X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=b9cf1ebc2472eedc29e1254b845b6ed0f8ff9cf1;hb=f53483a24f46fb3aa09052d8c00c0fc5d7d9dcca;hp=baf3b54dd625f6f6da15a6a63b04a5b08e8dad3b;hpb=1bba522f5ec82c43abd2ba4e84127b9c915dd020;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index baf3b54..b9cf1eb 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,58 +4,73 @@ \section[TcInstDecls]{Typechecking instance declarations} \begin{code} -module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where +module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls, + tcInstDecls2, tcAddDeclCtxt ) where #include "HsVersions.h" -import HsSyn ( HsDecl(..), InstDecl(..), - MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), - andMonoBindList + +import CmdLineOpts ( DynFlag(..) ) + +import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, + isClassDecl, isSourceInstDecl, toHsType + ) +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, + RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, + extractHsTyVars, maybeGenericMatch ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl ) import TcHsSyn ( TcMonoBinds, mkHsConApp ) - import TcBinds ( tcSpecSigs ) -import TcClassDcl ( tcMethodBind, checkFromThisClass ) -import TcMonad -import RnMonad ( RnNameSupply, FixityEnv ) -import Inst ( InstOrigin(..), - newDicts, newClassDicts, - LIE, emptyLIE, plusLIE, plusLIEs ) -import TcDeriv ( tcDeriving ) -import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcInstId, newDFunName +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 TcInstUtil ( InstInfo(..), classDataCon ) -import TcMonoType ( tcHsSigType ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( zonkTcSigTyVars ) - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, - foldBag, Bag +import Inst ( InstOrigin(..), newMethod, newMethodAtLoc, + newDicts, instToId, showLIE ) +import TcDeriv ( tcDeriving ) +import TcEnv ( tcExtendGlobalValEnv, + tcLookupClass, tcExtendTyVarEnv2, + tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId, + InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon, + simpleInstInfoTy, newDFunName ) -import CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances ) -import Class ( classBigSig ) +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, classBigSig ) import Var ( idName, idType ) -import Maybes ( maybeToBool, expectJust ) -import MkId ( mkDictFunId ) -import Module ( Module ) -import Name ( isLocallyDefined ) -import NameSet ( emptyNameSet ) -import PrelInfo ( eRROR_ID ) -import PprType ( pprConstraint ) -import TyCon ( isSynTyCon, tyConDerivings ) -import Type ( mkTyVarTys, splitSigmaTy, isTyVarTy, - splitTyConApp_maybe, splitDictTy_maybe, - splitAlgTyConApp_maybe, - classesToPreds, classesOfPreds, - unUsgTy, tyVarsOfTypes +import NameSet +import Id ( setIdLocalExported ) +import MkId ( mkDictFunId, rUNTIME_ERROR_ID ) +import FunDeps ( checkInstFDs ) +import Generics ( validGenericInstanceType ) +import Name ( getSrcLoc ) +import NameSet ( unitNameSet, emptyNameSet, nameSetToList ) +import TyCon ( TyCon ) +import TysWiredIn ( genericTyCons ) +import SrcLoc ( SrcLoc ) +import Unique ( Uniquable(..) ) +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 ) -import Subst ( mkTopTyVarSubst, substClasses ) -import VarSet ( mkVarSet, varSetElems ) -import TysWiredIn ( isFFIArgumentTy, isFFIResultTy ) -import Unique ( cCallableClassKey, cReturnableClassKey, hasKey ) +import Maybe ( catMaybes ) +import List ( partition ) import Outputable +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -131,75 +146,259 @@ Here, Bop1 \ldots Bopn bind the methods op1 \ldots opn, and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. \end{enumerate} + +%************************************************************************ +%* * +\subsection{Extracting instance decls} +%* * +%************************************************************************ + +Gather up the instance declarations from their various sources + \begin{code} -tcInstDecls1 :: ValueEnv -- Contains IdInfo for dfun ids - -> [RenamedHsDecl] - -> Module -- Module for deriving - -> FixityEnv -- For derivings - -> RnNameSupply -- For renaming derivings - -> TcM s (Bag InstInfo, - RenamedHsBinds) - -tcInstDecls1 unf_env decls mod fixs rn_name_supply - = -- Do the ordinary instance declarations - mapNF_Tc (tcInstDecl1 mod unf_env) - [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags -> +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 + mappM tcLocalInstDecl1 src_inst_decls `thenM` \ local_inst_infos -> + let - decl_inst_info = unionManyBags inst_info_bags + local_inst_info = catMaybes local_inst_infos + clas_decls = filter isClassDecl tycl_decls in - -- Handle "derived" instances; note that we only do derivings - -- for things in this module; we ignore deriving decls from - -- interfaces! - tcDeriving mod fixs rn_name_supply decl_inst_info - `thenTc` \ (deriv_inst_info, deriv_binds) -> + -- (2) Instances from generic class declarations + getGenericInstances clas_decls `thenM` \ generic_inst_info -> + + -- Next, construct the instance environment so far, consisting of + -- 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; 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} +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 `thenM_` + tcHsType poly_ty `thenM` \ poly_ty' -> let - full_inst_info = deriv_inst_info `unionBags` decl_inst_info + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in - returnTc (full_inst_info, deriv_binds) + 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 -tcInstDecl1 :: Module -> ValueEnv -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) +\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} -tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc) - = -- Prime error recovery, set source location - recoverNF_Tc (returnNF_Tc emptyBag) $ - tcAddSrcLoc src_loc $ - -- Type-check all the stuff before the "where" - tcHsSigType poly_ty `thenTc` \ poly_ty' -> +%************************************************************************ +%* * +\subsection{Extracting generic instance declaration from class declarations} +%* * +%************************************************************************ + +@getGenericInstances@ extracts the generic instance declarations from a class +declaration. For exmaple + + class C a where + op :: a -> a + + op{ x+y } (Inl v) = ... + op{ x+y } (Inr v) = ... + op{ x*y } (v :*: w) = ... + op{ 1 } Unit = ... + +gives rise to the instance declarations + + instance C (x+y) where + op (Inl v) = ... + op (Inr v) = ... + + instance C (x*y) where + op (v :*: w) = ... + + instance C 1 where + op Unit = ... + + +\begin{code} +getGenericInstances :: [RenamedTyClDecl] -> TcM [InstInfo] +getGenericInstances class_decls + = mappM get_generics class_decls `thenM` \ gen_inst_infos -> let - (tyvars, theta, dict_ty) = splitSigmaTy poly_ty' - constr = classesOfPreds theta - (clas, inst_tys) = case splitDictTy_maybe dict_ty of - Just ct -> ct - Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty) + gen_inst_info = concat gen_inst_infos in + if null gen_inst_info then + returnM [] + else + 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}) + = returnM [] -- Imported class decls + +get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tcdLoc = loc}) + | null groups + = returnM [] -- The comon case: no generic default methods + + | 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 + 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 + -- f {| a+b |} ... = ... + -- f {| x+y |} ... = ... + -- Then at this point we'll have an InstInfo for each + let + tc_inst_infos :: [(TyCon, InstInfo)] + tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] + + bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, + group `lengthExceeds` 1] + get_uniq (tc,_) = getUnique tc + in + 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) `thenM_` + + returnM inst_infos + + where + -- Group the declarations by type pattern + groups :: [(RenamedHsType, RenamedMonoBinds)] + groups = assocElts (getGenericBinds def_methods) + - (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] - scrutiniseInstanceHead clas inst_tys `thenNF_Tc_` - mapNF_Tc scrutiniseInstanceConstraint constr `thenNF_Tc_` - - -- Make the dfun id and return it - newDFunName mod clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> - returnNF_Tc (mkDictFunId dfun_name clas tyvars inst_tys constr) - - Just dfun_name -> -- An interface-file instance declaration - -- Make the dfun id and add info from interface file - let - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys constr - in - returnNF_Tc (tcAddImportedIdInfo unf_env dfun_id) - ) `thenNF_Tc` \ dfun_id -> - - returnTc (unitBag (InstInfo clas tyvars inst_tys constr dfun_id binds src_loc uprags)) +--------------------------------- +getGenericBinds :: RenamedMonoBinds -> Assoc RenamedHsType RenamedMonoBinds + -- Takes a group of method bindings, finds the generic ones, and returns + -- them in finite map indexed by the type parameter in the definition. + +getGenericBinds EmptyMonoBinds = emptyAssoc +getGenericBinds (AndMonoBinds m1 m2) + = plusAssoc_C AndMonoBinds (getGenericBinds m1) (getGenericBinds m2) + +getGenericBinds (FunMonoBind id infixop matches loc) + = mapAssoc wrap (foldl add emptyAssoc matches) + -- Using foldl not foldr is vital, else + -- we reverse the order of the bindings! + where + add env match = case maybeGenericMatch match of + Nothing -> env + Just (ty, match') -> extendAssoc_C (++) env (ty, [match']) + + wrap ms = FunMonoBind id infixop ms loc + +--------------------------------- +mkGenericInstance :: Class -> SrcLoc + -> (RenamedHsType, RenamedMonoBinds) + -> TcM InstInfo + +mkGenericInstance clas loc (hs_ty, binds) + -- Make a generic instance declaration + -- For example: instance (C a, C b) => C (a+b) where { binds } + + = -- Extract the universally quantified type variables + 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 GenPatCtxt hs_ty `thenM` \ inst_ty -> + checkTc (validGenericInstanceType inst_ty) + (badGenericInstanceType binds) `thenM_` + + -- Make the dictionary function. + newDFunName clas [inst_ty] loc `thenM` \ dfun_name -> + let + inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] + dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty] + in + + returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] }) \end{code} @@ -210,19 +409,12 @@ tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc) %************************************************************************ \begin{code} -tcInstDecls2 :: Bag InstInfo - -> NF_TcM s (LIE, TcMonoBinds) - +tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds tcInstDecls2 inst_decls - = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) 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) ============== The main purpose of @tcInstDecl2@ is to return a @HsBinds@ which defines @@ -289,127 +481,89 @@ is the @dfun_theta@ below. First comes the easy case of a non-local instance decl. -\begin{code} -tcInstDecl2 :: InstInfo -> NF_TcM s (LIE, TcMonoBinds) -tcInstDecl2 (InstInfo clas inst_tyvars inst_tys - inst_decl_theta - dfun_id monobinds - locn uprags) - | not (isLocallyDefined dfun_id) - = returnNF_Tc (emptyLIE, EmptyMonoBinds) +\begin{code} +tcInstDecl2 :: InstInfo -> TcM TcMonoBinds - | otherwise +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc locn $ - - -- Check that all the method bindings come from this class - checkFromThisClass clas monobinds `thenNF_Tc_` + 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 - tcInstId 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') = expectJust "tcInstDecl2" (splitDictTy_maybe 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 | (_, dm_id, _) <- op_items] - - -- Instantiate the theta found in the original instance decl - inst_decl_theta' = substClasses (mkTopTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')) - inst_decl_theta - - -- Instantiate the super-class context with inst_tys - sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys') sc_theta + -- Instantiate the super-class context with inst_tys + sc_theta' = substTheta (mkTyVarSubst class_tyvars inst_tys') sc_theta + origin = InstanceDeclOrigin in -- Create dictionary Ids from the specified instance contexts. - newClassDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) -> - newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) -> - newClassDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) -> - newClassDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - - tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' ( - tcExtendGlobalValEnv dm_ids ( - -- Default-method Ids may be mentioned in synthesised RHSs - - mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' - (classesToPreds inst_decl_theta') - monobinds uprags True) - op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) -> - - -- 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] + 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 - tcExtendGlobalValEnv [dfun_id] ( - tcSpecSigs dfun_prags - ) `thenTc` \ (prag_binds, prag_lie) -> + tcMethods clas inst_tyvars inst_tyvars' + dfun_theta' inst_tys' avail_insts + op_items binds `thenM` \ (meth_ids, meth_binds) -> - -- Check the overloading constraints of the methods and superclasses + -- 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) -> - -- tcMethodBind has checked that the class_tyvars havn't - -- been unified with each other or another type, but we must - -- still zonk them before passing them to tcSimplifyAndCheck - zonkTcSigTyVars inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars -> + -- Deal with 'SPECIALISE instance' pragmas by making them + -- look like SPECIALISE pragmas for the dfun let - inst_tyvars_set = mkVarSet zonked_inst_tyvars - - (meth_lies, meth_ids) = unzip meth_lies_w_ids - - -- These insts are in scope; quite a few, eh? - avail_insts = this_dict `plusLIE` - dfun_arg_dicts `plusLIE` - sc_dicts `plusLIE` - unionManyBags meth_lies - - methods_lie = plusLIEs insts_needed_s + 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 - - -- Ditto method bindings - tcAddErrCtxt methodCtxt ( - tcSimplifyAndCheck - (ptext SLIT("instance declaration context")) - inst_tyvars_set -- Local tyvars - avail_insts - methods_lie - ) `thenTc` \ (const_lie1, lie_binds1) -> - - -- Check that we *could* construct the superclass dictionaries, - -- even though we are *actually* going to pass the superclass dicts in; - -- the check ensures that the caller will never have - --a problem building them. - tcAddErrCtxt superClassCtxt ( - tcSimplifyAndCheck - (ptext SLIT("instance declaration context")) - inst_tyvars_set -- Local tyvars - inst_decl_dicts -- The instance dictionaries available - sc_dicts -- The superclass dicationaries reqd - ) `thenTc` \ _ -> - -- Ignore the result; we're only doing - -- this to make sure it can be done. - - -- Now do the simplification again, this time to get the - -- bindings; this time we use an enhanced "avails" - -- Ignore errors because they come from the *previous* tcSimplify - discardErrsTc ( - tcSimplifyAndCheck - (ptext SLIT("instance declaration context")) - inst_tyvars_set - dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts - -- get bound by just selecting from this_dict!! - sc_dicts - ) `thenTc` \ (const_lie2, lie_binds2) -> - + 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 = sc_dict_ids ++ meth_ids + 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) + -- 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 + -- + -- See Note [Inline dfuns] below dict_rhs | null scs_and_meths @@ -419,11 +573,11 @@ tcInstDecl2 (InstInfo clas inst_tyvars inst_tys -- 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) [(unUsgTy . 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 (sc_dict_ids ++ meth_ids)) + = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) -- We don't produce a binding for the dict_constr; instead we -- rely on the simplifier to unfold this saturated application -- We do this rather than generate an HsCon directly, because @@ -432,129 +586,274 @@ tcInstDecl2 (InstInfo clas inst_tyvars inst_tys -- 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 - dfun_arg_dicts_ids - [(inst_tyvars', dfun_id, this_dict_id)] - emptyNameSet -- No inlines (yet) - (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', local_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 - 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 + mapAndUnzipM do_one op_items `thenM` \ (meth_ids, meth_binds_s) -> + + returnM (meth_ids, andMonoBindList meth_binds_s) + + where + xtve = inst_tyvars `zip` inst_tyvars' + do_one op_item + = mkMethodBind InstanceDeclOrigin clas + inst_tys' monobinds op_item `thenM` \ (meth_inst, meth_info) -> + tcMethodBind xtve inst_tyvars' dfun_theta' + avail_insts uprags meth_info `thenM` \ meth_bind -> + -- Could add meth_insts to avail_insts, but not worth the bother + returnM (instToId meth_inst, meth_bind) + +-- 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 -> + getLIE (mapAndUnzipM (do_one inst_loc) op_items) `thenM` \ ((meth_ids, meth_binds), lie) -> + + tcSimplifyCheck + (ptext SLIT("newtype derived instance")) + inst_tyvars' avail_insts lie `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, _) + = newMethodAtLoc inst_loc sel_id inst_tys' `thenM` \ meth_inst -> + -- Like in mkMethodBind + newMethod InstanceDeclOrigin sel_id rep_tys' `thenM` \ rhs_id -> + -- The binding is like "op @ NewTy = op @ RepTy" + let + meth_id = instToId meth_inst + in + return (meth_id, VarMonoBind meth_id (HsVar rhs_id)) + + -- 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. -@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ +Alas! Alack! We can do the same for (instance D Int): -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. + $dfDInt = :D ds2 (opc dc) + dc = $dfCInt + ds2 = $p1 dc -We can also have instances for functions: @instance Foo (a -> b) ...@. +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} -scrutiniseInstanceConstraint (clas, tys) - | all isTyVarTy tys - || opt_AllowUndecidableInstances = returnNF_Tc () - | otherwise = addErrTc (instConstraintErr clas tys) - -scrutiniseInstanceHead 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 first_inst_tau)) || - (clas `hasKey` cReturnableClassKey && not (creturnable_type first_inst_tau)) - = addErrTc (nonBoxedPrimCCallErr clas first_inst_tau) - - -- DERIVING CHECK - -- It is obviously illegal to have an explicit instance - -- for something that we are also planning to `derive' - | maybeToBool alg_tycon_app_maybe && clas `elem` (tyConDerivings alg_tycon) - = addErrTc (derivingWhenInstanceExistsErr clas first_inst_tau) - -- Kind check will have ensured inst_taus is of length 1 - - -- Allow anything for AllowUndecidableInstances - | opt_AllowUndecidableInstances - = returnNF_Tc () - - -- If GlasgowExts then check at least one isn't a type variable - | opt_GlasgowExts - = if all isTyVarTy inst_taus then - addErrTc (instTypeErr clas inst_taus (text "There must be at least one non-type-variable in the instance head")) - else - returnNF_Tc () - - -- WITH HASKELL 1.4, MUST HAVE C (T a b c) - | not (length inst_taus == 1 && - maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor - not (isSynTyCon tycon) && -- ...but not a synonym - all isTyVarTy arg_tys && -- Applied to type variables - length (varSetElems (tyVarsOfTypes arg_tys)) == length arg_tys - -- This last condition checks that all the type variables are distinct - ) - = addErrTc (instTypeErr clas inst_taus - (text "the instance type must be of form (T a b c)" $$ - text "where T is not a synonym, and a,b,c are distinct type variables") - ) - - | otherwise - = returnNF_Tc () +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 - (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 - - -- Stuff for an *algebraic* data type - alg_tycon_app_maybe = splitAlgTyConApp_maybe first_inst_tau - -- The "Alg" part looks through synonyms - Just (alg_tycon, _, _) = alg_tycon_app_maybe - -ccallable_type ty = isFFIArgumentTy False {- Not safe call -} ty -creturnable_type ty = isFFIResultTy ty + doc = ptext SLIT("instance declaration superclass context") \end{code} -\begin{code} -instConstraintErr clas tys - = hang (ptext SLIT("Illegal constraint") <+> - quotes (pprConstraint clas tys) <+> - ptext SLIT("in instance context")) - 4 (ptext SLIT("(Instance contexts must constrain only type variables)")) - -instTypeErr clas tys msg - = sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys), - nest 4 (parens msg) - ] -derivingWhenInstanceExistsErr clas tycon - = hang (hsep [ptext SLIT("Deriving class"), - quotes (ppr clas), - ptext SLIT("type"), quotes (ppr tycon)]) - 4 (ptext SLIT("when an explicit instance exists")) + ------------------------------ + [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} +%* * +%************************************************************************ + +\begin{code} +tcAddDeclCtxt decl thing_inside + = addSrcLoc (tcdLoc decl) $ + addErrCtxt ctxt $ + thing_inside + where + thing = case decl of + ClassDecl {} -> "class" + TySynonym {} -> "type synonym" + TyData {tcdND = NewType} -> "newtype" + TyData {tcdND = DataType} -> "data type" + + ctxt = hsep [ptext SLIT("In the"), text thing, + ptext SLIT("declaration for"), quotes (ppr (tcdName decl))] + +instDeclCtxt inst_ty = ptext SLIT("In the instance declaration for") <+> quotes doc + where + doc = case inst_ty of + HsForAllTy _ _ (HsPredTy pred) -> ppr pred + HsPredTy pred -> ppr pred + other -> ppr inst_ty -- Don't expect this +\end{code} -nonBoxedPrimCCallErr clas inst_ty - = hang (ptext SLIT("Unacceptable instance type for ccall-ish class")) - 4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"), - ppr inst_ty]) +\begin{code} +badGenericInstanceType binds + = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), + nest 4 (ppr 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)), + ptext SLIT("All the type patterns for a generic type constructor must be identical") + ] + where + ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst) methodCtxt = ptext SLIT("When checking the methods of an instance declaration") -superClassCtxt = ptext SLIT("When checking the superclasses of an instance declaration") +superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration") \end{code}