X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcClassDcl.lhs;h=4f1f32c0f9f8176ba5d889f1e2a520506cbbd291;hp=30dfc7c5e72f919ee1e6793d9ccf50a4b5d61e14;hb=9d0c8f842e35dde3d570580cf62a32779f66a6de;hpb=49c98d143c382a1341e1046f5ca00819a25691ba diff --git a/compiler/typecheck/TcClassDcl.lhs b/compiler/typecheck/TcClassDcl.lhs index 30dfc7c..4f1f32c 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, mkMethodBind, + findMethodBind, tcInstanceMethodBody, + mkGenericDefMethBind, getGenericInstances, mkDefMethRdrName, tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn ) where @@ -22,20 +22,19 @@ import Inst import InstEnv import TcEnv import TcBinds -import TcHsType import TcSimplify -import TcUnify +import TcHsType import TcMType import TcType import TcRnMonad import Generics -import PrelInfo import Class import TyCon import Type import MkId import Id import Name +import Var import NameEnv import NameSet import OccName @@ -53,6 +52,8 @@ import List import BasicTypes import Bag import FastString + +import Control.Monad \end{code} @@ -105,10 +106,10 @@ type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communic -- between tcClassSigs and buildClass tcClassSigs clas sigs def_methods = do { dm_env <- checkDefaultBinds clas op_names def_methods - ; mappM (tcClassSig dm_env) op_sigs } + ; mapM (tcClassSig dm_env) op_sigs } where op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs] - op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs] + op_names = [n | (L _ (TypeSig (L _ n) _)) <- op_sigs] checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool) @@ -121,6 +122,7 @@ checkDefaultBinds clas ops binds = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds) return (mkNameEnv dm_infos) +checkDefaultBind :: Name -> [Name] -> HsBindLR Name Name -> TcM (Name, Bool) checkDefaultBind clas ops (FunBind {fun_id = L _ op, fun_matches = MatchGroup matches _ }) = do { -- Check that the op is from this class checkTc (op `elem` ops) (badMethodErr clas op) @@ -128,12 +130,13 @@ checkDefaultBind clas ops (FunBind {fun_id = L _ op, fun_matches = MatchGroup ma -- Check that all the defns ar generic, or none are ; checkTc (all_generic || none_generic) (mixedGenericErr op) - ; returnM (op, all_generic) + ; return (op, all_generic) } where n_generic = count (isJust . maybeGenericMatch) matches none_generic = n_generic == 0 all_generic = matches `lengthIs` n_generic +checkDefaultBind _ _ b = pprPanic "checkDefaultBind" (ppr b) tcClassSig :: NameEnv Bool -- Info about default methods; @@ -147,83 +150,26 @@ tcClassSig dm_env (L loc (TypeSig (L _ op_name) op_hs_ty)) Nothing -> NoDefMeth Just False -> DefMeth Just True -> GenDefMeth - ; returnM (op_name, dm, op_ty) } + ; return (op_name, dm, op_ty) } +tcClassSig _ s = pprPanic "tcClassSig" (ppr s) \end{code} %************************************************************************ %* * -\subsection[Default methods]{Default methods} + Class Declarations %* * %************************************************************************ -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 -\begin{verbatim} -class Foo a where - op1 :: a -> Bool - op2 :: Ord b => a -> b -> b -> b - - op1 x = True - op2 x y z = if (op1 x) && (y < z) then y else z -\end{verbatim} -we get the default methods: -\begin{verbatim} -defm.Foo.op1 :: forall a. Foo a => a -> Bool -defm.Foo.op1 = /\a -> \dfoo -> \x -> True - -defm.Foo.op2 :: forall a. Foo a => forall b. Ord b => a -> b -> b -> b -defm.Foo.op2 = /\ a -> \ dfoo -> /\ b -> \ dord -> \x y z -> - if (op1 a dfoo x) && (< b dord y z) then y else z -\end{verbatim} - -When we come across an instance decl, we may need to use the default -methods: -\begin{verbatim} -instance Foo Int where {} -\end{verbatim} -gives -\begin{verbatim} -const.Foo.Int.op1 :: Int -> Bool -const.Foo.Int.op1 = defm.Foo.op1 Int dfun.Foo.Int - -const.Foo.Int.op2 :: forall b. Ord b => Int -> b -> b -> b -const.Foo.Int.op2 = defm.Foo.op2 Int dfun.Foo.Int - -dfun.Foo.Int :: Foo Int -dfun.Foo.Int = (const.Foo.Int.op1, const.Foo.Int.op2) -\end{verbatim} -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 const.Foo.Int.op2 (or the type variable). - -\begin{verbatim} -instance Foo a => Foo [a] where {} - -dfun.Foo.List :: forall a. Foo a -> Foo [a] -dfun.Foo.List - = /\ a -> \ dfoo_a -> - let rec - op1 = defm.Foo.op1 [a] dfoo_list - op2 = defm.Foo.op2 [a] dfoo_list - dfoo_list = (op1, op2) - in - dfoo_list -\end{verbatim} - -@tcClassDecls2@ generates bindings for polymorphic default methods -(generic default methods have by now turned into instance declarations) - \begin{code} tcClassDecl2 :: LTyClDecl Name -- The class declaration -> TcM (LHsBinds Id, [Id]) tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, tcdMeths = default_binds})) - = recoverM (returnM (emptyLHsBinds, [])) $ - setSrcSpan loc $ - tcLookupLocatedClass class_name `thenM` \ clas -> + = recoverM (return (emptyLHsBinds, [])) $ + setSrcSpan loc $ + do { clas <- tcLookupLocatedClass class_name -- We make a separate binding for each default method. -- At one time I used a single AbsBinds for all of them, thus @@ -233,295 +179,215 @@ tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, -- dm1 = \d -> case ds d of (a,b,c) -> a -- And since ds is big, it doesn't get inlined, so we don't get good -- default methods. Better to make separate AbsBinds for each - 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 - - dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items] - -- Generate code for polymorphic default methods only - -- (Generic default methods have turned into instance decls by now.) - -- This is incompatible with Hugs, which expects a polymorphic - -- default method for every class op, regardless of whether or not - -- 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.) - in - mapAndUnzipM tc_dm dm_sel_ids `thenM` \ (defm_binds, dm_ids_s) -> - returnM (listToBag defm_binds, concat dm_ids_s) - -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 - - ; (_, meth_info) <- mkMethodBind origin clas inst_tys binds_in (sel_id, DefMeth) - ; loc <- getInstLoc origin - ; this_dict <- newDictBndr loc cls_pred - ; (defm_bind, insts_needed) <- getLIE (tcMethodBind tyvars [cls_pred] [this_dict] - sig_fn prag_fn meth_info) + ; let + (tyvars, _, _, op_items) = classBigSig clas + rigid_info = ClsSkol clas + prag_fn = mkPragFun sigs + sig_fn = mkTcSigFun sigs + clas_tyvars = tcSkolSigTyVars rigid_info tyvars + pred = mkClassPred clas (mkTyVarTys clas_tyvars) + ; inst_loc <- getInstLoc (SigOrigin rigid_info) + ; this_dict <- newDictBndr inst_loc pred + + ; let tc_dm = tcDefMeth rigid_info clas clas_tyvars [pred] + this_dict 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 (hence DefMeth) + -- (Generic default methods have turned into instance decls by now.) + -- This is incompatible with Hugs, which expects a polymorphic + -- default method for every class op, regardless of whether or not + -- 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) <- tcExtendTyVarEnv clas_tyvars $ + mapAndUnzipM tc_dm dm_sel_ids + + ; return (unionManyBags defm_binds, dm_ids) } + +tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d) - ; addErrCtxt (defltMethCtxt clas) $ do - - -- Check the context - { dict_binds <- tcSimplifyCheck - (ptext SLIT("class") <+> ppr clas) - 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 (_,dm_inst_id,_) = meth_info - sel_name = idName sel_id - inline_prags = filter isInlineLSig (prag_fn sel_name) - ; prags <- tcPrags dm_inst_id inline_prags - - ; let full_bind = AbsBinds tyvars - [instToId this_dict] - [(tyvars, local_dm_id, dm_inst_id, prags)] - (dict_binds `unionBags` defm_bind) - ; returnM (noLoc full_bind, [local_dm_id]) }} - -mkDefMethRdrName :: Id -> RdrName -mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc +tcDefMeth :: SkolemInfo -> Class -> [TyVar] -> ThetaType -> Inst -> LHsBinds Name + -> TcSigFun -> TcPragFun -> Id + -> TcM (LHsBinds Id, Id) +tcDefMeth rigid_info clas tyvars theta this_dict binds_in sig_fn prag_fn sel_id + = do { let sel_name = idName sel_id + ; local_dm_name <- newLocalName sel_name + ; 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 + + meth_sig_fn _ = sig_fn sel_name + meth_prag_fn _ = prag_fn sel_name + + ; (top_dm_id, bind) <- tcInstanceMethodBody rigid_info + clas tyvars [this_dict] theta (mkTyVarTys tyvars) + Nothing sel_id + local_dm_name + meth_sig_fn meth_prag_fn + meth_bind + + ; return (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 + +--------------- +tcInstanceMethodBody :: SkolemInfo -> Class -> [TcTyVar] -> [Inst] + -> TcThetaType -> [TcType] + -> Maybe (Inst, LHsBind Id) -> Id + -> Name -- The local method name + -> TcSigFun -> TcPragFun -> LHsBind Name + -> TcM (Id, LHsBinds Id) +tcInstanceMethodBody rigid_info clas tyvars dfun_dicts theta inst_tys + mb_this_bind sel_id local_meth_name + sig_fn prag_fn bind@(L loc _) + = do { let (sel_tyvars,sel_rho) = tcSplitForAllTys (idType sel_id) + rho_ty = ASSERT( length sel_tyvars == length inst_tys ) + substTyWith sel_tyvars inst_tys sel_rho + + (first_pred, local_meth_ty) = tcSplitPredFunTy_maybe rho_ty + `orElse` pprPanic "tcInstanceMethod" (ppr sel_id) + + local_meth_id = mkLocalId local_meth_name local_meth_ty + meth_ty = mkSigmaTy tyvars theta local_meth_ty + sel_name = idName sel_id + + -- The first predicate should be of form (C a b) + -- where C is the class in question + ; MASSERT( case getClassPredTys_maybe first_pred of + { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False } ) + + -- Typecheck the binding, first extending the envt + -- so that when tcInstSig looks up the local_meth_id to find + -- its signature, we'll find it in the environment + ; ((tc_bind, _), lie) <- getLIE $ + tcExtendIdEnv [local_meth_id] $ + tcPolyBinds TopLevel sig_fn prag_fn + NonRecursive NonRecursive + (unitBag bind) + + ; meth_id <- case rigid_info of + ClsSkol _ -> do { dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_name) + ; return (mkDefaultMethodId dm_name meth_ty) } + _other -> do { meth_name <- newLocalName sel_name + ; return (mkLocalId meth_name meth_ty) } + + ; let (avails, this_dict_bind) + = case mb_this_bind of + Nothing -> (dfun_dicts, emptyBag) + Just (this, bind) -> (this : dfun_dicts, unitBag bind) + + ; inst_loc <- getInstLoc (SigOrigin rigid_info) + ; lie_binds <- tcSimplifyCheck inst_loc tyvars avails lie + + ; let full_bind = L loc $ + AbsBinds tyvars dfun_lam_vars + [(tyvars, meth_id, local_meth_id, [])] + (this_dict_bind `unionBags` lie_binds + `unionBags` tc_bind) + + dfun_lam_vars = map instToVar dfun_dicts -- Includes equalities + + ; return (meth_id, unitBag full_bind) } \end{code} +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 + +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). + +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 error messages. But we want the +"$dm" to come 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. + %************************************************************************ %* * -\subsection{Typechecking a method} + Extracting generic instance declaration from class declarations %* * %************************************************************************ -@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. +@getGenericInstances@ extracts the generic instance declarations from a class +declaration. For exmaple -\begin{code} -type MethodSpec = (Id, -- Global selector Id - Id, -- Local Id (class tyvars instantiated) - LHsBind Name) -- Binding for the method - -tcMethodBind - :: [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] -- Available from context, used to simplify constraints - -- from the method body - -> TcSigFun -- For scoped tyvars, indexed by sel_name - -> TcPragFun -- Pragmas (e.g. inline pragmas), indexed by sel_name - -> MethodSpec -- Details of this method - -> TcM (LHsBinds Id) - -tcMethodBind inst_tyvars inst_theta avail_insts sig_fn prag_fn - (sel_id, meth_id, meth_bind) - = recoverM (returnM 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 + class C a where + op :: a -> a - let sel_name = idName sel_id - meth_sig_fn meth_name = ASSERT( meth_name == idName meth_id ) sig_fn sel_name - -- The meth_bind metions the meth_name, but sig_fn is indexed by sel_name - in - tcExtendTyVarEnv inst_tyvars ( - tcExtendIdEnv [meth_id] $ -- In scope for tcInstSig - addErrCtxt (methodCtxt sel_id) $ - getLIE $ - tcMonoBinds [meth_bind] meth_sig_fn Recursive - ) `thenM` \ ((meth_bind, mono_bind_infos), meth_lie) -> - - -- 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 + op{ x+y } (Inl v) = ... + op{ x+y } (Inr v) = ... + op{ x*y } (v :*: w) = ... + op{ 1 } Unit = ... - let - [(_, Just sig, local_meth_id)] = mono_bind_infos - in +gives rise to the instance declarations - addErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $ - newDictBndrs (sig_loc sig) (sig_theta sig) `thenM` \ meth_dicts -> - let - meth_tvs = sig_tvs sig - all_tyvars = meth_tvs ++ inst_tyvars - all_insts = avail_insts ++ meth_dicts - in - tcSimplifyCheck - (ptext SLIT("class or instance method") <+> quotes (ppr sel_id)) - all_tyvars all_insts meth_lie `thenM` \ lie_binds -> + instance C (x+y) where + op (Inl v) = ... + op (Inr v) = ... + + instance C (x*y) where + op (v :*: w) = ... - checkSigTyVars all_tyvars `thenM_` + instance C 1 where + op Unit = ... - tcPrags meth_id (prag_fn sel_name) `thenM` \ prags -> - 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) - in - returnM (unitBag poly_meth_bind) - - -mkMethodBind :: InstOrigin - -> Class -> [TcType] -- Class and instance types - -> LHsBinds Name -- Method binding (pick the right one from in here) - -> ClassOpItem - -> TcM (Maybe Inst, -- Method inst - MethodSpec) --- Find the binding for the specified method, or make --- up a suitable default method if it isn't there - -mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info) - = mkMethId origin clas sel_id inst_tys `thenM` \ (mb_inst, meth_id) -> - let - meth_name = idName meth_id - in - -- Figure out what method binding to use - -- If the user suppplied one, use it, else construct a default one - getSrcSpanM `thenM` \ loc -> - (case find_bind (idName sel_id) meth_name meth_binds of - Just user_bind -> returnM user_bind - Nothing -> - mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenM` \ rhs -> - -- Not infix decl - returnM (noLoc $ mkFunBind (noLoc meth_name) [mkSimpleMatch [] rhs]) - ) `thenM` \ meth_bind -> - - returnM (mb_inst, (sel_id, meth_id, meth_bind)) - -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 = 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 - -- If it's the only one, make a 'method' - getInstLoc origin `thenM` \ inst_loc -> - newMethod inst_loc sel_id inst_tys `thenM` \ meth_inst -> - returnM (Just meth_inst, instToId meth_inst) - else - -- 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.) - newUnique `thenM` \ uniq -> - getSrcSpanM `thenM` \ loc -> - let - real_tau = mkPhiTy (tail preds) tau - meth_id = mkUserLocal (getOccName sel_id) uniq real_tau - (srcSpanStart loc) --TODO - in - returnM (Nothing, meth_id) - - -- The user didn't supply a method binding, - -- so we have to make up a default binding - -- The RHS of a default method depends on the default-method info -mkDefMethRhs origin clas inst_tys sel_id loc DefMeth - = -- An polymorphic default method - lookupImportedName (mkDefMethRdrName sel_id) `thenM` \ dm_name -> - -- Might not be imported, but will be an OrigName - traceRn (text "mkDefMeth" <+> ppr dm_name) `thenM_` - returnM (nlHsVar dm_name) - -mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth - = -- No default method - -- Warn only if -fwarn-missing-methods - doptM Opt_WarnMissingMethods `thenM` \ warn -> - warnTc (isInstDecl origin - && warn - && reportIfUnused (getOccName sel_id)) - (omittedMethodWarn sel_id) `thenM_` - returnM error_rhs - where - error_rhs = noLoc $ HsLam (mkMatchGroup [mkSimpleMatch wild_pats simple_rhs]) - simple_rhs = nlHsApp (nlHsVar (getName nO_METHOD_BINDING_ERROR_ID)) - (nlHsLit (HsStringPrim (mkFastString error_msg))) - error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) - - -- When the type is of form t1 -> t2 -> t3 - -- make a default method like (\ _ _ -> noMethBind "blah") - -- rather than simply (noMethBind "blah") - -- Reason: if t1 or t2 are higher-ranked types we get n - -- silly ambiguity messages. - -- Example: f :: (forall a. Eq a => a -> a) -> Int - -- f = error "urk" - -- Here, tcSub tries to force (error "urk") to have the right type, - -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t) - -- where 't' is fresh ty var. This leads directly to "ambiguous t". - -- - -- NB: technically this changes the meaning of the default-default - -- method slightly, because `seq` can see the lambdas. Oh well. - (_,_,tau1) = tcSplitSigmaTy (idType sel_id) - (_,_,tau2) = tcSplitSigmaTy tau1 - -- Need two splits because the selector can have a type like - -- forall a. Foo a => forall b. Eq b => ... - (arg_tys, _) = tcSplitFunTys tau2 - wild_pats = [nlWildPat | ty <- arg_tys] - -mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth + +\begin{code} +mkGenericDefMethBind :: Class -> [Type] -> Id -> Name -> TcM (LHsBind Name) +mkGenericDefMethBind clas inst_tys sel_id meth_name = -- A generic default method -- If the method is defined generically, we can only do the job if the -- instance declaration is for a single-parameter type class with -- a type constructor applied to type arguments in the instance decl -- (checkTc, so False provokes the error) - ASSERT( isInstDecl origin ) -- We never get here from a class decl do { checkTc (isJust maybe_tycon) (badGenericInstance sel_id (notSimple inst_tys)) ; checkTc (tyConHasGenerics tycon) (badGenericInstance sel_id (notGeneric tycon)) ; dflags <- getDOpts - ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body" + ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Filling in method body" (vcat [ppr clas <+> ppr inst_tys, nest 2 (ppr sel_id <+> equals <+> ppr rhs)])) -- Rename it before returning it ; (rn_rhs, _) <- rnLExpr rhs - ; returnM rn_rhs } + ; return (noLoc $ mkFunBind (noLoc meth_name) [mkSimpleMatch [] rn_rhs]) } where rhs = mkGenericRhs sel_id clas_tyvar tycon @@ -529,92 +395,47 @@ mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth -- case we require that the instance decl is for a single-parameter -- type class with type variable arguments: -- instance (...) => C (T a b) - clas_tyvar = head (classTyVars clas) - Just tycon = maybe_tycon - maybe_tycon = case inst_tys of + clas_tyvar = ASSERT (not (null (classTyVars clas))) head (classTyVars clas) + Just tycon = maybe_tycon + maybe_tycon = case inst_tys of [ty] -> case tcSplitTyConApp_maybe ty of Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon - other -> Nothing - other -> Nothing - -isInstDecl (SigOrigin (InstSkol _)) = True -isInstDecl (SigOrigin (ClsSkol _)) = False -\end{code} + _ -> Nothing + _ -> Nothing -\begin{code} --- 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 sel_name meth_name binds - = foldlBag seqMaybe 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 -\end{code} - - -%************************************************************************ -%* * -\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] +--------------------------- +getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo Name] getGenericInstances class_decls - = do { gen_inst_infos <- mappM (addLocM get_generics) class_decls + = do { gen_inst_infos <- mapM (addLocM get_generics) class_decls ; let { gen_inst_info = concat gen_inst_infos } -- Return right away if there is no generic stuff - ; if null gen_inst_info then returnM [] + ; if null gen_inst_info then return [] else do -- Otherwise print it out { dflags <- getDOpts - ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" - (vcat (map pprInstInfoDetails gen_inst_info))) - ; returnM gen_inst_info }} + ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" + (vcat (map pprInstInfoDetails gen_inst_info))) + ; return gen_inst_info }} +get_generics :: TyClDecl Name -> TcM [InstInfo Name] get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods}) | null generic_binds - = returnM [] -- The comon case: no generic default methods + = return [] -- The comon case: no generic default methods | otherwise -- A source class decl with generic default methods - = recoverM (returnM []) $ - tcAddDeclCtxt decl $ - tcLookupLocatedClass class_name `thenM` \ clas -> + = recoverM (return []) $ + tcAddDeclCtxt decl $ do + clas <- tcLookupLocatedClass class_name -- Group by type, and -- make an InstInfo out of each group let groups = groupWith listToBag generic_binds - in - mappM (mkGenericInstance clas) groups `thenM` \ inst_infos -> + + inst_infos <- mapM (mkGenericInstance clas) groups -- Check that there is only one InstInfo for each type constructor -- The main way this can fail is if you write @@ -624,25 +445,26 @@ get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods}) -- -- The class should be unary, which is why simpleInstInfoTyCon should be ok let - tc_inst_infos :: [(TyCon, InstInfo)] + tc_inst_infos :: [(TyCon, InstInfo Name)] tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, group `lengthExceeds` 1] get_uniq (tc,_) = getUnique tc - in - mappM (addErrTc . dupGenericInsts) bad_groups `thenM_` + + mapM_ (addErrTc . dupGenericInsts) bad_groups -- Check that there is an InstInfo for each generic type constructor let missing = genericTyConNames `minusList` [tyConName tc | (tc,_) <- tc_inst_infos] - in - checkTc (null missing) (missingGenericInstances missing) `thenM_` - returnM inst_infos + checkTc (null missing) (missingGenericInstances missing) + + return inst_infos where generic_binds :: [(HsType Name, LHsBind Name)] generic_binds = getGenericBinds def_methods +get_generics decl = pprPanic "get_generics" (ppr decl) --------------------------------- @@ -651,6 +473,7 @@ getGenericBinds :: LHsBinds Name -> [(HsType Name, LHsBind Name)] -- them in finite map indexed by the type parameter in the definition. getGenericBinds binds = concat (map getGenericBind (bagToList binds)) +getGenericBind :: LHsBindLR Name Name -> [(HsType Name, LHsBindLR Name Name)] getGenericBind (L loc bind@(FunBind { fun_matches = MatchGroup matches ty })) = groupWith wrap (mapCatMaybes maybeGenericMatch matches) where @@ -659,12 +482,12 @@ getGenericBind _ = [] groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)] -groupWith op [] = [] +groupWith _ [] = [] groupWith op ((t,v):prs) = (t, op (v:vs)) : groupWith op rest where - vs = map snd this - (this,rest) = partition same_t prs - same_t (t',v) = t `eqPatType` t' + vs = map snd this + (this,rest) = partition same_t prs + same_t (t', _v) = t `eqPatType` t' eqPatLType :: LHsType Name -> LHsType Name -> Bool eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2 @@ -673,8 +496,8 @@ eqPatType :: HsType Name -> HsType Name -> Bool -- A very simple equality function, only for -- type patterns in generic function definitions. eqPatType (HsTyVar v1) (HsTyVar v2) = v1==v2 -eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 -eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t2 `eqPatLType` t2 && unLoc op1 == unLoc op2 +eqPatType (HsAppTy s1 t1) (HsAppTy s2 t2) = s1 `eqPatLType` s2 && t1 `eqPatLType` t2 +eqPatType (HsOpTy s1 op1 t1) (HsOpTy s2 op2 t2) = s1 `eqPatLType` s2 && t1 `eqPatLType` t2 && unLoc op1 == unLoc op2 eqPatType (HsNumTy n1) (HsNumTy n2) = n1 == n2 eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2 eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2 @@ -683,37 +506,37 @@ eqPatType _ _ = False --------------------------------- mkGenericInstance :: Class -> (HsType Name, LHsBinds Name) - -> TcM InstInfo + -> TcM (InstInfo Name) -mkGenericInstance clas (hs_ty, binds) +mkGenericInstance clas (hs_ty, binds) = do -- Make a generic instance declaration -- For example: instance (C a, C b) => C (a+b) where { binds } - = -- Extract the universally quantified type variables + -- Extract the universally quantified type variables -- and wrap them as forall'd tyvars, so that kind inference -- works in the standard way let sig_tvs = map (noLoc.UserTyVar) (nameSetToList (extractHsTyVars (noLoc hs_ty))) hs_forall_ty = noLoc $ mkExplicitHsForAllTy sig_tvs (noLoc []) (noLoc hs_ty) - in + -- Type-check the instance type, and check its form - tcHsSigType GenPatCtxt hs_forall_ty `thenM` \ forall_inst_ty -> + forall_inst_ty <- tcHsSigType GenPatCtxt hs_forall_ty let (tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty - in + checkTc (validGenericInstanceType inst_ty) - (badGenericInstanceType binds) `thenM_` + (badGenericInstanceType binds) -- Make the dictionary function. - getSrcSpanM `thenM` \ span -> - getOverlapFlag `thenM` \ overlap_flag -> - newDFunName clas [inst_ty] (srcSpanStart span) `thenM` \ dfun_name -> + span <- getSrcSpanM + overlap_flag <- getOverlapFlag + dfun_name <- newDFunName clas [inst_ty] span let inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty] ispec = mkLocalInstance dfun_id overlap_flag - in - returnM (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] }) + + return (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] }) \end{code} @@ -724,70 +547,73 @@ mkGenericInstance clas (hs_ty, binds) %************************************************************************ \begin{code} +tcAddDeclCtxt :: TyClDecl Name -> TcM a -> TcM a tcAddDeclCtxt decl thing_inside = addErrCtxt ctxt thing_inside where - thing = case decl of - ClassDecl {} -> "class" - TySynonym {} -> "type synonym" - TyFunction {} -> "type function signature" - TyData {tcdND = NewType} -> "newtype" ++ maybeSig - TyData {tcdND = DataType} -> "data type" ++ maybeSig - - maybeSig | isKindSigDecl decl = " signature" - | otherwise = "" + thing | isClassDecl decl = "class" + | isTypeDecl decl = "type synonym" ++ maybeInst + | isDataDecl decl = if tcdND decl == NewType + then "newtype" ++ maybeInst + else "data type" ++ maybeInst + | isFamilyDecl decl = "family" + | otherwise = panic "tcAddDeclCtxt/thing" - ctxt = hsep [ptext SLIT("In the"), text thing, - ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] + maybeInst | isFamInstDecl decl = " instance" + | otherwise = "" -defltMethCtxt clas - = ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas) - -methodCtxt sel_id - = ptext SLIT("In the definition for method") <+> quotes (ppr sel_id) + ctxt = hsep [ptext (sLit "In the"), text thing, + ptext (sLit "declaration for"), quotes (ppr (tcdName decl))] +badMethodErr :: Outputable a => a -> Name -> SDoc badMethodErr clas op - = hsep [ptext SLIT("Class"), quotes (ppr clas), - ptext SLIT("does not have a method"), quotes (ppr op)] + = hsep [ptext (sLit "Class"), quotes (ppr clas), + ptext (sLit "does not have a method"), quotes (ppr op)] +badATErr :: Class -> Name -> SDoc badATErr clas at - = hsep [ptext SLIT("Class"), quotes (ppr clas), - ptext SLIT("does not have an associated type"), quotes (ppr at)] - -omittedMethodWarn sel_id - = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id) + = hsep [ptext (sLit "Class"), quotes (ppr clas), + ptext (sLit "does not have an associated type"), quotes (ppr at)] +omittedATWarn :: Name -> SDoc omittedATWarn at - = ptext SLIT("No explicit AT declaration for") <+> quotes (ppr at) + = ptext (sLit "No explicit AT declaration for") <+> quotes (ppr at) +badGenericInstance :: Var -> SDoc -> SDoc badGenericInstance sel_id because - = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), + = sep [ptext (sLit "Can't derive generic code for") <+> quotes (ppr sel_id), because] +notSimple :: [Type] -> SDoc notSimple inst_tys - = vcat [ptext SLIT("because the instance type(s)"), + = vcat [ptext (sLit "because the instance type(s)"), nest 2 (ppr inst_tys), - ptext SLIT("is not a simple type of form (T a b c)")] + ptext (sLit "is not a simple type of form (T a1 ... an)")] +notGeneric :: TyCon -> SDoc notGeneric tycon - = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+> - ptext SLIT("was not compiled with -fgenerics")] + = vcat [ptext (sLit "because the instance type constructor") <+> quotes (ppr tycon) <+> + ptext (sLit "was not compiled with -XGenerics")] +badGenericInstanceType :: LHsBinds Name -> SDoc badGenericInstanceType binds - = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), + = vcat [ptext (sLit "Illegal type pattern in the generic bindings"), nest 4 (ppr binds)] +missingGenericInstances :: [Name] -> SDoc missingGenericInstances missing - = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing + = ptext (sLit "Missing type patterns for") <+> pprQuotedList missing +dupGenericInsts :: [(TyCon, InstInfo a)] -> SDoc dupGenericInsts tc_inst_infos - = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"), + = vcat [ptext (sLit "More than one type pattern for a single generic type constructor:"), nest 4 (vcat (map ppr_inst_ty tc_inst_infos)), - ptext SLIT("All the type patterns for a generic type constructor must be identical") + ptext (sLit "All the type patterns for a generic type constructor must be identical") ] where ppr_inst_ty (_,inst) = ppr (simpleInstInfoTy inst) +mixedGenericErr :: Name -> SDoc mixedGenericErr op - = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) + = ptext (sLit "Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) \end{code}