X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcClassDcl.lhs;h=1fd8706b3e3bade67024d5eb8798d3b901a9c618;hp=30dfc7c5e72f919ee1e6793d9ccf50a4b5d61e14;hb=9319fbaf14f420cbbd9e670093cc86c5f04b7800;hpb=49c98d143c382a1341e1046f5ca00819a25691ba diff --git a/compiler/typecheck/TcClassDcl.lhs b/compiler/typecheck/TcClassDcl.lhs index 30dfc7c..1fd8706 100644 --- a/compiler/typecheck/TcClassDcl.lhs +++ b/compiler/typecheck/TcClassDcl.lhs @@ -8,7 +8,7 @@ Typechecking class declarations \begin{code} module TcClassDcl ( tcClassSigs, tcClassDecl2, getGenericInstances, - MethodSpec, tcMethodBind, mkMethodBind, + MethodSpec, tcMethodBind, mkMethId, tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn ) where @@ -29,13 +29,13 @@ 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 +53,8 @@ import List import BasicTypes import Bag import FastString + +import Control.Monad \end{code} @@ -105,10 +107,10 @@ 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 +123,7 @@ 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 +131,13 @@ 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 +151,26 @@ 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 @@ -250,10 +197,14 @@ tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, -- 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) + + (defm_binds, dm_ids_s) <- mapAndUnzipM tc_dm dm_sel_ids + return (listToBag defm_binds, concat dm_ids_s) +tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d) +tcDefMeth :: InstOrigin -> Class -> [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 @@ -261,17 +212,19 @@ tcDefMeth origin clas tyvars binds_in sig_fn prag_fn sel_id 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) + ; (_, 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 - (ptext SLIT("class") <+> ppr clas) + loc tyvars [this_dict] insts_needed @@ -283,16 +236,15 @@ tcDefMeth origin clas tyvars binds_in sig_fn prag_fn sel_id -- 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 + ; let sel_name = idName sel_id inline_prags = filter isInlineLSig (prag_fn sel_name) - ; prags <- tcPrags dm_inst_id inline_prags + ; prags <- tcPrags meth_id inline_prags ; let full_bind = AbsBinds tyvars [instToId this_dict] - [(tyvars, local_dm_id, dm_inst_id, prags)] + [(tyvars, local_dm_id, meth_id, prags)] (dict_binds `unionBags` defm_bind) - ; returnM (noLoc full_bind, [local_dm_id]) }} + ; return (noLoc full_bind, [local_dm_id]) }} mkDefMethRdrName :: Id -> RdrName mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc @@ -316,23 +268,83 @@ type MethodSpec = (Id, -- Global selector Id LHsBind Name) -- Binding for the method tcMethodBind - :: [TcTyVar] -- Skolemised type variables for the + :: 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] -- Available from context, used to simplify constraints - -- from the method body + -> 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 - -> MethodSpec -- Details of this method + -> LHsBinds Name -- Method binding (pick the right one from in here) + -> ClassOpItem + -> TcId -- The method Id -> TcM (LHsBinds Id) -tcMethodBind inst_tyvars inst_theta avail_insts sig_fn prag_fn - (sel_id, meth_id, meth_bind) - = recoverM (returnM emptyLHsBinds) $ +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 + + 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 ]) + + mk_dm_app dm_id -- dm tys inst_dict + = mkLHsWrap (WpApp this_dict_id `WpCompose` mkWpTyApps inst_tys) + (L loc (HsVar dm_id)) + + +--------------------------- +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 @@ -340,81 +352,51 @@ tcMethodBind inst_tyvars inst_theta avail_insts sig_fn prag_fn -- Check the bindings; first adding inst_tyvars to the envt -- so that we don't quantify over them in nested places - - 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 - - let - [(_, Just sig, local_meth_id)] = mono_bind_infos - in - 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 -> - - checkSigTyVars all_tyvars `thenM_` - - tcPrags meth_id (prag_fn sel_name) `thenM` \ prags -> - let - poly_meth_bind = noLoc $ AbsBinds meth_tvs + 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 + + ; 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 + + ; lie_binds <- tcSimplifyCheck loc all_tyvars all_insts meth_lie + + ; checkSigTyVars all_tyvars + + ; 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) - in - returnM (unitBag poly_meth_bind) + ; return (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 +--------------------------- +mkMethId :: InstOrigin -> Class -> Id -> [TcType] -- Selector, and instance types -> TcM (Maybe Inst, Id) @@ -425,20 +407,20 @@ mkMethId origin clas sel_id inst_tys rho_ty = ASSERT( length tyvars == length inst_tys ) substTyWith tyvars inst_tys rho (preds,tau) = tcSplitPhiTy rho_ty - first_pred = head preds + 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 } + { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False } ) - if isSingleton preds then + if isSingleton preds then do -- 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 + 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 @@ -448,80 +430,48 @@ mkMethId origin clas sel_id inst_tys -- 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 -> + uniq <- newUnique + loc <- getSrcSpanM 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 + meth_id = mkUserLocal (getOccName sel_id) uniq real_tau loc + + return (Nothing, meth_id) + +--------------------------- +-- 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 + +--------------------------- +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 @@ -529,29 +479,88 @@ 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 + _ -> Nothing + _ -> Nothing -isInstDecl (SigOrigin (InstSkol _)) = True -isInstDecl (SigOrigin (ClsSkol _)) = False +isInstDecl :: InstOrigin -> Bool +isInstDecl (SigOrigin InstSkol) = True +isInstDecl (SigOrigin (ClsSkol _)) = False +isInstDecl o = pprPanic "isInstDecl" (ppr o) \end{code} -\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} +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! %************************************************************************ @@ -585,36 +594,37 @@ gives rise to the instance declarations \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 +634,26 @@ 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 +662,7 @@ 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 +671,12 @@ 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 +685,8 @@ 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 +695,37 @@ 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 +736,85 @@ 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 + 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" - maybeSig | isKindSigDecl decl = " signature" - | otherwise = "" + maybeInst | isFamInstDecl decl = " instance" + | otherwise = "" - ctxt = hsep [ptext SLIT("In the"), text thing, - ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] + 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) + = 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) + = 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), - 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)] + = 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) + = 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) + = 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}