X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcUnify.lhs;h=1868ad0d12f02381e3744a2aa0f4fe4866fc8325;hb=2423c249f5ca7785d0ec89eb33e72662da7561c1;hp=bd65c46bdca802dff46f113101b9ca9b6bd7c0d5;hpb=4e9dc3d744df308623463c7caa320d0cad1ae9d0;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs index bd65c46..1868ad0 100644 --- a/compiler/typecheck/TcUnify.lhs +++ b/compiler/typecheck/TcUnify.lhs @@ -1,7 +1,9 @@ % +% (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -\section{Type subsumption and unification} + +Type subsumption and unification \begin{code} module TcUnify ( @@ -25,60 +27,29 @@ module TcUnify ( #include "HsVersions.h" -import HsSyn ( ExprCoFn(..), idCoercion, isIdCoercion, (<.>) ) -import TypeRep ( Type(..), PredType(..) ) - -import TcMType ( lookupTcTyVar, LookupTyVarResult(..), - tcInstSkolType, tcInstBoxyTyVar, newKindVar, newMetaTyVar, - newBoxyTyVar, newBoxyTyVarTys, readFilledBox, - readMetaTyVar, writeMetaTyVar, newFlexiTyVarTy, - tcInstSkolTyVars, tcInstTyVar, - zonkTcKind, zonkType, zonkTcType, zonkTcTyVarsAndFV, - readKindVar, writeKindVar ) -import TcSimplify ( tcSimplifyCheck ) -import TcEnv ( tcGetGlobalTyVars, findGlobals ) -import TcIface ( checkWiredInTyCon ) +import HsSyn +import TypeRep + +import TcMType +import TcSimplify +import TcEnv +import TcIface import TcRnMonad -- TcType, amongst others -import TcType ( TcKind, TcType, TcTyVar, BoxyTyVar, TcTauType, - BoxySigmaType, BoxyRhoType, BoxyType, - TcTyVarSet, TcThetaType, TcTyVarDetails(..), BoxInfo(..), - SkolemInfo( GenSkol, UnkSkol ), MetaDetails(..), isImmutableTyVar, - pprSkolTvBinding, isTauTy, isTauTyCon, isSigmaTy, - mkFunTy, mkFunTys, mkTyConApp, isMetaTyVar, - tcSplitForAllTys, tcSplitAppTy_maybe, tcSplitFunTys, mkTyVarTys, - tcSplitSigmaTy, tyVarsOfType, mkPhiTy, mkTyVarTy, mkPredTy, - typeKind, mkForAllTys, mkAppTy, isBoxyTyVar, - tcView, exactTyVarsOfType, - tidyOpenType, tidyOpenTyVar, tidyOpenTyVars, - pprType, tidyKind, tidySkolemTyVar, isSkolemTyVar, isSigTyVar, - TvSubst, mkTvSubst, zipTyEnv, zipOpenTvSubst, emptyTvSubst, - substTy, substTheta, - lookupTyVar, extendTvSubst ) -import Kind ( Kind(..), SimpleKind, KindVar, isArgTypeKind, - openTypeKind, liftedTypeKind, unliftedTypeKind, - mkArrowKind, defaultKind, - isOpenTypeKind, argTypeKind, isLiftedTypeKind, isUnliftedTypeKind, - isSubKind, pprKind, splitKindFunTys ) -import TysPrim ( alphaTy, betaTy ) -import Inst ( newDicts, instToId ) -import TyCon ( TyCon, tyConArity, tyConTyVars, isSynTyCon ) -import TysWiredIn ( listTyCon ) -import Id ( Id, mkSysLocal ) -import Var ( Var, varName, tyVarKind, isTcTyVar, tcTyVarDetails ) +import TcType +import Type +import TysPrim +import Inst +import TyCon +import TysWiredIn +import Var import VarSet import VarEnv -import Name ( Name, isSystemName ) -import ErrUtils ( Message ) -import Maybes ( expectJust, isNothing ) -import BasicTypes ( Arity ) -import UniqSupply ( uniqsFromSupply ) -import Util ( notNull, equalLength ) +import Name +import ErrUtils +import Maybes +import BasicTypes +import Util import Outputable - --- Assertion imports -#ifdef DEBUG -import TcType ( isBoxyTy, isFlexi ) -#endif \end{code} %************************************************************************ @@ -94,7 +65,7 @@ tcInfer tc_infer ; res <- tc_infer (mkTyVarTy box) ; res_ty <- readFilledBox box -- Guaranteed filled-in by now ; return (res, res_ty) } -\end{code} +\end{code} %************************************************************************ @@ -109,7 +80,7 @@ subFunTys :: SDoc -- Somthing like "The function f has 3 arguments" -> Arity -- Expected # of args -> BoxyRhoType -- res_ty -> ([BoxySigmaType] -> BoxyRhoType -> TcM a) - -> TcM (ExprCoFn, a) + -> TcM (HsWrapper, a) -- Attempt to decompse res_ty to have enough top-level arrows to -- match the number of patterns in the match group -- @@ -147,13 +118,13 @@ subFunTys error_herald n_pats res_ty thing_inside loop n args_so_far res_ty | isSigmaTy res_ty -- Do this before checking n==0, because we -- guarantee to return a BoxyRhoType, not a BoxySigmaType - = do { (gen_fn, (co_fn, res)) <- tcGen res_ty emptyVarSet $ \ res_ty' -> + = do { (gen_fn, (co_fn, res)) <- tcGen res_ty emptyVarSet $ \ _ res_ty' -> loop n args_so_far res_ty' ; return (gen_fn <.> co_fn, res) } loop 0 args_so_far res_ty = do { res <- thing_inside (reverse args_so_far) res_ty - ; return (idCoercion, res) } + ; return (idHsWrapper, res) } loop n args_so_far (FunTy arg_ty res_ty) = do { (co_fn, res) <- loop (n-1) (arg_ty:args_so_far) res_ty @@ -177,7 +148,7 @@ subFunTys error_herald n_pats res_ty thing_inside Indirect ty -> loop n args_so_far ty Flexi -> do { (res_ty:arg_tys) <- withMetaTvs tv kinds mk_res_ty ; res <- thing_inside (reverse args_so_far ++ arg_tys) res_ty - ; return (idCoercion, res) } } + ; return (idHsWrapper, res) } } where mk_res_ty (res_ty' : arg_tys') = mkFunTys arg_tys' res_ty' mk_res_ty [] = panic "TcUnify.mk_res_ty1" @@ -511,7 +482,7 @@ boxy_match tmpl_tvs orig_tmpl_ty boxy_tvs orig_boxy_ty subst go (TyVarTy tv) b_ty | tv `elemVarSet` tmpl_tvs -- Template type variable in the template - , not (intersectsVarSet boxy_tvs (tyVarsOfType orig_boxy_ty)) + , boxy_tvs `disjointVarSet` tyVarsOfType orig_boxy_ty , typeKind b_ty `isSubKind` tyVarKind tv -- See Note [Matching kinds] = extendTvSubst subst tv boxy_ty' | otherwise @@ -593,38 +564,66 @@ expected_ty. \begin{code} ----------------- -tcSubExp :: BoxySigmaType -> BoxySigmaType -> TcM ExprCoFn -- Locally used only +tcSubExp :: BoxySigmaType -> BoxySigmaType -> TcM HsWrapper -- Locally used only -- (tcSub act exp) checks that -- act <= exp tcSubExp actual_ty expected_ty - = addErrCtxtM (unifyCtxt actual_ty expected_ty) - (tc_sub True actual_ty actual_ty expected_ty expected_ty) - -tcFunResTy :: Name -> BoxySigmaType -> BoxySigmaType -> TcM ExprCoFn -- Locally used only + = -- addErrCtxtM (unifyCtxt actual_ty expected_ty) $ + -- Adding the error context here leads to some very confusing error + -- messages, such as "can't match forall a. a->a with forall a. a->a" + -- Example is tcfail165: + -- do var <- newEmptyMVar :: IO (MVar (forall a. Show a => a -> String)) + -- putMVar var (show :: forall a. Show a => a -> String) + -- Here the info does not flow from the 'var' arg of putMVar to its 'show' arg + -- but after zonking it looks as if it does! + -- + -- So instead I'm adding the error context when moving from tc_sub to u_tys + + traceTc (text "tcSubExp" <+> ppr actual_ty <+> ppr expected_ty) >> + tc_sub SubOther actual_ty actual_ty False expected_ty expected_ty + +tcFunResTy :: Name -> BoxySigmaType -> BoxySigmaType -> TcM HsWrapper -- Locally used only tcFunResTy fun actual_ty expected_ty - = addErrCtxtM (checkFunResCtxt fun actual_ty expected_ty) $ - (tc_sub True actual_ty actual_ty expected_ty expected_ty) + = traceTc (text "tcFunResTy" <+> ppr actual_ty <+> ppr expected_ty) >> + tc_sub (SubFun fun) actual_ty actual_ty False expected_ty expected_ty ----------------- -tc_sub :: Outer -- See comments with uTys +data SubCtxt = SubDone -- Error-context already pushed + | SubFun Name -- Context is tcFunResTy + | SubOther -- Context is something else + +tc_sub :: SubCtxt -- How to add an error-context -> BoxySigmaType -- actual_ty, before expanding synonyms -> BoxySigmaType -- ..and after + -> InBox -- True <=> expected_ty is inside a box -> BoxySigmaType -- expected_ty, before -> BoxySigmaType -- ..and after - -> TcM ExprCoFn + -> TcM HsWrapper + -- The acual_ty is never inside a box +-- IMPORTANT pre-condition: if the args contain foralls, the bound type +-- variables are visible non-monadically +-- (i.e. tha args are sufficiently zonked) +-- This invariant is needed so that we can "see" the foralls, ad +-- e.g. in the SPEC rule where we just use splitSigmaTy + +tc_sub sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty + = tc_sub1 sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty + -- This indirection is just here to make + -- it easy to insert a debug trace! -tc_sub outer act_sty act_ty exp_sty exp_ty - | Just exp_ty' <- tcView exp_ty = tc_sub False act_sty act_ty exp_sty exp_ty' -tc_sub outer act_sty act_ty exp_sty exp_ty - | Just act_ty' <- tcView act_ty = tc_sub False act_sty act_ty' exp_sty exp_ty +tc_sub1 sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty + | Just exp_ty' <- tcView exp_ty = tc_sub sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty' +tc_sub1 sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty + | Just act_ty' <- tcView act_ty = tc_sub sub_ctxt act_sty act_ty' exp_ib exp_sty exp_ty ----------------------------------- -- Rule SBOXY, plus other cases when act_ty is a type variable -- Just defer to boxy matching -- This rule takes precedence over SKOL! -tc_sub outer act_sty (TyVarTy tv) exp_sty exp_ty - = do { uVar outer False tv False exp_sty exp_ty - ; return idCoercion } +tc_sub1 sub_ctxt act_sty (TyVarTy tv) exp_ib exp_sty exp_ty + = do { addSubCtxt sub_ctxt act_sty exp_sty $ + uVar True False tv exp_ib exp_sty exp_ty + ; return idHsWrapper } ----------------------------------- -- Skolemisation case (rule SKOL) @@ -637,10 +636,11 @@ tc_sub outer act_sty (TyVarTy tv) exp_sty exp_ty -- g :: Ord b => b->b -- Consider f g ! -tc_sub outer act_sty act_ty exp_sty exp_ty - | isSigmaTy exp_ty - = do { (gen_fn, co_fn) <- tcGen exp_ty act_tvs $ \ body_exp_ty -> - tc_sub False act_sty act_ty body_exp_ty body_exp_ty +tc_sub1 sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty + | not exp_ib, -- SKOL does not apply if exp_ty is inside a box + isSigmaTy exp_ty + = do { (gen_fn, co_fn) <- tcGen exp_ty act_tvs $ \ _ body_exp_ty -> + tc_sub sub_ctxt act_sty act_ty False body_exp_ty body_exp_ty ; return (gen_fn <.> co_fn) } where act_tvs = tyVarsOfType act_ty @@ -653,7 +653,7 @@ tc_sub outer act_sty act_ty exp_sty exp_ty -- expected_ty: Int -> Int -- co_fn e = e Int dOrdInt -tc_sub outer act_sty actual_ty exp_sty expected_ty +tc_sub1 sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty -- Implements the new SPEC rule in the Appendix of the paper -- "Boxy types: inference for higher rank types and impredicativity" -- (This appendix isn't in the published version.) @@ -667,63 +667,74 @@ tc_sub outer act_sty actual_ty exp_sty expected_ty -- boxy tyvars if pre-subsumption gives no info let (tyvars, theta, tau) = tcSplitSigmaTy actual_ty tau_tvs = exactTyVarsOfType tau - ; inst_tys <- preSubType tyvars tau_tvs tau expected_ty + ; inst_tys <- if exp_ib then -- Inside a box, do not do clever stuff + do { tyvars' <- mapM tcInstBoxyTyVar tyvars + ; return (mkTyVarTys tyvars') } + else -- Outside, do clever stuff + preSubType tyvars tau_tvs tau expected_ty ; let subst' = zipOpenTvSubst tyvars inst_tys tau' = substTy subst' tau -- Perform a full subsumption check - ; co_fn <- tc_sub False tau' tau' exp_sty expected_ty + ; traceTc (text "tc_sub_spec" <+> vcat [ppr actual_ty, + ppr tyvars <+> ppr theta <+> ppr tau, + ppr tau']) + ; co_fn2 <- tc_sub sub_ctxt tau' tau' exp_ib exp_sty expected_ty -- Deal with the dictionaries - ; dicts <- newDicts InstSigOrigin (substTheta subst' theta) - ; extendLIEs dicts - ; let inst_fn = CoApps (CoTyApps CoHole inst_tys) - (map instToId dicts) - ; return (co_fn <.> inst_fn) } + -- The origin gives a helpful origin when we have + -- a function with type f :: Int -> forall a. Num a => ... + -- This way the (Num a) dictionary gets an OccurrenceOf f origin + ; let orig = case sub_ctxt of + SubFun n -> OccurrenceOf n + other -> InstSigOrigin -- Unhelpful + ; co_fn1 <- instCall orig inst_tys (substTheta subst' theta) + ; return (co_fn2 <.> co_fn1) } ----------------------------------- -- Function case (rule F1) -tc_sub _ _ (FunTy act_arg act_res) _ (FunTy exp_arg exp_res) - = tc_sub_funs act_arg act_res exp_arg exp_res +tc_sub1 sub_ctxt act_sty (FunTy act_arg act_res) exp_ib exp_sty (FunTy exp_arg exp_res) + = addSubCtxt sub_ctxt act_sty exp_sty $ + tc_sub_funs act_arg act_res exp_ib exp_arg exp_res -- Function case (rule F2) -tc_sub outer act_sty act_ty@(FunTy act_arg act_res) exp_sty (TyVarTy exp_tv) +tc_sub1 sub_ctxt act_sty act_ty@(FunTy act_arg act_res) _ exp_sty (TyVarTy exp_tv) | isBoxyTyVar exp_tv - = do { cts <- readMetaTyVar exp_tv + = addSubCtxt sub_ctxt act_sty exp_sty $ + do { cts <- readMetaTyVar exp_tv ; case cts of - Indirect ty -> do { u_tys outer False act_sty act_ty True exp_sty ty - ; return idCoercion } + Indirect ty -> tc_sub SubDone act_sty act_ty True exp_sty ty Flexi -> do { [arg_ty,res_ty] <- withMetaTvs exp_tv fun_kinds mk_res_ty - ; tc_sub_funs act_arg act_res arg_ty res_ty } } + ; tc_sub_funs act_arg act_res True arg_ty res_ty } } where mk_res_ty [arg_ty', res_ty'] = mkFunTy arg_ty' res_ty' mk_res_ty other = panic "TcUnify.mk_res_ty3" fun_kinds = [argTypeKind, openTypeKind] -- Everything else: defer to boxy matching -tc_sub outer act_sty actual_ty exp_sty expected_ty - = do { u_tys outer False act_sty actual_ty False exp_sty expected_ty - ; return idCoercion } +tc_sub1 sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty + = do { addSubCtxt sub_ctxt act_sty exp_sty $ + u_tys True False act_sty actual_ty exp_ib exp_sty expected_ty + ; return idHsWrapper } ----------------------------------- -tc_sub_funs act_arg act_res exp_arg exp_res - = do { uTys False act_arg False exp_arg - ; co_fn_res <- tc_sub False act_res act_res exp_res exp_res +tc_sub_funs act_arg act_res exp_ib exp_arg exp_res + = do { uTys False act_arg exp_ib exp_arg + ; co_fn_res <- tc_sub SubDone act_res act_res exp_ib exp_res exp_res ; wrapFunResCoercion [exp_arg] co_fn_res } ----------------------------------- wrapFunResCoercion :: [TcType] -- Type of args - -> ExprCoFn -- HsExpr a -> HsExpr b - -> TcM ExprCoFn -- HsExpr (arg_tys -> a) -> HsExpr (arg_tys -> b) + -> HsWrapper -- HsExpr a -> HsExpr b + -> TcM HsWrapper -- HsExpr (arg_tys -> a) -> HsExpr (arg_tys -> b) wrapFunResCoercion arg_tys co_fn_res - | isIdCoercion co_fn_res = return idCoercion + | isIdHsWrapper co_fn_res = return idHsWrapper | null arg_tys = return co_fn_res | otherwise - = do { us <- newUniqueSupply - ; let arg_ids = zipWith (mkSysLocal FSLIT("sub")) (uniqsFromSupply us) arg_tys - ; return (CoLams arg_ids (co_fn_res <.> (CoApps CoHole arg_ids))) } + = do { arg_ids <- newSysLocalIds FSLIT("sub") arg_tys + ; return (mkWpLams arg_ids <.> co_fn_res <.> mkWpApps arg_ids) } \end{code} @@ -739,8 +750,8 @@ tcGen :: BoxySigmaType -- expected_ty -> TcTyVarSet -- Extra tyvars that the universally -- quantified tyvars of expected_ty -- must not be unified - -> (BoxyRhoType -> TcM result) -- spec_ty - -> TcM (ExprCoFn, result) + -> ([TcTyVar] -> BoxyRhoType -> TcM result) + -> TcM (HsWrapper, result) -- The expression has type: spec_ty -> expected_ty tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a forall-type @@ -749,22 +760,21 @@ tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a forall -- mention the *instantiated* tyvar names, so that we get a -- good error message "Rigid variable 'a' is bound by (forall a. a->a)" -- Hence the tiresome but innocuous fixM - ((forall_tvs, theta, rho_ty), skol_info) <- fixM (\ ~(_, skol_info) -> + ((tvs', theta', rho'), skol_info) <- fixM (\ ~(_, skol_info) -> do { (forall_tvs, theta, rho_ty) <- tcInstSkolType skol_info expected_ty - ; span <- getSrcSpanM - ; let skol_info = GenSkol forall_tvs (mkPhiTy theta rho_ty) span + -- Get loation from monad, not from expected_ty + ; let skol_info = GenSkol forall_tvs (mkPhiTy theta rho_ty) ; return ((forall_tvs, theta, rho_ty), skol_info) }) #ifdef DEBUG ; traceTc (text "tcGen" <+> vcat [text "extra_tvs" <+> ppr extra_tvs, text "expected_ty" <+> ppr expected_ty, - text "inst ty" <+> ppr forall_tvs <+> ppr theta <+> ppr rho_ty, - text "free_tvs" <+> ppr free_tvs, - text "forall_tvs" <+> ppr forall_tvs]) + text "inst ty" <+> ppr tvs' <+> ppr theta' <+> ppr rho', + text "free_tvs" <+> ppr free_tvs]) #endif -- Type-check the arg and unify with poly type - ; (result, lie) <- getLIE (thing_inside rho_ty) + ; (result, lie) <- getLIE (thing_inside tvs' rho') -- Check that the "forall_tvs" havn't been constrained -- The interesting bit here is that we must include the free variables @@ -777,22 +787,20 @@ tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a forall -- Conclusion: include the free vars of the expected_ty in the -- list of "free vars" for the signature check. - ; dicts <- newDicts (SigOrigin skol_info) theta - ; inst_binds <- tcSimplifyCheck sig_msg forall_tvs dicts lie + ; loc <- getInstLoc (SigOrigin skol_info) + ; dicts <- newDictBndrs loc theta' + ; inst_binds <- tcSimplifyCheck loc tvs' dicts lie - ; checkSigTyVarsWrt free_tvs forall_tvs + ; checkSigTyVarsWrt free_tvs tvs' ; traceTc (text "tcGen:done") ; let - -- This HsLet binds any Insts which came out of the simplification. - -- It's a bit out of place here, but using AbsBind involves inventing - -- a couple of new names which seems worse. - dict_ids = map instToId dicts - co_fn = CoTyLams forall_tvs $ CoLams dict_ids $ CoLet inst_binds CoHole + -- The WpLet binds any Insts which came out of the simplification. + dict_ids = map instToId dicts + co_fn = mkWpTyLams tvs' <.> mkWpLams dict_ids <.> WpLet inst_binds ; returnM (co_fn, result) } where free_tvs = tyVarsOfType expected_ty `unionVarSet` extra_tvs - sig_msg = ptext SLIT("expected type of an expression") \end{code} @@ -839,7 +847,8 @@ unifyTheta :: TcThetaType -> TcThetaType -> TcM () -- Acutal and expected types unifyTheta theta1 theta2 = do { checkTc (equalLength theta1 theta2) - (ptext SLIT("Contexts differ in length")) + (vcat [ptext SLIT("Contexts differ in length"), + nest 2 $ parens $ ptext SLIT("Use -fglasgow-exts to allow this")]) ; uList unifyPred theta1 theta2 } --------------- @@ -880,8 +889,12 @@ de-synonym'd version. This way we get better error messages. We call the first one \tr{ps_ty1}, \tr{ps_ty2} for ``possible synomym''. \begin{code} -type NoBoxes = Bool -- True <=> definitely no boxes in this type - -- False <=> there might be boxes (always safe) +type InBox = Bool -- True <=> we are inside a box + -- False <=> we are outside a box + -- The importance of this is that if we get "filled-box meets + -- filled-box", we'll look into the boxes and unify... but + -- we must not allow polytypes. But if we are in a box on + -- just one side, then we can allow polytypes type Outer = Bool -- True <=> this is the outer level of a unification -- so that the types being unified are the @@ -891,16 +904,18 @@ type Outer = Bool -- True <=> this is the outer level of a unification -- pop the context to remove the "Expected/Acutal" context uTysOuter, uTys - :: NoBoxes -> TcType -- ty1 is the *expected* type - -> NoBoxes -> TcType -- ty2 is the *actual* type + :: InBox -> TcType -- ty1 is the *expected* type + -> InBox -> TcType -- ty2 is the *actual* type -> TcM () -uTysOuter nb1 ty1 nb2 ty2 = u_tys True nb1 ty1 ty1 nb2 ty2 ty2 -uTys nb1 ty1 nb2 ty2 = u_tys False nb1 ty1 ty1 nb2 ty2 ty2 +uTysOuter nb1 ty1 nb2 ty2 = do { traceTc (text "uTysOuter" <+> ppr ty1 <+> ppr ty2) + ; u_tys True nb1 ty1 ty1 nb2 ty2 ty2 } +uTys nb1 ty1 nb2 ty2 = do { traceTc (text "uTys" <+> ppr ty1 <+> ppr ty2) + ; u_tys False nb1 ty1 ty1 nb2 ty2 ty2 } -------------- -uTys_s :: NoBoxes -> [TcType] -- ty1 is the *actual* types - -> NoBoxes -> [TcType] -- ty2 is the *expected* types +uTys_s :: InBox -> [TcType] -- ty1 is the *actual* types + -> InBox -> [TcType] -- ty2 is the *expected* types -> TcM () uTys_s nb1 [] nb2 [] = returnM () uTys_s nb1 (ty1:tys1) nb2 (ty2:tys2) = do { uTys nb1 ty1 nb2 ty2 @@ -909,8 +924,8 @@ uTys_s nb1 ty1s nb2 ty2s = panic "Unify.uTys_s: mismatched type lists!" -------------- u_tys :: Outer - -> NoBoxes -> TcType -> TcType -- ty1 is the *actual* type - -> NoBoxes -> TcType -> TcType -- ty2 is the *expected* type + -> InBox -> TcType -> TcType -- ty1 is the *actual* type + -> InBox -> TcType -> TcType -- ty2 is the *expected* type -> TcM () u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 @@ -957,15 +972,19 @@ u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 go _ ty1@(ForAllTy _ _) ty2@(ForAllTy _ _) | length tvs1 == length tvs2 = do { tvs <- tcInstSkolTyVars UnkSkol tvs1 -- Not a helpful SkolemInfo + -- Get location from monad, not from tvs1 ; let tys = mkTyVarTys tvs in_scope = mkInScopeSet (mkVarSet tvs) subst1 = mkTvSubst in_scope (zipTyEnv tvs1 tys) subst2 = mkTvSubst in_scope (zipTyEnv tvs2 tys) ; uTys nb1 (substTy subst1 body1) nb2 (substTy subst2 body2) - -- If both sides are inside a box, we should not have - -- a polytype at all. This check comes last, because - -- the error message is extremely unhelpful. + -- If both sides are inside a box, we are in a "box-meets-box" + -- situation, and we should not have a polytype at all. + -- If we get here we have two boxes, already filled with + -- the same polytype... but it should be a monotype. + -- This check comes last, because the error message is + -- extremely unhelpful. ; ifM (nb1 && nb2) (notMonoType ty1) } where @@ -1062,7 +1081,7 @@ uVar :: Outer -> Bool -- False => tyvar is the "expected" -- True => ty is the "expected" thing -> TcTyVar - -> NoBoxes -- True <=> definitely no boxes in t2 + -> InBox -- True <=> definitely no boxes in t2 -> TcTauType -> TcTauType -- printing and real versions -> TcM () @@ -1071,32 +1090,31 @@ uVar outer swapped tv1 nb2 ps_ty2 ty2 | otherwise = brackets (equals <+> ppr ty2) ; traceTc (text "uVar" <+> ppr swapped <+> sep [ppr tv1 <+> dcolon <+> ppr (tyVarKind tv1 ), - nest 2 (ptext SLIT(" :=: ")), + nest 2 (ptext SLIT(" <-> ")), ppr ps_ty2 <+> dcolon <+> ppr (typeKind ty2) <+> expansion]) ; details <- lookupTcTyVar tv1 ; case details of IndirectTv ty1 | swapped -> u_tys outer nb2 ps_ty2 ty2 True ty1 ty1 -- Swap back | otherwise -> u_tys outer True ty1 ty1 nb2 ps_ty2 ty2 -- Same order - -- The 'True' here says that ty1 - -- is definitely box-free - DoneTv details1 -> uUnfilledVar outer swapped tv1 details1 nb2 ps_ty2 ty2 + -- The 'True' here says that ty1 is now inside a box + DoneTv details1 -> uUnfilledVar outer swapped tv1 details1 ps_ty2 ty2 } ---------------- uUnfilledVar :: Outer -> Bool -- Args are swapped - -> TcTyVar -> TcTyVarDetails -- Tyvar 1 - -> NoBoxes -> TcTauType -> TcTauType -- Type 2 + -> TcTyVar -> TcTyVarDetails -- Tyvar 1 + -> TcTauType -> TcTauType -- Type 2 -> TcM () -- Invariant: tyvar 1 is not unified with anything -uUnfilledVar outer swapped tv1 details1 nb2 ps_ty2 ty2 +uUnfilledVar outer swapped tv1 details1 ps_ty2 ty2 | Just ty2' <- tcView ty2 = -- Expand synonyms; ignore FTVs - uUnfilledVar False swapped tv1 details1 nb2 ps_ty2 ty2' + uUnfilledVar False swapped tv1 details1 ps_ty2 ty2' -uUnfilledVar outer swapped tv1 details1 nb2 ps_ty2 (TyVarTy tv2) +uUnfilledVar outer swapped tv1 details1 ps_ty2 (TyVarTy tv2) | tv1 == tv2 -- Same type variable => no-op (but watch out for the boxy case) = case details1 of MetaTv BoxTv ref1 -- A boxy type variable meets itself; @@ -1109,14 +1127,14 @@ uUnfilledVar outer swapped tv1 details1 nb2 ps_ty2 (TyVarTy tv2) | otherwise = do { lookup2 <- lookupTcTyVar tv2 ; case lookup2 of - IndirectTv ty2' -> uUnfilledVar outer swapped tv1 details1 True ty2' ty2' + IndirectTv ty2' -> uUnfilledVar outer swapped tv1 details1 ty2' ty2' DoneTv details2 -> uUnfilledVars outer swapped tv1 details1 tv2 details2 } -uUnfilledVar outer swapped tv1 details1 nb2 ps_ty2 non_var_ty2 -- ty2 is not a type variable +uUnfilledVar outer swapped tv1 details1 ps_ty2 non_var_ty2 -- ty2 is not a type variable = case details1 of MetaTv (SigTv _) ref1 -> mis_match -- Can't update a skolem with a non-type-variable - MetaTv info ref1 -> uMetaVar swapped tv1 info ref1 nb2 ps_ty2 non_var_ty2 + MetaTv info ref1 -> uMetaVar swapped tv1 info ref1 ps_ty2 non_var_ty2 skolem_details -> mis_match where mis_match = unifyMisMatch outer swapped (TyVarTy tv1) ps_ty2 @@ -1124,12 +1142,12 @@ uUnfilledVar outer swapped tv1 details1 nb2 ps_ty2 non_var_ty2 -- ty2 is not a t ---------------- uMetaVar :: Bool -> TcTyVar -> BoxInfo -> IORef MetaDetails - -> NoBoxes -> TcType -> TcType + -> TcType -> TcType -> TcM () -- tv1 is an un-filled-in meta type variable (maybe boxy, maybe tau) -- ty2 is not a type variable -uMetaVar swapped tv1 BoxTv ref1 nb2 ps_ty2 non_var_ty2 +uMetaVar swapped tv1 BoxTv ref1 ps_ty2 non_var_ty2 = -- tv1 is a BoxTv. So we must unbox ty2, to ensure -- that any boxes in ty2 are filled with monotypes -- @@ -1147,7 +1165,7 @@ uMetaVar swapped tv1 BoxTv ref1 nb2 ps_ty2 non_var_ty2 #endif ; checkUpdateMeta swapped tv1 ref1 final_ty } -uMetaVar swapped tv1 info1 ref1 nb2 ps_ty2 non_var_ty2 +uMetaVar swapped tv1 info1 ref1 ps_ty2 non_var_ty2 = do { final_ty <- checkTauTvUpdate tv1 ps_ty2 -- Occurs check + monotype check ; checkUpdateMeta swapped tv1 ref1 final_ty } @@ -1221,7 +1239,7 @@ uUnfilledVars outer swapped tv1 (MetaTv info1 ref1) tv2 (MetaTv info2 ref2) k1_sub_k2 = k1 `isSubKind` k2 k2_sub_k1 = k2 `isSubKind` k1 - nicer_to_update_tv1 = isSystemName (varName tv1) + nicer_to_update_tv1 = isSystemName (Var.varName tv1) -- Try to update sys-y type variables in preference to ones -- gotten (say) by instantiating a polymorphic function with -- a user-written type sig @@ -1300,6 +1318,7 @@ checkTauTvUpdate orig_tv orig_ty go_pred (ClassP c tys) = do { tys' <- mapM go tys; return (ClassP c tys') } go_pred (IParam n ty) = do { ty' <- go ty; return (IParam n ty') } + go_pred (EqPred t1 t2) = do { t1' <- go t1; t2' <- go t2; return (EqPred t1' t2') } go_tyvar tv (SkolemTv _) = return (TyVarTy tv) go_tyvar tv (MetaTv box ref) @@ -1419,6 +1438,7 @@ unBox (TyVarTy tv) unBoxPred (ClassP cls tys) = do { tys' <- mapM unBox tys; return (ClassP cls tys') } unBoxPred (IParam ip ty) = do { ty' <- unBox ty; return (IParam ip ty') } +unBoxPred (EqPred ty1 ty2) = do { ty1' <- unBox ty1; ty2' <- unBox ty2; return (EqPred ty1' ty2') } \end{code} @@ -1448,24 +1468,28 @@ mkExpectedActualMsg act_ty exp_ty ---------------- -- If an error happens we try to figure out whether the function -- function has been given too many or too few arguments, and say so. -checkFunResCtxt fun actual_res_ty expected_res_ty tidy_env - = do { exp_ty' <- zonkTcType expected_res_ty - ; act_ty' <- zonkTcType actual_res_ty - ; let - (env1, exp_ty'') = tidyOpenType tidy_env exp_ty' - (env2, act_ty'') = tidyOpenType env1 act_ty' - (exp_args, _) = tcSplitFunTys exp_ty'' - (act_args, _) = tcSplitFunTys act_ty'' +addSubCtxt SubDone actual_res_ty expected_res_ty thing_inside + = thing_inside +addSubCtxt sub_ctxt actual_res_ty expected_res_ty thing_inside + = addErrCtxtM mk_err thing_inside + where + mk_err tidy_env + = do { exp_ty' <- zonkTcType expected_res_ty + ; act_ty' <- zonkTcType actual_res_ty + ; let (env1, exp_ty'') = tidyOpenType tidy_env exp_ty' + (env2, act_ty'') = tidyOpenType env1 act_ty' + (exp_args, _) = tcSplitFunTys exp_ty'' + (act_args, _) = tcSplitFunTys act_ty'' - len_act_args = length act_args - len_exp_args = length exp_args + len_act_args = length act_args + len_exp_args = length exp_args - message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun - | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun - | otherwise = mkExpectedActualMsg act_ty'' exp_ty'' - ; return (env2, message) } + message = case sub_ctxt of + SubFun fun | len_exp_args < len_act_args -> wrongArgsCtxt "too few" fun + | len_exp_args > len_act_args -> wrongArgsCtxt "too many" fun + other -> mkExpectedActualMsg act_ty'' exp_ty'' + ; return (env2, message) } - where wrongArgsCtxt too_many_or_few fun = ptext SLIT("Probable cause:") <+> quotes (ppr fun) <+> ptext SLIT("is applied to") <+> text too_many_or_few @@ -1551,20 +1575,15 @@ Unifying kinds is much, much simpler than unifying types. unifyKind :: TcKind -- Expected -> TcKind -- Actual -> TcM () -unifyKind LiftedTypeKind LiftedTypeKind = returnM () -unifyKind UnliftedTypeKind UnliftedTypeKind = returnM () - -unifyKind OpenTypeKind k2 | isOpenTypeKind k2 = returnM () -unifyKind ArgTypeKind k2 | isArgTypeKind k2 = returnM () - -- Respect sub-kinding +unifyKind (TyConApp kc1 []) (TyConApp kc2 []) + | isSubKindCon kc2 kc1 = returnM () -unifyKind (FunKind a1 r1) (FunKind a2 r2) - = do { unifyKind a2 a1; unifyKind r1 r2 } +unifyKind (FunTy a1 r1) (FunTy a2 r2) + = do { unifyKind a2 a1; unifyKind r1 r2 } -- Notice the flip in the argument, -- so that the sub-kinding works right - -unifyKind (KindVar kv1) k2 = uKVar False kv1 k2 -unifyKind k1 (KindVar kv2) = uKVar True kv2 k1 +unifyKind (TyVarTy kv1) k2 = uKVar False kv1 k2 +unifyKind k1 (TyVarTy kv2) = uKVar True kv2 k1 unifyKind k1 k2 = unifyKindMisMatch k1 k2 unifyKinds :: [TcKind] -> [TcKind] -> TcM () @@ -1578,19 +1597,19 @@ uKVar :: Bool -> KindVar -> TcKind -> TcM () uKVar swapped kv1 k2 = do { mb_k1 <- readKindVar kv1 ; case mb_k1 of - Nothing -> uUnboundKVar swapped kv1 k2 - Just k1 | swapped -> unifyKind k2 k1 - | otherwise -> unifyKind k1 k2 } + Flexi -> uUnboundKVar swapped kv1 k2 + Indirect k1 | swapped -> unifyKind k2 k1 + | otherwise -> unifyKind k1 k2 } ---------------- uUnboundKVar :: Bool -> KindVar -> TcKind -> TcM () -uUnboundKVar swapped kv1 k2@(KindVar kv2) +uUnboundKVar swapped kv1 k2@(TyVarTy kv2) | kv1 == kv2 = returnM () | otherwise -- Distinct kind variables = do { mb_k2 <- readKindVar kv2 ; case mb_k2 of - Just k2 -> uUnboundKVar swapped kv1 k2 - Nothing -> writeKindVar kv1 k2 } + Indirect k2 -> uUnboundKVar swapped kv1 k2 + Flexi -> writeKindVar kv1 k2 } uUnboundKVar swapped kv1 non_var_k2 = do { k2' <- zonkTcKind non_var_k2 @@ -1607,9 +1626,9 @@ uUnboundKVar swapped kv1 non_var_k2 kindOccurCheck kv1 k2 -- k2 is zonked = checkTc (not_in k2) (kindOccurCheckErr kv1 k2) where - not_in (KindVar kv2) = kv1 /= kv2 - not_in (FunKind a2 r2) = not_in a2 && not_in r2 - not_in other = True + not_in (TyVarTy kv2) = kv1 /= kv2 + not_in (FunTy a2 r2) = not_in a2 && not_in r2 + not_in other = True kindSimpleKind :: Bool -> Kind -> TcM SimpleKind -- (kindSimpleKind True k) returns a simple kind sk such that sk <: k @@ -1619,14 +1638,16 @@ kindSimpleKind :: Bool -> Kind -> TcM SimpleKind kindSimpleKind orig_swapped orig_kind = go orig_swapped orig_kind where - go sw (FunKind k1 k2) = do { k1' <- go (not sw) k1 - ; k2' <- go sw k2 - ; return (FunKind k1' k2') } - go True OpenTypeKind = return liftedTypeKind - go True ArgTypeKind = return liftedTypeKind - go sw LiftedTypeKind = return liftedTypeKind - go sw UnliftedTypeKind = return unliftedTypeKind - go sw k@(KindVar _) = return k -- KindVars are always simple + go sw (FunTy k1 k2) = do { k1' <- go (not sw) k1 + ; k2' <- go sw k2 + ; return (mkArrowKind k1' k2') } + go True k + | isOpenTypeKind k = return liftedTypeKind + | isArgTypeKind k = return liftedTypeKind + go sw k + | isLiftedTypeKind k = return liftedTypeKind + | isUnliftedTypeKind k = return unliftedTypeKind + go sw k@(TyVarTy _) = return k -- KindVars are always simple go swapped kind = failWithTc (ptext SLIT("Unexpected kind unification failure:") <+> ppr orig_swapped <+> ppr orig_kind) -- I think this can't actually happen @@ -1655,17 +1676,18 @@ unifyKindMisMatch ty1 ty2 unifyFunKind :: TcKind -> TcM (Maybe (TcKind, TcKind)) -- Like unifyFunTy, but does not fail; instead just returns Nothing -unifyFunKind (KindVar kvar) - = readKindVar kvar `thenM` \ maybe_kind -> +unifyFunKind (TyVarTy kvar) + = readKindVar kvar `thenM` \ maybe_kind -> case maybe_kind of - Just fun_kind -> unifyFunKind fun_kind - Nothing -> do { arg_kind <- newKindVar - ; res_kind <- newKindVar - ; writeKindVar kvar (mkArrowKind arg_kind res_kind) - ; returnM (Just (arg_kind,res_kind)) } + Indirect fun_kind -> unifyFunKind fun_kind + Flexi -> + do { arg_kind <- newKindVar + ; res_kind <- newKindVar + ; writeKindVar kvar (mkArrowKind arg_kind res_kind) + ; returnM (Just (arg_kind,res_kind)) } -unifyFunKind (FunKind arg_kind res_kind) = returnM (Just (arg_kind,res_kind)) -unifyFunKind other = returnM Nothing +unifyFunKind (FunTy arg_kind res_kind) = returnM (Just (arg_kind,res_kind)) +unifyFunKind other = returnM Nothing \end{code} %************************************************************************