X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcClassDcl.lhs;h=8fc8a24e7a522ecce3e255912cc634f8eacee143;hp=f431cd672a97690a40a1d87f546ab84ad083be77;hb=HEAD;hpb=80ef1f06253f1a20a63816c295e180e47cd9a347 diff --git a/compiler/typecheck/TcClassDcl.lhs b/compiler/typecheck/TcClassDcl.lhs index f431cd6..8fc8a24 100644 --- a/compiler/typecheck/TcClassDcl.lhs +++ b/compiler/typecheck/TcClassDcl.lhs @@ -6,57 +6,35 @@ Typechecking class declarations \begin{code} -{-# OPTIONS -w #-} --- The above warning supression flag is a temporary kludge. --- While working on this module you are encouraged to remove it and fix --- any warnings in the module. See --- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings --- for details - module TcClassDcl ( tcClassSigs, tcClassDecl2, - getGenericInstances, - MethodSpec, tcMethodBind, mkMethodBind, + findMethodBind, instantiateMethod, tcInstanceMethodBody, + mkGenericDefMethBind, tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn ) where #include "HsVersions.h" import HsSyn -import RnHsSyn -import RnExpr -import RnEnv -import Inst -import InstEnv import TcEnv +import TcPat( addInlinePrags ) import TcBinds -import TcHsType -import TcSimplify import TcUnify +import TcHsType import TcMType import TcType import TcRnMonad -import Generics -import PrelInfo +import BuildTyCl( TcMethInfo ) import Class -import TyCon -import Type -import MkId import Id import Name import NameEnv import NameSet -import OccName -import RdrName +import Var import Outputable -import PrelNames import DynFlags import ErrUtils -import Util -import Unique -import ListSetOps import SrcLoc import Maybes -import List import BasicTypes import Bag import FastString @@ -105,134 +83,61 @@ Death to "ExpandingDicts". %************************************************************************ \begin{code} -tcClassSigs :: Name -- Name of the class +tcClassSigs :: Name -- Name of the class -> [LSig Name] -> LHsBinds Name - -> TcM [TcMethInfo] - -type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communicate - -- between tcClassSigs and buildClass + -> TcM ([TcMethInfo], -- Exactly one for each method + NameEnv Type) -- Types of the generic-default methods tcClassSigs clas sigs def_methods - = do { dm_env <- checkDefaultBinds clas op_names def_methods - ; mapM (tcClassSig dm_env) op_sigs } - where - op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs] - op_names = [n | sig@(L _ (TypeSig (L _ n) _)) <- op_sigs] - + = do { gen_dm_prs <- mapM (addLocM tc_gen_sig) gen_sigs + ; let gen_dm_env = mkNameEnv gen_dm_prs -checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool) - -- Check default bindings - -- a) must be for a class op for this class - -- b) must be all generic or all non-generic - -- and return a mapping from class-op to Bool - -- where True <=> it's a generic default method -checkDefaultBinds clas ops binds - = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds) - return (mkNameEnv dm_infos) + ; op_info <- mapM (addLocM (tc_sig gen_dm_env)) vanilla_sigs -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) + ; let op_names = mkNameSet [ n | (n,_,_) <- op_info ] + ; sequence_ [ failWithTc (badMethodErr clas n) + | n <- dm_bind_names, not (n `elemNameSet` op_names) ] + -- Value binding for non class-method (ie no TypeSig) - -- Check that all the defns ar generic, or none are - ; checkTc (all_generic || none_generic) (mixedGenericErr op) + ; sequence_ [ failWithTc (badGenericMethod clas n) + | (n,_) <- gen_dm_prs, not (n `elem` dm_bind_names) ] + -- Generic signature without value binding - ; return (op, all_generic) - } + ; return (op_info, gen_dm_env) } where - n_generic = count (isJust . maybeGenericMatch) matches - none_generic = n_generic == 0 - all_generic = matches `lengthIs` n_generic - - -tcClassSig :: NameEnv Bool -- Info about default methods; - -> LSig Name - -> TcM TcMethInfo - -tcClassSig dm_env (L loc (TypeSig (L _ op_name) op_hs_ty)) - = setSrcSpan loc $ do - { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope - ; let dm = case lookupNameEnv dm_env op_name of - Nothing -> NoDefMeth - Just False -> DefMeth - Just True -> GenDefMeth - ; return (op_name, dm, op_ty) } + vanilla_sigs = [L loc (nm,ty) | L loc (TypeSig nm ty) <- sigs] + gen_sigs = [L loc (nm,ty) | L loc (GenericSig nm ty) <- sigs] + dm_bind_names :: [Name] -- These ones have a value binding in the class decl + dm_bind_names = [op | L _ (FunBind {fun_id = L _ op}) <- bagToList def_methods] + + tc_sig genop_env (L _ op_name, op_hs_ty) + = do { op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope + ; let dm | op_name `elemNameEnv` genop_env = GenericDM + | op_name `elem` dm_bind_names = VanillaDM + | otherwise = NoDM + ; return (op_name, dm, op_ty) } + + tc_gen_sig (L _ op_name, gen_hs_ty) + = do { gen_op_ty <- tcHsKindedType gen_hs_ty + ; return (op_name, gen_op_ty) } \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]) + -> TcM (LHsBinds Id) tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs, tcdMeths = default_binds})) - = recoverM (return (emptyLHsBinds, [])) $ - setSrcSpan loc $ do - clas <- tcLookupLocatedClass class_name + = 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 @@ -242,327 +147,178 @@ 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.) - - (defm_binds, dm_ids_s) <- mapAndUnzipM tc_dm dm_sel_ids - return (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) - - ; 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 (_,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) - ; return (noLoc full_bind, [local_dm_id]) }} - -mkDefMethRdrName :: Id -> RdrName -mkDefMethRdrName sel_id = mkDerivedRdrName (idName sel_id) mkDefaultMethodOcc -\end{code} + ; let + (tyvars, _, _, op_items) = classBigSig clas + prag_fn = mkPragFun sigs default_binds + sig_fn = mkSigFun sigs + clas_tyvars = tcSuperSkolTyVars tyvars + pred = mkClassPred clas (mkTyVarTys clas_tyvars) + ; this_dict <- newEvVar pred + ; traceTc "TIM2" (ppr sigs) + ; let tc_dm = tcDefMeth clas clas_tyvars + this_dict default_binds + sig_fn prag_fn -%************************************************************************ -%* * -\subsection{Typechecking a method} -%* * -%************************************************************************ + ; dm_binds <- tcExtendTyVarEnv clas_tyvars $ + mapM tc_dm op_items -@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. + ; return (unionManyBags dm_binds) } -\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 (return emptyLHsBinds) $ do - -- 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 - - 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 - - ((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) - - 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) = do - (mb_inst, meth_id) <- mkMethId origin clas sel_id inst_tys - let - meth_name = idName meth_id - - -- Figure out what method binding to use - -- If the user suppplied one, use it, else construct a default one - loc <- getSrcSpanM - meth_bind - <- case find_bind (idName sel_id) meth_name meth_binds of - Just user_bind -> return user_bind - Nothing -> do - rhs <- mkDefMethRhs origin clas inst_tys sel_id loc dm_info - -- Not infix decl - return (noLoc $ mkFunBind (noLoc meth_name) [mkSimpleMatch [] rhs]) - - return (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 = 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) - - -- 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 = do - -- An polymorphic default method - dm_name <- lookupImportedName (mkDefMethRdrName sel_id) - -- Might not be imported, but will be an OrigName - traceRn (text "mkDefMeth" <+> ppr dm_name) - return (nlHsVar dm_name) - -mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth = do - -- No default method - -- Warn only if -fwarn-missing-methods - warn <- doptM Opt_WarnMissingMethods - warnTc (isInstDecl origin - && warn - && reportIfUnused (getOccName sel_id)) - (omittedMethodWarn sel_id) - return error_rhs +tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d) + +tcDefMeth :: Class -> [TyVar] -> EvVar -> LHsBinds Name + -> SigFun -> PragFun -> ClassOpItem + -> TcM (LHsBinds TcId) +-- 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.) +tcDefMeth clas tyvars this_dict binds_in sig_fn prag_fn (sel_id, dm_info) + = case dm_info of + NoDefMeth -> do { mapM_ (addLocM (badDmPrag sel_id)) prags + ; return emptyBag } + DefMeth dm_name -> tc_dm dm_name + GenDefMeth dm_name -> tc_dm dm_name 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 - = -- 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 - ; 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 - ; return rn_rhs } + sel_name = idName sel_id + prags = prag_fn sel_name + dm_sig_fn _ = sig_fn sel_name + dm_bind = findMethodBind sel_name binds_in + `orElse` pprPanic "tcDefMeth" (ppr sel_id) + + -- Eg. class C a where + -- op :: forall b. Eq b => a -> [b] -> a + -- gen_op :: a -> a + -- generic gen_op :: D a => a -> a + -- The "local_dm_ty" is precisely the type in the above + -- type signatures, ie with no "forall a. C a =>" prefix + + tc_dm dm_name + = do { dm_id <- tcLookupId dm_name + ; local_dm_name <- newLocalName sel_name + -- Base the local_dm_name on the selector name, because + -- type errors from tcInstanceMethodBody come from here + + ; let local_dm_ty = instantiateMethod clas dm_id (mkTyVarTys tyvars) + local_dm_id = mkLocalId local_dm_name local_dm_ty + + ; dm_id_w_inline <- addInlinePrags dm_id prags + ; spec_prags <- tcSpecPrags dm_id prags + + ; warnTc (not (null spec_prags)) + (ptext (sLit "Ignoring SPECIALISE pragmas on default method") + <+> quotes (ppr sel_name)) + + ; tc_bind <- tcInstanceMethodBody (ClsSkol clas) tyvars [this_dict] + dm_id_w_inline local_dm_id dm_sig_fn + IsDefaultMethod dm_bind + + ; return (unitBag tc_bind) } + +--------------- +tcInstanceMethodBody :: SkolemInfo -> [TcTyVar] -> [EvVar] + -> Id -> Id + -> SigFun -> TcSpecPrags -> LHsBind Name + -> TcM (LHsBind Id) +tcInstanceMethodBody skol_info tyvars dfun_ev_vars + meth_id local_meth_id + meth_sig_fn specs + (L loc bind) + = do { -- 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 + let lm_bind = L loc (bind { fun_id = L loc (idName local_meth_id) }) + -- Substitute the local_meth_name for the binder + -- NB: the binding is always a FunBind + ; traceTc "TIM" (ppr local_meth_id $$ ppr (meth_sig_fn (idName local_meth_id))) + ; (ev_binds, (tc_bind, _)) + <- checkConstraints skol_info tyvars dfun_ev_vars $ + tcExtendIdEnv [local_meth_id] $ + tcPolyBinds TopLevel meth_sig_fn no_prag_fn + NonRecursive NonRecursive + [lm_bind] + + ; let full_bind = AbsBinds { abs_tvs = tyvars, abs_ev_vars = dfun_ev_vars + , abs_exports = [(tyvars, meth_id, local_meth_id, specs)] + , abs_ev_binds = ev_binds + , abs_binds = tc_bind } + + ; return (L loc full_bind) } where - rhs = mkGenericRhs sel_id clas_tyvar tycon - - -- The tycon is only used in the generic case, and in that - -- 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 = 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 + no_prag_fn _ = [] -- No pragmas for local_meth_id; + -- they are all for meth_id \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 +instantiateMethod :: Class -> Id -> [TcType] -> TcType +-- Take a class operation, say +-- op :: forall ab. C a => forall c. Ix c => (b,c) -> a +-- Instantiate it at [ty1,ty2] +-- Return the "local method type": +-- forall c. Ix x => (ty2,c) -> ty1 +instantiateMethod clas sel_id inst_tys + = ASSERT( ok_first_pred ) local_meth_ty + where + (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) + + ok_first_pred = case getClassPredTys_maybe first_pred of + Just (clas1, _tys) -> clas == clas1 + Nothing -> False + -- The first predicate should be of form (C a b) + -- where C is the class in question + + +--------------------------- +findMethodBind :: Name -- Selector name + -> LHsBinds Name -- A group of bindings + -> Maybe (LHsBind Name) -- The binding +findMethodBind sel_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 + f bind@(L _ (FunBind { fun_id = L _ op_name })) + | op_name == sel_name + = Just bind + f _other = Nothing \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{Extracting generic instance declaration from class declarations} + Extracting generic instance declaration from class declarations %* * %************************************************************************ @@ -589,140 +345,23 @@ gives rise to the instance declarations instance C 1 where op Unit = ... - \begin{code} -getGenericInstances :: [LTyClDecl Name] -> TcM [InstInfo] -getGenericInstances 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 return [] - else do - - -- Otherwise print it out - { dflags <- getDOpts - ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" - (vcat (map pprInstInfoDetails gen_inst_info))) - ; return gen_inst_info }} - -get_generics decl@(ClassDecl {tcdLName = class_name, tcdMeths = def_methods}) - | null generic_binds - = return [] -- The comon case: no generic default methods - - | otherwise -- A source class decl with generic default methods - = 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 - - 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 - -- f {| a+b |} ... = ... - -- f {| x+y |} ... = ... - -- Then at this point we'll have an InstInfo for each - -- - -- The class should be unary, which is why simpleInstInfoTyCon should be ok - let - tc_inst_infos :: [(TyCon, InstInfo)] - 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 - - 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] - - checkTc (null missing) (missingGenericInstances missing) - - return inst_infos - where - generic_binds :: [(HsType Name, LHsBind Name)] - generic_binds = getGenericBinds def_methods - - ---------------------------------- -getGenericBinds :: LHsBinds Name -> [(HsType Name, LHsBind Name)] - -- Takes a group of method bindings, finds the generic ones, and returns - -- them in finite map indexed by the type parameter in the definition. -getGenericBinds binds = concat (map getGenericBind (bagToList binds)) +mkGenericDefMethBind :: Class -> [Type] -> Id -> Name -> TcM (LHsBind Name) +mkGenericDefMethBind clas inst_tys sel_id dm_name + = -- A generic default method + -- If the method is defined generically, we only have to call the + -- dm_name. + do { dflags <- getDOpts + ; 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)])) -getGenericBind (L loc bind@(FunBind { fun_matches = MatchGroup matches ty })) - = groupWith wrap (mapCatMaybes maybeGenericMatch matches) + ; return (noLoc $ mkFunBind (noLoc (idName sel_id)) + [mkSimpleMatch [] rhs]) } where - wrap ms = L loc (bind { fun_matches = MatchGroup ms ty }) -getGenericBind _ - = [] - -groupWith :: ([a] -> b) -> [(HsType Name, a)] -> [(HsType Name, b)] -groupWith op [] = [] -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' - -eqPatLType :: LHsType Name -> LHsType Name -> Bool -eqPatLType t1 t2 = unLoc t1 `eqPatType` unLoc t2 - -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 (HsNumTy n1) (HsNumTy n2) = n1 == n2 -eqPatType (HsParTy t1) t2 = unLoc t1 `eqPatType` t2 -eqPatType t1 (HsParTy t2) = t1 `eqPatType` unLoc t2 -eqPatType _ _ = False - ---------------------------------- -mkGenericInstance :: Class - -> (HsType Name, LHsBinds Name) - -> TcM InstInfo - -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 - -- 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) - - -- Type-check the instance type, and check its form - forall_inst_ty <- tcHsSigType GenPatCtxt hs_forall_ty - let - (tyvars, inst_ty) = tcSplitForAllTys forall_inst_ty - - checkTc (validGenericInstanceType inst_ty) - (badGenericInstanceType binds) - - -- Make the dictionary function. - 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 - - return (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] }) + rhs = nlHsVar dm_name \end{code} - %************************************************************************ %* * Error messages @@ -730,6 +369,7 @@ mkGenericInstance clas (hs_ty, binds) = do %************************************************************************ \begin{code} +tcAddDeclCtxt :: TyClDecl Name -> TcM a -> TcM a tcAddDeclCtxt decl thing_inside = addErrCtxt ctxt thing_inside where @@ -739,61 +379,54 @@ tcAddDeclCtxt decl thing_inside then "newtype" ++ maybeInst else "data type" ++ maybeInst | isFamilyDecl decl = "family" + | otherwise = panic "tcAddDeclCtxt/thing" maybeInst | isFamInstDecl decl = " instance" | otherwise = "" - ctxt = hsep [ptext SLIT("In the"), text thing, - ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] - -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 clas at - = hsep [ptext SLIT("Class"), quotes (ppr clas), - ptext SLIT("does not have an associated type"), quotes (ppr at)] +badGenericMethod :: Outputable a => a -> Name -> SDoc +badGenericMethod clas op + = hsep [ptext (sLit "Class"), quotes (ppr clas), + ptext (sLit "has a generic-default signature without a binding"), quotes (ppr op)] -omittedMethodWarn sel_id - = ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id) +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)] +omittedATWarn :: Name -> SDoc omittedATWarn at - = ptext SLIT("No explicit AT declaration for") <+> quotes (ppr at) - -badGenericInstance sel_id because - = sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id), - because] - -notSimple inst_tys - = vcat [ptext SLIT("because the instance type(s)"), - nest 2 (ppr inst_tys), - ptext SLIT("is not a simple type of form (T a1 ... an)")] - -notGeneric tycon - = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+> - ptext SLIT("was not compiled with -fgenerics")] - + = ptext (sLit "No explicit AT declaration for") <+> quotes (ppr at) +{- +badGenericInstanceType :: LHsBinds Name -> SDoc badGenericInstanceType binds - = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), - nest 4 (ppr binds)] + = vcat [ptext (sLit "Illegal type pattern in the generic bindings"), + nest 2 (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:"), - nest 4 (vcat (map ppr_inst_ty tc_inst_infos)), - ptext SLIT("All the type patterns for a generic type constructor must be identical") + = vcat [ptext (sLit "More than one type pattern for a single generic type constructor:"), + nest 2 (vcat (map ppr_inst_ty tc_inst_infos)), + ptext (sLit "All the type patterns for a generic type constructor must be identical") ] where ppr_inst_ty (_,inst) = ppr (simpleInstInfoTy inst) - -mixedGenericErr op - = ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op) +-} +badDmPrag :: Id -> Sig Name -> TcM () +badDmPrag sel_id prag + = addErrTc (ptext (sLit "The") <+> hsSigDoc prag <+> ptext (sLit "for default method") + <+> quotes (ppr sel_id) + <+> ptext (sLit "lacks an accompanying binding")) \end{code}