X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcClassDcl.lhs;h=c3edcc4ca752ceeb97eb4296ab0082cecc8b1eff;hp=1fd8706b3e3bade67024d5eb8798d3b901a9c618;hb=f16dbbbe59cf3aa19c5fd384560a1b89076d7bc8;hpb=78260da4deee97a866ba83f8d73a8284b371f405 diff --git a/compiler/typecheck/TcClassDcl.lhs b/compiler/typecheck/TcClassDcl.lhs index 1fd8706..c3edcc4 100644 --- a/compiler/typecheck/TcClassDcl.lhs +++ b/compiler/typecheck/TcClassDcl.lhs @@ -7,8 +7,8 @@ Typechecking class declarations \begin{code} module TcClassDcl ( tcClassSigs, tcClassDecl2, - getGenericInstances, - MethodSpec, tcMethodBind, mkMethId, + findMethodBind, tcMethodBind, + mkGenericDefMethBind, getGenericInstances, mkDefMethRdrName, tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn ) where @@ -23,8 +23,6 @@ import InstEnv import TcEnv import TcBinds import TcHsType -import TcSimplify -import TcUnify import TcMType import TcType import TcRnMonad @@ -183,12 +181,13 @@ tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, let (tyvars, _, _, op_items) = classBigSig clas rigid_info = ClsSkol clas - origin = SigOrigin rigid_info prag_fn = mkPragFun sigs sig_fn = mkTcSigFun sigs clas_tyvars = tcSkolSigTyVars rigid_info tyvars - tc_dm = tcDefMeth origin clas clas_tyvars - default_binds sig_fn prag_fn + tc_dm = tcDefMeth clas_tyvars default_binds + sig_fn prag_fn + -- tc_dm is called only for a sel_id + -- that has a binding in default_binds dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items] -- Generate code for polymorphic default methods only @@ -198,260 +197,140 @@ tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, -- the programmer supplied an explicit default decl for the class. -- (If necessary we can fix that, but we don't have a convenient Id to hand.) - (defm_binds, dm_ids_s) <- mapAndUnzipM tc_dm dm_sel_ids - return (listToBag defm_binds, concat dm_ids_s) + (defm_binds, dm_ids) <- mapAndUnzipM tc_dm dm_sel_ids + return (unionManyBags defm_binds, dm_ids) tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d) -tcDefMeth :: InstOrigin -> Class -> [TyVar] -> LHsBinds Name +tcDefMeth :: [TyVar] -> LHsBinds Name -> TcSigFun -> TcPragFun -> Id - -> TcM (LHsBindLR Id Var, [Id]) -tcDefMeth origin clas tyvars binds_in sig_fn prag_fn sel_id - = do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_id) - ; let inst_tys = mkTyVarTys tyvars - dm_ty = idType sel_id -- Same as dict selector! - cls_pred = mkClassPred clas inst_tys - local_dm_id = mkDefaultMethodId dm_name dm_ty - - ; loc <- getInstLoc origin - ; this_dict <- newDictBndr loc cls_pred - ; (_, meth_id) <- mkMethId origin clas sel_id inst_tys - ; (defm_bind, insts_needed) <- getLIE $ - tcMethodBind origin tyvars [cls_pred] this_dict [] - sig_fn prag_fn binds_in - (sel_id, DefMeth) meth_id - - ; addErrCtxt (defltMethCtxt clas) $ do - - -- Check the context - { dict_binds <- tcSimplifyCheck - loc - tyvars - [this_dict] - insts_needed - - -- Simplification can do unification - ; checkSigTyVars tyvars - - -- Inline pragmas - -- We'll have an inline pragma on the local binding, made by tcMethodBind - -- but that's not enough; we want one on the global default method too - -- Specialisations, on the other hand, belong on the thing inside only, I think - ; let sel_name = idName sel_id - inline_prags = filter isInlineLSig (prag_fn sel_name) - ; prags <- tcPrags meth_id inline_prags - - ; let full_bind = AbsBinds tyvars - [instToId this_dict] - [(tyvars, local_dm_id, meth_id, prags)] - (dict_binds `unionBags` defm_bind) - ; return (noLoc full_bind, [local_dm_id]) }} - -mkDefMethRdrName :: Id -> RdrName -mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc -\end{code} + -> TcM (LHsBinds Id, Id) +tcDefMeth tyvars binds_in sig_fn prag_fn sel_id + = do { let sel_name = idName sel_id + ; dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_name) + ; uniq <- newUnique + ; let dm_ty = idType sel_id -- Same as dict selector! + local_dm_name = setNameUnique sel_name uniq + local_dm_id = mkLocalId local_dm_name dm_ty + top_dm_id = mkDefaultMethodId dm_name dm_ty + all_tvs = map tyVarName tyvars ++ (sig_fn sel_name `orElse` []) + -- Tyvars in scope are *both* the ones from the + -- class decl *and* ones from the method sig + + ; let meth_bind = findMethodBind sel_name local_dm_name binds_in + `orElse` pprPanic "tcDefMeth" (ppr sel_id) + -- We only call tcDefMeth on selectors for which + -- there is a binding in binds_in + + ; tc_meth_bind <- tcMethodBind all_tvs (prag_fn sel_name) + local_dm_id meth_bind + + -- See Note [Silly default-method bind] + ; let loc = getLoc meth_bind + top_bind = L loc $ VarBind top_dm_id $ + L loc $ HsWrap (WpLet tc_meth_bind) $ + HsVar local_dm_id + + ; return (unitBag top_bind, top_dm_id) } + +mkDefMethRdrName :: Name -> RdrName +mkDefMethRdrName sel_name = mkDerivedRdrName sel_name mkDefaultMethodOcc +--------------------------- +-- The renamer just puts the selector ID as the binder in the method binding +-- but we must use the method name; so we substitute it here. Crude but simple. +findMethodBind :: Name -> Name -- Selector and method name + -> LHsBinds Name -- A group of bindings + -> Maybe (LHsBind Name) -- The binding, with meth_name replacing sel_name +findMethodBind sel_name meth_name binds + = foldlBag mplus Nothing (mapBag f binds) + where + f (L loc1 bind@(FunBind { fun_id = L loc2 op_name })) + | op_name == sel_name + = Just (L loc1 (bind { fun_id = L loc2 meth_name })) + f _other = Nothing -%************************************************************************ -%* * -\subsection{Typechecking a method} -%* * -%************************************************************************ - -@tcMethodBind@ is used to type-check both default-method and -instance-decl method declarations. We must type-check methods one at a -time, because their signatures may have different contexts and -tyvar sets. - -\begin{code} -type MethodSpec = (Id, -- Global selector Id - Id, -- Local Id (class tyvars instantiated) - LHsBind Name) -- Binding for the method - -tcMethodBind - :: InstOrigin - -> [TcTyVar] -- Skolemised type variables for the - -- enclosing class/instance decl. - -- They'll be signature tyvars, and we - -- want to check that they don't get bound - -- Also they are scoped, so we bring them into scope - -- Always equal the range of the type envt - -> TcThetaType -- Available theta; it's just used for the error message - -> Inst -- Current dictionary (this_dict) - -> [Inst] -- Other stuff available from context, used to simplify - -- constraints from the method body (exclude this_dict) - -> TcSigFun -- For scoped tyvars, indexed by sel_name - -> TcPragFun -- Pragmas (e.g. inline pragmas), indexed by sel_name - -> LHsBinds Name -- Method binding (pick the right one from in here) - -> ClassOpItem - -> TcId -- The method Id - -> TcM (LHsBinds Id) - -tcMethodBind origin inst_tyvars inst_theta - this_dict extra_insts - sig_fn prag_fn meth_binds - (sel_id, dm_info) meth_id - | Just user_bind <- find_bind sel_name meth_name meth_binds - = -- If there is a user-supplied method binding, typecheck it - tc_method_bind inst_tyvars inst_theta (this_dict:extra_insts) - sig_fn prag_fn - sel_id meth_id user_bind - - | otherwise -- The user didn't supply a method binding, so we have to make - -- up a default binding, in a way depending on the default-method info - = case dm_info of - NoDefMeth -> do { warn <- doptM Opt_WarnMissingMethods - ; warnTc (isInstDecl origin - && warn -- Warn only if -fwarn-missing-methods - && reportIfUnused (getOccName sel_id)) - -- Don't warn about _foo methods - (omittedMethodWarn sel_id) - ; return (unitBag $ L loc (VarBind meth_id error_rhs)) } - - DefMeth -> do { -- An polymorphic default method - -- Might not be imported, but will be an OrigName - dm_name <- lookupImportedName (mkDefMethRdrName sel_id) - ; dm_id <- tcLookupId dm_name - -- Note [Default methods in instances] - ; return (unitBag $ L loc (VarBind meth_id (mk_dm_app dm_id))) } - - GenDefMeth -> ASSERT( isInstDecl origin ) -- We never get here from a class decl - do { meth_bind <- mkGenericDefMethBind clas inst_tys sel_id meth_name - ; tc_method_bind inst_tyvars inst_theta (this_dict:extra_insts) - sig_fn prag_fn - sel_id meth_id meth_bind } - - where - meth_name = idName meth_id - sel_name = idName sel_id - loc = getSrcSpan meth_id - (clas, inst_tys) = getDictClassTys this_dict +--------------------------- +tcMethodBind :: [Name] -> [LSig Name] -> Id + -> LHsBind Name -> TcM (LHsBinds Id) +tcMethodBind tyvars prags meth_id bind + = do { let sig_fn _ = Just tyvars + prag_fn _ = prags + + -- Typecheck the binding, first extending the envt + -- so that when tcInstSig looks up the meth_id to find + -- its signature, we'll find it in the environment + -- + -- If scoped type variables is on, they are brought + -- into scope by tcPolyBinds (via sig_fn) + -- + -- See Note [Polymorphic methods] + ; traceTc (text "tcMethodBind" <+> ppr meth_id <+> ppr tyvars) + ; (tc_binds, ids) <- tcExtendIdEnv [meth_id] $ + tcPolyBinds TopLevel sig_fn prag_fn + NonRecursive NonRecursive + (unitBag bind) + + ; ASSERT( ids == [meth_id] ) -- Binding for ONE method + return (unionManyBags tc_binds) } +\end{code} - this_dict_id = instToId this_dict - error_id = L loc (HsVar nO_METHOD_BINDING_ERROR_ID) - error_id_app = mkLHsWrap (WpTyApp (idType meth_id)) error_id - error_rhs = mkHsApp error_id_app $ L loc $ - HsLit (HsStringPrim (mkFastString error_msg)) - error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) +Note [Polymorphic methods] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + class Foo a where + op :: forall b. Ord b => a -> b -> b -> b + instance Foo c => Foo [c] where + op = e - mk_dm_app dm_id -- dm tys inst_dict - = mkLHsWrap (WpApp this_dict_id `WpCompose` mkWpTyApps inst_tys) - (L loc (HsVar dm_id)) +When typechecking the binding 'op = e', we'll have a meth_id for op +whose type is + op :: forall c. Foo c => forall b. Ord b => [c] -> b -> b -> b +So tcPolyBinds must be capable of dealing with nested polytypes; +and so it is. See TcBinds.tcMonoBinds (with type-sig case). ---------------------------- -tc_method_bind :: [TyVar] -> TcThetaType -> [Inst] -> (Name -> Maybe [Name]) - -> (Name -> [LSig Name]) -> Id -> Id -> LHsBind Name - -> TcRn (LHsBindsLR Id Var) -tc_method_bind inst_tyvars inst_theta avail_insts sig_fn prag_fn - sel_id meth_id meth_bind - = recoverM (return emptyLHsBinds) $ - -- If anything fails, recover returning no bindings. - -- This is particularly useful when checking the default-method binding of - -- a class decl. If we don't recover, we don't add the default method to - -- the type enviroment, and we get a tcLookup failure on $dmeth later. - - -- Check the bindings; first adding inst_tyvars to the envt - -- so that we don't quantify over them in nested places - - do { let sel_name = idName sel_id - meth_name = idName meth_id - meth_sig_fn name = ASSERT( name == meth_name ) sig_fn sel_name - -- The meth_bind metions the meth_name, but sig_fn is indexed by sel_name - - ; ((meth_bind, mono_bind_infos), meth_lie) - <- tcExtendTyVarEnv inst_tyvars $ - tcExtendIdEnv [meth_id] $ -- In scope for tcInstSig - addErrCtxt (methodCtxt sel_id) $ - getLIE $ - tcMonoBinds [meth_bind] meth_sig_fn Recursive - - -- Now do context reduction. We simplify wrt both the local tyvars - -- and the ones of the class/instance decl, so that there is - -- no problem with - -- class C a where - -- op :: Eq a => a -> b -> a - -- - -- We do this for each method independently to localise error messages +Note [Silly default-method bind] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When we pass the default method binding to the type checker, it must +look like op2 = e +not $dmop2 = e +otherwise the "$dm" stuff comes out in the interface file. So we +typecheck the former, and wrap it in a let, thus + $dmop2 = let op2 = e in op2 +This makes the error messages right. - ; let [(_, Just sig, local_meth_id)] = mono_bind_infos - loc = sig_loc sig - ; addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ do - { meth_dicts <- newDictBndrs loc (sig_theta sig) - ; let meth_tvs = sig_tvs sig - all_tyvars = meth_tvs ++ inst_tyvars - all_insts = avail_insts ++ meth_dicts +%************************************************************************ +%* * + Extracting generic instance declaration from class declarations +%* * +%************************************************************************ - ; lie_binds <- tcSimplifyCheck loc all_tyvars all_insts meth_lie +@getGenericInstances@ extracts the generic instance declarations from a class +declaration. For exmaple - ; checkSigTyVars all_tyvars + class C a where + op :: a -> a - ; prags <- tcPrags meth_id (prag_fn sel_name) - ; let poly_meth_bind = noLoc $ AbsBinds meth_tvs - (map instToId meth_dicts) - [(meth_tvs, meth_id, local_meth_id, prags)] - (lie_binds `unionBags` meth_bind) + op{ x+y } (Inl v) = ... + op{ x+y } (Inr v) = ... + op{ x*y } (v :*: w) = ... + op{ 1 } Unit = ... - ; return (unitBag poly_meth_bind) }} +gives rise to the instance declarations + instance C (x+y) where + op (Inl v) = ... + op (Inr v) = ... + + instance C (x*y) where + op (v :*: w) = ... ---------------------------- -mkMethId :: InstOrigin -> Class - -> Id -> [TcType] -- Selector, and instance types - -> TcM (Maybe Inst, Id) - --- mkMethId instantiates the selector Id at the specified types -mkMethId origin clas sel_id inst_tys - = let - (tyvars,rho) = tcSplitForAllTys (idType sel_id) - rho_ty = ASSERT( length tyvars == length inst_tys ) - substTyWith tyvars inst_tys rho - (preds,tau) = tcSplitPhiTy rho_ty - first_pred = ASSERT( not (null preds)) head preds - in - -- The first predicate should be of form (C a b) - -- where C is the class in question - ASSERT( not (null preds) && - case getClassPredTys_maybe first_pred of - { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False } - ) - if isSingleton preds then do - -- If it's the only one, make a 'method' - inst_loc <- getInstLoc origin - meth_inst <- newMethod inst_loc sel_id inst_tys - return (Just meth_inst, instToId meth_inst) - else do - -- If it's not the only one we need to be careful - -- For example, given 'op' defined thus: - -- class Foo a where - -- op :: (?x :: String) => a -> a - -- (mkMethId op T) should return an Inst with type - -- (?x :: String) => T -> T - -- That is, the class-op's context is still there. - -- BUT: it can't be a Method any more, because it breaks - -- INVARIANT 2 of methods. (See the data decl for Inst.) - uniq <- newUnique - loc <- getSrcSpanM - let - real_tau = mkPhiTy (tail preds) tau - meth_id = mkUserLocal (getOccName sel_id) uniq real_tau loc - - return (Nothing, meth_id) + instance C 1 where + op Unit = ... ---------------------------- --- The renamer just puts the selector ID as the binder in the method binding --- but we must use the method name; so we substitute it here. Crude but simple. -find_bind :: Name -> Name -- Selector and method name - -> LHsBinds Name -- A group of bindings - -> Maybe (LHsBind Name) -- The binding, with meth_name replacing sel_name -find_bind sel_name meth_name binds - = foldlBag mplus Nothing (mapBag f binds) - where - f (L loc1 bind@(FunBind { fun_id = L loc2 op_name })) | op_name == sel_name - = Just (L loc1 (bind { fun_id = L loc2 meth_name })) - f _other = Nothing ---------------------------- +\begin{code} mkGenericDefMethBind :: Class -> [Type] -> Id -> Name -> TcM (LHsBind Name) mkGenericDefMethBind clas inst_tys sel_id meth_name = -- A generic default method @@ -487,113 +366,8 @@ mkGenericDefMethBind clas inst_tys sel_id meth_name _ -> Nothing _ -> Nothing -isInstDecl :: InstOrigin -> Bool -isInstDecl (SigOrigin InstSkol) = True -isInstDecl (SigOrigin (ClsSkol _)) = False -isInstDecl o = pprPanic "isInstDecl" (ppr o) -\end{code} - - -Note [Default methods] -~~~~~~~~~~~~~~~~~~~~~~~ -The default methods for a class are each passed a dictionary for the -class, so that they get access to the other methods at the same type. -So, given the class decl - - class Foo a where - op1 :: a -> Bool - op2 :: forall b. Ord b => a -> b -> b -> b - - op1 x = True - op2 x y z = if (op1 x) && (y < z) then y else z - -we get the default methods: - - $dmop1 :: forall a. Foo a => a -> Bool - $dmop1 = /\a -> \dfoo -> \x -> True - - $dmop2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b - $dmop2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z -> - if (op1 a dfoo x) && (< b dord y z) then y else z - -When we come across an instance decl, we may need to use the default methods: - - instance Foo Int where {} - - $dFooInt :: Foo Int - $dFooInt = MkFoo ($dmop1 Int $dFooInt) - ($dmop2 Int $dFooInt) - -Notice that, as with method selectors above, we assume that dictionary -application is curried, so there's no need to mention the Ord dictionary -in the application of $dmop2. - - instance Foo a => Foo [a] where {} - - $dFooList :: forall a. Foo a -> Foo [a] - $dFooList = /\ a -> \ dfoo_a -> - let rec - op1 = defm.Foo.op1 [a] dfoo_list - op2 = defm.Foo.op2 [a] dfoo_list - dfoo_list = MkFoo ($dmop1 [a] dfoo_list) - ($dmop2 [a] dfoo_list) - in - dfoo_list - -Note [Default methods in instances] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Consider this - - class Baz v x where - foo :: x -> x - foo y = y - - instance Baz Int Int - -From the class decl we get - - $dmfoo :: forall v x. Baz v x => x -> x - -Notice that the type is ambiguous. That's fine, though. The instance decl generates - - $dBazIntInt = MkBaz ($dmfoo Int Int $dBazIntInt) - -BUT this does mean we must generate the dictionary translation directly, rather -than generating source-code and type-checking it. That was the bug ing -Trac #1061. In any case it's less work to generate the translated version! - - -%************************************************************************ -%* * -\subsection{Extracting generic instance declaration from class declarations} -%* * -%************************************************************************ -@getGenericInstances@ extracts the generic instance declarations from a class -declaration. For exmaple - - class C a where - op :: a -> a - - op{ x+y } (Inl v) = ... - op{ x+y } (Inr v) = ... - op{ x*y } (v :*: w) = ... - op{ 1 } Unit = ... - -gives rise to the instance declarations - - instance C (x+y) where - op (Inl v) = ... - op (Inr v) = ... - - instance C (x*y) where - op (v :*: w) = ... - - instance C 1 where - op Unit = ... - - -\begin{code} +--------------------------- getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo Name] getGenericInstances class_decls = do { gen_inst_infos <- mapM (addLocM get_generics) class_decls @@ -754,14 +528,6 @@ tcAddDeclCtxt decl thing_inside ctxt = hsep [ptext (sLit "In the"), text thing, ptext (sLit "declaration for"), quotes (ppr (tcdName decl))] -defltMethCtxt :: Class -> SDoc -defltMethCtxt clas - = ptext (sLit "When checking the default methods for class") <+> quotes (ppr clas) - -methodCtxt :: Var -> SDoc -methodCtxt sel_id - = ptext (sLit "In the definition for method") <+> quotes (ppr sel_id) - badMethodErr :: Outputable a => a -> Name -> SDoc badMethodErr clas op = hsep [ptext (sLit "Class"), quotes (ppr clas), @@ -772,10 +538,6 @@ badATErr clas at = hsep [ptext (sLit "Class"), quotes (ppr clas), ptext (sLit "does not have an associated type"), quotes (ppr at)] -omittedMethodWarn :: Id -> SDoc -omittedMethodWarn sel_id - = ptext (sLit "No explicit method nor default method for") <+> quotes (ppr sel_id) - omittedATWarn :: Name -> SDoc omittedATWarn at = ptext (sLit "No explicit AT declaration for") <+> quotes (ppr at)