X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=4a1203a8363f93ffa0c36197f38d0d9774f68369;hb=2767767f7b4acf89f56d18231f143b60429631f6;hp=533058fa093b8dd941a29395219b76198402a5f1;hpb=4161ba13916463f8e67259498eacf22744160e1f;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index 533058f..4a1203a 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -12,54 +12,49 @@ module TcBinds ( tcBindsAndThen, tcTopBinds, import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun ) import {-# SOURCE #-} TcExpr ( tcExpr ) -import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), StmtCtxt(..), - Match(..), collectMonoBinders, andMonoBinds +import CmdLineOpts ( opt_NoMonomorphismRestriction ) +import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), + Match(..), HsMatchContext(..), + collectMonoBinders, andMonoBinds ) import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds ) import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet ) import TcMonad import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..), - newDicts, tyVarsOfInst, instToId, - getAllFunDepsOfLIE, getIPsOfLIE, zonkFunDeps + newDicts, instToId ) import TcEnv ( tcExtendLocalValEnv, - newSpecPragmaId, newLocalId, - tcLookupTyCon, - tcGetGlobalTyVars, tcExtendGlobalTyVars + newSpecPragmaId, newLocalId ) -import TcSimplify ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts ) -import TcImprove ( tcImprove ) -import TcMonoType ( tcHsSigType, checkSigTyVars, +import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted, tcSimplifyToDicts ) +import TcMonoType ( tcHsSigType, UserTypeCtxt(..), checkSigTyVars, TcSigInfo(..), tcTySig, maybeSig, sigCtxt ) import TcPat ( tcPat ) import TcSimplify ( bindInstsOfLocalFuns ) -import TcType ( TcThetaType, newTyVarTy, newTyVar, - zonkTcTypes, zonkTcThetaType, zonkTcTyVarToTyVar +import TcMType ( newTyVarTy, newTyVar, + zonkTcTyVarToTyVar, + unifyTauTy, unifyTauTyLists + ) +import TcType ( mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType, + mkPredTy, mkForAllTy, isUnLiftedType, + unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind ) -import TcUnify ( unifyTauTy, unifyTauTyLists ) import CoreFVs ( idFreeTyVars ) -import Id ( mkVanillaId, setInlinePragma ) +import Id ( mkLocalId, setInlinePragma ) import Var ( idType, idName ) import IdInfo ( InlinePragInfo(..) ) import Name ( Name, getOccName, getSrcLoc ) import NameSet -import Type ( mkTyVarTy, tyVarsOfTypes, mkTyConApp, - mkForAllTys, mkFunTys, - mkPredTy, mkForAllTy, isUnLiftedType, - isUnboxedType, unboxedTypeKind, boxedTypeKind, openTypeKind - ) -import FunDeps ( tyVarFunDep, oclose ) import Var ( tyVarKind ) import VarSet import Bag import Util ( isIn ) import Maybes ( maybeToBool ) -import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNotTopLevel ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isNotTopLevel ) import FiniteMap ( listToFM, lookupFM ) -import PrelNames ( ioTyConName, mainKey, hasKey ) import Outputable \end{code} @@ -141,7 +136,7 @@ tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next -- Create specialisations of functions bound here -- We want to keep non-recursive things non-recursive - -- so that we desugar unboxed bindings correctly + -- so that we desugar unlifted bindings correctly case (top_lvl, is_rec) of -- For the top level don't bother will all this bindInstsOfLocalFuns stuff @@ -182,32 +177,6 @@ tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next ) \end{code} -An aside. The original version of @tcBindsAndThen@ which lacks a -combiner function, appears below. Though it is perfectly well -behaved, it cannot be typed by Haskell, because the recursive call is -at a different type to the definition itself. There aren't too many -examples of this, which is why I thought it worth preserving! [SLPJ] - -\begin{pseudocode} -% tcBindsAndThen -% :: RenamedHsBinds -% -> TcM (thing, LIE, thing_ty)) -% -> TcM ((TcHsBinds, thing), LIE, thing_ty) -% -% tcBindsAndThen EmptyBinds do_next -% = do_next `thenTc` \ (thing, lie, thing_ty) -> -% returnTc ((EmptyBinds, thing), lie, thing_ty) -% -% tcBindsAndThen (ThenBinds binds1 binds2) do_next -% = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) -% `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> -% -% returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) -% -% tcBindsAndThen (MonoBind bind sigs is_rec) do_next -% = tcBindAndThen bind sigs do_next -\end{pseudocode} - %************************************************************************ %* * @@ -239,142 +208,55 @@ tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec -- If typechecking the binds fails, then return with each -- signature-less binder given type (forall a.a), to minimise subsequent -- error messages - newTyVar boxedTypeKind `thenNF_Tc` \ alpha_tv -> + newTyVar liftedTypeKind `thenNF_Tc` \ alpha_tv -> let forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) binder_names = collectMonoBinders mbind poly_ids = map mk_dummy binder_names mk_dummy name = case maybeSig tc_ty_sigs name of Just (TySigInfo _ poly_id _ _ _ _ _ _) -> poly_id -- Signature - Nothing -> mkVanillaId name forall_a_a -- No signature + Nothing -> mkLocalId name forall_a_a -- No signature in returnTc (EmptyMonoBinds, emptyLIE, poly_ids) - ) $ + ) $ -- TYPECHECK THE BINDINGS tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) -> - - -- CHECK THAT THE SIGNATURES MATCH - -- (must do this before getTyVarsToGen) - checkSigMatch top_lvl binder_names mono_ids tc_ty_sigs `thenTc` \ maybe_sig_theta -> - - -- IMPROVE the LIE - -- Force any unifications dictated by functional dependencies. - -- Because unification may happen, it's important that this step - -- come before: - -- - computing vars over which to quantify - -- - zonking the generalized type vars - let lie_avail = case maybe_sig_theta of - Nothing -> emptyLIE - Just (_, la) -> la - lie_avail_req = lie_avail `plusLIE` lie_req in - tcImprove lie_avail_req `thenTc_` - - -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen - -- The tyvars_not_to_gen are free in the environment, and hence - -- candidates for generalisation, but sometimes the monomorphism - -- restriction means we can't generalise them nevertheless - let - mono_id_tys = map idType mono_ids - in - getTyVarsToGen is_unrestricted mono_id_tys lie_req `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) -> - - -- Finally, zonk the generalised type variables to real TyVars - -- This commits any unbound kind variables to boxed kind - -- I'm a little worried that such a kind variable might be - -- free in the environment, but I don't think it's possible for - -- this to happen when the type variable is not free in the envt - -- (which it isn't). SLPJ Nov 98 - mapTc zonkTcTyVarToTyVar (varSetElems tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list -> let - real_tyvars_to_gen = mkVarSet real_tyvars_to_gen_list - -- It's important that the final list - -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully - -- zonked, *including boxity*, because they'll be included in the forall types of - -- the polymorphic Ids, and instances of these Ids will be generated from them. - -- - -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass - -- real_tyvars_to_gen + tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids in - -- SIMPLIFY THE LIE - tcExtendGlobalTyVars tyvars_not_to_gen ( - let ips = getIPsOfLIE lie_avail_req in - if null real_tyvars_to_gen_list && (null ips || not is_unrestricted) then - -- No polymorphism, and no IPs, so no need to simplify context - returnTc (lie_req, EmptyMonoBinds, []) - else - case maybe_sig_theta of - Nothing -> - -- No signatures, so just simplify the lie - -- NB: no signatures => no polymorphic recursion, so no - -- need to use lie_avail (which will be empty anyway) - tcSimplify (text "tcBinds1" <+> ppr binder_names) - real_tyvars_to_gen lie_req `thenTc` \ (lie_free, dict_binds, lie_bound) -> - returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound)) - - Just (sig_theta, lie_avail) -> - -- There are signatures, and their context is sig_theta - -- Furthermore, lie_avail is an LIE containing the 'method insts' - -- for the things bound here - - zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' -> - newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) -> - -- It's important that sig_theta is zonked, because - -- dict_id is later used to form the type of the polymorphic thing, - -- and forall-types must be zonked so far as their bound variables - -- are concerned - - let - -- The "givens" is the stuff available. We get that from - -- the context of the type signature, BUT ALSO the lie_avail - -- so that polymorphic recursion works right (see comments at end of fn) - givens = dicts_sig `plusLIE` lie_avail - in - - -- Check that the needed dicts can be expressed in - -- terms of the signature ones - tcAddErrCtxt (bindSigsCtxt tysig_names) $ - tcSimplifyAndCheck - (ptext SLIT("type signature for") <+> pprQuotedList binder_names) - real_tyvars_to_gen givens lie_req `thenTc` \ (lie_free, dict_binds) -> - - returnTc (lie_free, dict_binds, dict_ids) - - ) `thenTc` \ (lie_free, dict_binds, dicts_bound) -> - - -- GET THE FINAL MONO_ID_TYS - zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types -> - - - -- CHECK FOR BOGUS UNPOINTED BINDINGS - (if any isUnLiftedType zonked_mono_id_types then - -- Unlifted bindings must be non-recursive, - -- not top level, and non-polymorphic - checkTc (isNotTopLevel top_lvl) - (unliftedBindErr "Top-level" mbind) `thenTc_` - checkTc (case is_rec of {Recursive -> False; NonRecursive -> True}) - (unliftedBindErr "Recursive" mbind) `thenTc_` - checkTc (null real_tyvars_to_gen_list) - (unliftedBindErr "Polymorphic" mbind) - else - returnTc () - ) `thenTc_` - - ASSERT( not (any ((== unboxedTypeKind) . tyVarKind) real_tyvars_to_gen_list) ) - -- The instCantBeGeneralised stuff in tcSimplify should have - -- already raised an error if we're trying to generalise an - -- unboxed tyvar (NB: unboxed tyvars are always introduced - -- along with a class constraint) and it's better done there - -- because we have more precise origin information. - -- That's why we just use an ASSERT here. - - - -- BUILD THE POLYMORPHIC RESULT IDs - mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids -> + -- GENERALISE + tcAddSrcLoc (minimum (map getSrcLoc binder_names)) $ + tcAddErrCtxt (genCtxt binder_names) $ + generalise binder_names mbind tau_tvs lie_req tc_ty_sigs + `thenTc` \ (tc_tyvars_to_gen, lie_free, dict_binds, dict_ids) -> + + + -- ZONK THE GENERALISED TYPE VARIABLES TO REAL TyVars + -- This commits any unbound kind variables to boxed kind, by unification + -- It's important that the final quanfified type variables + -- are fully zonked, *including boxity*, because they'll be + -- included in the forall types of the polymorphic Ids. + -- At calls of these Ids we'll instantiate fresh type variables from + -- them, and we use their boxity then. + mapNF_Tc zonkTcTyVarToTyVar tc_tyvars_to_gen `thenNF_Tc` \ real_tyvars_to_gen -> + + -- ZONK THE Ids + -- It's important that the dict Ids are zonked, including the boxity set + -- in the previous step, because they are later used to form the type of + -- the polymorphic thing, and forall-types must be zonked so far as + -- their bound variables are concerned + mapNF_Tc zonkId dict_ids `thenNF_Tc` \ zonked_dict_ids -> + mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids -> + + -- CHECK FOR BOGUS UNLIFTED BINDINGS + checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids `thenTc_` + + -- BUILD THE POLYMORPHIC RESULT IDs let exports = zipWith mk_export binder_names zonked_mono_ids - dict_tys = map idType dicts_bound + dict_tys = map idType zonked_dict_ids inlines = mkNameSet [name | InlineSig name _ loc <- inline_sigs] no_inlines = listToFM ([(name, IMustNotBeINLINEd False phase) | NoInlineSig name phase loc <- inline_sigs] ++ @@ -394,53 +276,78 @@ tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec case maybeSig tc_ty_sigs binder_name of Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) -> (sig_tyvars, sig_poly_id) - Nothing -> (real_tyvars_to_gen_list, new_poly_id) + Nothing -> (real_tyvars_to_gen, new_poly_id) - new_poly_id = mkVanillaId binder_name poly_ty - poly_ty = mkForAllTys real_tyvars_to_gen_list + new_poly_id = mkLocalId binder_name poly_ty + poly_ty = mkForAllTys real_tyvars_to_gen $ mkFunTys dict_tys - $ idType (zonked_mono_id) + $ idType zonked_mono_id -- It's important to build a fully-zonked poly_ty, because -- we'll slurp out its free type variables when extending the -- local environment (tcExtendLocalValEnv); if it's not zonked -- it appears to have free tyvars that aren't actually free -- at all. - - pat_binders :: [Name] - pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds) in - -- CHECK FOR UNBOXED BINDERS IN PATTERN BINDINGS - mapTc (\id -> checkTc (not (idName id `elem` pat_binders - && isUnboxedType (idType id))) - (unboxedPatBindErr id)) zonked_mono_ids - `thenTc_` + + traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds), + exports, [idType poly_id | (_, poly_id, _) <- exports])) `thenTc_` -- BUILD RESULTS returnTc ( - -- pprTrace "binding.." (ppr ((dicts_bound, dict_binds), exports, [idType poly_id | (_, poly_id, _) <- exports])) $ - AbsBinds real_tyvars_to_gen_list - dicts_bound - exports - inlines - (dict_binds `andMonoBinds` mbind'), - lie_free, - [poly_id | (_, poly_id, _) <- exports] + AbsBinds real_tyvars_to_gen + zonked_dict_ids + exports + inlines + (dict_binds `andMonoBinds` mbind'), + lie_free, + [poly_id | (_, poly_id, _) <- exports] ) - where - tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- tc_ty_sigs] - is_unrestricted = isUnRestrictedGroup tysig_names mbind - -justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds -justPatBindings (AndMonoBinds b1 b2) binds = - justPatBindings b1 (justPatBindings b2 binds) -justPatBindings other_bind binds = binds attachNoInlinePrag no_inlines bndr = case lookupFM no_inlines (idName bndr) of Just prag -> bndr `setInlinePragma` prag Nothing -> bndr + +checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids + = ASSERT( not (any ((eqKind unliftedTypeKind) . tyVarKind) real_tyvars_to_gen) ) + -- The instCantBeGeneralised stuff in tcSimplify should have + -- already raised an error if we're trying to generalise an + -- unboxed tyvar (NB: unboxed tyvars are always introduced + -- along with a class constraint) and it's better done there + -- because we have more precise origin information. + -- That's why we just use an ASSERT here. + + -- Check that pattern-bound variables are not unlifted + (if or [ (idName id `elem` pat_binders) && isUnLiftedType (idType id) + | id <- zonked_mono_ids ] then + addErrTc (unliftedBindErr "Pattern" mbind) + else + returnTc () + ) `thenTc_` + + -- Unlifted bindings must be non-recursive, + -- not top level, non-polymorphic, and not pattern bound + if any (isUnLiftedType . idType) zonked_mono_ids then + checkTc (isNotTopLevel top_lvl) + (unliftedBindErr "Top-level" mbind) `thenTc_` + checkTc (isNonRec is_rec) + (unliftedBindErr "Recursive" mbind) `thenTc_` + checkTc (null real_tyvars_to_gen) + (unliftedBindErr "Polymorphic" mbind) + else + returnTc () + + where + pat_binders :: [Name] + pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds) + + justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds + justPatBindings (AndMonoBinds b1 b2) binds = + justPatBindings b1 (justPatBindings b2 binds) + justPatBindings other_bind binds = binds \end{code} + Polymorphic recursion ~~~~~~~~~~~~~~~~~~~~~ The game plan for polymorphic recursion in the code above is @@ -503,6 +410,90 @@ is doing. %* * %************************************************************************ +\begin{code} +generalise binder_names mbind tau_tvs lie_req sigs + | not is_unrestricted -- RESTRICTED CASE + = -- Check signature contexts are empty + checkTc (all is_mono_sig sigs) + (restrictedBindCtxtErr binder_names) `thenTc_` + + -- Now simplify with exactly that set of tyvars + -- We have to squash those Methods + tcSimplifyRestricted doc tau_tvs lie_req `thenTc` \ (qtvs, lie_free, binds) -> + + -- Check that signature type variables are OK + checkSigsTyVars sigs `thenTc_` + + returnTc (qtvs, lie_free, binds, []) + + | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS + = tcSimplifyInfer doc tau_tvs lie_req + + | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS + = -- CHECKING CASE: Unrestricted group, there are type signatures + -- Check signature contexts are empty + checkSigsCtxts sigs `thenTc` \ (sig_avails, sig_dicts) -> + + -- Check that the needed dicts can be + -- expressed in terms of the signature ones + tcSimplifyInferCheck doc tau_tvs sig_avails lie_req `thenTc` \ (forall_tvs, lie_free, dict_binds) -> + + -- Check that signature type variables are OK + checkSigsTyVars sigs `thenTc_` + + returnTc (forall_tvs, lie_free, dict_binds, sig_dicts) + + where + is_unrestricted | opt_NoMonomorphismRestriction = True + | otherwise = isUnRestrictedGroup tysig_names mbind + + tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- sigs] + is_mono_sig (TySigInfo _ _ _ theta _ _ _ _) = null theta + + doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names + +----------------------- + -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE + -- The type signatures on a mutually-recursive group of definitions + -- must all have the same context (or none). + -- + -- We unify them because, with polymorphic recursion, their types + -- might not otherwise be related. This is a rather subtle issue. + -- ToDo: amplify +checkSigsCtxts sigs@(TySigInfo _ id1 sig_tvs theta1 _ _ _ src_loc : other_sigs) + = tcAddSrcLoc src_loc $ + mapTc_ check_one other_sigs `thenTc_` + if null theta1 then + returnTc ([], []) -- Non-overloaded type signatures + else + newDicts SignatureOrigin theta1 `thenNF_Tc` \ sig_dicts -> + let + -- The "sig_avails" is the stuff available. We get that from + -- the context of the type signature, BUT ALSO the lie_avail + -- so that polymorphic recursion works right (see comments at end of fn) + sig_avails = sig_dicts ++ sig_meths + in + returnTc (sig_avails, map instToId sig_dicts) + where + sig1_dict_tys = map mkPredTy theta1 + n_sig1_theta = length theta1 + sig_meths = concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs] + + check_one sig@(TySigInfo _ id _ theta _ _ _ src_loc) + = tcAddErrCtxt (sigContextsCtxt id1 id) $ + checkTc (length theta == n_sig1_theta) sigContextsErr `thenTc_` + unifyTauTyLists sig1_dict_tys (map mkPredTy theta) + +checkSigsTyVars sigs = mapTc_ check_one sigs + where + check_one (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc) + = tcAddSrcLoc src_loc $ + tcAddErrCtxtM (sigCtxt (sig_msg id) sig_tyvars sig_theta sig_tau) $ + checkSigTyVars sig_tyvars (idFreeTyVars id) + + sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id) +\end{code} + @getTyVarsToGen@ decides what type variables to generalise over. For a "restricted group" -- see the monomorphism restriction @@ -531,6 +522,8 @@ generalise. We must be careful about doing this: Another, more common, example is when there's a Method inst in the LIE, whose type might very well involve non-overloaded type variables. + [NOTE: Jan 2001: I don't understand the problem here so I'm doing + the simple thing instead] (b) On the other hand, we mustn't generalise tyvars which are constrained, because we are going to pass on out the unmodified LIE, with those @@ -541,43 +534,6 @@ constrained tyvars. We don't use any of the results, except to find which tyvars are constrained. \begin{code} -getTyVarsToGen is_unrestricted mono_id_tys lie - = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars -> - zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys -> - let - body_tyvars = tyVarsOfTypes zonked_mono_id_tys `minusVarSet` free_tyvars - fds = getAllFunDepsOfLIE lie - in - if is_unrestricted - then - -- We need to augment the type variables that appear explicitly in - -- the type by those that are determined by the functional dependencies. - -- e.g. suppose our type is C a b => a -> a - -- with the fun-dep a->b - -- Then we should generalise over b too; otherwise it will be - -- reported as ambiguous. - zonkFunDeps fds `thenNF_Tc` \ fds' -> - let tvFundep = tyVarFunDep fds' - extended_tyvars = oclose tvFundep body_tyvars - in - returnNF_Tc (emptyVarSet, extended_tyvars) - else - -- This recover and discard-errs is to avoid duplicate error - -- messages; this, after all, is an "extra" call to tcSimplify - recoverNF_Tc (returnNF_Tc (emptyVarSet, body_tyvars)) $ - discardErrsTc $ - - tcSimplify (text "getTVG") body_tyvars lie `thenTc` \ (_, _, constrained_dicts) -> - let - -- ASSERT: dicts_sig is already zonked! - constrained_tyvars = foldrBag (unionVarSet . tyVarsOfInst) emptyVarSet constrained_dicts - reduced_tyvars_to_gen = body_tyvars `minusVarSet` constrained_tyvars - in - returnTc (constrained_tyvars, reduced_tyvars_to_gen) -\end{code} - - -\begin{code} isUnRestrictedGroup :: [Name] -- Signatures given for these -> RenamedMonoBinds -> Bool @@ -613,7 +569,7 @@ tcMonoBinds :: RenamedMonoBinds -> TcM (TcMonoBinds, LIE, -- LIE required [Name], -- Bound names - [TcId]) -- Corresponding monomorphic bound things + [TcId]) -- Corresponding monomorphic bound things tcMonoBinds mbinds tc_ty_sigs is_rec = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) -> @@ -651,15 +607,20 @@ tcMonoBinds mbinds tc_ty_sigs is_rec returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids) where - -- This function is used when dealing with a LHS binder; we make a monomorphic - -- version of the Id. We check for type signatures + -- This function is used when dealing with a LHS binder; + -- we make a monomorphic version of the Id. + -- We check for a type signature; if there is one, we use the mono_id + -- from the signature. This is how we make sure the tau part of the + -- signature actually maatches the type of the LHS; then tc_mb_pats + -- ensures the LHS and RHS have the same type + tc_pat_bndr name pat_ty = case maybeSig tc_ty_sigs name of Nothing -> newLocalId (getOccName name) pat_ty (getSrcLoc name) Just (TySigInfo _ _ _ _ _ mono_id _ _) - -> tcAddSrcLoc (getSrcLoc name) $ + -> tcAddSrcLoc (getSrcLoc name) $ unifyTauTy (idType mono_id) pat_ty `thenTc_` returnTc mono_id @@ -713,7 +674,7 @@ tcMonoBinds mbinds tc_ty_sigs is_rec complete_it xve = tcAddSrcLoc locn $ tcAddErrCtxt (patMonoBindsCtxt bind) $ tcExtendLocalValEnv xve $ - tcGRHSs grhss pat_ty PatBindRhs `thenTc` \ (grhss', lie) -> + tcGRHSs PatBindRhs grhss pat_ty `thenTc` \ (grhss', lie) -> returnTc (PatMonoBind pat' grhss' locn, lie) in returnTc (complete_it, lie_req, tvs, ids, lie_avail) @@ -721,105 +682,8 @@ tcMonoBinds mbinds tc_ty_sigs is_rec -- Figure out the appropriate kind for the pattern, -- and generate a suitable type variable kind = case is_rec of - Recursive -> boxedTypeKind -- Recursive, so no unboxed types - NonRecursive -> openTypeKind -- Non-recursive, so we permit unboxed types -\end{code} - -%************************************************************************ -%* * -\subsection{Signatures} -%* * -%************************************************************************ - -@checkSigMatch@ does the next step in checking signature matching. -The tau-type part has already been unified. What we do here is to -check that this unification has not over-constrained the (polymorphic) -type variables of the original signature type. - -The error message here is somewhat unsatisfactory, but it'll do for -now (ToDo). - -\begin{code} -checkSigMatch :: TopLevelFlag -> [Name] -> [TcId] -> [TcSigInfo] -> TcM (Maybe (TcThetaType, LIE)) -checkSigMatch top_lvl binder_names mono_ids sigs - | main_bound_here - = -- First unify the main_id with IO t, for any old t - tcSetErrCtxt mainTyCheckCtxt ( - tcLookupTyCon ioTyConName `thenTc` \ ioTyCon -> - newTyVarTy boxedTypeKind `thenNF_Tc` \ t_tv -> - unifyTauTy ((mkTyConApp ioTyCon [t_tv])) - (idType main_mono_id) - ) `thenTc_` - - -- Now check the signatures - -- Must do this after the unification with IO t, - -- in case of a silly signature like - -- main :: forall a. a - -- The unification to IO t will bind the type variable 'a', - -- which is just waht check_one_sig looks for - mapTc check_one_sig sigs `thenTc_` - mapTc check_main_ctxt sigs `thenTc_` - returnTc (Just ([], emptyLIE)) - - | not (null sigs) - = mapTc check_one_sig sigs `thenTc_` - mapTc check_one_ctxt all_sigs_but_first `thenTc_` - returnTc (Just (theta1, sig_lie)) - - | otherwise - = returnTc Nothing -- No constraints from type sigs - - where - (TySigInfo _ id1 _ theta1 _ _ _ _ : all_sigs_but_first) = sigs - - sig1_dict_tys = mk_dict_tys theta1 - n_sig1_dict_tys = length sig1_dict_tys - sig_lie = mkLIE (concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs]) - - maybe_main = find_main top_lvl binder_names mono_ids - main_bound_here = maybeToBool maybe_main - Just main_mono_id = maybe_main - - -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK - -- Doesn't affect substitution - check_one_sig (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxtM (sigCtxt (sig_msg id) sig_tyvars sig_theta sig_tau) $ - checkSigTyVars sig_tyvars (idFreeTyVars id) - - - -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE - -- The type signatures on a mutually-recursive group of definitions - -- must all have the same context (or none). - -- - -- We unify them because, with polymorphic recursion, their types - -- might not otherwise be related. This is a rather subtle issue. - -- ToDo: amplify - check_one_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (sigContextsCtxt id1 id) $ - checkTc (length this_sig_dict_tys == n_sig1_dict_tys) - sigContextsErr `thenTc_` - unifyTauTyLists sig1_dict_tys this_sig_dict_tys - where - this_sig_dict_tys = mk_dict_tys theta - - -- CHECK THAT FOR A GROUP INVOLVING Main.main, all - -- the signature contexts are empty (what a bore) - check_main_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc) - = tcAddSrcLoc src_loc $ - checkTc (null theta) (mainContextsErr id) - - mk_dict_tys theta = map mkPredTy theta - - sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id) - - -- Search for Main.main in the binder_names, return corresponding mono_id - find_main NotTopLevel binder_names mono_ids = Nothing - find_main TopLevel binder_names mono_ids = go binder_names mono_ids - go [] [] = Nothing - go (n:ns) (m:ms) | n `hasKey` mainKey = Just m - | otherwise = go ns ms + Recursive -> liftedTypeKind -- Recursive, so no unlifted types + NonRecursive -> openTypeKind -- Non-recursive, so we permit unlifted types \end{code} @@ -872,14 +736,14 @@ tcSpecSigs (SpecSig name poly_ty src_loc : sigs) tcAddErrCtxt (valSpecSigCtxt name poly_ty) $ -- Get and instantiate its alleged specialised type - tcHsSigType poly_ty `thenTc` \ sig_ty -> + tcHsSigType (FunSigCtxt name) poly_ty `thenTc` \ sig_ty -> -- Check that f has a more general type, and build a RHS for -- the spec-pragma-id at the same time tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) -> -- Squeeze out any Methods (see comments with tcSimplifyToDicts) - tcSimplifyToDicts spec_lie `thenTc` \ (spec_lie1, spec_binds) -> + tcSimplifyToDicts spec_lie `thenTc` \ (spec_dicts, spec_binds) -> -- Just specialise "f" by building a SpecPragmaId binding -- It is the thing that makes sure we don't prematurely @@ -889,7 +753,7 @@ tcSpecSigs (SpecSig name poly_ty src_loc : sigs) -- Do the rest and combine tcSpecSigs sigs `thenTc` \ (binds_rest, lie_rest) -> returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr), - lie_rest `plusLIE` spec_lie1) + lie_rest `plusLIE` mkLIE spec_dicts) tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE) @@ -913,41 +777,34 @@ valSpecSigCtxt v ty nest 4 (ppr v <+> dcolon <+> ppr ty)] ----------------------------------------------- -unboxedPatBindErr id - = ptext SLIT("variable in a lazy pattern binding has unboxed type: ") - <+> quotes (ppr id) - ------------------------------------------------ -bindSigsCtxt ids - = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids - ------------------------------------------------ -sigContextsErr - = ptext SLIT("Mismatched contexts") +sigContextsErr = ptext SLIT("Mismatched contexts") sigContextsCtxt s1 s2 = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"), quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)]) 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)")) -mainContextsErr id - | id `hasKey` mainKey = ptext SLIT("Main.main cannot be overloaded") - | otherwise - = quotes (ppr id) <+> ptext SLIT("cannot be overloaded") <> char ',' <> -- sigh; workaround for cpp's inability to deal - ptext SLIT("because it is mutually recursive with Main.main") -- with commas inside SLIT strings. - -mainTyCheckCtxt - = hsep [ptext SLIT("When checking that"), quotes (ptext SLIT("main")), - ptext SLIT("has the required type")] - ----------------------------------------------- unliftedBindErr flavour mbind - = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed")) + = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:")) 4 (ppr mbind) +----------------------------------------------- existentialExplode mbinds = hang (vcat [text "My brain just exploded.", text "I can't handle pattern bindings for existentially-quantified constructors.", text "In the binding group"]) 4 (ppr mbinds) + +----------------------------------------------- +restrictedBindCtxtErr binder_names + = hang (ptext SLIT("Illegal overloaded type signature(s)")) + 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names, + ptext SLIT("that falls under the monomorphism restriction")]) + +genCtxt binder_names + = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names + +-- Used in error messages +pprBinders bndrs = pprWithCommas ppr bndrs \end{code}