X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcUnify.lhs;h=821a1cc086112319b5d0662bca8f9c6146d8e852;hb=b99310f05faee2abec850da4349fcd5c0498f7ca;hp=39c3cbda27829ba4718e952781f0783be76bda9f;hpb=e0ab62c1879c97b1db44b23150b2e260a9ec48cf;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcUnify.lhs b/compiler/typecheck/TcUnify.lhs index 39c3cbd..821a1cc 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 ( @@ -17,7 +19,7 @@ module TcUnify ( -------------------------------- -- Holes - tcInfer, subFunTys, unBox, stripBoxyType, withBox, + tcInfer, subFunTys, unBox, refineBox, refineBoxToTau, withBox, boxyUnify, boxyUnifyList, zapToMonotype, boxySplitListTy, boxySplitTyConApp, boxySplitAppTy, wrapFunResCoercion @@ -25,61 +27,30 @@ module TcUnify ( #include "HsVersions.h" -import HsSyn ( HsWrapper(..), idHsWrapper, isIdHsWrapper, (<.>), - mkWpLams, mkWpTyLams, mkWpApps ) -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 Type ( Kind, SimpleKind, KindVar, - openTypeKind, liftedTypeKind, unliftedTypeKind, - mkArrowKind, defaultKind, - argTypeKind, isLiftedTypeKind, isUnliftedTypeKind, - isSubKind, pprKind, splitKindFunTys, isSubKindCon, - isOpenTypeKind, isArgTypeKind ) -import TysPrim ( alphaTy, betaTy ) -import Inst ( newDictBndrsO, instCall, instToId ) -import TyCon ( TyCon, tyConArity, tyConTyVars, isSynTyCon ) -import TysWiredIn ( listTyCon ) -import Id ( Id ) -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 Util ( notNull, equalLength ) +import Module +import Name +import ErrUtils +import Maybes +import BasicTypes +import Util import Outputable - --- Assertion imports -#ifdef DEBUG -import TcType ( isBoxyTy, isFlexi ) -#endif \end{code} %************************************************************************ @@ -95,7 +66,7 @@ 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} %************************************************************************ @@ -142,13 +113,14 @@ subFunTys error_herald n_pats res_ty thing_inside where -- In 'loop', the parameter 'arg_tys' accumulates -- the arg types so far, in *reverse order* + -- INVARIANT: res_ty :: * loop n args_so_far res_ty | Just res_ty' <- tcView res_ty = loop n args_so_far res_ty' 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) } @@ -172,7 +144,7 @@ subFunTys error_herald n_pats res_ty thing_inside else loop n args_so_far (FunTy arg_ty' res_ty') } loop n args_so_far (TyVarTy tv) - | not (isImmutableTyVar tv) + | isTyConableTyVar tv = do { cts <- readMetaTyVar tv ; case cts of Indirect ty -> loop n args_so_far ty @@ -223,10 +195,12 @@ boxySplitTyConApp tc orig_ty return (args ++ args_so_far) loop n_req args_so_far (AppTy fun arg) + | n_req > 0 = loop (n_req - 1) (arg:args_so_far) fun loop n_req args_so_far (TyVarTy tv) - | not (isImmutableTyVar tv) + | isTyConableTyVar tv + , res_kind `isSubKind` tyVarKind tv = do { cts <- readMetaTyVar tv ; case cts of Indirect ty -> loop n_req args_so_far ty @@ -235,7 +209,7 @@ boxySplitTyConApp tc orig_ty } where mk_res_ty arg_tys' = mkTyConApp tc arg_tys' - arg_kinds = map tyVarKind (take n_req (tyConTyVars tc)) + (arg_kinds, res_kind) = splitKindFunTysN n_req (tyConKind tc) loop _ _ _ = boxySplitFailure (mkTyConApp tc (mkTyVarTys (tyConTyVars tc))) orig_ty @@ -248,7 +222,8 @@ boxySplitListTy exp_ty = do { [elt_ty] <- boxySplitTyConApp listTyCon exp_ty ---------------------- boxySplitAppTy :: BoxyRhoType -- Type to split: m a -> TcM (BoxySigmaType, BoxySigmaType) -- Returns m, a --- Assumes (m: * -> k), where k is the kind of the incoming type +-- If the incoming type is a mutable type variable of kind k, then +-- boxySplitAppTy returns a new type variable (m: * -> k); note the *. -- If the incoming type is boxy, then so are the result types; and vice versa boxySplitAppTy orig_ty @@ -262,7 +237,7 @@ boxySplitAppTy orig_ty = return (fun_ty, arg_ty) loop (TyVarTy tv) - | not (isImmutableTyVar tv) + | isTyConableTyVar tv = do { cts <- readMetaTyVar tv ; case cts of Indirect ty -> loop ty @@ -552,7 +527,7 @@ boxyLub orig_ty1 orig_ty2 -- Look inside type synonyms, but only if the naive version fails go ty1 ty2 | Just ty1' <- tcView ty1 = go ty1' ty2 - | Just ty2' <- tcView ty1 = go ty1 ty2' + | Just ty2' <- tcView ty2 = go ty1 ty2' -- For now, we don't look inside ForAlls, PredTys go ty1 ty2 = orig_ty1 -- Default @@ -637,7 +612,8 @@ tc_sub :: SubCtxt -- How to add an error-context -- 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 + = traceTc (text "tc_sub" <+> ppr act_ty $$ ppr 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! @@ -667,9 +643,11 @@ tc_sub1 sub_ctxt act_sty (TyVarTy tv) exp_ib exp_sty exp_ty -- Consider f g ! 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 -> + | isSigmaTy exp_ty + = if exp_ib then -- SKOL does not apply if exp_ty is inside a box + defer_to_boxy_matching sub_ctxt act_sty act_ty exp_ib exp_sty exp_ty + else 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 @@ -712,7 +690,13 @@ tc_sub1 sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty ; co_fn2 <- tc_sub sub_ctxt tau' tau' exp_ib exp_sty expected_ty -- Deal with the dictionaries - ; co_fn1 <- instCall InstSigOrigin inst_tys (substTheta subst' theta) + -- 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) } ----------------------------------- @@ -737,10 +721,17 @@ tc_sub1 sub_ctxt act_sty act_ty@(FunTy act_arg act_res) _ exp_sty (TyVarTy exp_t -- Everything else: defer to boxy matching tc_sub1 sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty + = defer_to_boxy_matching sub_ctxt act_sty actual_ty exp_ib exp_sty expected_ty + +----------------------------------- +defer_to_boxy_matching 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 + u_tys outer False act_sty actual_ty exp_ib exp_sty expected_ty ; return idHsWrapper } - + where + outer = case sub_ctxt of -- Ugh + SubDone -> False + other -> True ----------------------------------- tc_sub_funs act_arg act_res exp_ib exp_arg exp_res @@ -774,7 +765,7 @@ tcGen :: BoxySigmaType -- expected_ty -> TcTyVarSet -- Extra tyvars that the universally -- quantified tyvars of expected_ty -- must not be unified - -> (BoxyRhoType -> TcM result) -- spec_ty + -> ([TcTyVar] -> BoxyRhoType -> TcM result) -> TcM (HsWrapper, result) -- The expression has type: spec_ty -> expected_ty @@ -784,22 +775,21 @@ 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 @@ -812,20 +802,20 @@ 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 <- newDictBndrsO (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 -- The WpLet binds any Insts which came out of the simplification. dict_ids = map instToId dicts - co_fn = mkWpTyLams forall_tvs <.> mkWpLams dict_ids <.> WpLet inst_binds + 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} @@ -872,7 +862,8 @@ 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 } --------------- @@ -966,8 +957,51 @@ u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 go outer (TyVarTy tyvar1) ty2 = uVar outer False tyvar1 nb2 orig_ty2 ty2 go outer ty1 (TyVarTy tyvar2) = uVar outer True tyvar2 nb1 orig_ty1 ty1 -- "True" means args swapped + + -- The case for sigma-types must *follow* the variable cases + -- because a boxy variable can be filed with a polytype; + -- but must precede FunTy, because ((?x::Int) => ty) look + -- like a FunTy; there isn't necy a forall at the top + go _ ty1 ty2 + | isSigmaTy ty1 || isSigmaTy ty2 + = do { checkM (equalLength tvs1 tvs2) + (unifyMisMatch outer False orig_ty1 orig_ty2) + + ; tvs <- tcInstSkolTyVars UnkSkol tvs1 -- Not a helpful SkolemInfo + -- Get location from monad, not from tvs1 + ; let tys = mkTyVarTys tvs + in_scope = mkInScopeSet (mkVarSet tvs) + phi1 = substTy (mkTvSubst in_scope (zipTyEnv tvs1 tys)) body1 + phi2 = substTy (mkTvSubst in_scope (zipTyEnv tvs2 tys)) body2 + (theta1,tau1) = tcSplitPhiTy phi1 + (theta2,tau2) = tcSplitPhiTy phi2 + + ; addErrCtxtM (unifyForAllCtxt tvs phi1 phi2) $ do + { checkM (equalLength theta1 theta2) + (unifyMisMatch outer False orig_ty1 orig_ty2) + + ; uPreds False nb1 theta1 nb2 theta2 + ; uTys nb1 tau1 nb2 tau2 + + -- Check for escape; e.g. (forall a. a->b) ~ (forall a. a->a) + ; free_tvs <- zonkTcTyVarsAndFV (varSetElems (tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2)) + ; ifM (any (`elemVarSet` free_tvs) tvs) + (bleatEscapedTvs free_tvs tvs tvs) + + -- 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 + (tvs1, body1) = tcSplitForAllTys ty1 + (tvs2, body2) = tcSplitForAllTys ty2 + -- Predicates - go outer (PredTy p1) (PredTy p2) = uPred outer nb1 p1 nb2 p2 + go outer (PredTy p1) (PredTy p2) = uPred False nb1 p1 nb2 p2 -- Type constructors must match go _ (TyConApp con1 tys1) (TyConApp con2 tys2) @@ -993,26 +1027,6 @@ u_tys outer nb1 orig_ty1 ty1 nb2 orig_ty2 ty2 | Just (s1,t1) <- tcSplitAppTy_maybe ty1 = do { uTys nb1 s1 nb2 s2; uTys nb1 t1 nb2 t2 } - go _ ty1@(ForAllTy _ _) ty2@(ForAllTy _ _) - | length tvs1 == length tvs2 - = do { tvs <- tcInstSkolTyVars UnkSkol tvs1 -- Not a helpful SkolemInfo - ; 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 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 - (tvs1, body1) = tcSplitForAllTys ty1 - (tvs2, body2) = tcSplitForAllTys ty2 -- Anything else fails go outer _ _ = unifyMisMatch outer False orig_ty1 orig_ty2 @@ -1023,6 +1037,10 @@ uPred outer nb1 (IParam n1 t1) nb2 (IParam n2 t2) uPred outer nb1 (ClassP c1 tys1) nb2 (ClassP c2 tys2) | c1 == c2 = uTys_s nb1 tys1 nb2 tys2 -- Guaranteed equal lengths because the kinds check uPred outer _ p1 _ p2 = unifyMisMatch outer False (mkPredTy p1) (mkPredTy p2) + +uPreds outer nb1 [] nb2 [] = return () +uPreds outer nb1 (p1:ps1) nb2 (p2:ps2) = uPred outer nb1 p1 nb2 p2 >> uPreds outer nb1 ps1 nb2 ps2 +uPreds outer nb1 ps1 nb2 ps2 = panic "uPreds" \end{code} Note [Tycon app] @@ -1262,7 +1280,7 @@ 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 @@ -1363,7 +1381,11 @@ checkTauTvUpdate orig_tv orig_ty ; case mb_tys' of Just tys' -> return (TyConApp tc tys') -- Retain the synonym (the common case) - Nothing -> go (expectJust "checkTauTvUpdate" + Nothing | isOpenTyCon tc + -> notMonoArgs (TyConApp tc tys) + -- Synonym families must have monotype args + | otherwise + -> go (expectJust "checkTauTvUpdate" (tcView (TyConApp tc tys))) -- Try again, expanding the synonym } @@ -1403,16 +1425,27 @@ But we should not reject the program, because A t = (). Rather, we should bind t to () (= non_var_ty2). \begin{code} -stripBoxyType :: BoxyType -> TcM TcType --- Strip all boxes from the input type, returning a non-boxy type. --- It's fine for there to be a polytype inside a box (c.f. unBox) --- All of the boxes should have been filled in by now; --- hence we return a TcType -stripBoxyType ty = zonkType strip_tv ty - where - strip_tv tv = ASSERT( not (isBoxyTyVar tv) ) return (TyVarTy tv) - -- strip_tv will be called for *Flexi* meta-tyvars - -- There should not be any Boxy ones; hence the ASSERT +refineBox :: TcType -> TcM TcType +-- Unbox the outer box of a boxy type (if any) +refineBox ty@(TyVarTy box_tv) + | isMetaTyVar box_tv + = do { cts <- readMetaTyVar box_tv + ; case cts of + Flexi -> return ty + Indirect ty -> return ty } +refineBox other_ty = return other_ty + +refineBoxToTau :: TcType -> TcM TcType +-- Unbox the outer box of a boxy type, filling with a monotype if it is empty +-- Like refineBox except for the "fill with monotype" part. +refineBoxToTau ty@(TyVarTy box_tv) + | isMetaTyVar box_tv + , MetaTv BoxTv ref <- tcTyVarDetails box_tv + = do { cts <- readMutVar ref + ; case cts of + Flexi -> fillBoxWithTau box_tv ref + Indirect ty -> return ty } +refineBoxToTau other_ty = return other_ty zapToMonotype :: BoxySigmaType -> TcM TcTauType -- Subtle... we must zap the boxy res_ty @@ -1519,6 +1552,16 @@ addSubCtxt sub_ctxt actual_res_ty expected_res_ty thing_inside <+> ptext SLIT("arguments") ------------------ +unifyForAllCtxt tvs phi1 phi2 env + = returnM (env2, msg) + where + (env', tvs') = tidyOpenTyVars env tvs -- NB: not tidyTyVarBndrs + (env1, phi1') = tidyOpenType env' phi1 + (env2, phi2') = tidyOpenType env1 phi2 + msg = vcat [ptext SLIT("When matching") <+> quotes (ppr (mkForAllTys tvs' phi1')), + ptext SLIT(" and") <+> quotes (ppr (mkForAllTys tvs' phi2'))] + +------------------ unifyKindCtxt swapped tv1 ty2 tidy_env -- not swapped => tv1 expected, ty2 inferred -- tv1 and ty2 are zonked already = returnM msg @@ -1542,31 +1585,59 @@ unifyMisMatch outer swapped ty1 ty2 else failWithTcM (env, msg) } +----------------------- +misMatchMsg :: TcType -> TcType -> TcM (TidyEnv, SDoc) +-- Generate the message when two types fail to match, +-- going to some trouble to make it helpful misMatchMsg ty1 ty2 = do { env0 <- tcInitTidyEnv - ; (env1, pp1, extra1) <- ppr_ty env0 ty1 - ; (env2, pp2, extra2) <- ppr_ty env1 ty2 + ; (env1, pp1, extra1) <- ppr_ty env0 ty1 ty2 + ; (env2, pp2, extra2) <- ppr_ty env1 ty2 ty1 ; return (env2, sep [sep [ptext SLIT("Couldn't match expected type") <+> pp1, nest 7 (ptext SLIT("against inferred type") <+> pp2)], - nest 2 extra1, nest 2 extra2]) } - -ppr_ty :: TidyEnv -> TcType -> TcM (TidyEnv, SDoc, SDoc) -ppr_ty env ty - = do { ty' <- zonkTcType ty - ; let (env1,tidy_ty) = tidyOpenType env ty' - simple_result = (env1, quotes (ppr tidy_ty), empty) - ; case tidy_ty of - TyVarTy tv - | isSkolemTyVar tv || isSigTyVar tv - -> return (env2, pp_rigid tv', pprSkolTvBinding tv') - | otherwise -> return simple_result - where - (env2, tv') = tidySkolemTyVar env1 tv - other -> return simple_result } + nest 2 (extra1 $$ extra2)]) } + +ppr_ty :: TidyEnv -> TcType -> TcType -> TcM (TidyEnv, SDoc, SDoc) +ppr_ty env ty other_ty + = do { ty' <- zonkTcType ty + ; let (env1, tidy_ty) = tidyOpenType env ty' + ; (env2, extra) <- ppr_extra env1 tidy_ty other_ty + ; return (env2, quotes (ppr tidy_ty), extra) } + +-- (ppr_extra env ty other_ty) shows extra info about 'ty' +ppr_extra env (TyVarTy tv) other_ty + | isSkolemTyVar tv || isSigTyVar tv + = return (env1, pprSkolTvBinding tv1) where - pp_rigid tv = quotes (ppr tv) <+> parens (ptext SLIT("a rigid variable")) + (env1, tv1) = tidySkolemTyVar env tv + +ppr_extra env (TyConApp tc1 _) (TyConApp tc2 _) + | getOccName tc1 == getOccName tc2 + = -- This case helps with messages that would otherwise say + -- Could not match 'T' does not match 'M.T' + -- which is not helpful + do { this_mod <- getModule + ; return (env, quotes (ppr tc1) <+> ptext SLIT("is defined") <+> mk_mod this_mod) } + where + tc_mod = nameModule (getName tc1) + tc_pkg = modulePackageId tc_mod + tc2_pkg = modulePackageId (nameModule (getName tc2)) + mk_mod this_mod + | tc_mod == this_mod = ptext SLIT("in this module") + + | not home_pkg && tc2_pkg /= tc_pkg = pp_pkg + -- Suppress the module name if (a) it's from another package + -- (b) other_ty isn't from that same package + + | otherwise = ptext SLIT("in module") <+> quotes (ppr tc_mod) <+> pp_pkg + where + home_pkg = tc_pkg == modulePackageId this_mod + pp_pkg | home_pkg = empty + | otherwise = ptext SLIT("in package") <+> quotes (ppr tc_pkg) +ppr_extra env ty other_ty = return (env, empty) -- Normal case +----------------------- notMonoType ty = do { ty' <- zonkTcType ty ; env0 <- tcInitTidyEnv @@ -1574,6 +1645,13 @@ notMonoType ty msg = ptext SLIT("Cannot match a monotype with") <+> quotes (ppr tidy_ty) ; failWithTcM (env1, msg) } +notMonoArgs ty + = do { ty' <- zonkTcType ty + ; env0 <- tcInitTidyEnv + ; let (env1, tidy_ty) = tidyOpenType env0 ty' + msg = ptext SLIT("Arguments of synonym family must be monotypes") <+> quotes (ppr tidy_ty) + ; failWithTcM (env1, msg) } + occurCheck tyvar ty = do { env0 <- tcInitTidyEnv ; ty' <- zonkTcType ty @@ -1731,6 +1809,10 @@ unifyFunKind other = returnM Nothing checkExpectedKind :: Outputable a => a -> TcKind -> TcKind -> TcM () -- A fancy wrapper for 'unifyKind', which tries -- to give decent error messages. +-- (checkExpectedKind ty act_kind exp_kind) +-- checks that the actual kind act_kind is compatible +-- with the expected kind exp_kind +-- The first argument, ty, is used only in the error message generation checkExpectedKind ty act_kind exp_kind | act_kind `isSubKind` exp_kind -- Short cut for a very common case = returnM ()