X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=6b17d3afb4f5f311f6bea25553123d38d04a5dd7;hb=e79e33b9d9cb29fb77494c814e28ee833b4939f8;hp=b992ce1458c9a477b40430e980f2a53a47da76ab;hpb=9e93335020e64a811dbbb223e1727c76933a93ae;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index b992ce1..6b17d3a 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,77 +4,71 @@ \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(..) ) -import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..), +import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), - andMonoBindList, collectMonoBinders, isClassDecl, toHsType + 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 TcMType ( tcInstTyVars, checkValidTheta, checkValidInstHead, instTypeErr, - UserTypeCtxt(..), SourceTyCtxt(..) ) -import TcType ( tcSplitDFunTy, mkClassPred, mkTyVarTy, - tcSplitSigmaTy, tcSplitPredTy_maybe, getClassPredTys +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 Inst ( InstOrigin(..), - newDicts, instToId, - LIE, mkLIE, emptyLIE, plusLIE, plusLIEs ) +import Inst ( InstOrigin(..), tcInstClassOp, newDicts, instToId, showLIE ) import TcDeriv ( tcDeriving ) -import TcEnv ( TcEnv, tcExtendGlobalValEnv, - tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcLookupClass, - InstInfo(..), pprInstInfo, simpleInstInfoTyCon, - simpleInstInfoTy, newDFunName, - isLocalThing, +import TcEnv ( tcExtendGlobalValEnv, + tcLookupClass, tcExtendTyVarEnv2, + tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId, + InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon, + simpleInstInfoTy, newDFunName ) -import InstEnv ( InstEnv, extendInstEnv ) import PprType ( pprClassPred ) -import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType, checkSigTyVars ) -import TcSimplify ( tcSimplifyCheck ) -import HscTypes ( HomeSymbolTable, DFunId, - ModDetails(..), PackageInstEnv, PersistentRenamerState - ) - -import Subst ( substTy, substTheta ) +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 Id ( setIdLocalExported ) -import MkId ( mkDictFunId ) +import NameSet +import MkId ( mkDictFunId, rUNTIME_ERROR_ID ) import FunDeps ( checkInstFDs ) import Generics ( validGenericInstanceType ) -import Module ( Module, foldModuleEnv ) import Name ( getSrcLoc ) import NameSet ( unitNameSet, emptyNameSet, nameSetToList ) -import PrelInfo ( eRROR_ID ) import TyCon ( TyCon ) -import Subst ( mkTopTyVarSubst, substTheta ) import TysWiredIn ( genericTyCons ) -import Name ( Name ) import SrcLoc ( SrcLoc ) import Unique ( Uniquable(..) ) import Util ( lengthExceeds ) -import BasicTypes ( NewOrData(..), Fixity ) +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 @@ -160,123 +154,110 @@ 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 - --- pprTrace "tcInstDecls" (vcat [ppr imported_dfuns, ppr hst_dfuns]) $ - - 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 inst_env dfuns - = getDOptsTc `thenTc` \ dflags -> - let - (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) + -- 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 --- Type-check all the stuff before the "where" -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 $ - tcAddErrCtxt (instDeclCtxt poly_ty) $ +tcLocalInstDecl1 :: RenamedInstDecl + -> TcM (Maybe InstInfo) -- Nothing if there was an error + -- A source-file instance declaration + -- Type-check all the stuff before the "where" + -- + -- 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 `thenTc_` - tcHsType poly_ty `thenTc` \ poly_ty' -> + kcHsSigType poly_ty `thenM_` + tcHsType poly_ty `thenM` \ poly_ty' -> let (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' - (clas,inst_tys) = case tcSplitPredTy_maybe tau of { Just st -> getClassPredTys st } - -- The checkValidInstHead makes sure these splits succeed 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] - checkValidTheta InstThetaCtxt theta `thenTc_` - checkValidInstHead tau `thenTc_` - checkTc (checkInstFDs theta clas inst_tys) - (instTypeErr (pprClassPred clas inst_tys) msg) `thenTc_` - newDFunName clas inst_tys src_loc - - Just dfun_name -> -- An interface-file instance declaration - returnNF_Tc dfun_name - ) `thenNF_Tc` \ dfun_name -> - let - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta - in - returnTc [InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = uprags }] + 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} +Imported instance declarations + +\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} + %************************************************************************ %* * @@ -311,33 +292,33 @@ 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 source class decl with generic default methods - = recoverNF_Tc (returnNF_Tc []) $ - tcAddDeclCtxt decl $ - tcLookupClass class_name `thenTc` \ clas -> + = 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 @@ -352,15 +333,15 @@ get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, 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 @@ -404,20 +385,18 @@ mkGenericInstance clas loc (hs_ty, binds) tcHsTyVars sig_tvs (kcHsSigType hs_ty) $ \ tyvars -> -- Type-check the instance type, and check its form - tcHsSigType GenPatCtxt 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} @@ -428,18 +407,10 @@ 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) ============== @@ -510,106 +481,71 @@ 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))) $ - - -- Instantiate the instance decl with tc-style type variables + recoverM (returnM EmptyMonoBinds) $ + addSrcLoc (getSrcLoc dfun_id) $ + addErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $ let - (inst_tyvars, dfun_theta, clas, inst_tys) = tcSplitDFunTy (idType dfun_id) + 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 - tcInstTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) -> - let - inst_tys' = map (substTy tenv) inst_tys - dfun_theta' = substTheta tenv dfun_theta - origin = InstanceDeclOrigin + -- Instantiate the instance decl with tc-style type variables + tcInstType InstTv inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') -> + let + 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 + 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' ( - -- The type variable from the dict fun actually scope - -- over the bindings. They were gotten from - -- the original instance declaration - tcExtendGlobalValEnv dm_ids ( - -- Default-method Ids may be mentioned in synthesised RHSs - - mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' - dfun_theta' - monobinds uprags True) - op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) -> - - -- 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] - 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 + 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) -> - -- 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) -> + tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts + `thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) -> - checkSigTyVars inst_tyvars' emptyVarSet `thenNF_Tc` \ zonked_inst_tyvars -> + -- Deal with 'SPECIALISE instance' pragmas by making them + -- look like SPECIALISE pragmas for the dfun + let + 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] ( + tcExtendTyVarEnv2 xtve $ + tcSpecSigs spec_prags + ) `thenM` \ prag_binds -> -- 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) + scs_and_meths = map instToId sc_dicts ++ meth_ids this_dict_id = instToId this_dict inlines | null dfun_arg_dicts = emptyNameSet | otherwise = unitNameSet (idName dfun_id) @@ -621,6 +557,8 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, -- 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 @@ -630,8 +568,8 @@ 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) @@ -643,28 +581,173 @@ 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', local_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 (text "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 - returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie, - main_bind `AndMonoBinds` prag_binds) + mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` + + -- Make the method bindings + let + mk_method_bind = mkMethodBind InstanceDeclOrigin clas inst_tys' monobinds + in + 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. + -- + -- BUT WATCH OUT! If the method type mentions the class variable, then + -- this optimisation is not right. Consider + -- class C a where + -- op :: Eq a => a + -- + -- instance C Int where + -- op = op + -- The occurrence of 'op' on the rhs gives rise to a constraint + -- op at Int + -- The trouble is that the 'meth_inst' for op, which is 'available', also + -- looks like 'op at Int'. But they are not the same. + let + all_insts = avail_insts ++ catMaybes 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 ([meth_id | (_,meth_id,_) <- meth_infos], + 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: + + 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 + +And now we've defined the superclass in terms of itself. + + +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} +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) -> + + -- It's possible that the superclass stuff might have done unification + checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars -> + + -- We must simplify this all the way down + -- lest we build superclass loops + -- See Note [Superclass loops] above + tcSimplifyTop sc_lie `thenM` \ sc_binds2 -> + + returnM (zonked_inst_tyvars, sc_binds1, sc_binds2) + + where + doc = ptext SLIT("instance declaration superclass context") +\end{code} + + ------------------------------ - Inlining dfuns unconditionally + [Inline dfuns] Inlining dfuns unconditionally ------------------------------ The code above unconditionally inlines dict funs. Here's why. @@ -762,8 +845,8 @@ simplified: only zeze2 is extracted and its body is simplified. \begin{code} tcAddDeclCtxt decl thing_inside - = tcAddSrcLoc (tcdLoc decl) $ - tcAddErrCtxt ctxt $ + = addSrcLoc (tcdLoc decl) $ + addErrCtxt ctxt $ thing_inside where thing = case decl of