X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=76b87cee041eec3810d108241ab64896239ebdeb;hb=d8a9b534050f62f65d9db0d69aad9733f687ef8b;hp=9b53a04dd29e438062f7b2edebd2f0f23a5d6f59;hpb=d68887047bcfb9021151f768fe1a22df2d3fbe1e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 9b53a04..76b87ce 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,80 +4,75 @@ \section[TcInstDecls]{Typechecking instance declarations} \begin{code} -module TcInstDcls ( tcInstDecls1, tcInstDecls2, tcAddDeclCtxt ) where +module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls1, addInstDFuns, + tcInstDecls2, initInstEnv, tcAddDeclCtxt ) where #include "HsVersions.h" -import CmdLineOpts ( DynFlag(..), dopt ) +import CmdLineOpts ( DynFlag(..) ) -import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..), - MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), - andMonoBindList, collectMonoBinders, isClassDecl, toHsType +import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), + MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), + andMonoBindList, collectMonoBinders, + isClassDecl, toHsType ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl, +import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, extractHsTyVars, maybeGenericMatch ) import TcHsSyn ( TcMonoBinds, mkHsConApp ) import TcBinds ( tcSpecSigs ) -import TcClassDcl ( tcMethodBind, badMethodErr ) +import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr ) import TcMonad -import TcType ( tcInstType ) -import Inst ( InstOrigin(..), - newDicts, instToId, +import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr, + UserTypeCtxt(..), SourceTyCtxt(..) ) +import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys, + tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, + TyVarDetails(..) + ) +import Inst ( InstOrigin(..), newDicts, instToId, LIE, mkLIE, emptyLIE, plusLIE, plusLIEs ) import TcDeriv ( tcDeriving ) -import TcEnv ( TcEnv, tcExtendGlobalValEnv, - tcExtendTyVarEnvForMeths, - tcAddImportedIdInfo, tcLookupClass, +import TcEnv ( tcExtendGlobalValEnv, tcExtendLocalValEnv2, + tcLookupId, tcLookupClass, tcExtendTyVarEnv2, InstInfo(..), pprInstInfo, simpleInstInfoTyCon, - simpleInstInfoTy, newDFunName, tcExtendTyVarEnv, - isLocalThing, + simpleInstInfoTy, newDFunName ) import InstEnv ( InstEnv, extendInstEnv ) -import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType, checkSigTyVars ) -import TcSimplify ( tcSimplifyCheck ) -import HscTypes ( HomeSymbolTable, DFunId, - ModDetails(..), PackageInstEnv, PersistentRenamerState +import PprType ( pprClassPred ) +import TcMonoType ( tcSigPolyId, tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType ) +import TcUnify ( checkSigTyVars ) +import TcSimplify ( tcSimplifyCheck, tcSimplifyTop ) +import HscTypes ( HomeSymbolTable, DFunId, FixityEnv, + PersistentCompilerState(..), PersistentRenamerState, + ModDetails(..) ) - +import Subst ( mkTyVarSubst, substTheta ) import DataCon ( classDataCon ) -import Class ( Class, DefMeth(..), classBigSig ) +import Class ( Class, classBigSig ) import Var ( idName, idType ) -import VarSet ( emptyVarSet ) -import Maybes ( maybeToBool ) -import MkId ( mkDictFunId ) +import Id ( setIdLocalExported ) +import MkId ( mkDictFunId, unsafeCoerceId, rUNTIME_ERROR_ID ) import FunDeps ( checkInstFDs ) import Generics ( validGenericInstanceType ) import Module ( Module, foldModuleEnv ) import Name ( getSrcLoc ) -import NameSet ( emptyNameSet, unitNameSet, nameSetToList ) -import PrelInfo ( eRROR_ID ) -import PprType ( pprClassPred, pprPred ) -import TyCon ( TyCon, isSynTyCon ) -import Type ( splitDFunTy, isTyVarTy, - splitTyConApp_maybe, splitDictTy, - splitForAllTys, - tyVarsOfTypes, mkClassPred, mkTyVarTy, - isTyVarClassPred, inheritablePred - ) -import Subst ( mkTopTyVarSubst, substTheta ) -import VarSet ( varSetElems ) -import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIImportResultTy ) -import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey ) -import Name ( Name ) +import NameSet ( unitNameSet, emptyNameSet, nameSetToList ) +import TyCon ( TyCon ) +import TysWiredIn ( genericTyCons ) import SrcLoc ( SrcLoc ) -import VarSet ( varSetElems ) import Unique ( Uniquable(..) ) -import BasicTypes ( NewOrData(..), Fixity ) +import Util ( lengthExceeds, isSingleton ) +import BasicTypes ( NewOrData(..) ) +import UnicodeUtil ( stringToUtf8 ) import ErrUtils ( dumpIfSet_dyn ) import ListSetOps ( Assoc, emptyAssoc, plusAssoc_C, mapAssoc, - assocElts, extendAssoc_C, - equivClassesByUniq, minusList + assocElts, extendAssoc_C, equivClassesByUniq, minusList ) -import List ( partition ) +import Maybe ( catMaybes ) import Outputable +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -163,115 +158,125 @@ and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. Gather up the instance declarations from their various sources \begin{code} -tcInstDecls1 :: PackageInstEnv - -> PersistentRenamerState - -> HomeSymbolTable -- Contains instances - -> TcEnv -- Contains IdInfo for dfun ids - -> (Name -> Maybe Fixity) -- for deriving Show and Read - -> Module -- Module for deriving - -> [RenamedHsDecl] - -> TcM (PackageInstEnv, InstEnv, [InstInfo], RenamedHsBinds) - -tcInstDecls1 inst_env0 prs hst unf_env get_fixity this_mod decls - = let - inst_decls = [inst_decl | InstD inst_decl <- decls] - tycl_decls = [decl | TyClD decl <- decls] - clas_decls = filter isClassDecl tycl_decls - in +tcInstDecls1 -- Deal with source-code instance decls + :: PersistentRenamerState + -> InstEnv -- Imported instance envt + -> FixityEnv -- for deriving Show and Read + -> Module -- Module for deriving + -> [RenamedTyClDecl] -- For deriving stuff + -> [RenamedInstDecl] -- Source code instance decls + -> TcM (InstEnv, -- the full inst env + [InstInfo], -- instance decls to process; contains all dfuns + -- for this module + RenamedHsBinds) -- derived instances + +tcInstDecls1 prs inst_env get_fixity this_mod + tycl_decls inst_decls +-- The incoming inst_env includes all the imported instances already + = checkNoErrsTc $ + -- 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 inst_decls `thenNF_Tc` \ inst_infos -> + mapNF_Tc tcLocalInstDecl1 inst_decls `thenNF_Tc` \ local_inst_infos -> + let + local_inst_info = catMaybes local_inst_infos + clas_decls = filter isClassDecl tycl_decls + in -- (2) Instances from generic class declarations getGenericInstances clas_decls `thenTc` \ generic_inst_info -> -- Next, construct the instance environment so far, consisting of - -- a) cached non-home-package InstEnv (gotten from pcs) pcs_insts pcs - -- b) imported instance decls (not in the home package) inst_env1 - -- c) other modules in this package (gotten from hst) inst_env2 - -- d) local instance decls inst_env3 - -- e) generic instances inst_env4 - -- The result of (b) replaces the cached InstEnv in the PCS - let - (local_inst_info, imported_inst_info) - = partition (isLocalThing this_mod . iDFunId) (concat inst_infos) - - imported_dfuns = map (tcAddImportedIdInfo unf_env . iDFunId) - imported_inst_info - hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst - in - addInstDFuns inst_env0 imported_dfuns `thenNF_Tc` \ inst_env1 -> - addInstDFuns inst_env1 hst_dfuns `thenNF_Tc` \ inst_env2 -> - addInstInfos inst_env2 local_inst_info `thenNF_Tc` \ inst_env3 -> - addInstInfos inst_env3 generic_inst_info `thenNF_Tc` \ inst_env4 -> + -- a) imported instance decls (from this module) inst_env1 + -- b) local instance decls inst_env2 + -- c) generic instances final_inst_env + addInstInfos inst_env local_inst_info `thenNF_Tc` \ inst_env1 -> + addInstInfos inst_env1 generic_inst_info `thenNF_Tc` \ inst_env2 -> -- (3) Compute instances from "deriving" clauses; -- note that we only do derivings for things in this module; -- we ignore deriving decls from interfaces! -- This stuff computes a context for the derived instance decl, so it - -- needs to know about all the instances possible; hecne inst_env4 - tcDeriving prs this_mod inst_env4 get_fixity tycl_decls - `thenTc` \ (deriv_inst_info, deriv_binds) -> - addInstInfos inst_env4 deriv_inst_info `thenNF_Tc` \ final_inst_env -> + -- needs to know about all the instances possible; hence inst_env4 + tcDeriving prs this_mod inst_env2 + get_fixity tycl_decls `thenTc` \ (deriv_inst_info, deriv_binds) -> + addInstInfos inst_env2 deriv_inst_info `thenNF_Tc` \ final_inst_env -> - returnTc (inst_env1, - final_inst_env, + returnTc (final_inst_env, generic_inst_info ++ deriv_inst_info ++ local_inst_info, deriv_binds) +initInstEnv :: PersistentCompilerState -> HomeSymbolTable -> NF_TcM InstEnv +-- Initialise the instance environment from the +-- persistent compiler state and the home symbol table +initInstEnv pcs hst + = let + pkg_inst_env = pcs_insts pcs + hst_dfuns = foldModuleEnv ((++) . md_insts) [] hst + in + addInstDFuns pkg_inst_env hst_dfuns + 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 -> +addInstDFuns inst_env dfuns + = getDOptsTc `thenNF_Tc` \ dflags -> let - (inst_env', errs) = extendInstEnv dflags dfuns infos + (inst_env', errs) = extendInstEnv dflags inst_env dfuns in addErrsTc errs `thenNF_Tc_` + traceTc (text "Adding instances:" <+> vcat (map pp dfuns)) `thenTc_` returnTc inst_env' + where + pp dfun = ppr dfun <+> dcolon <+> ppr (idType dfun) \end{code} \begin{code} -tcInstDecl1 :: RenamedInstDecl -> NF_TcM [InstInfo] --- Deal with a single instance declaration -tcInstDecl1 decl@(InstDecl poly_ty binds uprags maybe_dfun_name src_loc) - = -- Prime error recovery, set source location - recoverNF_Tc (returnNF_Tc []) $ - tcAddSrcLoc src_loc $ +tcIfaceInstDecls1 :: [RenamedInstDecl] -> NF_TcM [DFunId] +tcIfaceInstDecls1 decls = mapNF_Tc tcIfaceInstDecl1 decls - -- Type-check all the stuff before the "where" - tcAddErrCtxt (instDeclCtxt poly_ty) ( - tcHsSigType poly_ty - ) `thenTc` \ poly_ty' -> - let - (tyvars, theta, clas, inst_tys) = splitDFunTy poly_ty' - in +tcIfaceInstDecl1 :: RenamedInstDecl -> NF_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 +tcIfaceInstDecl1 decl@(InstDecl poly_ty binds uprags (Just dfun_name) src_loc) + = tcLookupId dfun_name - (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] - getDOptsTc `thenTc` \ dflags -> - checkInstValidity dflags theta clas inst_tys `thenTc_` - - -- Make the dfun id and return it - newDFunName 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) -> +tcLocalInstDecl1 :: RenamedInstDecl + -> NF_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 + recoverNF_Tc (returnNF_Tc Nothing) $ + tcAddSrcLoc src_loc $ + tcAddErrCtxt (instDeclCtxt poly_ty) $ + -- Typecheck the instance type itself. We can't use + -- tcHsSigType, because it's not a valid user type. + kcHsSigType poly_ty `thenTc_` + tcHsType poly_ty `thenTc` \ poly_ty' -> let - dfun_id = mkDictFunId dfun_name clas tyvars inst_tys theta + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in - returnTc [InstInfo { iDFunId = dfun_id, - iBinds = binds, iPrags = uprags }] + checkValidTheta InstThetaCtxt theta `thenTc_` + checkValidInstHead tau `thenTc` \ (clas,inst_tys) -> + checkTc (checkInstFDs theta clas inst_tys) + (instTypeErr (pprClassPred clas inst_tys) msg) `thenTc_` + newDFunName clas inst_tys src_loc `thenNF_Tc` \ dfun_name -> + returnTc (Just (InstInfo { iDFunId = mkDictFunId dfun_name clas tyvars inst_tys theta, + iBinds = binds, iPrags = uprags })) + where + msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class")) \end{code} @@ -315,7 +320,7 @@ getGenericInstances class_decls if null gen_inst_info then returnTc [] else - getDOptsTc `thenTc` \ dflags -> + getDOptsTc `thenNF_Tc` \ dflags -> ioToTc (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" (vcat (map pprInstInfo gen_inst_info))) `thenNF_Tc_` @@ -328,7 +333,7 @@ get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, | null groups = returnTc [] -- The comon case: no generic default methods - | otherwise -- A local class decl with generic default methods + | otherwise -- A source class decl with generic default methods = recoverNF_Tc (returnNF_Tc []) $ tcAddDeclCtxt decl $ tcLookupClass class_name `thenTc` \ clas -> @@ -346,7 +351,7 @@ get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, - length group > 1] + group `lengthExceeds` 1] get_uniq (tc,_) = getUnique tc in mapTc (addErrTc . dupGenericInsts) bad_groups `thenTc_` @@ -395,12 +400,13 @@ mkGenericInstance clas loc (hs_ty, binds) -- 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 $ + 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 hs_ty `thenTc` \ inst_ty -> + tcHsSigType GenPatCtxt hs_ty `thenTc` \ inst_ty -> checkTc (validGenericInstanceType inst_ty) (badGenericInstanceType binds) `thenTc_` @@ -408,12 +414,10 @@ mkGenericInstance clas loc (hs_ty, binds) newDFunName 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 + dfun_id = mkDictFunId dfun_name clas tyvars [inst_ty] inst_theta in - returnTc (InstInfo { iDFunId = dfun_id, - iBinds = binds, iPrags = [] }) + returnTc (InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = [] }) \end{code} @@ -506,107 +510,106 @@ First comes the easy case of a non-local instance decl. \begin{code} -tcInstDecl2 :: InstInfo -> NF_TcM (LIE, TcMonoBinds) --- tcInstDecl2 is called *only* on InstInfos +tcInstDecl2 :: InstInfo -> TcM (LIE, TcMonoBinds) -tcInstDecl2 (InstInfo { iDFunId = dfun_id, - iBinds = monobinds, iPrags = uprags }) +tcInstDecl2 (NewTypeDerived { iDFunId = dfun_id }) + = tcInstType InstTv (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') -> + newDicts InstanceDeclOrigin dfun_theta' `thenNF_Tc` \ rep_dicts -> + let + rep_dict_id = ASSERT( isSingleton rep_dicts ) + instToId (head rep_dicts) -- Derived newtypes have just one dict arg + + body = TyLam inst_tyvars' $ + DictLam [rep_dict_id] $ + (HsVar unsafeCoerceId `TyApp` [idType rep_dict_id, inst_head']) + `HsApp` + (HsVar rep_dict_id) + -- You might wonder why we have the 'coerce'. It's because the + -- type equality mechanism isn't clever enough; see comments with Type.eqType. + -- So Lint complains if we don't have this. + in + returnTc (emptyLIE, VarMonoBind dfun_id body) + +tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = monobinds, iPrags = uprags }) = -- Prime error recovery recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $ tcAddSrcLoc (getSrcLoc dfun_id) $ tcAddErrCtxt (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 - tcInstType (idType dfun_id) `thenNF_Tc` \ (inst_tyvars', dfun_theta', dict_ty') -> + tcInstType InstTv inst_ty `thenNF_Tc` \ (inst_tyvars', dfun_theta', inst_head') -> let - (clas, inst_tys') = splitDictTy dict_ty' - origin = InstanceDeclOrigin - + Just pred = tcSplitPredTy_maybe inst_head' + (clas, inst_tys') = getClassPredTys pred (class_tyvars, sc_theta, _, op_items) = classBigSig clas - dm_ids = [dm_id | (_, DefMeth dm_id) <- op_items] - sel_names = [idName sel_id | (sel_id, _) <- op_items] - -- Instantiate the super-class context with inst_tys - sc_theta' = substTheta (mkTopTyVarSubst class_tyvars inst_tys') sc_theta - - -- Find any definitions in monobinds that aren't from the class - bad_bndrs = collectMonoBinders monobinds `minusList` sel_names - - -- 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 (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 -> + newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts -> + newDicts origin [pred] `thenNF_Tc` \ [this_dict] -> + -- Default-method Ids may be mentioned in synthesised RHSs, + -- but they'll already be in the environment. + -- Check that all the method bindings come from this class - mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_` + mkMethodBinds clas inst_tys' op_items monobinds `thenTc` \ (meth_insts, meth_infos) -> - -- Create dictionary Ids from the specified instance contexts. - newDicts origin sc_theta' `thenNF_Tc` \ sc_dicts -> - newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts -> - newDicts origin [mkClassPred clas inst_tys'] `thenNF_Tc` \ [this_dict] -> + let -- These insts are in scope; quite a few, eh? + avail_insts = [this_dict] ++ dfun_arg_dicts ++ + sc_dicts ++ meth_insts - tcExtendTyVarEnvForMeths inst_tyvars inst_tyvars' ( - tcExtendGlobalValEnv dm_ids ( - -- Default-method Ids may be mentioned in synthesised RHSs + xtve = inst_tyvars `zip` inst_tyvars' + tc_meth = tcMethodBind xtve inst_tyvars' dfun_theta' avail_insts + in + mapAndUnzipTc tc_meth meth_infos `thenTc` \ (meth_binds_s, meth_lie_s) -> - mapAndUnzip3Tc (tcMethodBind clas origin inst_tyvars' inst_tys' - dfun_theta' - monobinds uprags True) - op_items - )) `thenTc` \ (method_binds_s, insts_needed_s, meth_insts) -> + -- Figure out bindings for the superclass context + tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts + `thenTc` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) -> -- 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] + spec_prags = [ SpecSig (idName dfun_id) ty loc + | SpecInstSig ty loc <- uprags] in + tcExtendGlobalValEnv [dfun_id] ( - tcSpecSigs dfun_prags + tcExtendTyVarEnv2 xtve $ + tcExtendLocalValEnv2 [(idName sel_id, tcSigPolyId sig) + | (sel_id, sig, _) <- meth_infos] $ + -- Map sel_id to the local method name we are using + tcSpecSigs spec_prags ) `thenTc` \ (prag_binds, prag_lie) -> - -- Check the overloading constraints of the methods and superclasses - let - -- These insts are in scope; quite a few, eh? - avail_insts = [this_dict] ++ - dfun_arg_dicts ++ - sc_dicts ++ - meth_insts - - methods_lie = plusLIEs insts_needed_s - in - - -- Simplify the constraints from methods - tcAddErrCtxt methodCtxt ( - tcSimplifyCheck - (ptext SLIT("instance declaration context")) - inst_tyvars' - avail_insts - methods_lie - ) `thenTc` \ (const_lie1, lie_binds1) -> - - -- Figure out bindings for the superclass context - tcAddErrCtxt superClassCtxt ( - tcSimplifyCheck - (ptext SLIT("instance declaration context")) - inst_tyvars' - dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts - -- get bound by just selecting from this_dict!! - (mkLIE sc_dicts) - ) `thenTc` \ (const_lie2, lie_binds2) -> - - checkSigTyVars inst_tyvars' emptyVarSet `thenNF_Tc` \ zonked_inst_tyvars -> - -- Create the result bindings let + local_dfun_id = setIdLocalExported dfun_id + -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId + dict_constr = classDataCon clas scs_and_meths = map instToId (sc_dicts ++ meth_insts) this_dict_id = instToId this_dict - inlines = unitNameSet (idName dfun_id) + 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 dict_rhs | null scs_and_meths @@ -616,8 +619,8 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, -- emit an error message. This in turn means that we don't -- mention the constructor, which doesn't exist for CCallable, CReturnable -- Hardly beautiful, but only three extra lines. - HsApp (TyApp (HsVar eRROR_ID) [idType this_dict_id]) - (HsLit (HsString msg)) + HsApp (TyApp (HsVar rUNTIME_ERROR_ID) [idType this_dict_id]) + (HsLit (HsStringPrim (mkFastString (stringToUtf8 msg)))) | otherwise -- The common case = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) @@ -629,26 +632,102 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, -- than needing to be repeated here. where - msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas)) - - dict_bind = VarMonoBind this_dict_id dict_rhs - method_binds = andMonoBindList method_binds_s - - main_bind - = AbsBinds - zonked_inst_tyvars - (map instToId dfun_arg_dicts) - [(inst_tyvars', dfun_id, this_dict_id)] - inlines - (lie_binds1 `AndMonoBinds` - lie_binds2 `AndMonoBinds` - method_binds `AndMonoBinds` - dict_bind) + msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas) + + dict_bind = VarMonoBind this_dict_id dict_rhs + meth_binds = andMonoBindList meth_binds_s + all_binds = sc_binds_inner `AndMonoBinds` meth_binds `AndMonoBinds` dict_bind + + main_bind = AbsBinds + zonked_inst_tyvars + (map instToId dfun_arg_dicts) + [(inst_tyvars', local_dfun_id, this_dict_id)] + inlines all_binds in - returnTc (const_lie1 `plusLIE` const_lie2 `plusLIE` prag_lie, - main_bind `AndMonoBinds` prag_binds) + returnTc (plusLIEs meth_lie_s `plusLIE` prag_lie, + main_bind `AndMonoBinds` prag_binds `AndMonoBinds` sc_binds_outer) +\end{code} + +Superclass loops +~~~~~~~~~~~~~~~~ +We have to be very, very careful when generating superclasses, lest we +accidentally build a loop. Here's an example: + + class S a + + class S a => C a where { opc :: a -> a } + class S b => D b where { opd :: b -> b } + + instance C Int where + opc = opd + + instance D Int where + opd = opc + +From (instance C Int) we get the constraint set {ds1:S Int, dd:D Int} +Simplifying, we may well get: + $dfCInt = :C ds1 (opd dd) + dd = $dfDInt + ds1 = $p1 dd +Notice that we spot that we can extract ds1 from dd. + +Alas! Alack! We can do the same for (instance D Int): + + $dfDInt = :D ds2 (opc dc) + dc = $dfCInt + ds2 = $p1 dc + +And now we've defined the superclass in terms of itself. + + +Solution: treat the superclass context separately, and simplify it +all the way down to nothing on its own. Don't toss any 'free' parts +out to be simplified together with other bits of context. +Hence the tcSimplifyTop below. + +At a more basic level, don't include this_dict in the context wrt +which we simplify sc_dicts, else sc_dicts get bound by just selecting +from this_dict!! + +\begin{code} +tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts + = tcAddErrCtxt superClassCtxt $ + tcSimplifyCheck doc inst_tyvars' + dfun_arg_dicts + (mkLIE sc_dicts) `thenTc` \ (sc_lie, sc_binds1) -> + + -- It's possible that the superclass stuff might have done unification + checkSigTyVars inst_tyvars' `thenTc` \ zonked_inst_tyvars -> + + -- We must simplify this all the way down + -- lest we build superclass loops + -- See notes about superclass loops above + tcSimplifyTop sc_lie `thenTc` \ sc_binds2 -> + + returnTc (zonked_inst_tyvars, sc_binds1, sc_binds2) + + where + doc = ptext SLIT("instance declaration superclass context") \end{code} +\begin{code} +mkMethodBinds clas inst_tys' op_items monobinds + = -- Check that all the method bindings come from this class + mapTc (addErrTc . badMethodErr clas) bad_bndrs `thenNF_Tc_` + + -- Make the method bindings + mapAndUnzipTc mk_method_bind op_items + + where + mk_method_bind op_item = mkMethodBind InstanceDeclOrigin clas + inst_tys' monobinds op_item + + -- Find any definitions in monobinds that aren't from the class + sel_names = [idName sel_id | (sel_id, _) <- op_items] + bad_bndrs = collectMonoBinders monobinds `minusList` sel_names +\end{code} + + ------------------------------ Inlining dfuns unconditionally ------------------------------ @@ -742,102 +821,6 @@ simplified: only zeze2 is extracted and its body is simplified. %************************************************************************ %* * -\subsection{Checking for a decent instance type} -%* * -%************************************************************************ - -@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ - -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) ...@. - -\begin{code} -checkInstValidity dflags theta clas inst_tys - | null errs = returnTc () - | otherwise = addErrsTc errs `thenNF_Tc_` failTc - where - errs = checkInstHead dflags theta clas inst_tys ++ - [err | pred <- theta, err <- checkInstConstraint dflags pred] - -checkInstConstraint dflags pred - -- Checks whether a predicate is legal in the - -- context of an instance declaration - | ok = [] - | otherwise = [instConstraintErr pred] - where - ok = inheritablePred pred && - (isTyVarClassPred pred || arbitrary_preds_ok) - - arbitrary_preds_ok = dopt Opt_AllowUndecidableInstances dflags - - -checkInstHead dflags theta clas inst_taus - | -- CCALL CHECK - -- A user declaration of a CCallable/CReturnable instance - -- must be for a "boxed primitive" type. - (clas `hasKey` cCallableClassKey - && not (ccallable_type dflags first_inst_tau)) - || - (clas `hasKey` cReturnableClassKey - && not (creturnable_type first_inst_tau)) - = [nonBoxedPrimCCallErr clas first_inst_tau] - - -- If GlasgowExts then check at least one isn't a type variable - | dopt Opt_GlasgowExts dflags - = -- GlasgowExts case - check_tyvars dflags clas inst_taus ++ check_fundeps dflags theta clas inst_taus - - -- 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 - ) - = [instTypeErr clas inst_taus - (text "the instance type must be of form (T a b c)" $$ - text "where T is not a synonym, and a,b,c are distinct type variables")] - - | otherwise - = [] - - where - (first_inst_tau : _) = inst_taus - - -- Stuff for algebraic or -> type - maybe_tycon_app = splitTyConApp_maybe first_inst_tau - Just (tycon, arg_tys) = maybe_tycon_app - - ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty - creturnable_type ty = isFFIImportResultTy dflags ty - -check_tyvars dflags clas inst_taus - -- Check that at least one isn't a type variable - -- unless -fallow-undecideable-instances - | dopt Opt_AllowUndecidableInstances dflags = [] - | not (all isTyVarTy inst_taus) = [] - | otherwise = [the_err] - where - the_err = instTypeErr clas inst_taus msg - msg = ptext SLIT("There must be at least one non-type-variable in the instance head") - $$ ptext SLIT("Use -fallow-undecidable-instances to lift this restriction") - -check_fundeps dflags theta clas inst_taus - | checkInstFDs theta clas inst_taus = [] - | otherwise = [the_err] - where - the_err = instTypeErr clas inst_taus msg - msg = ptext SLIT("the instance types do not agree with the functional dependencies of the class") -\end{code} - - -%************************************************************************ -%* * \subsection{Error messages} %* * %************************************************************************ @@ -866,12 +849,6 @@ instDeclCtxt inst_ty = ptext SLIT("In the instance declaration for") <+> quotes \end{code} \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)] @@ -879,8 +856,6 @@ badGenericInstanceType 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)), @@ -889,16 +864,6 @@ dupGenericInsts tc_inst_infos where ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst) -instTypeErr clas tys msg - = sep [ptext SLIT("Illegal instance declaration for") <+> - quotes (pprClassPred clas tys), - nest 4 (parens msg) - ] - -nonBoxedPrimCCallErr clas inst_ty - = hang (ptext SLIT("Unacceptable instance type for ccall-ish class")) - 4 (pprClassPred clas [inst_ty]) - 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}