X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=f6e6a996a9bf48a385b81903d90b2ea37fa28a91;hb=bee714f24278a678cd7082421cc27da4b9c4d72a;hp=53e30cc2b8bee50b40cd590d6da093dd7a2fc8ce;hpb=ecb2ccfb36c2b2b9605082eb6a0b0349ecb7dcfb;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 53e30cc..f6e6a99 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -9,11 +9,12 @@ module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where #include "HsVersions.h" -import CmdLineOpts ( DynFlag(..), dopt ) +import CmdLineOpts ( DynFlag(..) ) import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..), - MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), - andMonoBindList, collectMonoBinders, isClassDecl + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, + isClassDecl, isIfaceInstDecl, toHsType ) import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl, RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, @@ -23,59 +24,53 @@ import TcHsSyn ( TcMonoBinds, mkHsConApp ) import TcBinds ( tcSpecSigs ) import TcClassDcl ( tcMethodBind, badMethodErr ) import TcMonad -import TcType ( tcInstType ) -import Inst ( InstOrigin(..), - newDicts, newClassDicts, instToId, +import TcMType ( tcInstSigType, checkValidTheta, checkValidInstHead, instTypeErr, + UserTypeCtxt(..), SourceTyCtxt(..) ) +import TcType ( mkClassPred, mkTyVarTy, mkTyVarTys, tcSplitForAllTys, + tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, + TyVarDetails(..) + ) +import Inst ( InstOrigin(..), newDicts, instToId, LIE, mkLIE, emptyLIE, plusLIE, plusLIEs ) import TcDeriv ( tcDeriving ) -import TcEnv ( TcEnv, tcExtendGlobalValEnv, - tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcLookupClass, +import TcEnv ( TcEnv, tcExtendGlobalValEnv, isLocalThing, + tcExtendTyVarEnvForMeths, tcLookupId, tcLookupClass, InstInfo(..), pprInstInfo, simpleInstInfoTyCon, - simpleInstInfoTy, newDFunName, tcExtendTyVarEnv, - isLocalThing, + simpleInstInfoTy, newDFunName ) import InstEnv ( InstEnv, extendInstEnv ) -import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType, checkSigTyVars ) +import PprType ( pprClassPred ) +import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType ) +import TcUnify ( checkSigTyVars ) import TcSimplify ( tcSimplifyCheck ) import HscTypes ( HomeSymbolTable, DFunId, ModDetails(..), PackageInstEnv, PersistentRenamerState ) - +import Subst ( substTy, substTheta ) import DataCon ( classDataCon ) -import Class ( Class, DefMeth(..), classBigSig ) +import Class ( Class, classBigSig ) import Var ( idName, idType ) import VarSet ( emptyVarSet ) -import Maybes ( maybeToBool ) -import MkId ( mkDictFunId ) +import Id ( setIdLocalExported ) +import MkId ( mkDictFunId, unsafeCoerceId, eRROR_ID ) import FunDeps ( checkInstFDs ) import Generics ( validGenericInstanceType ) import Module ( Module, foldModuleEnv ) import Name ( getSrcLoc ) -import NameSet ( emptyNameSet, nameSetToList ) -import PrelInfo ( eRROR_ID ) -import PprType ( pprClassPred, pprPred ) -import TyCon ( TyCon, isSynTyCon ) -import Type ( splitDFunTy, isTyVarTy, - splitTyConApp_maybe, splitDictTy, - splitForAllTys, - tyVarsOfTypes, mkClassPred, mkTyVarTy, - getClassTys_maybe - ) -import Subst ( mkTopTyVarSubst, substClasses ) -import VarSet ( varSetElems ) -import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIImportResultTy ) -import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey ) +import NameSet ( unitNameSet, emptyNameSet, nameSetToList ) +import TyCon ( TyCon ) +import Subst ( mkTopTyVarSubst, substTheta ) +import TysWiredIn ( genericTyCons ) import Name ( Name ) import SrcLoc ( SrcLoc ) -import VarSet ( varSetElems ) import Unique ( Uniquable(..) ) +import Util ( lengthExceeds, isSingleton ) import BasicTypes ( NewOrData(..), Fixity ) import ErrUtils ( dumpIfSet_dyn ) import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc, - assocElts, extendAssoc_C, - equivClassesByUniq, minusList + assocElts, extendAssoc_C, equivClassesByUniq, minusList ) +import Maybe ( catMaybes ) import List ( partition ) import Outputable \end{code} @@ -177,38 +172,55 @@ tcInstDecls1 inst_env0 prs hst unf_env get_fixity this_mod decls inst_decls = [inst_decl | InstD inst_decl <- decls] tycl_decls = [decl | TyClD decl <- decls] clas_decls = filter isClassDecl tycl_decls + (iface_inst_ds, local_inst_ds) = partition isIfaceInstDecl inst_decls in -- (1) Do the ordinary instance declarations - mapNF_Tc tcInstDecl1 inst_decls `thenNF_Tc` \ inst_infos -> + mapNF_Tc tcLocalInstDecl1 local_inst_ds `thenNF_Tc` \ local_inst_infos -> + mapNF_Tc tcImportedInstDecl1 iface_inst_ds `thenNF_Tc` \ iface_dfuns -> -- (2) Instances from generic class declarations 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 + -- a) cached non-home-package InstEnv (gotten from pcs) inst_env0 -- b) imported instance decls (not in the home package) inst_env1 - -- c) other modules in this package (gotten from hst) inst_env2 - -- d) local instance decls inst_env3 - -- e) generic instances inst_env4 + -- c) imported instance decls (from this module) inst_env2 + -- c) other modules in this package (gotten from hst) inst_env3 + -- d) local instance decls inst_env4 + -- e) generic instances inst_env5 -- The result of (b) replaces the cached InstEnv in the PCS + -- + -- Note that iface_dfuns may contain not only insts that we demand-loaded + -- from package interface files, but also instances from the current module + -- in the case where we are loading this module's interface file in GHCi, + -- so we partition the iface_dfuns into package instances and local instances + -- below so that we don't end up with home package instances in the PCS. + -- + -- There can't be any instance declarations from the home + -- package other than from the current module (with the + -- compilation manager) because they are loaded explicitly by + -- the compilation manager. The partition is really only + -- necessary when we're under control of the compilation + -- manager. let - (local_inst_info, imported_inst_info) - = partition (isLocalThing this_mod . iDFunId) (concat inst_infos) + local_inst_info = catMaybes local_inst_infos + (local_iface_dfuns, pkg_iface_dfuns) = partition (isLocalThing this_mod) iface_dfuns + hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst + in - imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId) - imported_inst_info - hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst - in - addInstDFuns inst_env0 imported_dfuns `thenNF_Tc` \ inst_env1 -> +-- pprTrace "tcInstDecls" (vcat [ppr imported_dfuns, ppr hst_dfuns]) $ + + addInstDFuns inst_env0 pkg_iface_dfuns `thenNF_Tc` \ inst_env1 -> addInstDFuns inst_env1 hst_dfuns `thenNF_Tc` \ inst_env2 -> - addInstInfos inst_env2 local_inst_info `thenNF_Tc` \ inst_env3 -> - addInstInfos inst_env3 generic_inst_info `thenNF_Tc` \ inst_env4 -> + addInstDFuns inst_env2 local_iface_dfuns `thenNF_Tc` \ inst_env3 -> + addInstInfos inst_env3 local_inst_info `thenNF_Tc` \ inst_env4 -> + addInstInfos inst_env4 generic_inst_info `thenNF_Tc` \ inst_env5 -> -- (3) Compute instances from "deriving" clauses; -- note that we only do derivings for things in this module; -- 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 + -- needs to know about all the instances possible; hence inst_env4 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 -> @@ -222,56 +234,60 @@ addInstInfos :: InstEnv -> [InstInfo] -> NF_TcM InstEnv addInstInfos inst_env infos = addInstDFuns inst_env (map iDFunId infos) addInstDFuns :: InstEnv -> [DFunId] -> NF_TcM InstEnv -addInstDFuns dfuns infos - = getDOptsTc `thenTc` \ dflags -> +addInstDFuns inst_env dfuns + = getDOptsTc `thenNF_Tc` \ dflags -> let - (inst_env', errs) = extendInstEnv dflags dfuns infos + (inst_env', errs) = extendInstEnv dflags inst_env dfuns in addErrsTc errs `thenNF_Tc_` + traceTc (text "Adding instances:" <+> vcat (map pp dfuns)) `thenTc_` returnTc inst_env' + where + pp dfun = ppr dfun <+> dcolon <+> ppr (idType dfun) \end{code} \begin{code} -tcInstDecl1 :: RenamedInstDecl -> NF_TcM [InstInfo] --- Deal with a single instance declaration -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 $ - +tcImportedInstDecl1 :: RenamedInstDecl -> NF_TcM DFunId + -- An interface-file instance declaration + -- Should be in scope by now, because we should + -- have sucked in its interface-file definition + -- So it will be replete with its unfolding etc +tcImportedInstDecl1 decl@(InstDecl poly_ty binds uprags (Just dfun_name) src_loc) + = tcLookupId dfun_name + + +tcLocalInstDecl1 :: RenamedInstDecl + -> NF_TcM (Maybe InstInfo) -- Nothing if there was an error + -- A source-file instance declaration -- Type-check all the stuff before the "where" - tcAddErrCtxt (instDeclCtxt poly_ty) ( - tcHsSigType poly_ty - ) `thenTc` \ poly_ty' -> - let - (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty' - in - - (case maybe_dfun_name of - Nothing -> -- A source-file instance declaration - - -- Check for respectable instance type, and context - -- but only do this for non-imported instance decls. - -- Imported ones should have been checked already, and may indeed - -- contain something illegal in normal Haskell, notably - -- instance CCallable [Char] - getDOptsTc `thenTc` \ dflags -> - checkInstValidity dflags theta clas inst_tys `thenTc_` - - -- Make the dfun id and return it - newDFunName clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> - returnNF_Tc (True, dfun_name) - - Just dfun_name -> -- An interface-file instance declaration - -- Make the dfun id - returnNF_Tc (False, dfun_name) - ) `thenNF_Tc` \ (is_local, dfun_name) -> + -- + -- We check for respectable instance type, and context + -- but only do this for non-imported instance decls. + -- Imported ones should have been checked already, and may indeed + -- contain something illegal in normal Haskell, notably + -- instance CCallable [Char] +tcLocalInstDecl1 decl@(InstDecl poly_ty binds uprags Nothing src_loc) + = -- Prime error recovery, set source location + recoverNF_Tc (returnNF_Tc Nothing) $ + tcAddSrcLoc src_loc $ + tcAddErrCtxt (instDeclCtxt poly_ty) $ + -- Typecheck the instance type itself. We can't use + -- tcHsSigType, because it's not a valid user type. + kcHsSigType poly_ty `thenTc_` + tcHsType poly_ty `thenTc` \ poly_ty' -> let - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in - returnTc [InstInfo { iDFunId = dfun_id, - iBinds = binds, iPrags = uprags }] + checkValidTheta InstThetaCtxt theta `thenTc_` + checkValidInstHead tau `thenTc` \ (clas,inst_tys) -> + checkTc (checkInstFDs theta clas inst_tys) + (instTypeErr (pprClassPred clas inst_tys) msg) `thenTc_` + newDFunName clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> + returnTc (Just (InstInfo { iDFunId = mkDictFunId dfun_name clas tyvars inst_tys theta, + iBinds = binds, iPrags = uprags })) + where + msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class")) \end{code} @@ -315,7 +331,7 @@ getGenericInstances class_decls if null gen_inst_info then returnTc [] else - getDOptsTc `thenTc` \ dflags -> + getDOptsTc `thenNF_Tc` \ dflags -> ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" (vcat (map pprInstInfo gen_inst_info))) `thenNF_Tc_` @@ -328,7 +344,7 @@ get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, | null groups = returnTc [] -- The comon case: no generic default methods - | otherwise -- A local class decl with generic default methods + | otherwise -- A source class decl with generic default methods = recoverNF_Tc (returnNF_Tc []) $ tcAddDeclCtxt decl $ tcLookupClass class_name `thenTc` \ clas -> @@ -346,7 +362,7 @@ get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, - length group > 1] + group `lengthExceeds` 1] get_uniq (tc,_) = getUnique tc in mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_` @@ -395,12 +411,13 @@ mkGenericInstance clas loc (hs_ty, binds) -- 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 -> + tcHsSigType GenPatCtxt hs_ty `thenTc` \ inst_ty -> checkTc (validGenericInstanceType inst_ty) (badGenericInstanceType binds) `thenTc_` @@ -408,12 +425,10 @@ mkGenericInstance clas loc (hs_ty, binds) 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 + dfun_id = mkDictFunId dfun_name clas tyvars [inst_ty] inst_theta in - returnTc (InstInfo { iDFunId = dfun_id, - iBinds = binds, iPrags = [] }) + returnTc (InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = [] }) \end{code} @@ -506,54 +521,70 @@ 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 -> TcM (LIE, TcMonoBinds) + +tcInstDecl2 (NewTypeDerived { iDFunId = dfun_id }) + = tcInstSigType InstTv (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') -> + newDicts InstanceDeclOrigin dfun_theta' `thenNF_Tc` \ rep_dicts -> + let + rep_dict_id = ASSERT( isSingleton rep_dicts ) + instToId (head rep_dicts) -- Derived newtypes have just one dict arg + + body = TyLam inst_tyvars' $ + DictLam [rep_dict_id] $ + (HsVar unsafeCoerceId `TyApp` [idType rep_dict_id, inst_head']) + `HsApp` + (HsVar rep_dict_id) + -- You might wonder why we have the 'coerce'. It's because the + -- type equality mechanism isn't clever enough; see comments with Type.eqType. + -- So Lint complains if we don't have this. + in + returnTc (emptyLIE, VarMonoBind dfun_id body) -tcInstDecl2 (InstInfo { iDFunId = dfun_id, - iBinds = monobinds, iPrags = uprags }) +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = monobinds, iPrags = uprags }) = -- 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 - tcInstType (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> + tcInstSigType InstTv (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') -> let - (clas, inst_tys') = splitDictTy dict_ty' - origin = InstanceDeclOrigin - + Just pred = tcSplitPredTy_maybe inst_head' + (clas, inst_tys') = getClassPredTys pred (class_tyvars, sc_theta, _, op_items) = classBigSig clas - dm_ids = [dm_id | (_, DefMeth dm_id) <- op_items] 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 - - -- The type variable from the dict fun actually scope - -- over the bindings. They were gotten from - -- the original instance declaration - (inst_tyvars, _) = splitForAllTys (idType dfun_id) + bad_bndrs = collectMonoBinders monobinds `minusList` sel_names + (inst_tyvars, _) = tcSplitForAllTys (idType dfun_id) + origin = InstanceDeclOrigin in -- Check that all the method bindings come from this class mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_` -- Create dictionary Ids from the specified instance contexts. - newClassDicts origin sc_theta' `thenNF_Tc` \ sc_dicts -> - newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts -> - newClassDicts origin [(clas,inst_tys')] `thenNF_Tc` \ [this_dict] -> + 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 ( - -- Default-method Ids may be mentioned in synthesised RHSs + -- The type variable from the dict fun actually scope + -- over the bindings. They were gotten from + -- the original instance declaration + + -- Default-method Ids may be mentioned in synthesised RHSs, + -- but they'll already be in the environment. mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' dfun_theta' monobinds uprags True) op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) -> + ) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) -> -- Deal with SPECIALISE instance pragmas by making them -- look like SPECIALISE pragmas for the dfun @@ -598,9 +629,22 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, -- Create the result bindings let + local_dfun_id = setIdLocalExported dfun_id + -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId + dict_constr = classDataCon clas scs_and_meths = map instToId (sc_dicts ++ meth_insts) this_dict_id = instToId this_dict + inlines | null dfun_arg_dicts = emptyNameSet + | otherwise = 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. + -- + -- BUT: don't inline it if it's a constant dictionary; + -- we'll get all the benefit without inlining, and we get + -- a **lot** of code duplication if we inline it dict_rhs | null scs_and_meths @@ -632,8 +676,8 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, = AbsBinds zonked_inst_tyvars (map instToId dfun_arg_dicts) - [(inst_tyvars', dfun_id, this_dict_id)] - emptyNameSet -- No inlines (yet) + [(inst_tyvars', local_dfun_id, this_dict_id)] + inlines (lie_binds1 `AndMonoBinds` lie_binds2 `AndMonoBinds` method_binds `AndMonoBinds` @@ -643,99 +687,95 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, main_bind `AndMonoBinds` prag_binds) \end{code} - -%************************************************************************ -%* * -\subsection{Checking for a decent instance type} -%* * -%************************************************************************ - -@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ - -The exceptions to this syntactic checking: (1)~if the @GlasgowExts@ -flag is on, or (2)~the instance is imported (they must have been -compiled elsewhere). In these cases, we let them go through anyway. - -We can also have instances for functions: @instance Foo (a -> b) ...@. - -\begin{code} -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 - | dopt Opt_AllowUndecidableInstances dflags - = [] - - | Just (clas,tys) <- getClassTys_maybe pred, - all isTyVarTy tys - = [] - - | otherwise - = [instConstraintErr pred] - -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 - && not (ccallable_type dflags first_inst_tau)) - || - (clas `hasKey` cReturnableClassKey - && not (creturnable_type first_inst_tau)) - = [nonBoxedPrimCCallErr clas first_inst_tau] - - -- If GlasgowExts then check at least one isn't a type variable - | 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 - ) - = [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 - - -- Stuff for algebraic or -> type - 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 = 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") - -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} + ------------------------------ + 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. %************************************************************************ @@ -768,12 +808,6 @@ instDeclCtxt inst_ty = ptext SLIT("In the instance declaration for") <+> quotes \end{code} \begin{code} -instConstraintErr pred - = hang (ptext SLIT("Illegal constraint") <+> - quotes (pprPred pred) <+> - ptext SLIT("in instance context")) - 4 (ptext SLIT("(Instance contexts must constrain only type variables)")) - badGenericInstanceType binds = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), nest 4 (ppr binds)] @@ -781,8 +815,6 @@ badGenericInstanceType binds missingGenericInstances missing = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing - - 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)), @@ -791,16 +823,6 @@ dupGenericInsts tc_inst_infos where ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst) -instTypeErr clas tys msg - = 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 (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}