X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=3fec58dd0a402b6d98daa0bc0e4f6b5518ca10e8;hb=1cdafe99abae1628f34ca8c064e3a8c0fcdbd079;hp=54967ac78c85ff3682e10be0e48b934cca532f8d;hpb=47eef4b5780f0a5b5a37847097842daebd0f9285;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 54967ac..3fec58d 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,78 +4,45 @@ \section[TcInstDecls]{Typechecking instance declarations} \begin{code} -module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where +module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where #include "HsVersions.h" - -import CmdLineOpts ( DynFlag(..), dopt ) - -import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), - MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), - andMonoBindList, collectMonoBinders, isClassDecl - ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl, RenamedMonoBinds, - RenamedTyClDecl, RenamedHsType, - extractHsTyVars, maybeGenericMatch - ) -import TcHsSyn ( TcMonoBinds, mkHsConApp ) -import TcBinds ( tcSpecSigs ) -import TcClassDcl ( tcMethodBind, badMethodErr ) -import TcMonad -import Inst ( InstOrigin(..), - newDicts, newClassDicts, - LIE, emptyLIE, plusLIE, plusLIEs ) +import HsSyn +import TcBinds ( mkPragFun, tcPrags, badBootDeclErr ) +import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr, + tcClassDecl2, getGenericInstances ) +import TcRnMonad +import TcMType ( tcSkolSigType, checkValidTheta, checkValidInstHead, + checkInstTermination, instTypeErr, + checkAmbiguity, SourceTyCtxt(..) ) +import TcType ( mkClassPred, tyVarsOfType, + tcSplitSigmaTy, tcSplitDFunHead, mkTyVarTys, + SkolemInfo(InstSkol), tcSplitDFunTy, pprClassPred ) +import Inst ( tcInstClassOp, newDicts, instToId, showLIE, + getOverlapFlag, tcExtendLocalInstEnv ) +import InstEnv ( mkLocalInstance, instanceDFunId ) import TcDeriv ( tcDeriving ) -import TcEnv ( TcEnv, tcExtendGlobalValEnv, - tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcInstId, tcLookupClass, - InstInfo(..), pprInstInfo, simpleInstInfoTyCon, simpleInstInfoTy, - newDFunName, tcExtendTyVarEnv +import TcEnv ( InstInfo(..), InstBindings(..), + newDFunName, tcExtendIdEnv ) -import InstEnv ( InstEnv, extendInstEnv ) -import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( zonkTcSigTyVars ) -import HscTypes ( HomeSymbolTable, DFunId, - ModDetails(..), PackageInstEnv, PersistentRenamerState - ) - -import Bag ( unionManyBags ) +import TcHsType ( kcHsSigType, tcHsKindedType ) +import TcUnify ( checkSigTyVars ) +import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses ) +import Type ( zipOpenTvSubst, substTheta, substTys ) import DataCon ( classDataCon ) -import Class ( Class, DefMeth(..), classBigSig ) -import Var ( idName, idType ) -import Maybes ( maybeToBool ) -import MkId ( mkDictFunId ) -import Generics ( validGenericInstanceType ) -import Module ( Module, foldModuleEnv ) -import Name ( getSrcLoc ) -import NameSet ( emptyNameSet, nameSetToList ) -import PrelInfo ( eRROR_ID ) -import PprType ( pprConstraint, pprPred ) -import TyCon ( TyCon, isSynTyCon ) -import Type ( splitDFunTy, isTyVarTy, - splitTyConApp_maybe, splitDictTy, - splitAlgTyConApp_maybe, splitForAllTys, - unUsgTy, tyVarsOfTypes, mkClassPred, mkTyVarTy, - getClassTys_maybe - ) -import Subst ( mkTopTyVarSubst, substClasses ) -import VarSet ( mkVarSet, varSetElems ) -import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIResultTy ) -import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey ) -import Name ( Name ) -import SrcLoc ( SrcLoc ) -import VarSet ( varSetElems ) -import Unique ( Uniquable(..) ) -import BasicTypes ( NewOrData(..), Fixity ) -import ErrUtils ( dumpIfSet_dyn ) -import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc, - assocElts, extendAssoc_C, - equivClassesByUniq, minusList - ) -import List ( partition ) +import Class ( classBigSig ) +import Var ( Id, idName, idType ) +import MkId ( mkDictFunId, rUNTIME_ERROR_ID ) +import FunDeps ( checkInstFDs ) +import Name ( Name, getSrcLoc ) +import Maybe ( catMaybes ) +import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart ) +import ListSetOps ( minusList ) import Outputable +import Bag +import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) ) +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -161,251 +128,90 @@ and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. Gather up the instance declarations from their various sources \begin{code} -tcInstDecls1 :: PackageInstEnv - -> PersistentRenamerState - -> HomeSymbolTable -- Contains instances - -> TcEnv -- Contains IdInfo for dfun ids - -> (Name -> Maybe Fixity) -- for deriving Show and Read - -> Module -- Module for deriving - -> [TyCon] - -> [RenamedHsDecl] - -> TcM (PackageInstEnv, InstEnv, [InstInfo], RenamedHsBinds) - -tcInstDecls1 inst_env0 prs hst unf_env get_fixity mod tycons decls - = let - inst_decls = [inst_decl | InstD inst_decl <- decls] - tycl_decls = [decl | TyClD decl <- decls] - clas_decls = filter isClassDecl tycl_decls - in +tcInstDecls1 -- Deal with both source-code and imported instance decls + :: [LTyClDecl Name] -- For deriving stuff + -> [LInstDecl Name] -- Source code instance decls + -> TcM (TcGblEnv, -- The full inst env + [InstInfo], -- Source-code instance decls to process; + -- contains all dfuns for this module + HsValBinds Name) -- Supporting bindings for derived instances + +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) + -- (1) Do the ordinary instance declarations - mapNF_Tc (tcInstDecl1 mod unf_env) inst_decls `thenNF_Tc` \ inst_infos -> + mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos -> + let + local_inst_info = catMaybes local_inst_infos + clas_decls = filter (isClassDecl.unLoc) tycl_decls + in -- (2) Instances from generic class declarations - getGenericInstances mod clas_decls `thenTc` \ generic_inst_info -> + getGenericInstances clas_decls `thenM` \ generic_inst_info -> -- Next, construct the instance environment so far, consisting of - -- a) cached non-home-package InstEnv (gotten from pcs) pcs_insts pcs - -- b) imported instance decls (not in the home package) inst_env1 - -- c) other modules in this package (gotten from hst) inst_env2 - -- d) local instance decls inst_env3 - -- e) generic instances inst_env4 - -- The result of (b) replaces the cached InstEnv in the PCS - let - (local_inst_info, imported_inst_info) = partition iLocal (concat inst_infos) - - imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId) - imported_inst_info - hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst - in - addInstDFuns inst_env0 imported_dfuns `thenNF_Tc` \ inst_env1 -> - addInstDFuns inst_env1 hst_dfuns `thenNF_Tc` \ inst_env2 -> - addInstInfos inst_env2 local_inst_info `thenNF_Tc` \ inst_env3 -> - addInstInfos inst_env3 generic_inst_info `thenNF_Tc` \ inst_env4 -> + -- a) local instance decls + -- b) generic instances + addInsts local_inst_info $ + addInsts generic_inst_info $ -- (3) Compute instances from "deriving" clauses; - -- note that we only do derivings for things in this module; - -- we ignore deriving decls from interfaces! -- This stuff computes a context for the derived instance decl, so it - -- needs to know about all the instances possible; hecne inst_env4 - tcDeriving prs mod inst_env4 get_fixity tycl_decls `thenTc` \ (deriv_inst_info, deriv_binds) -> - addInstInfos inst_env4 deriv_inst_info `thenNF_Tc` \ final_inst_env -> - - returnTc (inst_env1, - final_inst_env, - generic_inst_info ++ deriv_inst_info ++ local_inst_info, - deriv_binds) - -addInstInfos :: InstEnv -> [InstInfo] -> NF_TcM InstEnv -addInstInfos inst_env infos = addInstDFuns inst_env (map iDFunId infos) - -addInstDFuns :: InstEnv -> [DFunId] -> NF_TcM InstEnv -addInstDFuns dfuns infos - = getDOptsTc `thenTc` \ dflags -> - extendInstEnv dflags dfuns infos `bind` \ (inst_env', errs) -> - addErrsTc errs `thenNF_Tc_` - returnTc inst_env' - where - bind x f = f x - + -- needs to know about all the instances possible; hence inst_env4 + tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds) -> + addInsts deriv_inst_info $ + + getGblEnv `thenM` \ gbl_env -> + returnM (gbl_env, + generic_inst_info ++ deriv_inst_info ++ local_inst_info, + deriv_binds) + +addInsts :: [InstInfo] -> TcM a -> TcM a +addInsts infos thing_inside + = tcExtendLocalInstEnv (map iSpec infos) thing_inside \end{code} \begin{code} -tcInstDecl1 :: Module -> TcEnv -> RenamedInstDecl -> NF_TcM [InstInfo] --- Deal with a single instance declaration -tcInstDecl1 mod unf_env (InstDecl poly_ty binds uprags maybe_dfun_name src_loc) - = -- Prime error recovery, set source location - recoverNF_Tc (returnNF_Tc []) $ - tcAddSrcLoc src_loc $ - +tcLocalInstDecl1 :: LInstDecl Name + -> TcM (Maybe InstInfo) -- Nothing if there was an error + -- A source-file instance declaration -- Type-check all the stuff before the "where" - tcHsSigType poly_ty `thenTc` \ poly_ty' -> - let - (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty' - in - - (case maybe_dfun_name of - Nothing -> -- A source-file instance declaration - - -- Check for respectable instance type, and context - -- but only do this for non-imported instance decls. - -- Imported ones should have been checked already, and may indeed - -- contain something illegal in normal Haskell, notably - -- instance CCallable [Char] - scrutiniseInstanceHead clas inst_tys `thenNF_Tc_` - mapNF_Tc scrutiniseInstanceConstraint theta `thenNF_Tc_` - - -- Make the dfun id and return it - newDFunName mod clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> - returnNF_Tc (True, dfun_name) - - Just dfun_name -> -- An interface-file instance declaration - -- Make the dfun id - returnNF_Tc (False, dfun_name) - ) `thenNF_Tc` \ (is_local, dfun_name) -> - - let - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta - in - returnTc [InstInfo { iLocal = is_local, iDFunId = dfun_id, - iBinds = binds, iPrags = uprags }] -\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 :: Module -> [RenamedTyClDecl] -> TcM [InstInfo] -getGenericInstances mod class_decls - = mapTc (get_generics mod) class_decls `thenTc` \ gen_inst_infos -> + -- + -- We check for respectable instance type, and context +tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags)) + = -- Prime error recovery, set source location + recoverM (returnM Nothing) $ + setSrcSpan loc $ + addErrCtxt (instDeclCtxt1 poly_ty) $ + + -- Typecheck the instance type itself. We can't use + -- tcHsSigType, because it's not a valid user type. + kcHsSigType poly_ty `thenM` \ kinded_ty -> + tcHsKindedType kinded_ty `thenM` \ poly_ty' -> let - gen_inst_info = concat gen_inst_infos + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in - getDOptsTc `thenTc` \ dflags -> - ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" - (vcat (map pprInstInfo gen_inst_info))) - `thenNF_Tc_` - returnTc gen_inst_info - -get_generics mod decl@(ClassDecl context class_name tyvar_names - fundeps class_sigs def_methods - name_list loc) - | null groups - = returnTc [] -- The comon case: - -- no generic default methods, or - -- its an imported class decl (=> has no methods at all) - - | otherwise -- A local class decl with generic default methods - = recoverNF_Tc (returnNF_Tc []) $ - tcAddDeclCtxt decl $ - tcLookupClass class_name `thenTc` \ clas -> - - -- Make an InstInfo out of each group - mapTc (mkGenericInstance mod clas loc) groups `thenTc` \ 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, - length group > 1] - get_uniq (tc,_) = getUnique tc + checkValidTheta InstThetaCtxt theta `thenM_` + checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_` + checkValidInstHead tau `thenM` \ (clas,inst_tys) -> + checkInstTermination theta inst_tys `thenM_` + checkTc (checkInstFDs theta clas inst_tys) + (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_` + newDFunName clas inst_tys (srcSpanStart loc) `thenM` \ dfun_name -> + getOverlapFlag `thenM` \ overlap_flag -> + let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys + ispec = mkLocalInstance dfun overlap_flag in - mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_` - -- Check that there is an InstInfo for each generic type constructor - let - missing = genericTyCons `minusList` [tc | (tc,_) <- tc_inst_infos] - in - checkTc (null missing) (missingGenericInstances missing) `thenTc_` - - returnTc inst_infos + tcIsHsBoot `thenM` \ is_boot -> + checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags)) + badBootDeclErr `thenM_` + returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags })) 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 (foldr add emptyAssoc matches) - where - add match env = case maybeGenericMatch match of - Nothing -> env - Just (ty, match') -> extendAssoc_C (++) env (ty, [match']) - - wrap ms = FunMonoBind id infixop ms loc - ---------------------------------- -mkGenericInstance :: Module -> Class -> SrcLoc - -> (RenamedHsType, RenamedMonoBinds) - -> TcM InstInfo - -mkGenericInstance mod 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 - tcTyVars (nameSetToList (extractHsTyVars hs_ty)) - (kcHsSigType hs_ty) `thenTc` \ tyvars -> - tcExtendTyVarEnv tyvars $ - - -- Type-check the instance type, and check its form - tcHsSigType hs_ty `thenTc` \ inst_ty -> - checkTc (validGenericInstanceType inst_ty) - (badGenericInstanceType binds) `thenTc_` - - -- Make the dictionary function. - newDFunName mod clas [inst_ty] loc `thenNF_Tc` \ dfun_name -> - let - inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] - inst_tys = [inst_ty] - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys inst_theta - in - - returnTc (InstInfo { iLocal = True, iDFunId = dfun_id, - iBinds = binds, iPrags = [] }) + msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class")) \end{code} @@ -416,18 +222,27 @@ mkGenericInstance mod clas loc (hs_ty, binds) %************************************************************************ \begin{code} -tcInstDecls2 :: [InstInfo] - -> NF_TcM (LIE, TcMonoBinds) - -tcInstDecls2 inst_decls --- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls - = foldr combine (returnNF_Tc (emptyLIE, EmptyMonoBinds)) - (map tcInstDecl2 inst_decls) - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `AndMonoBinds` binds2) +tcInstDecls2 :: [LTyClDecl Name] -> [InstInfo] + -> TcM (LHsBinds Id, TcLclEnv) +-- (a) From each class declaration, +-- generate any default-method bindings +-- (b) From each instance decl +-- generate the dfun binding + +tcInstDecls2 tycl_decls inst_decls + = do { -- (a) Default methods from class decls + (dm_binds_s, dm_ids_s) <- mapAndUnzipM tcClassDecl2 $ + filter (isClassDecl.unLoc) tycl_decls + ; tcExtendIdEnv (concat dm_ids_s) $ do + + -- (b) instance declarations + ; inst_binds_s <- mappM tcInstDecl2 inst_decls + + -- Done + ; let binds = unionManyBags dm_binds_s `unionBags` + unionManyBags inst_binds_s + ; tcl_env <- getLclEnv -- Default method Ids in here + ; returnM (binds, tcl_env) } \end{code} ======= New documentation starts here (Sept 92) ============== @@ -496,128 +311,89 @@ is the @dfun_theta@ below. First comes the easy case of a non-local instance decl. -\begin{code} -tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds) -tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, - iBinds = monobinds, iPrags = uprags }) - | not is_local - = returnNF_Tc (emptyLIE, EmptyMonoBinds) - - | otherwise - = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ - tcAddSrcLoc (getSrcLoc dfun_id) $ +\begin{code} +tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) - -- Instantiate the instance decl with tc-style type variables - tcInstId dfun_id `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> +tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds }) + = let + dfun_id = instanceDFunId ispec + rigid_info = InstSkol dfun_id + inst_ty = idType dfun_id + in + -- Prime error recovery + recoverM (returnM emptyLHsBinds) $ + setSrcSpan (srcLocSpan (getSrcLoc dfun_id)) $ + addErrCtxt (instDeclCtxt2 (idType dfun_id)) $ + + -- Instantiate the instance decl with skolem constants + tcSkolSigType rigid_info inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') -> + -- These inst_tyvars' 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! let - (clas, inst_tys') = splitDictTy dict_ty' - origin = InstanceDeclOrigin - + (clas, inst_tys') = tcSplitDFunHead inst_head' (class_tyvars, sc_theta, _, op_items) = classBigSig clas - dm_ids = [dm_id | (_, DefMeth dm_id) <- op_items] - sel_names = [idName sel_id | (sel_id, _) <- op_items] - -- Instantiate the super-class context with inst_tys - sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys') sc_theta - - -- Find any definitions in monobinds that aren't from the class - bad_bndrs = collectMonoBinders monobinds `minusList` sel_names - - -- The type variable from the dict fun actually scope - -- over the bindings. They were gotten from - -- the original instance declaration - (inst_tyvars, _) = splitForAllTys (idType dfun_id) + sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta + origin = SigOrigin rigid_info in - -- Check that all the method bindings come from this class - mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_` - -- Create dictionary Ids from the specified instance contexts. - newClassDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) -> - newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) -> - newClassDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> - - tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' ( - tcExtendGlobalValEnv dm_ids ( - -- Default-method Ids may be mentioned in synthesised RHSs - - mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' - dfun_theta' - monobinds uprags True) - op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) -> - - -- Deal with SPECIALISE instance pragmas by making them - -- look like SPECIALISE pragmas for the dfun - let - dfun_prags = [SpecSig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags] + newDicts InstScOrigin sc_theta' `thenM` \ sc_dicts -> + newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts -> + newDicts origin [mkClassPred clas inst_tys'] `thenM` \ [this_dict] -> + -- Default-method Ids may be mentioned in synthesised RHSs, + -- but they'll already be in the environment. + + -- Typecheck the methods + let -- These insts are in scope; quite a few, eh? + avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts in - tcExtendGlobalValEnv [dfun_id] ( - tcSpecSigs dfun_prags - ) `thenTc` \ (prag_binds, prag_lie) -> - - -- 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 before passing them to tcSimplifyAndCheck - zonkTcSigTyVars inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars -> + tcMethods origin clas inst_tyvars' + dfun_theta' inst_tys' avail_insts + op_items binds `thenM` \ (meth_ids, meth_binds) -> + + -- Figure out bindings for the superclass context + -- Don't include this_dict in the 'givens', else + -- sc_dicts get bound by just selecting from this_dict!! + addErrCtxt superClassCtxt + (tcSimplifySuperClasses inst_tyvars' + dfun_arg_dicts + sc_dicts) `thenM` \ sc_binds -> + + -- It's possible that the superclass stuff might unified one + -- of the inst_tyavars' with something in the envt + checkSigTyVars inst_tyvars' `thenM_` + + -- Deal with 'SPECIALISE instance' pragmas 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 + specs = case binds of + VanillaInst _ prags -> filter isSpecInstLSig prags + other -> [] 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) -> + tcPrags dfun_id specs `thenM` \ prags -> - -- 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) -> - - -- 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 + inline_prag | null dfun_arg_dicts = [] + | otherwise = [InlinePrag (Inline AlwaysActive True)] + -- 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 eRROR_ID) [(unUsgTy . idType) this_dict_id]) - (HsLit (HsString msg)) - - | otherwise -- The common case - = mkHsConApp dict_constr inst_tys' (map HsVar (sc_dict_ids ++ meth_ids)) + = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) -- We don't produce a binding for the dict_constr; instead we -- rely on the simplifier to unfold this saturated application -- We do this rather than generate an HsCon directly, because @@ -626,113 +402,205 @@ tcInstDecl2 (InstInfo { iLocal = is_local, iDFunId = dfun_id, -- than needing to be repeated here. where - msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas)) - - dict_bind = VarMonoBind this_dict_id dict_rhs - method_binds = andMonoBindList method_binds_s - - main_bind - = AbsBinds - zonked_inst_tyvars - dfun_arg_dicts_ids - [(inst_tyvars', dfun_id, this_dict_id)] - emptyNameSet -- No inlines (yet) - (lie_binds1 `AndMonoBinds` - lie_binds2 `AndMonoBinds` - method_binds `AndMonoBinds` - dict_bind) + msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas) + + dict_bind = noLoc (VarBind this_dict_id dict_rhs) + all_binds = dict_bind `consBag` (sc_binds `unionBags` meth_binds) + + main_bind = noLoc $ AbsBinds + inst_tyvars' + (map instToId dfun_arg_dicts) + [(inst_tyvars', dfun_id, this_dict_id, + inline_prag ++ prags)] + all_binds in - returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie, - main_bind `AndMonoBinds` prag_binds) -\end{code} + showLIE (text "instance") `thenM_` + returnM (unitBag main_bind) -%************************************************************************ -%* * -\subsection{Checking for a decent instance type} -%* * -%************************************************************************ +tcMethods origin clas 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 = collectHsBindBinders monobinds `minusList` sel_names + in + mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` -@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ + -- Make the method bindings + let + mk_method_bind = mkMethodBind origin clas inst_tys' monobinds + in + mapAndUnzipM mk_method_bind op_items `thenM` \ (meth_insts, meth_infos) -> + + -- And type check them + -- It's really worth making meth_insts available to the tcMethodBind + -- Consider instance Monad (ST s) where + -- {-# INLINE (>>) #-} + -- (>>) = ...(>>=)... + -- If we don't include meth_insts, we end up with bindings like this: + -- rec { dict = MkD then bind ... + -- then = inline_me (... (GHC.Base.>>= dict) ...) + -- bind = ... } + -- The trouble is that (a) 'then' and 'dict' are mutually recursive, + -- and (b) the inline_me prevents us inlining the >>= selector, which + -- would unravel the loop. Result: (>>) ends up as a loop breaker, and + -- is not inlined across modules. Rather ironic since this does not + -- happen without the INLINE pragma! + -- + -- Solution: make meth_insts available, so that 'then' refers directly + -- to the local 'bind' rather than going via the dictionary. + -- + -- BUT WATCH OUT! If the method type mentions the class variable, then + -- this optimisation is not right. Consider + -- class C a where + -- op :: Eq a => a + -- + -- instance C Int where + -- op = op + -- The occurrence of 'op' on the rhs gives rise to a constraint + -- op at Int + -- The trouble is that the 'meth_inst' for op, which is 'available', also + -- looks like 'op at Int'. But they are not the same. + let + prag_fn = mkPragFun uprags + all_insts = avail_insts ++ catMaybes meth_insts + tc_method_bind = tcMethodBind inst_tyvars' dfun_theta' all_insts prag_fn + meth_ids = [meth_id | (_,meth_id,_) <- meth_infos] + in -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. + mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> + + returnM (meth_ids, unionManyBags meth_binds_s) -We can also have instances for functions: @instance Foo (a -> b) ...@. -\begin{code} -scrutiniseInstanceConstraint pred - = getDOptsTc `thenTc` \ dflags -> case () of - () - | dopt Opt_AllowUndecidableInstances dflags - -> returnNF_Tc () - - | Just (clas,tys) <- getClassTys_maybe pred, - all isTyVarTy tys - -> returnNF_Tc () - - | otherwise - -> addErrTc (instConstraintErr pred) - -scrutiniseInstanceHead clas inst_taus - = getDOptsTc `thenTc` \ dflags -> case () of - () - | -- CCALL CHECK - -- A user declaration of a CCallable/CReturnable instance - -- must be for a "boxed primitive" type. - (clas `hasKey` cCallableClassKey - && not (ccallable_type dflags first_inst_tau)) - || - (clas `hasKey` cReturnableClassKey - && not (creturnable_type first_inst_tau)) - -> addErrTc (nonBoxedPrimCCallErr clas first_inst_tau) - - -- Allow anything for AllowUndecidableInstances - | dopt Opt_AllowUndecidableInstances dflags - -> returnNF_Tc () - - -- If GlasgowExts then check at least one isn't a type variable - | dopt Opt_GlasgowExts dflags - -> 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 () +-- Derived newtype instances +tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' + avail_insts op_items (NewTypeDerived rep_tys) + = getInstLoc origin `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 `unionBags` listToBag meth_binds) where - (first_inst_tau : _) = inst_taus - - -- Stuff for algebraic or -> type - maybe_tycon_app = splitTyConApp_maybe first_inst_tau - Just (tycon, arg_tys) = maybe_tycon_app - - -- Stuff for an *algebraic* data type - alg_tycon_app_maybe = splitAlgTyConApp_maybe first_inst_tau - -- The "Alg" part looks through synonyms - Just (alg_tycon, _, _) = alg_tycon_app_maybe - - ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty - creturnable_type ty = isFFIResultTy ty + 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, noLoc (VarBind meth_id (nlHsVar (instToId rhs_inst))), rhs_inst) + + -- Instantiate rep_tys with the relevant type variables + -- This looks a bit odd, because inst_tyvars' are the skolemised version + -- of the type variables in the instance declaration; but rep_tys doesn't + -- have the skolemised version, so we substitute them in here + rep_tys' = substTys subst rep_tys + subst = zipOpenTvSubst inst_tyvars' (mkTyVarTys inst_tyvars') \end{code} + ------------------------------ + [Inline dfuns] Inlining dfuns unconditionally + ------------------------------ + +The code above unconditionally inlines dict funs. Here's why. +Consider this program: + + test :: Int -> Int -> Bool + test x y = (x,y) == (y,x) || test y x + -- Recursive to avoid making it inline. + +This needs the (Eq (Int,Int)) instance. If we inline that dfun +the code we end up with is good: + + Test.$wtest = + \r -> case ==# [ww ww1] of wild { + PrelBase.False -> Test.$wtest ww1 ww; + PrelBase.True -> + case ==# [ww1 ww] of wild1 { + PrelBase.False -> Test.$wtest ww1 ww; + PrelBase.True -> PrelBase.True []; + }; + }; + Test.test = \r [w w1] + case w of w2 { + PrelBase.I# ww -> + case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; }; + }; + +If we don't inline the dfun, the code is not nearly as good: + + (==) = case PrelTup.$fEq(,) PrelBase.$fEqInt PrelBase.$fEqInt of tpl { + PrelBase.:DEq tpl1 tpl2 -> tpl2; + }; + + Test.$wtest = + \r [ww ww1] + let { y = PrelBase.I#! [ww1]; } in + let { x = PrelBase.I#! [ww]; } in + let { sat_slx = PrelTup.(,)! [y x]; } in + let { sat_sly = PrelTup.(,)! [x y]; + } in + case == sat_sly sat_slx of wild { + PrelBase.False -> Test.$wtest ww1 ww; + PrelBase.True -> PrelBase.True []; + }; + + Test.test = + \r [w w1] + case w of w2 { + PrelBase.I# ww -> + case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; }; + }; + +Why doesn't GHC inline $fEq? Because it looks big: + + PrelTup.zdfEqZ1T{-rcX-} + = \ @ a{-reT-} :: * @ b{-reS-} :: * + zddEq{-rf6-} _Ks :: {PrelBase.Eq{-23-} a{-reT-}} + zddEq1{-rf7-} _Ks :: {PrelBase.Eq{-23-} b{-reS-}} -> + let { + zeze{-rf0-} _Kl :: (b{-reS-} -> b{-reS-} -> PrelBase.Bool{-3c-}) + zeze{-rf0-} = PrelBase.zeze{-01L-}@ b{-reS-} zddEq1{-rf7-} } in + let { + zeze1{-rf3-} _Kl :: (a{-reT-} -> a{-reT-} -> PrelBase.Bool{-3c-}) + zeze1{-rf3-} = PrelBase.zeze{-01L-} @ a{-reT-} zddEq{-rf6-} } in + let { + zeze2{-reN-} :: ((a{-reT-}, b{-reS-}) -> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-}) + zeze2{-reN-} = \ ds{-rf5-} _Ks :: (a{-reT-}, b{-reS-}) + ds1{-rf4-} _Ks :: (a{-reT-}, b{-reS-}) -> + case ds{-rf5-} + of wild{-reW-} _Kd { (a1{-rf2-} _Ks, a2{-reZ-} _Ks) -> + case ds1{-rf4-} + of wild1{-reX-} _Kd { (b1{-rf1-} _Ks, b2{-reY-} _Ks) -> + PrelBase.zaza{-r4e-} + (zeze1{-rf3-} a1{-rf2-} b1{-rf1-}) + (zeze{-rf0-} a2{-reZ-} b2{-reY-}) + } + } } in + let { + a1{-reR-} :: ((a{-reT-}, b{-reS-})-> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-}) + a1{-reR-} = \ a2{-reV-} _Ks :: (a{-reT-}, b{-reS-}) + b1{-reU-} _Ks :: (a{-reT-}, b{-reS-}) -> + PrelBase.not{-r6I-} (zeze2{-reN-} a2{-reV-} b1{-reU-}) + } in + PrelBase.zdwZCDEq{-r8J-} @ (a{-reT-}, b{-reS-}) a1{-reR-} zeze2{-reN-}) + +and it's not as bad as it seems, because it's further dramatically +simplified: only zeze2 is extracted and its body is simplified. + + %************************************************************************ %* * \subsection{Error messages} @@ -740,57 +608,17 @@ scrutiniseInstanceHead clas inst_taus %************************************************************************ \begin{code} -tcAddDeclCtxt decl thing_inside - = tcAddSrcLoc loc $ - tcAddErrCtxt ctxt $ - thing_inside +instDeclCtxt1 hs_inst_ty + = inst_decl_ctxt (case unLoc hs_inst_ty of + HsForAllTy _ _ _ (L _ (HsPredTy pred)) -> ppr pred + HsPredTy pred -> ppr pred + other -> ppr hs_inst_ty) -- Don't expect this +instDeclCtxt2 dfun_ty + = inst_decl_ctxt (ppr (mkClassPred cls tys)) where - (name, loc, thing) - = case decl of - (ClassDecl _ name _ _ _ _ _ loc) -> (name, loc, "class") - (TySynonym name _ _ loc) -> (name, loc, "type synonym") - (TyData NewType _ name _ _ _ _ loc _ _) -> (name, loc, "newtype") - (TyData DataType _ name _ _ _ _ loc _ _) -> (name, loc, "data type") - - ctxt = hsep [ptext SLIT("In the"), text thing, - ptext SLIT("declaration for"), quotes (ppr name)] -\end{code} + (_,_,cls,tys) = tcSplitDFunTy dfun_ty -\begin{code} -instConstraintErr pred - = hang (ptext SLIT("Illegal constraint") <+> - quotes (pprPred pred) <+> - ptext SLIT("in instance context")) - 4 (ptext SLIT("(Instance contexts must constrain only type variables)")) - -badGenericInstanceType binds - = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), - nest 4 (ppr binds)] - -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) - -instTypeErr clas tys msg - = sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys), - nest 4 (parens msg) - ] - -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]) - -methodCtxt = ptext SLIT("When checking the methods of an instance declaration") -\end{code} +inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc - +superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration") +\end{code}