X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=b30af59741a722eda57a08c2cf1186b0a95f19d7;hb=0877011afd5886ee06df2e2723d631ff0686324f;hp=324ee715a2cb6f5404942c896d829df1e255f49a;hpb=cf158e40f528a008226e730f1e47ca6efa9ea8ad;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 324ee71..b30af59 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,80 +4,72 @@ \section[TcInstDecls]{Typechecking instance declarations} \begin{code} -module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where +module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls, + 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, toHsType +import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, + isClassDecl, isSourceInstDecl, toHsType ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl, +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, 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, instToId, - LIE, mkLIE, emptyLIE, plusLIE, plusLIEs ) -import TcDeriv ( tcDeriving ) -import TcEnv ( TcEnv, tcExtendGlobalValEnv, - tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcLookupClass, - InstInfo(..), pprInstInfo, simpleInstInfoTyCon, - simpleInstInfoTy, newDFunName, tcExtendTyVarEnv, - isLocalThing, +import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr ) +import TcRnMonad +import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr, + checkAmbiguity, UserTypeCtxt(..), SourceTyCtxt(..) ) +import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys, tyVarsOfType, + tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, mkTyVarTys, + TyVarDetails(..) ) -import InstEnv ( InstEnv, extendInstEnv ) -import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType, checkSigTyVars ) -import TcSimplify ( tcSimplifyCheck ) -import HscTypes ( HomeSymbolTable, DFunId, - ModDetails(..), PackageInstEnv, PersistentRenamerState +import Inst ( InstOrigin(..), tcInstClassOp, newDicts, instToId, showLIE ) +import TcDeriv ( tcDeriving ) +import TcEnv ( tcExtendGlobalValEnv, + tcLookupClass, tcExtendTyVarEnv2, + tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId, + InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon, + simpleInstInfoTy, newDFunName ) - +import PprType ( pprClassPred ) +import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType ) +import TcUnify ( checkSigTyVars ) +import TcSimplify ( tcSimplifyCheck, tcSimplifyTop ) +import HscTypes ( DFunId ) +import Subst ( mkTyVarSubst, substTheta, substTy ) 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 NameSet +import Id ( setIdLocalExported ) +import MkId ( mkDictFunId, rUNTIME_ERROR_ID ) import FunDeps ( checkInstFDs ) import Generics ( validGenericInstanceType ) -import Module ( Module, foldModuleEnv ) import Name ( getSrcLoc ) -import NameSet ( emptyNameSet, unitNameSet, nameSetToList ) -import PrelInfo ( eRROR_ID ) -import PprType ( pprClassPred, pprPred ) -import TyCon ( TyCon, isSynTyCon ) -import Type ( splitDFunTy, isTyVarTy, - splitTyConApp_maybe, splitDictTy, - splitForAllTys, - tyVarsOfTypes, mkClassPred, mkTyVarTy, - isTyVarClassPred, inheritablePred - ) -import Subst ( mkTopTyVarSubst, substTheta ) -import VarSet ( varSetElems ) -import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIImportResultTy ) -import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey ) -import Name ( Name ) +import NameSet ( unitNameSet, emptyNameSet, nameSetToList ) +import TyCon ( TyCon ) +import TysWiredIn ( genericTyCons ) import SrcLoc ( SrcLoc ) -import VarSet ( varSetElems ) import Unique ( Uniquable(..) ) -import BasicTypes ( NewOrData(..), Fixity ) +import Util ( lengthExceeds ) +import BasicTypes ( NewOrData(..) ) +import UnicodeUtil ( stringToUtf8 ) import ErrUtils ( dumpIfSet_dyn ) import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc, - assocElts, extendAssoc_C, - equivClassesByUniq, minusList + assocElts, extendAssoc_C, equivClassesByUniq, minusList ) -import List ( partition ) +import Maybe ( catMaybes ) +import List ( partition ) import Outputable +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -163,115 +155,108 @@ and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. Gather up the instance declarations from their various sources \begin{code} -tcInstDecls1 :: PackageInstEnv - -> PersistentRenamerState - -> HomeSymbolTable -- Contains instances - -> TcEnv -- Contains IdInfo for dfun ids - -> (Name -> Maybe Fixity) -- for deriving Show and Read - -> Module -- Module for deriving - -> [RenamedHsDecl] - -> TcM (PackageInstEnv, InstEnv, [InstInfo], RenamedHsBinds) - -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 +tcInstDecls1 -- Deal with both source-code and imported instance decls + :: [RenamedTyClDecl] -- For deriving stuff + -> [RenamedInstDecl] -- Source code instance decls + -> TcM (TcGblEnv, -- The full inst env + [InstInfo], -- Source-code instance decls to process; + -- contains all dfuns for this module + RenamedHsBinds, -- Supporting bindings for derived instances + FreeVars) -- And the free vars of the derived code + +tcInstDecls1 tycl_decls inst_decls + = checkNoErrs $ + -- Stop if addInstInfos etc discovers any errors + -- (they recover, so that we get more than one error each round) + let + (src_inst_decls, iface_inst_decls) = partition isSourceInstDecl inst_decls in + + -- (0) Deal with the imported instance decls + tcIfaceInstDecls iface_inst_decls `thenM` \ imp_dfuns -> + tcExtendInstEnv imp_dfuns $ + -- (1) Do the ordinary instance declarations - mapNF_Tc tcInstDecl1 inst_decls `thenNF_Tc` \ inst_infos -> + mappM tcLocalInstDecl1 src_inst_decls `thenM` \ local_inst_infos -> + let + local_inst_info = catMaybes local_inst_infos + clas_decls = filter isClassDecl tycl_decls + in -- (2) Instances from generic class declarations - getGenericInstances clas_decls `thenTc` \ generic_inst_info -> + getGenericInstances clas_decls `thenM` \ generic_inst_info -> -- Next, construct the instance environment so far, consisting of - -- a) cached non-home-package InstEnv (gotten from pcs) pcs_insts pcs - -- 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 - -- The result of (b) replaces the cached InstEnv in the PCS - let - (local_inst_info, imported_inst_info) - = partition (isLocalThing this_mod . iDFunId) (concat inst_infos) - - 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 -> - 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 -> + -- a) imported instance decls (from this module) + -- b) local instance decls + -- c) generic instances + tcExtendLocalInstEnv local_inst_info $ + tcExtendLocalInstEnv generic_inst_info $ -- (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 - 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, - final_inst_env, - generic_inst_info ++ deriv_inst_info ++ local_inst_info, - deriv_binds) - -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 -> - let - (inst_env', errs) = extendInstEnv dflags dfuns infos - in - addErrsTc errs `thenNF_Tc_` - returnTc inst_env' + -- needs to know about all the instances possible; hence inst_env4 + tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds, fvs) -> + tcExtendLocalInstEnv deriv_inst_info $ + + getGblEnv `thenM` \ gbl_env -> + returnM (gbl_env, + generic_inst_info ++ deriv_inst_info ++ local_inst_info, + deriv_binds, fvs) \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 $ - +tcLocalInstDecl1 :: RenamedInstDecl + -> 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' -> + -- + -- 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 + recoverM (returnM Nothing) $ + addSrcLoc src_loc $ + addErrCtxt (instDeclCtxt poly_ty) $ + + -- Typecheck the instance type itself. We can't use + -- tcHsSigType, because it's not a valid user type. + kcHsSigType poly_ty `thenM_` + tcHsType poly_ty `thenM` \ poly_ty' -> let - (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty' + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in + checkValidTheta InstThetaCtxt theta `thenM_` + checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_` + checkValidInstHead tau `thenM` \ (clas,inst_tys) -> + checkTc (checkInstFDs theta clas inst_tys) + (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_` + newDFunName clas inst_tys src_loc `thenM` \ dfun_name -> + returnM (Just (InstInfo { iDFunId = mkDictFunId dfun_name tyvars theta clas inst_tys, + iBinds = VanillaInst binds uprags })) + where + msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class")) +\end{code} - (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) -> +Imported instance declarations - let - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta - in - returnTc [InstInfo { iDFunId = dfun_id, - iBinds = binds, iPrags = uprags }] +\begin{code} +tcIfaceInstDecls :: [RenamedInstDecl] -> TcM [DFunId] +-- Deal with the instance decls, +tcIfaceInstDecls decls = mappM tcIfaceInstDecl decls + +tcIfaceInstDecl :: RenamedInstDecl -> 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 +tcIfaceInstDecl decl@(InstDecl poly_ty binds uprags (Just dfun_name) src_loc) + = tcLookupGlobalId dfun_name \end{code} @@ -308,33 +293,33 @@ gives rise to the instance declarations \begin{code} getGenericInstances :: [RenamedTyClDecl] -> TcM [InstInfo] getGenericInstances class_decls - = mapTc get_generics class_decls `thenTc` \ gen_inst_infos -> + = mappM get_generics class_decls `thenM` \ gen_inst_infos -> let gen_inst_info = concat gen_inst_infos in if null gen_inst_info then - returnTc [] + returnM [] 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 + getDOpts `thenM` \ dflags -> + ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" + (vcat (map pprInstInfo gen_inst_info))) + `thenM_` + returnM gen_inst_info get_generics decl@(ClassDecl {tcdMeths = Nothing}) - = returnTc [] -- Imported class decls + = returnM [] -- 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 + = returnM [] -- The comon case: no generic default methods - | otherwise -- A local class decl with generic default methods - = recoverNF_Tc (returnNF_Tc []) $ - tcAddDeclCtxt decl $ - tcLookupClass class_name `thenTc` \ clas -> + | otherwise -- A source class decl with generic default methods + = recoverM (returnM []) $ + tcAddDeclCtxt decl $ + tcLookupClass class_name `thenM` \ clas -> -- Make an InstInfo out of each group - mapTc (mkGenericInstance clas loc) groups `thenTc` \ inst_infos -> + mappM (mkGenericInstance clas loc) groups `thenM` \ inst_infos -> -- Check that there is only one InstInfo for each type constructor -- The main way this can fail is if you write @@ -346,18 +331,18 @@ 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_` + mappM (addErrTc . dupGenericInsts) bad_groups `thenM_` -- Check that there is an InstInfo for each generic type constructor let missing = genericTyCons `minusList` [tc | (tc,_) <- tc_inst_infos] in - checkTc (null missing) (missingGenericInstances missing) `thenTc_` + checkTc (null missing) (missingGenericInstances missing) `thenM_` - returnTc inst_infos + returnM inst_infos where -- Group the declarations by type pattern @@ -395,25 +380,24 @@ 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 `thenM` \ inst_ty -> checkTc (validGenericInstanceType inst_ty) - (badGenericInstanceType binds) `thenTc_` + (badGenericInstanceType binds) `thenM_` -- Make the dictionary function. - newDFunName clas [inst_ty] loc `thenNF_Tc` \ dfun_name -> + newDFunName clas [inst_ty] loc `thenM` \ 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 tyvars inst_theta clas [inst_ty] in - returnTc (InstInfo { iDFunId = dfun_id, - iBinds = binds, iPrags = [] }) + returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] }) \end{code} @@ -424,18 +408,10 @@ mkGenericInstance clas loc (hs_ty, binds) %************************************************************************ \begin{code} -tcInstDecls2 :: [InstInfo] - -> NF_TcM (LIE, TcMonoBinds) - +tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds tcInstDecls2 inst_decls --- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls - = foldr combine (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - (map tcInstDecl2 inst_decls) - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) + = mappM tcInstDecl2 inst_decls `thenM` \ binds_s -> + returnM (andMonoBindList binds_s) \end{code} ======= New documentation starts here (Sept 92) ============== @@ -506,107 +482,84 @@ 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 TcMonoBinds -tcInstDecl2 (InstInfo { iDFunId = dfun_id, - iBinds = monobinds, iPrags = uprags }) +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc (getSrcLoc dfun_id) $ - tcAddErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $ + recoverM (returnM EmptyMonoBinds) $ + addSrcLoc (getSrcLoc dfun_id) $ + addErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $ + let + inst_ty = idType dfun_id + (inst_tyvars, _) = tcSplitForAllTys inst_ty + -- The tyvars of the instance decl scope over the 'where' part + -- Those tyvars are inside the dfun_id's type, which is a bit + -- bizarre, but OK so long as you realise it! + in -- Instantiate the instance decl with tc-style type variables - tcInstType (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> + tcInstType InstTv inst_ty `thenM` \ (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' = 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) + sc_theta' = substTheta (mkTyVarSubst class_tyvars inst_tys') sc_theta + 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. - 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 + newDicts origin sc_theta' `thenM` \ sc_dicts -> + newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts -> + newDicts origin [pred] `thenM` \ [this_dict] -> + -- Default-method Ids may be mentioned in synthesised RHSs, + -- but they'll already be in the environment. + + ------------------ + -- Typecheck the methods + let -- These insts are in scope; quite a few, eh? + avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts + in + tcMethods clas inst_tyvars inst_tyvars' + dfun_theta' inst_tys' avail_insts + op_items binds `thenM` \ (meth_ids, meth_binds) -> - mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' - dfun_theta' - monobinds uprags True) - op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) -> + -- Figure out bindings for the superclass context + tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts + `thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) -> - -- Deal with SPECIALISE instance pragmas by making them + -- Deal with 'SPECIALISE instance' pragmas by making them -- look like SPECIALISE pragmas for the dfun let - dfun_prags = [SpecSig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags] + uprags = case binds of + VanillaInst _ uprags -> uprags + other -> [] + spec_prags = [ SpecSig (idName dfun_id) ty loc + | SpecInstSig ty loc <- uprags ] + xtve = inst_tyvars `zip` inst_tyvars' in tcExtendGlobalValEnv [dfun_id] ( - tcSpecSigs dfun_prags - ) `thenTc` \ (prag_binds, prag_lie) -> - - -- Check the overloading constraints of the methods and superclasses - let - -- These insts are in scope; quite a few, eh? - avail_insts = [this_dict] ++ - dfun_arg_dicts ++ - sc_dicts ++ - meth_insts - - methods_lie = plusLIEs insts_needed_s - in - - -- Simplify the constraints from methods - tcAddErrCtxt methodCtxt ( - tcSimplifyCheck - (ptext SLIT("instance declaration context")) - inst_tyvars' - avail_insts - methods_lie - ) `thenTc` \ (const_lie1, lie_binds1) -> - - -- Figure out bindings for the superclass context - tcAddErrCtxt superClassCtxt ( - tcSimplifyCheck - (ptext SLIT("instance declaration context")) - inst_tyvars' - dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts - -- get bound by just selecting from this_dict!! - (mkLIE sc_dicts) - ) `thenTc` \ (const_lie2, lie_binds2) -> - - checkSigTyVars inst_tyvars' emptyVarSet `thenNF_Tc` \ zonked_inst_tyvars -> + tcExtendTyVarEnv2 xtve $ + tcSpecSigs spec_prags + ) `thenM` \ prag_binds -> -- Create the result bindings let dict_constr = classDataCon clas - scs_and_meths = map instToId (sc_dicts ++ meth_insts) + scs_and_meths = map instToId sc_dicts ++ meth_ids this_dict_id = instToId this_dict - inlines = unitNameSet (idName dfun_id) + 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. + -- 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 + -- + -- See Note [Inline dfuns] below dict_rhs | null scs_and_meths @@ -616,8 +569,8 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, -- emit an error message. This in turn means that we don't -- mention the constructor, which doesn't exist for CCallable, CReturnable -- Hardly beautiful, but only three extra lines. - HsApp (TyApp (HsVar eRROR_ID) [idType this_dict_id]) - (HsLit (HsString msg)) + HsApp (TyApp (HsVar rUNTIME_ERROR_ID) [idType this_dict_id]) + (HsLit (HsStringPrim (mkFastString (stringToUtf8 msg)))) | otherwise -- The common case = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) @@ -629,123 +582,249 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, -- than needing to be repeated here. where - msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas)) - - dict_bind = VarMonoBind this_dict_id dict_rhs - method_binds = andMonoBindList method_binds_s - - main_bind - = AbsBinds - zonked_inst_tyvars - (map instToId dfun_arg_dicts) - [(inst_tyvars', dfun_id, this_dict_id)] - inlines - (lie_binds1 `AndMonoBinds` - lie_binds2 `AndMonoBinds` - method_binds `AndMonoBinds` - dict_bind) + msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas) + + dict_bind = VarMonoBind this_dict_id dict_rhs + all_binds = sc_binds_inner `AndMonoBinds` meth_binds `AndMonoBinds` dict_bind + + main_bind = AbsBinds + zonked_inst_tyvars + (map instToId dfun_arg_dicts) + [(inst_tyvars', dfun_id, this_dict_id)] + inlines all_binds + in + showLIE "instance" `thenM_` + returnM (main_bind `AndMonoBinds` prag_binds `AndMonoBinds` sc_binds_outer) + + +tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' + avail_insts op_items (VanillaInst monobinds uprags) + = -- Check that all the method bindings come from this class + let + sel_names = [idName sel_id | (sel_id, _) <- op_items] + bad_bndrs = collectMonoBinders monobinds `minusList` sel_names + in + mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` + + -- Make the method bindings + let + mk_method_bind = mkMethodBind InstanceDeclOrigin clas inst_tys' monobinds in - returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie, - main_bind `AndMonoBinds` prag_binds) + mapAndUnzipM mk_method_bind op_items `thenM` \ (meth_insts, meth_infos) -> + + -- And type check them + -- It's really worth making meth_insts available to the tcMethodBind + -- Consider instance Monad (ST s) where + -- {-# INLINE (>>) #-} + -- (>>) = ...(>>=)... + -- If we don't include meth_insts, we end up with bindings like this: + -- rec { dict = MkD then bind ... + -- then = inline_me (... (GHC.Base.>>= dict) ...) + -- bind = ... } + -- The trouble is that (a) 'then' and 'dict' are mutually recursive, + -- and (b) the inline_me prevents us inlining the >>= selector, which + -- would unravel the loop. Result: (>>) ends up as a loop breaker, and + -- is not inlined across modules. Rather ironic since this does not + -- happen without the INLINE pragma! + -- + -- Solution: make meth_insts available, so that 'then' refers directly + -- to the local 'bind' rather than going via the dictionary. + let + all_insts = avail_insts ++ meth_insts + xtve = inst_tyvars `zip` inst_tyvars' + tc_method_bind = tcMethodBind xtve inst_tyvars' dfun_theta' all_insts uprags + in + mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> + + returnM (map instToId meth_insts, andMonoBindList meth_binds_s) + + +-- Derived newtype instances +tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' + avail_insts op_items (NewTypeDerived rep_tys) + = getInstLoc InstanceDeclOrigin `thenM` \ inst_loc -> + mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) -> + + tcSimplifyCheck + (ptext SLIT("newtype derived instance")) + inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds -> + + -- I don't think we have to do the checkSigTyVars thing + + returnM (meth_ids, lie_binds `AndMonoBinds` andMonoBindList meth_binds) + + where + do_one inst_loc (sel_id, _) + = -- The binding is like "op @ NewTy = op @ RepTy" + -- Make the *binder*, like in mkMethodBind + tcInstClassOp inst_loc sel_id inst_tys' `thenM` \ meth_inst -> + + -- Make the *occurrence on the rhs* + tcInstClassOp inst_loc sel_id rep_tys' `thenM` \ rhs_inst -> + let + meth_id = instToId meth_inst + in + return (meth_id, VarMonoBind meth_id (HsVar (instToId rhs_inst)), rhs_inst) + + -- Instantiate rep_tys with the relevant type variables + rep_tys' = map (substTy subst) rep_tys + subst = mkTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars') \end{code} +Note: [Superclass loops] +~~~~~~~~~~~~~~~~~~~~~~~~~ +We have to be very, very careful when generating superclasses, lest we +accidentally build a loop. Here's an example: -%************************************************************************ -%* * -\subsection{Checking for a decent instance type} -%* * -%************************************************************************ + class S a + + class S a => C a where { opc :: a -> a } + class S b => D b where { opd :: b -> b } + + instance C Int where + opc = opd + + instance D Int where + opd = opc + +From (instance C Int) we get the constraint set {ds1:S Int, dd:D Int} +Simplifying, we may well get: + $dfCInt = :C ds1 (opd dd) + dd = $dfDInt + ds1 = $p1 dd +Notice that we spot that we can extract ds1 from dd. + +Alas! Alack! We can do the same for (instance D Int): + + $dfDInt = :D ds2 (opc dc) + dc = $dfCInt + ds2 = $p1 dc -@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ +And now we've defined the superclass in terms of itself. -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) ...@. +Solution: treat the superclass context separately, and simplify it +all the way down to nothing on its own. Don't toss any 'free' parts +out to be simplified together with other bits of context. +Hence the tcSimplifyTop below. + +At a more basic level, don't include this_dict in the context wrt +which we simplify sc_dicts, else sc_dicts get bound by just selecting +from this_dict!! \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 - -- 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 - && 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)" $$ - text "where T is not a synonym, and a,b,c are distinct type variables")] - - | otherwise - = [] +tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts + = addErrCtxt superClassCtxt $ + getLIE (tcSimplifyCheck doc inst_tyvars' + dfun_arg_dicts + sc_dicts) `thenM` \ (sc_binds1, sc_lie) -> - where - (first_inst_tau : _) = inst_taus + -- It's possible that the superclass stuff might have done unification + checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars -> - -- Stuff for algebraic or -> type - maybe_tycon_app = splitTyConApp_maybe first_inst_tau - Just (tycon, arg_tys) = maybe_tycon_app + -- We must simplify this all the way down + -- lest we build superclass loops + -- See Note [Superclass loops] above + tcSimplifyTop sc_lie `thenM` \ sc_binds2 -> - ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty - creturnable_type ty = isFFIImportResultTy dflags ty - -check_tyvars dflags clas inst_taus - -- Check that at least one isn't a type variable - -- unless -fallow-undecideable-instances - | dopt Opt_AllowUndecidableInstances dflags = [] - | not (all isTyVarTy inst_taus) = [] - | otherwise = [the_err] - where - the_err = instTypeErr clas inst_taus msg - msg = ptext SLIT("There must be at least one non-type-variable in the instance head") - $$ ptext SLIT("Use -fallow-undecidable-instances to lift this restriction") + returnM (zonked_inst_tyvars, sc_binds1, sc_binds2) -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") + doc = ptext SLIT("instance declaration superclass context") \end{code} + ------------------------------ + [Inline dfuns] 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. + + %************************************************************************ %* * \subsection{Error messages} @@ -754,8 +833,8 @@ check_fundeps dflags theta clas inst_taus \begin{code} tcAddDeclCtxt decl thing_inside - = tcAddSrcLoc (tcdLoc decl) $ - tcAddErrCtxt ctxt $ + = addSrcLoc (tcdLoc decl) $ + addErrCtxt ctxt $ thing_inside where thing = case decl of @@ -776,12 +855,6 @@ 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)] @@ -789,8 +862,6 @@ 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)), @@ -799,16 +870,6 @@ 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}