -- NB: in_scope_tvs include both coercion variables + -- *and* the tyvars in their kinds + + refineOne co = refine co ty1 ty2 + where + (ty1, ty2) = coercionKind co + + refine co (TyVarTy tv) ty = unitVarEnv tv (co, ty) + refine co (TyConApp _ tys) (TyConApp _ tys') = refineArgs co tys tys' + refine _ (PredTy _) (PredTy _) = + error "Unify.matchRefine: PredTy" + refine co (FunTy arg res) (FunTy arg' res') = + refine (mkRightCoercion (mkLeftCoercion co)) arg arg' + `plusVarEnv` + refine (mkRightCoercion co) res res' + refine co (AppTy fun arg) (AppTy fun' arg') = + refine (mkLeftCoercion co) fun fun' + `plusVarEnv` + refine (mkRightCoercion co) arg arg' + refine co (ForAllTy tv ty) (ForAllTy _tv ty') = + refine (mkForAllCoercion tv co) ty ty' `delVarEnv` tv + refine _ _ _ = error "RcGadt.matchRefine: mismatch" + + refineArgs :: Coercion -> [Type] -> [Type] -> InternalReft + refineArgs co tys tys' = + fst $ foldr refineArg (emptyVarEnv, id) (zip tys tys') + where + refineArg (ty, ty') (reft, coWrapper) + = (refine (mkRightCoercion (coWrapper co)) ty ty' `plusVarEnv` reft, + mkLeftCoercion . coWrapper) +\end{code} + + +%************************************************************************ +%* * + Unification +%* * +%************************************************************************ + +\begin{code} +tcUnifyTys :: (TyVar -> BindFlag) + -> [Type] -> [Type] + -> Maybe TvSubst -- A regular one-shot substitution +-- The two types may have common type variables, and indeed do so in the +-- second call to tcUnifyTys in FunDeps.checkClsFD +-- +tcUnifyTys bind_fn tys1 tys2 + = maybeErrToMaybe $ initUM bind_fn $ + do { subst <- unifyList emptyTvSubstEnv tys1 tys2 + + -- Find the fixed point of the resulting non-idempotent substitution + ; let in_scope = mkInScopeSet (tvs1 `unionVarSet` tvs2) + tv_env = fixTvSubstEnv in_scope subst + + ; return (mkTvSubst in_scope tv_env) } + where + tvs1 = tyVarsOfTypes tys1 + tvs2 = tyVarsOfTypes tys2 + +---------------------------- +-- XXX Can we do this more nicely, by exploiting laziness? +-- Or avoid needing it in the first place? +fixTvSubstEnv :: InScopeSet -> TvSubstEnv -> TvSubstEnv +fixTvSubstEnv in_scope env = f env + where + f e = let e' = mapUFM (substTy (mkTvSubst in_scope e)) e + in if and $ eltsUFM $ intersectUFM_C tcEqType e e' + then e + else f e' + +\end{code} + + +%************************************************************************ +%* * + The workhorse +%* * +%************************************************************************ + +\begin{code} +unify :: TvSubstEnv -- An existing substitution to extend + -> Type -> Type -- Types to be unified, and witness of their equality + -> UM TvSubstEnv -- Just the extended substitution, + -- Nothing if unification failed +-- We do not require the incoming substitution to be idempotent, +-- nor guarantee that the outgoing one is. That's fixed up by +-- the wrappers. + +-- Respects newtypes, PredTypes + +-- in unify, any NewTcApps/Preds should be taken at face value +unify subst (TyVarTy tv1) ty2 = uVar subst tv1 ty2 +unify subst ty1 (TyVarTy tv2) = uVar subst tv2 ty1 + +unify subst ty1 ty2 | Just ty1' <- tcView ty1 = unify subst ty1' ty2 +unify subst ty1 ty2 | Just ty2' <- tcView ty2 = unify subst ty1 ty2' + +unify subst (PredTy p1) (PredTy p2) = unify_pred subst p1 p2 + +unify subst (TyConApp tyc1 tys1) (TyConApp tyc2 tys2) + | tyc1 == tyc2 = unify_tys subst tys1 tys2 + +unify subst (FunTy ty1a ty1b) (FunTy ty2a ty2b) + = do { subst' <- unify subst ty1a ty2a + ; unify subst' ty1b ty2b } + + -- Applications need a bit of care! + -- They can match FunTy and TyConApp, so use splitAppTy_maybe + -- NB: we've already dealt with type variables and Notes, + -- so if one type is an App the other one jolly well better be too +unify subst (AppTy ty1a ty1b) ty2 + | Just (ty2a, ty2b) <- repSplitAppTy_maybe ty2 + = do { subst' <- unify subst ty1a ty2a + ; unify subst' ty1b ty2b } + +unify subst ty1 (AppTy ty2a ty2b) + | Just (ty1a, ty1b) <- repSplitAppTy_maybe ty1 + = do { subst' <- unify subst ty1a ty2a + ; unify subst' ty1b ty2b } + +unify _ ty1 ty2 = failWith (misMatch ty1 ty2) + -- ForAlls?? + +------------------------------ +unify_pred :: TvSubstEnv -> PredType -> PredType -> UM TvSubstEnv +unify_pred subst (ClassP c1 tys1) (ClassP c2 tys2) + | c1 == c2 = unify_tys subst tys1 tys2 +unify_pred subst (IParam n1 t1) (IParam n2 t2) + | n1 == n2 = unify subst t1 t2 +unify_pred _ p1 p2 = failWith (misMatch (PredTy p1) (PredTy p2)) + +------------------------------ +unify_tys :: TvSubstEnv -> [Type] -> [Type] -> UM TvSubstEnv +unify_tys subst xs ys = unifyList subst xs ys + +unifyList :: TvSubstEnv -> [Type] -> [Type] -> UM TvSubstEnv +unifyList subst orig_xs orig_ys + = go subst orig_xs orig_ys + where + go subst [] [] = return subst + go subst (x:xs) (y:ys) = do { subst' <- unify subst x y + ; go subst' xs ys } + go _ _ _ = failWith (lengthMisMatch orig_xs orig_ys) + +--------------------------------- +uVar :: TvSubstEnv -- An existing substitution to extend + -> TyVar -- Type variable to be unified + -> Type -- with this type + -> UM TvSubstEnv + +-- PRE-CONDITION: in the call (uVar swap r tv1 ty), we know that +-- if swap=False (tv1~ty) +-- if swap=True (ty~tv1) + +uVar subst tv1 ty + = -- Check to see whether tv1 is refined by the substitution + case (lookupVarEnv subst tv1) of + Just ty' -> unify subst ty' ty -- Yes, call back into unify' + Nothing -> uUnrefined subst -- No, continue + tv1 ty ty + +uUnrefined :: TvSubstEnv -- An existing substitution to extend + -> TyVar -- Type variable to be unified + -> Type -- with this type + -> Type -- (version w/ expanded synonyms) + -> UM TvSubstEnv + +-- We know that tv1 isn't refined + +uUnrefined subst tv1 ty2 ty2' + | Just ty2'' <- tcView ty2' + = uUnrefined subst tv1 ty2 ty2'' -- Unwrap synonyms + -- This is essential, in case we have + -- type Foo a = a + -- and then unify a ~ Foo a + +uUnrefined subst tv1 ty2 (TyVarTy tv2) + | tv1 == tv2 -- Same type variable + = return subst + + -- Check to see whether tv2 is refined + | Just ty' <- lookupVarEnv subst tv2 + = uUnrefined subst 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 + (Skolem, Skolem) -> failWith (misMatch ty1 ty2) + (Skolem, _) -> bind tv2 ty1 + } + + | k1 `isSubKind` k2 = bindTv subst tv2 ty1 -- Must update tv2 + | k2 `isSubKind` k1 = bindTv subst 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 ty + +uUnrefined subst 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 tv1 ty2 -- Bind tyvar to the synonym if poss + where + k1 = tyVarKind tv1 + k2 = typeKind ty2' + +substTvSet :: TvSubstEnv -> TyVarSet -> TyVarSet +-- Apply the non-idempotent substitution to a set of type variables, +-- remembering that the substitution isn't necessarily idempotent +substTvSet subst tvs + = foldVarSet (unionVarSet . get) emptyVarSet tvs + where + get tv = case lookupVarEnv subst tv of + Nothing -> unitVarSet tv + Just ty -> substTvSet subst (tyVarsOfType ty) + +bindTv :: TvSubstEnv -> TyVar -> Type -> UM TvSubstEnv +bindTv subst tv ty -- ty is not a type variable + = do { b <- tvBindFlag tv + ; case b of + Skolem -> failWith (misMatch (TyVarTy tv) ty) + BindMe -> return $ extendVarEnv subst tv ty + } +\end{code} + +%************************************************************************ +%* * + Binding decisions +%* * +%************************************************************************ + +\begin{code} +data BindFlag + = BindMe -- A regular type variable + + | Skolem -- This type variable is a skolem constant + -- Don't bind it; it only matches itself +\end{code} + + +%************************************************************************ +%* * + Unification monad +%* * +%************************************************************************ + +\begin{code} +newtype UM a = UM { unUM :: (TyVar -> BindFlag) + -> MaybeErr Message a } + +instance Monad UM where + return a = UM (\_tvs -> Succeeded a) + fail s = UM (\_tvs -> Failed (text s)) + m >>= k = UM (\tvs -> case unUM m tvs of + Failed err -> Failed err + Succeeded v -> unUM (k v) tvs) + +initUM :: (TyVar -> BindFlag) -> UM a -> MaybeErr Message a +initUM badtvs um = unUM um badtvs + +tvBindFlag :: TyVar -> UM BindFlag +tvBindFlag tv = UM (\tv_fn -> Succeeded (tv_fn tv)) + +failWith :: Message -> UM a +failWith msg = UM (\_tv_fn -> Failed msg) + +maybeErrToMaybe :: MaybeErr fail succ -> Maybe succ +maybeErrToMaybe (Succeeded a) = Just a +maybeErrToMaybe (Failed _) = Nothing +\end{code} + + +%************************************************************************ +%* * + Error reporting + We go to a lot more trouble to tidy the types + in TcUnify. Maybe we'll end up having to do that + here too, but I'll leave it for now. +%* * +%************************************************************************ + +\begin{code} +misMatch :: Type -> Type -> SDoc +misMatch t1 t2 + = ptext (sLit "Can't match types") <+> quotes (ppr t1) <+> + ptext (sLit "and") <+> quotes (ppr t2) + +lengthMisMatch :: [Type] -> [Type] -> SDoc +lengthMisMatch tys1 tys2 + = sep [ptext (sLit "Can't match unequal length lists"), + nest 2 (ppr tys1), nest 2 (ppr tys2) ] + +kindMisMatch :: TyVar -> Type -> SDoc +kindMisMatch tv1 t2 + = vcat [ptext (sLit "Can't match kinds") <+> quotes (ppr (tyVarKind tv1)) <+> + ptext (sLit "and") <+> quotes (ppr (typeKind t2)), + ptext (sLit "when matching") <+> quotes (ppr tv1) <+> + ptext (sLit "with") <+> quotes (ppr t2)] + +occursCheck :: TyVar -> Type -> SDoc +occursCheck tv ty + = hang (ptext (sLit "Can't construct the infinite type")) + 2 (ppr tv <+> equals <+> ppr ty) +\end{code}