X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=b30af59741a722eda57a08c2cf1186b0a95f19d7;hb=0877011afd5886ee06df2e2723d631ff0686324f;hp=d99f93ddc2e232817a18831d9ae81476fadee439;hpb=d133b73a4d4717892ced072d05e039a54ede0ceb;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index d99f93d..b30af59 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,65 +4,72 @@ \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(..), - HsBinds(..), MonoBinds(..), - HsExpr(..), InPat(..), HsLit(..), Sig(..), - collectMonoBinders, andMonoBindList + +import CmdLineOpts ( DynFlag(..) ) + +import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, + isClassDecl, isSourceInstDecl, toHsType ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl ) -import TcHsSyn ( TcMonoBinds, - maybeBoxedPrimType +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, + RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, + extractHsTyVars, maybeGenericMatch ) - -import TcBinds ( tcPragmaSigs ) -import TcClassDcl ( tcMethodBind, badMethodErr ) -import TcMonad -import RnMonad ( RnNameSupply, Fixities ) -import Inst ( Inst, InstOrigin(..), - newDicts, LIE, emptyLIE, plusLIE, plusLIEs ) -import TcDeriv ( tcDeriving ) -import TcEnv ( ValueEnv, tcExtendGlobalValEnv, tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcInstId +import TcHsSyn ( TcMonoBinds, mkHsConApp ) +import TcBinds ( tcSpecSigs ) +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 ( tcHsTopType ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( TcTyVar, zonkTcTyVarBndr ) - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, - foldBag, bagToList, Bag +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 CmdLineOpts ( opt_GlasgowExts, opt_AllowUndecidableInstances ) -import Class ( classBigSig, Class ) -import Var ( setIdInfo, idName, idType, Id, TyVar ) -import DataCon ( isNullaryDataCon, dataConArgTys, dataConId ) -import Maybes ( maybeToBool, catMaybes, expectJust ) -import MkId ( mkDictFunId ) -import Module ( Module ) -import Name ( nameOccName, isLocallyDefined, NamedThing(..) ) -import PrelVals ( eRROR_ID ) -import PprType ( pprConstraint ) -import SrcLoc ( SrcLoc ) -import TyCon ( isSynTyCon, isDataTyCon, tyConDerivings ) -import Type ( Type, isUnLiftedType, mkTyVarTys, - splitSigmaTy, isTyVarTy, - splitTyConApp_maybe, splitDictTy_maybe, unUsgTy, - splitAlgTyConApp_maybe, - tyVarsOfTypes, substTopTheta +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 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 VarEnv ( zipVarEnv ) -import VarSet ( mkVarSet, varSetElems ) -import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon ) -import TysWiredIn ( stringTy ) -import Unique ( Unique, cCallableClassKey, cReturnableClassKey, Uniquable(..) ) +import Maybe ( catMaybes ) +import List ( partition ) import Outputable +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -138,95 +145,275 @@ Here, Bop1 \ldots Bopn bind the methods op1 \ldots opn, and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. \end{enumerate} -\begin{code} -tcInstDecls1 :: ValueEnv -- Contains IdInfo for dfun ids - -> [RenamedHsDecl] - -> Module -- module name for deriving - -> Fixities - -> RnNameSupply -- for renaming derivings - -> TcM s (Bag InstInfo, - RenamedHsBinds) - -tcInstDecls1 unf_env decls mod_name fixs rn_name_supply - = -- Do the ordinary instance declarations - mapNF_Tc (tcInstDecl1 unf_env mod_name) - [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags -> - let - decl_inst_info = unionManyBags inst_info_bags - in - -- Handle "derived" instances; note that we only do derivings - -- for things in this module; we ignore deriving decls from - -- interfaces! - tcDeriving mod_name fixs rn_name_supply decl_inst_info - `thenTc` \ (deriv_inst_info, deriv_binds) -> +%************************************************************************ +%* * +\subsection{Extracting instance decls} +%* * +%************************************************************************ + +Gather up the instance declarations from their various sources + +\begin{code} +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 - full_inst_info = deriv_inst_info `unionBags` decl_inst_info + (src_inst_decls, iface_inst_decls) = partition isSourceInstDecl inst_decls in - returnTc (full_inst_info, deriv_binds) - -tcInstDecl1 :: ValueEnv -> Module -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) + -- (0) Deal with the imported instance decls + tcIfaceInstDecls iface_inst_decls `thenM` \ imp_dfuns -> + tcExtendInstEnv imp_dfuns $ -tcInstDecl1 unf_env mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc) - = -- Prime error recovery, set source location - recoverNF_Tc (returnNF_Tc emptyBag) $ - tcAddSrcLoc src_loc $ + -- (1) Do the ordinary instance declarations + mappM tcLocalInstDecl1 src_inst_decls `thenM` \ local_inst_infos -> - -- Type-check all the stuff before the "where" - tcHsTopType poly_ty `thenTc` \ poly_ty' -> let - (tyvars, theta, dict_ty) = splitSigmaTy poly_ty' - (clas, inst_tys) = case splitDictTy_maybe dict_ty of - Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty) - Just pair -> pair + local_inst_info = catMaybes local_inst_infos + clas_decls = filter isClassDecl tycl_decls in + -- (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} - -- Check for respectable instance type, and context +\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] - (if isLocallyDefined dfun_name then - scrutiniseInstanceHead clas inst_tys `thenNF_Tc_` - mapNF_Tc scrutiniseInstanceConstraint theta - else - returnNF_Tc [] - ) `thenNF_Tc_` - - -- Make the dfun id and constant-method ids +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 - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta - - -- Add info from interface file - final_dfun_id = tcAddImportedIdInfo unf_env dfun_id + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in - returnTc (unitBag (InstInfo clas tyvars inst_tys theta - final_dfun_id - binds src_loc 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} %************************************************************************ %* * -\subsection{Type-checking instance declarations, pass 2} +\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} -tcInstDecls2 :: Bag InstInfo - -> NF_TcM s (LIE, TcMonoBinds) +getGenericInstances :: [RenamedTyClDecl] -> TcM [InstInfo] +getGenericInstances class_decls + = mappM get_generics class_decls `thenM` \ gen_inst_infos -> + let + 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] -tcInstDecls2 inst_decls - = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls + 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) + + +--------------------------------- +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 - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) + 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} +%************************************************************************ +%* * +\subsection{Type-checking instance declarations, pass 2} +%* * +%************************************************************************ + +\begin{code} +tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds +tcInstDecls2 inst_decls + = 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 @@ -293,144 +480,86 @@ 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) - -{- - -- I deleted this "optimisation" because when importing these - -- instance decls the renamer would look for the dfun bindings and they weren't there. - -- This would be fixable, but it seems simpler just to produce a tiny void binding instead, - -- even though it's never used. - - -- This case deals with CCallable etc, which don't need any bindings - | isNoDictClass clas - = returnNF_Tc (emptyLIE, EmptyBinds) --} - - | otherwise +tcInstDecl2 :: InstInfo -> TcM TcMonoBinds + +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc locn $ + 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') + Just pred = tcSplitPredTy_maybe inst_head' + (clas, inst_tys') = getClassPredTys pred + (class_tyvars, sc_theta, _, op_items) = classBigSig clas - origin = InstanceDeclOrigin - - (class_tyvars, - sc_theta, sc_sel_ids, - op_sel_ids, defm_ids) = classBigSig clas - - -- Instantiate the theta found in the original instance decl - inst_decl_theta' = substTopTheta (zipVarEnv inst_tyvars (mkTyVarTys inst_tyvars')) - inst_decl_theta - - -- Instantiate the super-class context with inst_tys - sc_theta' = substTopTheta (zipVarEnv 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. - newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) -> - newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) -> - newDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) -> - newDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - - -- Check that all the method bindings come from this class - let - check_from_this_class (bndr, loc) - | nameOccName bndr `elem` sel_names = returnNF_Tc () - | otherwise = tcAddSrcLoc loc $ - addErrTc (badMethodErr bndr clas) - sel_names = map getOccName op_sel_ids - bndrs = bagToList (collectMonoBinders monobinds) + 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 - mapNF_Tc check_from_this_class bndrs `thenNF_Tc_` - - tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' ( - tcExtendGlobalValEnv (catMaybes defm_ids) ( - -- Default-method Ids may be mentioned in synthesised RHSs + 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' inst_decl_theta' - monobinds uprags True) - (op_sel_ids `zip` defm_ids) - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) -> + -- 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 + -- Deal with 'SPECIALISE instance' pragmas by making them + -- look like SPECIALISE pragmas for the dfun let - dfun_prags = [Sig (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] ( - tcPragmaSigs dfun_prags - ) `thenTc` \ (prag_info_fn, prag_binds, prag_lie) -> - - -- Check the overloading constraints of the methods and superclasses - - -- tcMethodBind has checked that the class_tyvars havn't - -- been unified with each other or another type, but we must - -- still zonk them - mapNF_Tc zonkTcTyVarBndr inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars -> - let - inst_tyvars_set = mkVarSet zonked_inst_tyvars - - (meth_lies, meth_ids) = unzip meth_lies_w_ids - - -- These insts are in scope; quite a few, eh? - avail_insts = this_dict `plusLIE` - dfun_arg_dicts `plusLIE` - sc_dicts `plusLIE` - unionManyBags meth_lies - - methods_lie = plusLIEs insts_needed_s - 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) -> - + tcExtendTyVarEnv2 xtve $ + tcSpecSigs spec_prags + ) `thenM` \ prag_binds -> -- Create the result bindings let dict_constr = classDataCon clas - scs_and_meths = sc_dict_ids ++ meth_ids + scs_and_meths = map instToId sc_dicts ++ meth_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 @@ -440,198 +569,307 @@ 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]) - (HsLitOut (HsString msg) stringTy) + HsApp (TyApp (HsVar rUNTIME_ERROR_ID) [idType this_dict_id]) + (HsLit (HsStringPrim (mkFastString (stringToUtf8 msg)))) | otherwise -- The common case - = foldl HsApp (TyApp (HsVar (dataConId 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 -- it means that the special cases (e.g. dictionary with only one - -- member) are dealt with by the common MkId.mkDataConId code rather + -- member) are dealt with by the common MkId.mkDataConWrapId code rather -- 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 - - final_dfun_id = setIdInfo dfun_id (prag_info_fn (idName dfun_id)) - -- Pretty truesome - main_bind - = AbsBinds - zonked_inst_tyvars - dfun_arg_dicts_ids - [(inst_tyvars', final_dfun_id, this_dict_id)] - (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 + 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 - returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie, - main_bind `AndMonoBinds` prag_binds) + 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): -@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ + $dfDInt = :D ds2 (opc dc) + dc = $dfCInt + ds2 = $p1 dc -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. +And now we've defined the superclass in terms of itself. -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} -scrutiniseInstanceConstraint (clas, tys) - | all isTyVarTy tys - || opt_AllowUndecidableInstances = returnNF_Tc () - | otherwise = addErrTc (instConstraintErr clas tys) - -scrutiniseInstanceHead clas inst_taus - | -- CCALL CHECK (a).... urgh! - -- To verify that a user declaration of a CCallable/CReturnable - -- instance is OK, we must be able to see the constructor(s) - -- of the instance type (see next guard.) - -- - -- We flag this separately to give a more precise error msg. - -- - (getUnique clas == cCallableClassKey || getUnique clas == cReturnableClassKey) - && is_alg_tycon_app && not constructors_visible - = addErrTc (invisibleDataConPrimCCallErr clas first_inst_tau) - - | -- CCALL CHECK (b) - -- A user declaration of a CCallable/CReturnable instance - -- must be for a "boxed primitive" type. - (getUnique clas == cCallableClassKey && not (ccallable_type first_inst_tau)) || - (getUnique clas == 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 + doc = ptext SLIT("instance declaration superclass context") +\end{code} - -- 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 - is_alg_tycon_app = maybeToBool alg_tycon_app_maybe - Just (alg_tycon, _, data_cons) = alg_tycon_app_maybe + ------------------------------ + [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. - constructors_visible = not (null data_cons) - --- These conditions come directly from what the DsCCall is capable of. --- Totally grotesque. Green card should solve this. +%************************************************************************ +%* * +\subsection{Error messages} +%* * +%************************************************************************ -ccallable_type ty = isUnLiftedType ty || -- Allow CCallable Int# etc - maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc - ty == stringTy || - byte_arr_thing +\begin{code} +tcAddDeclCtxt decl thing_inside + = addSrcLoc (tcdLoc decl) $ + addErrCtxt ctxt $ + thing_inside where - byte_arr_thing = case splitAlgTyConApp_maybe ty of - Just (tycon, ty_args, [data_con]) | isDataTyCon tycon -> - length data_con_arg_tys == 2 && - maybeToBool maybe_arg2_tycon && - (arg2_tycon == byteArrayPrimTyCon || - arg2_tycon == mutableByteArrayPrimTyCon) - where - data_con_arg_tys = dataConArgTys data_con ty_args - (data_con_arg_ty1 : data_con_arg_ty2 : _) = data_con_arg_tys - maybe_arg2_tycon = splitTyConApp_maybe data_con_arg_ty2 - Just (arg2_tycon,_) = maybe_arg2_tycon - - other -> False - -creturnable_type ty = maybeToBool (maybeBoxedPrimType ty) || - -- Or, a data type with a single nullary constructor - case (splitAlgTyConApp_maybe ty) of - Just (tycon, tys_applied, [data_con]) - -> isNullaryDataCon data_con - other -> False + 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} \begin{code} -instConstraintErr clas tys - = hang (ptext SLIT("Illegal constaint") <+> - 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) +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") ] - -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")) - -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]) - -{- - Declaring CCallable & CReturnable instances in a module different - from where the type was defined. Caused by importing data type - abstractly (either programmatically or by the renamer being over-eager - in its pruning.) --} -invisibleDataConPrimCCallErr clas inst_ty - = hang (hsep [ptext SLIT("Constructors for"), quotes (ppr inst_ty), - ptext SLIT("not visible when checking"), - quotes (ppr clas), ptext SLIT("instance")]) - 4 (hsep [text "(Try either importing", ppr inst_ty, - text "non-abstractly or compile using -fno-prune-tydecls ..)"]) + 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}