X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=6b17d3afb4f5f311f6bea25553123d38d04a5dd7;hb=e9440920bbcd7487eeab42972a648a401a519873;hp=96177adefa2ef305431533e8789f9de577b02072;hpb=1fb1ab5d53a09607e7f6d2450806760688396387;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 96177ad..6b17d3a 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -1,90 +1,74 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcInstDecls]{Typechecking instance declarations} \begin{code} +module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls, + tcInstDecls2, tcAddDeclCtxt ) where + #include "HsVersions.h" -module TcInstDcls ( - tcInstDecls1, - tcInstDecls2, - processInstBinds - ) where - - -IMP_Ubiq() - -import HsSyn ( HsDecl(..), InstDecl(..), TyDecl, ClassDecl, DefaultDecl, - FixityDecl, IfaceSig, Sig(..), - SpecInstSig(..), HsBinds(..), Bind(..), - MonoBinds(..), GRHSsAndBinds, Match, - InPat(..), OutPat(..), HsExpr(..), HsLit(..), - Stmt, DoOrListComp, ArithSeqInfo, Fake, Fixity, - HsType(..), HsTyVar ) -import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedMonoBinds), - SYN_IE(RenamedInstDecl), SYN_IE(RenamedFixityDecl), - SYN_IE(RenamedSig), SYN_IE(RenamedSpecInstSig), SYN_IE(RenamedHsDecl) - ) -import TcHsSyn ( TcIdOcc(..), SYN_IE(TcHsBinds), - SYN_IE(TcMonoBinds), SYN_IE(TcExpr), tcIdType, - mkHsTyLam, mkHsTyApp, - mkHsDictLam, mkHsDictApp ) +import CmdLineOpts ( DynFlag(..) ) -import TcMonad -import RnMonad ( SYN_IE(RnNameSupply) ) -import Inst ( Inst, InstOrigin(..), SYN_IE(InstanceMapper), - newDicts, newMethod, SYN_IE(LIE), emptyLIE, plusLIE ) -import TcBinds ( tcPragmaSigs, checkSigTyVars ) -import TcDeriv ( tcDeriving ) -import TcEnv ( tcLookupClass, newLocalId, tcExtendGlobalTyVars ) -import SpecEnv ( SpecEnv ) -import TcGRHSs ( tcGRHSsAndBinds ) -import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs ) -import TcKind ( TcKind, unifyKind ) -import TcMatches ( tcMatchesFun ) -import TcMonoType ( tcTyVarScope, tcContext, tcHsTypeKind ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( SYN_IE(TcType), SYN_IE(TcTyVar), SYN_IE(TcTyVarSet), - tcInstSigTyVars, tcInstType, tcInstTheta, tcInstTcType +import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, + isClassDecl, isSourceInstDecl, toHsType ) -import Unify ( unifyTauTy, unifyTauTyLists ) - - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, - concatBag, foldBag, bagToList ) -import CmdLineOpts ( opt_GlasgowExts, opt_CompilingGhcInternals, - opt_OmitDefaultInstanceMethods, - opt_SpecialiseOverloaded +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, + RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, + extractHsTyVars, maybeGenericMatch ) -import Class ( GenClass, GenClassOp, - classBigSig, classOps, classOpLocalType, - classOpTagByOccName_maybe - ) -import Id ( GenId, idType, isDefaultMethodId_maybe, isNullaryDataCon, dataConArgTys ) -import PrelInfo ( isCcallishClass ) -import ListSetOps ( minusList ) -import Maybes ( maybeToBool, expectJust ) -import Name ( getOccString, occNameString, moduleString, isLocallyDefined, OccName, Name{--O only-} ) -import PrelVals ( nO_EXPLICIT_METHOD_ERROR_ID ) -import PprType ( GenType, GenTyVar, GenClass, GenClassOp, TyCon, - pprParendGenType +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 PprStyle -import SrcLoc ( SrcLoc ) -import Pretty -import TyCon ( isSynTyCon, derivedFor ) -import Type ( GenType(..), SYN_IE(ThetaType), mkTyVarTys, isPrimType, - splitSigmaTy, splitAppTys, isTyVarTy, matchTy, mkSigmaTy, - getTyCon_maybe, maybeAppTyCon, - maybeBoxedPrimType, maybeAppDataTyCon, splitRhoTy, eqTy +import Inst ( InstOrigin(..), tcInstClassOp, newDicts, instToId, showLIE ) +import TcDeriv ( tcDeriving ) +import TcEnv ( tcExtendGlobalValEnv, + tcLookupClass, tcExtendTyVarEnv2, + tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId, + InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon, + simpleInstInfoTy, newDFunName + ) +import PprType ( pprClassPred ) +import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType ) +import TcUnify ( checkSigTyVars ) +import TcSimplify ( tcSimplifyCheck, tcSimplifyTop ) +import HscTypes ( DFunId ) +import Subst ( mkTyVarSubst, substTheta, substTy ) +import DataCon ( classDataCon ) +import Class ( Class, classBigSig ) +import Var ( idName, idType ) +import NameSet +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 TyVar ( GenTyVar, SYN_IE(GenTyVarSet), mkTyVarSet, unionTyVarSets ) -import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon ) -import TysWiredIn ( stringTy ) -import Unique ( Unique, cCallableClassKey, cReturnableClassKey ) -import Util ( zipEqual, panic, pprPanic, pprTrace ) +import Maybe ( catMaybes ) +import List ( partition ) +import Outputable +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -160,71 +144,259 @@ 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 -- 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 + 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} + \begin{code} -tcInstDecls1 :: [RenamedHsDecl] - -> Module -- module name for deriving - -> RnNameSupply -- for renaming derivings - -> TcM s (Bag InstInfo, - RenamedHsBinds, - PprStyle -> Pretty) - -tcInstDecls1 decls mod_name rn_name_supply - = -- Do the ordinary instance declarations - mapNF_Tc (tcInstDecl1 mod_name) - [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags -> +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 - decl_inst_info = unionManyBags inst_info_bags + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in - -- Handle "derived" instances; note that we only do derivings - -- for things in this module; we ignore deriving decls from - -- interfaces! We pass fixities, because they may be used - -- in deriving Read and Show. - tcDeriving mod_name rn_name_supply decl_inst_info - `thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) -> + 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{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 - full_inst_info = deriv_inst_info `unionBags` decl_inst_info + gen_inst_info = concat gen_inst_infos in - returnTc (full_inst_info, deriv_binds, ddump_deriv) + 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_` -tcInstDecl1 :: Module -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) + -- 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_` -tcInstDecl1 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 $ + returnM inst_infos - -- Look things up - tcLookupClass class_name `thenTc` \ (clas_kind, clas) -> + where + -- Group the declarations by type pattern + groups :: [(RenamedHsType, RenamedMonoBinds)] + groups = assocElts (getGenericBinds def_methods) - -- Typecheck the context and instance type - tcTyVarScope tyvar_names (\ tyvars -> - tcContext context `thenTc` \ theta -> - tcHsTypeKind inst_ty `thenTc` \ (tau_kind, tau) -> - unifyKind clas_kind tau_kind `thenTc_` - returnTc (tyvars, theta, tau) - ) `thenTc` \ (inst_tyvars, inst_theta, inst_tau) -> - -- Check for respectable instance type - scrutiniseInstanceType dfun_name clas inst_tau - `thenTc` \ (inst_tycon,arg_tys) -> +--------------------------------- +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. - -- Make the dfun id and constant-method ids - mkInstanceRelatedIds dfun_name - clas inst_tyvars inst_tau inst_theta - `thenNF_Tc` \ (dfun_id, dfun_theta) -> +getGenericBinds EmptyMonoBinds = emptyAssoc +getGenericBinds (AndMonoBinds m1 m2) + = plusAssoc_C AndMonoBinds (getGenericBinds m1) (getGenericBinds m2) - returnTc (unitBag (InstInfo clas inst_tyvars inst_tau inst_theta - dfun_theta dfun_id - binds src_loc uprags)) +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 - (tyvar_names, context, dict_ty) = case poly_ty of - HsForAllTy tvs cxt dict_ty -> (tvs, cxt, dict_ty) - other -> ([], [], poly_ty) - (class_name, inst_ty) = case dict_ty of - MonoDictTy cls ty -> (cls,ty) - other -> pprPanic "Malformed intance decl" (ppr PprDebug poly_ty) + 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} @@ -235,19 +407,12 @@ tcInstDecl1 mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc) %************************************************************************ \begin{code} -tcInstDecls2 :: Bag InstInfo - -> NF_TcM s (LIE s, TcHsBinds s) - +tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds tcInstDecls2 inst_decls - = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyBinds)) inst_decls - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `ThenBinds` 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 @@ -314,626 +479,409 @@ is the @dfun_theta@ below. First comes the easy case of a non-local instance decl. -\begin{code} -tcInstDecl2 :: InstInfo - -> NF_TcM s (LIE s, TcHsBinds s) -tcInstDecl2 (InstInfo clas inst_tyvars inst_ty - inst_decl_theta dfun_theta - dfun_id monobinds - locn uprags) - | not (isLocallyDefined dfun_id) - = returnNF_Tc (emptyLIE, EmptyBinds) +\begin{code} +tcInstDecl2 :: InstInfo -> TcM TcMonoBinds - | otherwise +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc locn $ - - -- Get the class signature - tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) -> - let - (class_tyvar, - super_classes, sc_sel_ids, - class_ops, op_sel_ids, defm_ids) = classBigSig clas - in - tcInstType tenv inst_ty `thenNF_Tc` \ inst_ty' -> - tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' -> - tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' -> + recoverM (returnM EmptyMonoBinds) $ + addSrcLoc (getSrcLoc dfun_id) $ + addErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $ let - sc_theta' = super_classes `zip` repeat inst_ty' - origin = InstanceDeclOrigin - mk_method sel_id = newMethod origin (RealId sel_id) [inst_ty'] + 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 - -- 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_ty')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - -- Create method variables - mapAndUnzipNF_Tc mk_method op_sel_ids `thenNF_Tc` \ (meth_insts_s, meth_ids) -> - - -- Collect available Insts + -- Instantiate the instance decl with tc-style type variables + tcInstType InstTv inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') -> let - inst_tyvars_set' = mkTyVarSet inst_tyvars' - - avail_insts -- These insts are in scope; quite a few, eh? - = unionManyBags (this_dict : dfun_arg_dicts : meth_insts_s) + Just pred = tcSplitPredTy_maybe inst_head' + (clas, inst_tys') = getClassPredTys pred + (class_tyvars, sc_theta, _, op_items) = classBigSig clas - mk_method_expr - = makeInstanceDeclDefaultMethodExpr locn clas meth_ids defm_ids inst_ty' this_dict_id + -- Instantiate the super-class context with inst_tys + sc_theta' = substTheta (mkTyVarSubst class_tyvars inst_tys') sc_theta + origin = InstanceDeclOrigin in - tcExtendGlobalTyVars inst_tyvars_set' ( - processInstBinds clas mk_method_expr avail_insts meth_ids monobinds - ) `thenTc` \ (insts_needed, method_mbinds) -> - let - -- Create the dict and method binds - dict_bind - = VarMonoBind this_dict_id (Dictionary sc_dict_ids meth_ids) + -- Create dictionary Ids from the specified instance contexts. + 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) -> - dict_and_method_binds - = dict_bind `AndMonoBinds` method_mbinds + -- 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) -> - in - -- Check the overloading constraints of the methods and superclasses - tcAddErrCtxt (bindSigCtxt meth_ids) ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars - avail_insts - (sc_dicts `unionBags` insts_needed) -- Need to get defns for all these - ) `thenTc` \ (const_lie, super_binds) -> - - -- 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 superClassSigCtxt ( - tcSimplifyAndCheck - 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 process any SPECIALIZE pragmas for the methods + -- Deal with 'SPECIALISE instance' pragmas by making them + -- look like SPECIALISE pragmas for the dfun let - spec_sigs = [ s | s@(SpecSig _ _ _ _) <- 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 - tcPragmaSigs spec_sigs `thenTc` \ (_, spec_binds, spec_lie) -> - let - -- Complete the binding group, adding any spec_binds - inst_binds - = AbsBinds - inst_tyvars' - dfun_arg_dicts_ids - [(this_dict_id, RealId dfun_id)] - super_binds - (RecBind dict_and_method_binds) - - `ThenBinds` - spec_binds - in - - returnTc (const_lie `plusLIE` spec_lie, inst_binds) -\end{code} - -The next function makes a default method which calls the global default method, at -the appropriate instance type. + tcExtendGlobalValEnv [dfun_id] ( + tcExtendTyVarEnv2 xtve $ + tcSpecSigs spec_prags + ) `thenM` \ prag_binds -> -See the notes under default decls in TcClassDcl.lhs. - -\begin{code} -makeInstanceDeclDefaultMethodExpr - :: SrcLoc - -> Class - -> [TcIdOcc s] - -> [Id] - -> TcType s - -> TcIdOcc s - -> Int - -> NF_TcM s (TcExpr s) - -makeInstanceDeclDefaultMethodExpr src_loc clas meth_ids defm_ids inst_ty this_dict tag - | not defm_is_err -- Not sure that the default method is just error message - = -- def_op_id = defm_id inst_ty this_dict - returnNF_Tc (mkHsDictApp (mkHsTyApp (HsVar (RealId defm_id)) [inst_ty]) [this_dict]) - - | otherwise -- There's definitely no default decl in the class, - -- so we produce a warning, and a better run=time error message too - = warnTc True (omitDefaultMethodWarn clas_op clas_name inst_ty) - `thenNF_Tc_` - - returnNF_Tc (HsApp (mkHsTyApp (HsVar (RealId nO_EXPLICIT_METHOD_ERROR_ID)) [tcIdType meth_id]) - (HsLitOut (HsString (_PK_ error_msg)) stringTy)) - where - idx = tag - 1 - meth_id = meth_ids !! idx - defm_id = defm_ids !! idx - - Just (_, _, defm_is_err) = isDefaultMethodId_maybe defm_id - - error_msg = ppShow 80 (ppSep [ppr PprForUser clas_op, ppPStr SLIT("at"), ppr PprForUser src_loc]) - - clas_op = (classOps clas) !! idx - clas_name = getOccString clas -\end{code} - - - -%************************************************************************ -%* * -\subsection{Processing each method} -%* * -%************************************************************************ - -@processInstBinds@ returns a @MonoBinds@ which binds -all the method ids (which are passed in). It is used - - both for instance decls, - - and to compile the default-method declarations in a class decl. - -Any method ids which don't have a binding have a suitable default -binding created for them. The actual right-hand side used is -created using a function which is passed in, because the right thing to -do differs between instance and class decls. - -\begin{code} -processInstBinds - :: Class - -> (Int -> NF_TcM s (TcExpr s)) -- Function to make default method - -> LIE s -- available Insts - -> [TcIdOcc s] -- Local method ids in tag order - -- (instance tyvars are free in their types) - -> RenamedMonoBinds - -> TcM s (LIE s, -- These are required - TcMonoBinds s) - -processInstBinds clas mk_default_method_rhs avail_insts method_ids monobinds - = - -- Process the explicitly-given method bindings - processInstBinds1 clas avail_insts method_ids monobinds - `thenTc` \ (tags, insts_needed_in_methods, method_binds) -> - - -- Find the methods not handled, and make default method bindings for them. + -- Create the result bindings let - unmentioned_tags = [1.. length method_ids] `minusList` tags + dict_constr = classDataCon clas + 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 + = -- Blatant special case for CCallable, CReturnable + -- If the dictionary is empty then we should never + -- select anything from it, so we make its RHS just + -- 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 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) + -- 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.mkDataConWrapId code rather + -- than needing to be repeated here. + + where + 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 - mapNF_Tc mk_default_method unmentioned_tags - `thenNF_Tc` \ default_bind_list -> + showLIE (text "instance") `thenM_` + returnM (main_bind `AndMonoBinds` prag_binds `AndMonoBinds` sc_binds_outer) - returnTc (insts_needed_in_methods, - foldr AndMonoBinds method_binds default_bind_list) - where - -- From a tag construct us the passed-in function to construct - -- the binding for the default method - mk_default_method tag = mk_default_method_rhs tag `thenNF_Tc` \ rhs -> - returnNF_Tc (VarMonoBind (method_ids !! (tag-1)) rhs) -\end{code} - -\begin{code} -processInstBinds1 - :: Class - -> LIE s -- available Insts - -> [TcIdOcc s] -- Local method ids in tag order (instance tyvars are free), - -> RenamedMonoBinds - -> TcM s ([Int], -- Class-op tags accounted for - LIE s, -- These are required - TcMonoBinds s) - -processInstBinds1 clas avail_insts method_ids EmptyMonoBinds - = returnTc ([], emptyLIE, EmptyMonoBinds) - -processInstBinds1 clas avail_insts method_ids (AndMonoBinds mb1 mb2) - = processInstBinds1 clas avail_insts method_ids mb1 - `thenTc` \ (op_tags1,dicts1,method_binds1) -> - processInstBinds1 clas avail_insts method_ids mb2 - `thenTc` \ (op_tags2,dicts2,method_binds2) -> - returnTc (op_tags1 ++ op_tags2, - dicts1 `unionBags` dicts2, - AndMonoBinds method_binds1 method_binds2) -\end{code} -\begin{code} -processInstBinds1 clas avail_insts method_ids mbind - = - -- Find what class op is being defined here. The complication is - -- that we could have a PatMonoBind or a FunMonoBind. If the - -- former, it should only bind a single variable, or else we're in - -- trouble (I'm not sure what the static semantics of methods - -- defined in a pattern binding with multiple patterns is!) - -- Renamer has reduced us to these two cases. +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 - (op,locn) = case mbind of - FunMonoBind op _ _ locn -> (op, locn) - PatMonoBind (VarPatIn op) _ locn -> (op, locn) - - occ = getOccName op - origin = InstanceDeclOrigin + sel_names = [idName sel_id | (sel_id, _) <- op_items] + bad_bndrs = collectMonoBinders monobinds `minusList` sel_names in - tcAddSrcLoc locn $ + mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` - -- Make a method id for the method + -- Make the method bindings let - maybe_tag = classOpTagByOccName_maybe clas occ - (Just tag) = maybe_tag - method_id = method_ids !! (tag-1) - method_ty = tcIdType method_id + mk_method_bind = mkMethodBind InstanceDeclOrigin clas inst_tys' monobinds in - -- check that the method mentioned is actually in the class: - checkMaybeTc maybe_tag (instMethodNotInClassErr occ clas) `thenTc_` - - tcInstTcType method_ty `thenNF_Tc` \ (method_tyvars, method_rho) -> + 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 - (method_theta, method_tau) = splitRhoTy method_rho + 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 - newDicts origin method_theta `thenNF_Tc` \ (method_dicts,method_dict_ids) -> - - case (method_tyvars, method_dict_ids) of + mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> + + returnM ([meth_id | (_,meth_id,_) <- meth_infos], + andMonoBindList meth_binds_s) - ([],[]) -> -- The simple case; no local polymorphism or overloading in the method - -- Type check the method itself - tcMethodBind method_id method_tau mbind `thenTc` \ (mbind', lieIop) -> - returnTc ([tag], lieIop, mbind') +-- 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 -> - other -> -- It's a locally-polymorphic and/or overloaded method; UGH! + -- I don't think we have to do the checkSigTyVars thing - -- Make a new id for (a) the local, non-overloaded method - -- and (b) the locally-overloaded method - -- The latter is needed just so we can return an AbsBinds wrapped - -- up inside a MonoBinds. + returnM (meth_ids, lie_binds `AndMonoBinds` andMonoBindList meth_binds) - - -- Make the method_tyvars into signature tyvars so they - -- won't get unified with anything. - tcInstSigTyVars method_tyvars `thenNF_Tc` \ (sig_tyvars, sig_tyvar_tys, _) -> - unifyTauTyLists sig_tyvar_tys (mkTyVarTys method_tyvars) `thenTc_` - - newLocalId occ method_tau `thenNF_Tc` \ local_id -> - newLocalId occ method_ty `thenNF_Tc` \ copy_id -> - let - tc_local_id = TcId local_id - tc_copy_id = TcId copy_id - sig_tyvar_set = mkTyVarSet sig_tyvars - in - -- Typecheck the method - tcMethodBind tc_local_id method_tau mbind `thenTc` \ (mbind', lieIop) -> - - -- Check the overloading part of the signature. - - -- =========== POSSIBLE BUT NOT DONE ================= - -- Simplify everything fully, even though some - -- constraints could "really" be left to the next - -- level out. The case which forces this is - -- - -- class Foo a where { op :: Bar a => a -> a } - -- - -- Here we must simplify constraints on "a" to catch all - -- the Bar-ish things. - - -- We don't do this because it's currently illegal Haskell (not sure why), - -- and because the local type of the method would have a context at - -- the front with no for-all, which confuses the hell out of everything! - -- ==================================================== - - tcAddErrCtxt (methodSigCtxt op method_ty) ( - checkSigTyVars - sig_tyvars method_tau `thenTc_` - - tcSimplifyAndCheck - sig_tyvar_set - (method_dicts `plusLIE` avail_insts) - lieIop - ) `thenTc` \ (f_dicts, dict_binds) -> - - - returnTc ([tag], - f_dicts, - VarMonoBind method_id - (HsLet - (AbsBinds - method_tyvars - method_dict_ids - [(tc_local_id, tc_copy_id)] - dict_binds - (NonRecBind mbind')) - (HsVar tc_copy_id))) -\end{code} - -\begin{code} -tcMethodBind :: TcIdOcc s -> TcType s -> RenamedMonoBinds - -> TcM s (TcMonoBinds s, LIE s) - -tcMethodBind meth_id meth_ty (FunMonoBind name inf matches locn) - = tcMatchesFun name meth_ty matches `thenTc` \ (rhs', lie) -> - returnTc (FunMonoBind meth_id inf rhs' locn, lie) - -tcMethodBind meth_id meth_ty pbind@(PatMonoBind pat grhss_and_binds locn) - -- pat is sure to be a (VarPatIn op) - = tcAddErrCtxt (patMonoBindsCtxt pbind) $ - tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, rhs_ty) -> - unifyTauTy meth_ty rhs_ty `thenTc_` - returnTc (PatMonoBind (VarPat meth_id) grhss_and_binds' locn, lie) + 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{Type-checking specialise instance pragmas} -%* * -%************************************************************************ + class S a -\begin{code} -{- LATER -tcSpecInstSigs :: E -> CE -> TCE - -> Bag InstInfo -- inst decls seen (declared and derived) - -> [RenamedSpecInstSig] -- specialise instance upragmas - -> TcM (Bag InstInfo) -- new, overlapped, inst decls - -tcSpecInstSigs e ce tce inst_infos [] - = returnTc emptyBag - -tcSpecInstSigs e ce tce inst_infos sigs - = buildInstanceEnvs inst_infos `thenTc` \ inst_mapper -> - tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ spec_inst_infos -> - returnTc spec_inst_infos - where - tc_inst_spec_sigs inst_mapper [] - = returnNF_Tc emptyBag - tc_inst_spec_sigs inst_mapper (sig:sigs) - = tcSpecInstSig e ce tce inst_infos inst_mapper sig `thenNF_Tc` \ info_sig -> - tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ info_sigs -> - returnNF_Tc (info_sig `unionBags` info_sigs) - -tcSpecInstSig :: E -> CE -> TCE - -> Bag InstInfo - -> InstanceMapper - -> RenamedSpecInstSig - -> NF_TcM (Bag InstInfo) - -tcSpecInstSig e ce tce inst_infos inst_mapper (SpecInstSig class_name ty src_loc) - = recoverTc emptyBag ( - tcAddSrcLoc src_loc ( - let - clas = lookupCE ce class_name -- Renamer ensures this can't fail + 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 - -- Make some new type variables, named as in the specialised instance type - ty_names = extractHsTyNames ???is_tyvarish_name??? ty - (tmpl_e,inst_tmpls,inst_tmpl_tys) = mkTVE ty_names - in - babyTcMtoTcM (tcInstanceType ce tce tmpl_e True src_loc ty) - `thenTc` \ inst_ty -> - let - maybe_tycon = case maybeAppDataTyCon inst_ty of - Just (tc,_,_) -> Just tc - Nothing -> Nothing +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. - maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos - in - -- Check that we have a local instance declaration to specialise - checkMaybeTc maybe_unspec_inst - (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_` +Alas! Alack! We can do the same for (instance D Int): - -- Create tvs to substitute for tmpls while simplifying the context - copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) -> - let - Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta - _ _ binds _ uprag) = maybe_unspec_inst + $dfDInt = :D ds2 (opc dc) + dc = $dfCInt + ds2 = $p1 dc - subst = case matchTy unspec_inst_ty inst_ty of - Just subst -> subst - Nothing -> panic "tcSpecInstSig:matchTy" +And now we've defined the superclass in terms of itself. - subst_theta = instantiateThetaTy subst unspec_theta - subst_tv_theta = instantiateThetaTy tv_e subst_theta - mk_spec_origin clas ty - = InstanceSpecOrigin inst_mapper clas ty src_loc - -- I'm VERY SUSPICIOUS ABOUT THIS - -- the inst-mapper is in a knot at this point so it's no good - -- looking at it in tcSimplify... - in - tcSimplifyThetas mk_spec_origin subst_tv_theta - `thenTc` \ simpl_tv_theta -> - let - simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ] +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. - tv_tmpl_map = zipEqual "tcSpecInstSig" inst_tv_tys inst_tmpl_tys - tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv - in - mkInstanceRelatedIds - clas inst_tmpls inst_ty simpl_theta uprag - `thenNF_Tc` \ (dfun_id, dfun_theta, const_meth_ids) -> - - getSwitchCheckerTc `thenNF_Tc` \ sw_chkr -> - (if sw_chkr SpecialiseTrace then - pprTrace "Specialised Instance: " - (ppAboves [ppCat [if null simpl_theta then ppNil else ppr PprDebug simpl_theta, - if null simpl_theta then ppNil else ppPStr SLIT("=>"), - ppr PprDebug clas, - pprParendGenType PprDebug inst_ty], - ppCat [ppPStr SLIT(" derived from:"), - if null unspec_theta then ppNil else ppr PprDebug unspec_theta, - if null unspec_theta then ppNil else ppPStr SLIT("=>"), - ppr PprDebug clas, - pprParendGenType PprDebug unspec_inst_ty]]) - else id) ( - - returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta - dfun_theta dfun_id - binds src_loc uprag)) - ))) - - -lookup_unspec_inst clas maybe_tycon inst_infos - = case filter (match_info match_inst_ty) (bagToList inst_infos) of - [] -> Nothing - (info:_) -> Just info - where - match_info match_ty (InstInfo inst_clas _ inst_ty _ _ _ _ _ from_here _ _ _) - = from_here && clas == inst_clas && - match_ty inst_ty && is_plain_instance inst_ty +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!! - match_inst_ty = case maybe_tycon of - Just tycon -> match_tycon tycon - Nothing -> match_fun +\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) -> - match_tycon tycon inst_ty = case (maybeAppDataTyCon inst_ty) of - Just (inst_tc,_,_) -> tycon == inst_tc - Nothing -> False + -- It's possible that the superclass stuff might have done unification + checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars -> - match_fun inst_ty = isFunType inst_ty + -- 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) -is_plain_instance inst_ty - = case (maybeAppDataTyCon inst_ty) of - Just (_,tys,_) -> all isTyVarTemplateTy tys - Nothing -> case maybeUnpackFunTy inst_ty of - Just (arg, res) -> isTyVarTemplateTy arg && isTyVarTemplateTy res - Nothing -> error "TcInstDecls:is_plain_instance" --} + where + doc = ptext SLIT("instance declaration superclass context") \end{code} -Checking for a decent instance type -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -@scrutiniseInstanceType@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ + ------------------------------ + [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. -The exceptions to this syntactic checking: (1)~if the @GlasgowExts@ -flag is on, or (2)~the instance is imported (they must have been -compiled elsewhere). In these cases, we let them go through anyway. -We can also have instances for functions: @instance Foo (a -> b) ...@. +%************************************************************************ +%* * +\subsection{Error messages} +%* * +%************************************************************************ \begin{code} -scrutiniseInstanceType dfun_name clas inst_tau - -- TYCON CHECK - | not (maybeToBool inst_tycon_maybe) || isSynTyCon inst_tycon - = failTc (instTypeErr inst_tau) - - -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1) - | not (isLocallyDefined dfun_name) - = returnTc (inst_tycon,arg_tys) - - -- TYVARS CHECK - | not (all isTyVarTy arg_tys || - opt_GlasgowExts) - = failTc (instTypeErr inst_tau) - - -- DERIVING CHECK - -- It is obviously illegal to have an explicit instance - -- for something that we are also planning to `derive' - -- Though we can have an explicit instance which is more - -- specific than the derived instance - | clas `derivedFor` inst_tycon - && all isTyVarTy arg_tys - = failTc (derivingWhenInstanceExistsErr clas inst_tycon) - - | -- CCALL CHECK - -- A user declaration of a CCallable/CReturnable instance - -- must be for a "boxed primitive" type. - (uniqueOf clas == cCallableClassKey && not (ccallable_type inst_tau)) || - (uniqueOf clas == cReturnableClassKey && not (creturnable_type inst_tau)) - = failTc (nonBoxedPrimCCallErr clas inst_tau) - - | otherwise - = returnTc (inst_tycon,arg_tys) - +tcAddDeclCtxt decl thing_inside + = addSrcLoc (tcdLoc decl) $ + addErrCtxt ctxt $ + thing_inside where - (possible_tycon, arg_tys) = splitAppTys inst_tau - inst_tycon_maybe = getTyCon_maybe possible_tycon - inst_tycon = expectJust "tcInstDecls1:inst_tycon" inst_tycon_maybe - --- These conditions come directly from what the DsCCall is capable of. --- Totally grotesque. Green card should solve this. - -ccallable_type ty = isPrimType ty || -- Allow CCallable Int# etc - maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc - ty `eqTy` stringTy || - byte_arr_thing - where - byte_arr_thing = case maybeAppDataTyCon ty of - Just (tycon, ty_args, [data_con]) -> --- pprTrace "cc1" (ppSep [ppr PprDebug tycon, ppr PprDebug data_con, --- ppSep (map (ppr PprDebug) data_con_arg_tys)])( - length data_con_arg_tys == 2 && - maybeToBool maybe_arg2_tycon && --- pprTrace "cc2" (ppSep [ppr PprDebug 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 = maybeAppTyCon 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 (maybeAppDataTyCon 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} - -instTypeErr ty sty - = case ty of - SynTy tc _ _ -> ppBesides [ppPStr SLIT("The type synonym `"), ppr sty tc, rest_of_msg] - TyVarTy tv -> ppBesides [ppPStr SLIT("The type variable `"), ppr sty tv, rest_of_msg] - other -> ppBesides [ppPStr SLIT("The type `"), ppr sty ty, rest_of_msg] - where - rest_of_msg = ppPStr SLIT("' cannot be used as an instance type.") - -derivingWhenInstanceExistsErr clas tycon sty - = ppHang (ppBesides [ppPStr SLIT("Deriving class `"), - ppr sty clas, - ppPStr SLIT("' type `"), ppr sty tycon, ppChar '\'']) - 4 (ppPStr SLIT("when an explicit instance exists")) - -derivingWhenInstanceImportedErr inst_mod clas tycon sty - = ppHang (ppBesides [ppPStr SLIT("Deriving class `"), - ppr sty clas, - ppPStr SLIT("' type `"), ppr sty tycon, ppChar '\'']) - 4 (ppBesides [ppPStr SLIT("when an instance declared in module `"), - pp_mod, ppPStr SLIT("' has been imported")]) - where - pp_mod = ppBesides [ppPStr SLIT("module `"), ppPStr inst_mod, ppChar '\''] - -nonBoxedPrimCCallErr clas inst_ty sty - = ppHang (ppPStr SLIT("Unacceptable instance type for ccall-ish class")) - 4 (ppBesides [ ppPStr SLIT("class `"), ppr sty clas, ppPStr SLIT("' type `"), - ppr sty inst_ty, ppChar '\'']) - -omitDefaultMethodWarn clas_op clas_name inst_ty sty - = ppCat [ppPStr SLIT("Warning: Omitted default method for"), - ppr sty clas_op, ppPStr SLIT("in instance"), - ppStr clas_name, pprParendGenType sty inst_ty] - -instMethodNotInClassErr occ clas sty - = ppHang (ppPStr SLIT("Instance mentions a method not in the class")) - 4 (ppBesides [ppPStr SLIT("class `"), ppr sty clas, ppPStr SLIT("' method `"), - ppr sty occ, ppChar '\'']) - -patMonoBindsCtxt pbind sty - = ppHang (ppPStr SLIT("In a pattern binding:")) - 4 (ppr sty pbind) - -methodSigCtxt name ty sty - = ppHang (ppBesides [ppPStr SLIT("When matching the definition of class method `"), - ppr sty name, ppPStr SLIT("' to its signature :") ]) - 4 (ppr sty ty) - -bindSigCtxt method_ids sty - = ppHang (ppPStr SLIT("When checking type signatures for: ")) - 4 (ppInterleave (ppStr ", ") (map (ppr sty) method_ids)) - -superClassSigCtxt sty - = ppPStr SLIT("When checking superclass constraints on instance declaration") - +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 super-classes of an instance declaration") \end{code}