X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=59d04ebb86fb93b20cd6867bc50580c1d55d42f4;hb=f16228e47dbaf4c5eb710bf507b3b61bc5ad7122;hp=8b145d504dd1b0e39ec490cf410d1b363eeb22f4;hpb=f74e9e28c66072f93150fe026f87549e2f255128;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 8b145d5..59d04eb 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -11,58 +11,61 @@ module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where import CmdLineOpts ( DynFlag(..), dopt ) -import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), - MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), - andMonoBindList, collectMonoBinders, isClassDecl +import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..), + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, isClassDecl, toHsType ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl, RenamedMonoBinds, - RenamedTyClDecl, RenamedHsType, +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl, + RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, extractHsTyVars, maybeGenericMatch ) import TcHsSyn ( TcMonoBinds, mkHsConApp ) import TcBinds ( tcSpecSigs ) import TcClassDcl ( tcMethodBind, badMethodErr ) import TcMonad +import TcType ( tcInstType ) import Inst ( InstOrigin(..), - newDicts, newClassDicts, - LIE, emptyLIE, plusLIE, plusLIEs ) + newDicts, instToId, + LIE, mkLIE, emptyLIE, plusLIE, plusLIEs ) import TcDeriv ( tcDeriving ) import TcEnv ( TcEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcInstId, tcLookupClass, - InstInfo(..), pprInstInfo, simpleInstInfoTyCon, simpleInstInfoTy, - newDFunName, tcExtendTyVarEnv + tcAddImportedIdInfo, tcLookupClass, + InstInfo(..), pprInstInfo, simpleInstInfoTyCon, + simpleInstInfoTy, newDFunName, tcExtendTyVarEnv, + isLocalThing, ) import InstEnv ( InstEnv, extendInstEnv ) -import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( zonkTcSigTyVars ) +import TcMonoType ( tcHsTyVars, tcHsSigType, kcHsSigType, checkSigTyVars ) +import TcSimplify ( tcSimplifyCheck ) import HscTypes ( HomeSymbolTable, DFunId, ModDetails(..), PackageInstEnv, PersistentRenamerState ) -import Bag ( unionManyBags ) import DataCon ( classDataCon ) import Class ( Class, DefMeth(..), classBigSig ) import Var ( idName, idType ) +import VarSet ( emptyVarSet ) import Maybes ( maybeToBool ) import MkId ( mkDictFunId ) +import FunDeps ( checkInstFDs ) import Generics ( validGenericInstanceType ) import Module ( Module, foldModuleEnv ) import Name ( getSrcLoc ) -import NameSet ( emptyNameSet, nameSetToList ) +import NameSet ( unitNameSet, nameSetToList ) import PrelInfo ( eRROR_ID ) -import PprType ( pprConstraint, pprPred ) +import PprType ( pprClassPred, pprPred ) import TyCon ( TyCon, isSynTyCon ) import Type ( splitDFunTy, isTyVarTy, splitTyConApp_maybe, splitDictTy, splitForAllTys, tyVarsOfTypes, mkClassPred, mkTyVarTy, - getClassTys_maybe + isTyVarClassPred, inheritablePred ) -import Subst ( mkTopTyVarSubst, substClasses ) -import VarSet ( mkVarSet, varSetElems ) -import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIResultTy ) +import Subst ( mkTopTyVarSubst, substTheta ) +import VarSet ( varSetElems ) +import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIImportResultTy ) +import ForeignCall ( Safety(..) ) import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey ) import Name ( Name ) import SrcLoc ( SrcLoc ) @@ -167,21 +170,20 @@ tcInstDecls1 :: PackageInstEnv -> TcEnv -- Contains IdInfo for dfun ids -> (Name -> Maybe Fixity) -- for deriving Show and Read -> Module -- Module for deriving - -> [TyCon] -> [RenamedHsDecl] -> TcM (PackageInstEnv, InstEnv, [InstInfo], RenamedHsBinds) -tcInstDecls1 inst_env0 prs hst unf_env get_fixity mod tycons decls +tcInstDecls1 inst_env0 prs hst unf_env get_fixity this_mod decls = let inst_decls = [inst_decl | InstD inst_decl <- decls] tycl_decls = [decl | TyClD decl <- decls] clas_decls = filter isClassDecl tycl_decls in -- (1) Do the ordinary instance declarations - mapNF_Tc (tcInstDecl1 mod unf_env) inst_decls `thenNF_Tc` \ inst_infos -> + mapNF_Tc tcInstDecl1 inst_decls `thenNF_Tc` \ inst_infos -> -- (2) Instances from generic class declarations - getGenericInstances mod clas_decls `thenTc` \ generic_inst_info -> + getGenericInstances clas_decls `thenTc` \ generic_inst_info -> -- Next, construct the instance environment so far, consisting of -- a) cached non-home-package InstEnv (gotten from pcs) pcs_insts pcs @@ -191,7 +193,8 @@ tcInstDecls1 inst_env0 prs hst unf_env get_fixity mod tycons decls -- e) generic instances inst_env4 -- The result of (b) replaces the cached InstEnv in the PCS let - (local_inst_info, imported_inst_info) = partition iLocal (concat inst_infos) + (local_inst_info, imported_inst_info) + = partition (isLocalThing this_mod . iDFunId) (concat inst_infos) imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId) imported_inst_info @@ -207,7 +210,8 @@ tcInstDecls1 inst_env0 prs hst unf_env get_fixity mod tycons decls -- we ignore deriving decls from interfaces! -- This stuff computes a context for the derived instance decl, so it -- needs to know about all the instances possible; hecne inst_env4 - tcDeriving prs mod inst_env4 get_fixity tycl_decls `thenTc` \ (deriv_inst_info, deriv_binds) -> + tcDeriving prs this_mod inst_env4 get_fixity tycl_decls + `thenTc` \ (deriv_inst_info, deriv_binds) -> addInstInfos inst_env4 deriv_inst_info `thenNF_Tc` \ final_inst_env -> returnTc (inst_env1, @@ -221,24 +225,25 @@ addInstInfos inst_env infos = addInstDFuns inst_env (map iDFunId infos) addInstDFuns :: InstEnv -> [DFunId] -> NF_TcM InstEnv addInstDFuns dfuns infos = getDOptsTc `thenTc` \ dflags -> - extendInstEnv dflags dfuns infos `bind` \ (inst_env', errs) -> + let + (inst_env', errs) = extendInstEnv dflags dfuns infos + in addErrsTc errs `thenNF_Tc_` returnTc inst_env' - where - bind x f = f x - \end{code} \begin{code} -tcInstDecl1 :: Module -> TcEnv -> RenamedInstDecl -> NF_TcM [InstInfo] +tcInstDecl1 :: RenamedInstDecl -> NF_TcM [InstInfo] -- Deal with a single instance declaration -tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc) +tcInstDecl1 decl@(InstDecl poly_ty binds uprags maybe_dfun_name src_loc) = -- Prime error recovery, set source location recoverNF_Tc (returnNF_Tc []) $ tcAddSrcLoc src_loc $ -- Type-check all the stuff before the "where" - tcHsSigType poly_ty `thenTc` \ poly_ty' -> + tcAddErrCtxt (instDeclCtxt poly_ty) ( + tcHsSigType poly_ty + ) `thenTc` \ poly_ty' -> let (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty' in @@ -251,11 +256,11 @@ tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc) -- Imported ones should have been checked already, and may indeed -- contain something illegal in normal Haskell, notably -- instance CCallable [Char] - scrutiniseInstanceHead clas inst_tys `thenNF_Tc_` - mapNF_Tc scrutiniseInstanceConstraint theta `thenNF_Tc_` + getDOptsTc `thenTc` \ dflags -> + checkInstValidity dflags theta clas inst_tys `thenTc_` -- Make the dfun id and return it - newDFunName mod clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> + newDFunName clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> returnNF_Tc (True, dfun_name) Just dfun_name -> -- An interface-file instance declaration @@ -266,7 +271,7 @@ tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc) let dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta in - returnTc [InstInfo { iLocal = is_local, iDFunId = dfun_id, + returnTc [InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = uprags }] \end{code} @@ -302,25 +307,27 @@ gives rise to the instance declarations \begin{code} -getGenericInstances :: Module -> [RenamedTyClDecl] -> TcM [InstInfo] -getGenericInstances mod class_decls - = mapTc (get_generics mod) class_decls `thenTc` \ gen_inst_infos -> +getGenericInstances :: [RenamedTyClDecl] -> TcM [InstInfo] +getGenericInstances class_decls + = mapTc get_generics class_decls `thenTc` \ gen_inst_infos -> let gen_inst_info = concat gen_inst_infos in + if null gen_inst_info then + returnTc [] + else getDOptsTc `thenTc` \ dflags -> ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" (vcat (map pprInstInfo gen_inst_info))) `thenNF_Tc_` returnTc gen_inst_info -get_generics mod decl@(ClassDecl context class_name tyvar_names - fundeps class_sigs def_methods - name_list loc) +get_generics decl@(ClassDecl {tcdMeths = Nothing}) + = returnTc [] -- Imported class decls + +get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tcdLoc = loc}) | null groups - = returnTc [] -- The comon case: - -- no generic default methods, or - -- its an imported class decl (=> has no methods at all) + = returnTc [] -- The comon case: no generic default methods | otherwise -- A local class decl with generic default methods = recoverNF_Tc (returnNF_Tc []) $ @@ -328,7 +335,7 @@ get_generics mod decl@(ClassDecl context class_name tyvar_names tcLookupClass class_name `thenTc` \ clas -> -- Make an InstInfo out of each group - mapTc (mkGenericInstance mod clas loc) groups `thenTc` \ inst_infos -> + mapTc (mkGenericInstance clas loc) groups `thenTc` \ inst_infos -> -- Check that there is only one InstInfo for each type constructor -- The main way this can fail is if you write @@ -380,18 +387,19 @@ getGenericBinds (FunMonoBind id infixop matches loc) wrap ms = FunMonoBind id infixop ms loc --------------------------------- -mkGenericInstance :: Module -> Class -> SrcLoc +mkGenericInstance :: Class -> SrcLoc -> (RenamedHsType, RenamedMonoBinds) -> TcM InstInfo -mkGenericInstance mod clas loc (hs_ty, binds) +mkGenericInstance clas loc (hs_ty, binds) -- Make a generic instance declaration -- For example: instance (C a, C b) => C (a+b) where { binds } = -- Extract the universally quantified type variables - tcTyVars (nameSetToList (extractHsTyVars hs_ty)) - (kcHsSigType hs_ty) `thenTc` \ tyvars -> - tcExtendTyVarEnv tyvars $ + let + sig_tvs = map UserTyVar (nameSetToList (extractHsTyVars hs_ty)) + in + tcHsTyVars sig_tvs (kcHsSigType hs_ty) $ \ tyvars -> -- Type-check the instance type, and check its form tcHsSigType hs_ty `thenTc` \ inst_ty -> @@ -399,14 +407,14 @@ mkGenericInstance mod clas loc (hs_ty, binds) (badGenericInstanceType binds) `thenTc_` -- Make the dictionary function. - newDFunName mod clas [inst_ty] loc `thenNF_Tc` \ dfun_name -> + newDFunName clas [inst_ty] loc `thenNF_Tc` \ dfun_name -> let inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] inst_tys = [inst_ty] dfun_id = mkDictFunId dfun_name clas tyvars inst_tys inst_theta in - returnTc (InstInfo { iLocal = True, iDFunId = dfun_id, + returnTc (InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = [] }) \end{code} @@ -498,21 +506,20 @@ is the @dfun_theta@ below. First comes the easy case of a non-local instance decl. + \begin{code} tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds) +-- tcInstDecl2 is called *only* on InstInfos -tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = monobinds, iPrags = uprags }) - | not is_local - = returnNF_Tc (emptyLIE, EmptyMonoBinds) - - | otherwise = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc (getSrcLoc dfun_id) $ + recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ + tcAddSrcLoc (getSrcLoc dfun_id) $ + tcAddErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $ -- Instantiate the instance decl with tc-style type variables - tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> + tcInstType (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> let (clas, inst_tys') = splitDictTy dict_ty' origin = InstanceDeclOrigin @@ -523,7 +530,7 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, sel_names = [idName sel_id | (sel_id, _) <- op_items] -- Instantiate the super-class context with inst_tys - sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys') sc_theta + sc_theta' = substTheta (mkTopTyVarSubst class_tyvars inst_tys') sc_theta -- Find any definitions in monobinds that aren't from the class bad_bndrs = collectMonoBinders monobinds `minusList` sel_names @@ -537,9 +544,9 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_` -- Create dictionary Ids from the specified instance contexts. - newClassDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) -> - newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) -> - newClassDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> + newDicts origin sc_theta' `thenNF_Tc` \ sc_dicts -> + newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts -> + newDicts origin [mkClassPred clas inst_tys'] `thenNF_Tc` \ [this_dict] -> tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' ( tcExtendGlobalValEnv dm_ids ( @@ -549,7 +556,7 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, dfun_theta' monobinds uprags True) op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) -> + )) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) -> -- Deal with SPECIALISE instance pragmas by making them -- look like SPECIALISE pragmas for the dfun @@ -561,51 +568,47 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, ) `thenTc` \ (prag_binds, prag_lie) -> -- Check the overloading constraints of the methods and superclasses - - -- tcMethodBind has checked that the class_tyvars havn't - -- been unified with each other or another type, but we must - -- still zonk them before passing them to tcSimplifyAndCheck - zonkTcSigTyVars inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars -> let - inst_tyvars_set = mkVarSet zonked_inst_tyvars - - (meth_lies, meth_ids) = unzip meth_lies_w_ids - -- These insts are in scope; quite a few, eh? - avail_insts = this_dict `plusLIE` - dfun_arg_dicts `plusLIE` - sc_dicts `plusLIE` - unionManyBags meth_lies + avail_insts = [this_dict] ++ + dfun_arg_dicts ++ + sc_dicts ++ + meth_insts - methods_lie = plusLIEs insts_needed_s + methods_lie = plusLIEs insts_needed_s in - -- Ditto method bindings + -- Simplify the constraints from methods tcAddErrCtxt methodCtxt ( - tcSimplifyAndCheck + tcSimplifyCheck (ptext SLIT("instance declaration context")) - inst_tyvars_set -- Local tyvars + inst_tyvars' avail_insts methods_lie ) `thenTc` \ (const_lie1, lie_binds1) -> - -- Now do the simplification again, this time to get the - -- bindings; this time we use an enhanced "avails" - -- Ignore errors because they come from the *previous* tcSimplify - discardErrsTc ( - tcSimplifyAndCheck + -- Figure out bindings for the superclass context + tcAddErrCtxt superClassCtxt ( + tcSimplifyCheck (ptext SLIT("instance declaration context")) - inst_tyvars_set + inst_tyvars' dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts -- get bound by just selecting from this_dict!! - sc_dicts - ) `thenTc` \ (const_lie2, lie_binds2) -> - + (mkLIE sc_dicts) + ) `thenTc` \ (const_lie2, lie_binds2) -> + + checkSigTyVars inst_tyvars' emptyVarSet `thenNF_Tc` \ zonked_inst_tyvars -> -- Create the result bindings let dict_constr = classDataCon clas - scs_and_meths = sc_dict_ids ++ meth_ids + scs_and_meths = map instToId (sc_dicts ++ meth_insts) + this_dict_id = instToId this_dict + inlines = unitNameSet (idName dfun_id) + -- Always inline the dfun; this is an experimental decision + -- because it makes a big performance difference sometimes. + -- Often it means we can do the method selection, and then + -- inline the method as well. Marcin's idea; see comments below. dict_rhs | null scs_and_meths @@ -619,7 +622,7 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, (HsLit (HsString msg)) | otherwise -- The common case - = mkHsConApp dict_constr inst_tys' (map HsVar (sc_dict_ids ++ meth_ids)) + = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) -- We don't produce a binding for the dict_constr; instead we -- rely on the simplifier to unfold this saturated application -- We do this rather than generate an HsCon directly, because @@ -636,9 +639,9 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, main_bind = AbsBinds zonked_inst_tyvars - dfun_arg_dicts_ids + (map instToId dfun_arg_dicts) [(inst_tyvars', dfun_id, this_dict_id)] - emptyNameSet -- No inlines (yet) + inlines (lie_binds1 `AndMonoBinds` lie_binds2 `AndMonoBinds` method_binds `AndMonoBinds` @@ -648,6 +651,96 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, main_bind `AndMonoBinds` prag_binds) \end{code} + ------------------------------ + Inlining dfuns unconditionally + ------------------------------ + +The code above unconditionally inlines dict funs. Here's why. +Consider this program: + + test :: Int -> Int -> Bool + test x y = (x,y) == (y,x) || test y x + -- Recursive to avoid making it inline. + +This needs the (Eq (Int,Int)) instance. If we inline that dfun +the code we end up with is good: + + Test.$wtest = + \r -> case ==# [ww ww1] of wild { + PrelBase.False -> Test.$wtest ww1 ww; + PrelBase.True -> + case ==# [ww1 ww] of wild1 { + PrelBase.False -> Test.$wtest ww1 ww; + PrelBase.True -> PrelBase.True []; + }; + }; + Test.test = \r [w w1] + case w of w2 { + PrelBase.I# ww -> + case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; }; + }; + +If we don't inline the dfun, the code is not nearly as good: + + (==) = case PrelTup.$fEq(,) PrelBase.$fEqInt PrelBase.$fEqInt of tpl { + PrelBase.:DEq tpl1 tpl2 -> tpl2; + }; + + Test.$wtest = + \r [ww ww1] + let { y = PrelBase.I#! [ww1]; } in + let { x = PrelBase.I#! [ww]; } in + let { sat_slx = PrelTup.(,)! [y x]; } in + let { sat_sly = PrelTup.(,)! [x y]; + } in + case == sat_sly sat_slx of wild { + PrelBase.False -> Test.$wtest ww1 ww; + PrelBase.True -> PrelBase.True []; + }; + + Test.test = + \r [w w1] + case w of w2 { + PrelBase.I# ww -> + case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; }; + }; + +Why doesn't GHC inline $fEq? Because it looks big: + + PrelTup.zdfEqZ1T{-rcX-} + = \ @ a{-reT-} :: * @ b{-reS-} :: * + zddEq{-rf6-} _Ks :: {PrelBase.Eq{-23-} a{-reT-}} + zddEq1{-rf7-} _Ks :: {PrelBase.Eq{-23-} b{-reS-}} -> + let { + zeze{-rf0-} _Kl :: (b{-reS-} -> b{-reS-} -> PrelBase.Bool{-3c-}) + zeze{-rf0-} = PrelBase.zeze{-01L-}@ b{-reS-} zddEq1{-rf7-} } in + let { + zeze1{-rf3-} _Kl :: (a{-reT-} -> a{-reT-} -> PrelBase.Bool{-3c-}) + zeze1{-rf3-} = PrelBase.zeze{-01L-} @ a{-reT-} zddEq{-rf6-} } in + let { + zeze2{-reN-} :: ((a{-reT-}, b{-reS-}) -> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-}) + zeze2{-reN-} = \ ds{-rf5-} _Ks :: (a{-reT-}, b{-reS-}) + ds1{-rf4-} _Ks :: (a{-reT-}, b{-reS-}) -> + case ds{-rf5-} + of wild{-reW-} _Kd { (a1{-rf2-} _Ks, a2{-reZ-} _Ks) -> + case ds1{-rf4-} + of wild1{-reX-} _Kd { (b1{-rf1-} _Ks, b2{-reY-} _Ks) -> + PrelBase.zaza{-r4e-} + (zeze1{-rf3-} a1{-rf2-} b1{-rf1-}) + (zeze{-rf0-} a2{-reZ-} b2{-reY-}) + } + } } in + let { + a1{-reR-} :: ((a{-reT-}, b{-reS-})-> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-}) + a1{-reR-} = \ a2{-reV-} _Ks :: (a{-reT-}, b{-reS-}) + b1{-reU-} _Ks :: (a{-reT-}, b{-reS-}) -> + PrelBase.not{-r6I-} (zeze2{-reN-} a2{-reV-} b1{-reU-}) + } in + PrelBase.zdwZCDEq{-r8J-} @ (a{-reT-}, b{-reS-}) a1{-reR-} zeze2{-reN-}) + +and it's not as bad as it seems, because it's further dramatically +simplified: only zeze2 is extracted and its body is simplified. + %************************************************************************ %* * @@ -665,23 +758,27 @@ compiled elsewhere). In these cases, we let them go through anyway. We can also have instances for functions: @instance Foo (a -> b) ...@. \begin{code} -scrutiniseInstanceConstraint pred - = getDOptsTc `thenTc` \ dflags -> case () of - () - | dopt Opt_AllowUndecidableInstances dflags - -> returnNF_Tc () - - | Just (clas,tys) <- getClassTys_maybe pred, - all isTyVarTy tys - -> returnNF_Tc () - - | otherwise - -> addErrTc (instConstraintErr pred) - -scrutiniseInstanceHead clas inst_taus - = getDOptsTc `thenTc` \ dflags -> case () of - () - | -- CCALL CHECK +checkInstValidity dflags theta clas inst_tys + | null errs = returnTc () + | otherwise = addErrsTc errs `thenNF_Tc_` failTc + where + errs = checkInstHead dflags theta clas inst_tys ++ + [err | pred <- theta, err <- checkInstConstraint dflags pred] + +checkInstConstraint dflags pred + -- Checks whether a predicate is legal in the + -- context of an instance declaration + | ok = [] + | otherwise = [instConstraintErr pred] + where + ok = inheritablePred pred && + (isTyVarClassPred pred || arbitrary_preds_ok) + + arbitrary_preds_ok = dopt Opt_AllowUndecidableInstances dflags + + +checkInstHead dflags theta clas inst_taus + | -- CCALL CHECK -- A user declaration of a CCallable/CReturnable instance -- must be for a "boxed primitive" type. (clas `hasKey` cCallableClassKey @@ -689,34 +786,27 @@ scrutiniseInstanceHead clas inst_taus || (clas `hasKey` cReturnableClassKey && not (creturnable_type first_inst_tau)) - -> addErrTc (nonBoxedPrimCCallErr clas first_inst_tau) - - -- Allow anything for AllowUndecidableInstances - | dopt Opt_AllowUndecidableInstances dflags - -> returnNF_Tc () + = [nonBoxedPrimCCallErr clas first_inst_tau] -- If GlasgowExts then check at least one isn't a type variable - | dopt Opt_GlasgowExts dflags - -> if all isTyVarTy inst_taus - then addErrTc (instTypeErr clas inst_taus - (text "There must be at least one non-type-variable in the instance head")) - else returnNF_Tc () + | dopt Opt_GlasgowExts dflags + = -- GlasgowExts case + check_tyvars dflags clas inst_taus ++ check_fundeps dflags theta clas inst_taus -- WITH HASKELL 1.4, MUST HAVE C (T a b c) - | not (length inst_taus == 1 && - maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor - not (isSynTyCon tycon) && -- ...but not a synonym - all isTyVarTy arg_tys && -- Applied to type variables - length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys - -- This last condition checks that all the type variables are distinct - ) - -> addErrTc (instTypeErr clas inst_taus - (text "the instance type must be of form (T a b c)" $$ - text "where T is not a synonym, and a,b,c are distinct type variables") - ) - - | otherwise - -> returnNF_Tc () + | not (length inst_taus == 1 && + maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor + not (isSynTyCon tycon) && -- ...but not a synonym + all isTyVarTy arg_tys && -- Applied to type variables + length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys + -- This last condition checks that all the type variables are distinct + ) + = [instTypeErr clas inst_taus + (text "the instance type must be of form (T a b c)" $$ + text "where T is not a synonym, and a,b,c are distinct type variables")] + + | otherwise + = [] where (first_inst_tau : _) = inst_taus @@ -725,8 +815,26 @@ scrutiniseInstanceHead clas inst_taus maybe_tycon_app = splitTyConApp_maybe first_inst_tau Just (tycon, arg_tys) = maybe_tycon_app - ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty - creturnable_type ty = isFFIResultTy ty + ccallable_type dflags ty = isFFIArgumentTy dflags PlayRisky ty + creturnable_type ty = isFFIImportResultTy dflags ty + +check_tyvars dflags clas inst_taus + -- Check that at least one isn't a type variable + -- unless -fallow-undecideable-instances + | dopt Opt_AllowUndecidableInstances dflags = [] + | not (all isTyVarTy inst_taus) = [] + | otherwise = [the_err] + where + the_err = instTypeErr clas inst_taus msg + msg = ptext SLIT("There must be at least one non-type-variable in the instance head") + $$ ptext SLIT("Use -fallow-undecidable-instances to lift this restriction") + +check_fundeps dflags theta clas inst_taus + | checkInstFDs theta clas inst_taus = [] + | otherwise = [the_err] + where + the_err = instTypeErr clas inst_taus msg + msg = ptext SLIT("the instance types do not agree with the functional dependencies of the class") \end{code} @@ -738,19 +846,25 @@ scrutiniseInstanceHead clas inst_taus \begin{code} tcAddDeclCtxt decl thing_inside - = tcAddSrcLoc loc $ + = tcAddSrcLoc (tcdLoc decl) $ tcAddErrCtxt ctxt $ thing_inside where - (name, loc, thing) - = case decl of - (ClassDecl _ name _ _ _ _ _ loc) -> (name, loc, "class") - (TySynonym name _ _ loc) -> (name, loc, "type synonym") - (TyData NewType _ name _ _ _ _ loc _ _) -> (name, loc, "newtype") - (TyData DataType _ name _ _ _ _ loc _ _) -> (name, loc, "data type") + thing = case decl of + ClassDecl {} -> "class" + TySynonym {} -> "type synonym" + TyData {tcdND = NewType} -> "newtype" + TyData {tcdND = DataType} -> "data type" ctxt = hsep [ptext SLIT("In the"), text thing, - ptext SLIT("declaration for"), quotes (ppr name)] + ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] + +instDeclCtxt inst_ty = ptext SLIT("In the instance declaration for") <+> quotes doc + where + doc = case inst_ty of + HsForAllTy _ _ (HsPredTy pred) -> ppr pred + HsPredTy pred -> ppr pred + other -> ppr inst_ty -- Don't expect this \end{code} \begin{code} @@ -778,16 +892,15 @@ dupGenericInsts tc_inst_infos ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst) instTypeErr clas tys msg - = sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys), + = sep [ptext SLIT("Illegal instance declaration for") <+> + quotes (pprClassPred clas tys), nest 4 (parens msg) ] nonBoxedPrimCCallErr clas inst_ty = hang (ptext SLIT("Unacceptable instance type for ccall-ish class")) - 4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"), - ppr inst_ty]) + 4 (pprClassPred clas [inst_ty]) methodCtxt = ptext SLIT("When checking the methods of an instance declaration") +superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration") \end{code} - -