X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=3fec58dd0a402b6d98daa0bc0e4f6b5518ca10e8;hb=1cdafe99abae1628f34ca8c064e3a8c0fcdbd079;hp=b30af59741a722eda57a08c2cf1186b0a95f19d7;hpb=0877011afd5886ee06df2e2723d631ff0686324f;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index b30af59..3fec58d 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -4,71 +4,44 @@ \section[TcInstDecls]{Typechecking instance declarations} \begin{code} -module TcInstDcls ( tcInstDecls1, tcIfaceInstDecls, - tcInstDecls2, tcAddDeclCtxt ) where +module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where #include "HsVersions.h" - -import CmdLineOpts ( DynFlag(..) ) - -import HsSyn ( InstDecl(..), TyClDecl(..), HsType(..), - MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..), - andMonoBindList, collectMonoBinders, - isClassDecl, isSourceInstDecl, toHsType - ) -import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, - RenamedMonoBinds, RenamedTyClDecl, RenamedHsType, - extractHsTyVars, maybeGenericMatch - ) -import TcHsSyn ( TcMonoBinds, mkHsConApp ) -import TcBinds ( tcSpecSigs ) -import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr ) +import HsSyn +import TcBinds ( mkPragFun, tcPrags, badBootDeclErr ) +import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr, + tcClassDecl2, getGenericInstances ) import TcRnMonad -import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr, - checkAmbiguity, UserTypeCtxt(..), SourceTyCtxt(..) ) -import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys, tyVarsOfType, - tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, mkTyVarTys, - TyVarDetails(..) - ) -import Inst ( InstOrigin(..), tcInstClassOp, newDicts, instToId, showLIE ) +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 ( tcExtendGlobalValEnv, - tcLookupClass, tcExtendTyVarEnv2, - tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId, - InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon, - simpleInstInfoTy, newDFunName +import TcEnv ( InstInfo(..), InstBindings(..), + newDFunName, tcExtendIdEnv ) -import PprType ( pprClassPred ) -import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType ) +import TcHsType ( kcHsSigType, tcHsKindedType ) import TcUnify ( checkSigTyVars ) -import TcSimplify ( tcSimplifyCheck, tcSimplifyTop ) -import HscTypes ( DFunId ) -import Subst ( mkTyVarSubst, substTheta, substTy ) +import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses ) +import Type ( zipOpenTvSubst, substTheta, substTys ) import DataCon ( classDataCon ) -import Class ( Class, classBigSig ) -import Var ( idName, idType ) -import NameSet -import Id ( setIdLocalExported ) +import Class ( classBigSig ) +import Var ( Id, idName, idType ) 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 Name ( Name, getSrcLoc ) import Maybe ( catMaybes ) -import List ( partition ) +import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart ) +import ListSetOps ( minusList ) import Outputable +import Bag +import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) ) import FastString \end{code} @@ -156,248 +129,89 @@ 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 + :: [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 - RenamedHsBinds, -- Supporting bindings for derived instances - FreeVars) -- And the free vars of the derived code + 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) - 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 -> + mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos -> let local_inst_info = catMaybes local_inst_infos - clas_decls = filter isClassDecl tycl_decls + clas_decls = filter (isClassDecl.unLoc) tycl_decls in -- (2) Instances from generic class declarations - getGenericInstances clas_decls `thenM` \ generic_inst_info -> + 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 $ + -- 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; hence inst_env4 - tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds, fvs) -> - tcExtendLocalInstEnv deriv_inst_info $ + tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds) -> + addInsts deriv_inst_info $ - getGblEnv `thenM` \ gbl_env -> + getGblEnv `thenM` \ gbl_env -> returnM (gbl_env, generic_inst_info ++ deriv_inst_info ++ local_inst_info, - deriv_binds, fvs) + deriv_binds) + +addInsts :: [InstInfo] -> TcM a -> TcM a +addInsts infos thing_inside + = tcExtendLocalInstEnv (map iSpec infos) thing_inside \end{code} \begin{code} -tcLocalInstDecl1 :: RenamedInstDecl +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" -- -- 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) +tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags)) = -- Prime error recovery, set source location recoverM (returnM Nothing) $ - addSrcLoc src_loc $ - addErrCtxt (instDeclCtxt poly_ty) $ + 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_` - tcHsType poly_ty `thenM` \ poly_ty' -> + kcHsSigType poly_ty `thenM` \ kinded_ty -> + tcHsKindedType kinded_ty `thenM` \ poly_ty' -> let (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in 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 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 - gen_inst_info = concat gen_inst_infos - in - if null gen_inst_info then - returnM [] - else - getDOpts `thenM` \ dflags -> - ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Generic instances" - (vcat (map pprInstInfo gen_inst_info))) - `thenM_` - returnM gen_inst_info - -get_generics decl@(ClassDecl {tcdMeths = Nothing}) - = returnM [] -- Imported class decls - -get_generics decl@(ClassDecl {tcdName = class_name, tcdMeths = Just def_methods, tcdLoc = loc}) - | null groups - = returnM [] -- The comon case: no generic default methods - - | otherwise -- A source class decl with generic default methods - = recoverM (returnM []) $ - tcAddDeclCtxt decl $ - tcLookupClass class_name `thenM` \ clas -> - - -- Make an InstInfo out of each group - mappM (mkGenericInstance clas loc) groups `thenM` \ inst_infos -> - - -- Check that there is only one InstInfo for each type constructor - -- The main way this can fail is if you write - -- f {| a+b |} ... = ... - -- f {| x+y |} ... = ... - -- Then at this point we'll have an InstInfo for each - let - tc_inst_infos :: [(TyCon, InstInfo)] - tc_inst_infos = [(simpleInstInfoTyCon i, i) | i <- inst_infos] - - bad_groups = [group | group <- equivClassesByUniq get_uniq tc_inst_infos, - group `lengthExceeds` 1] - get_uniq (tc,_) = getUnique tc - in - mappM (addErrTc . dupGenericInsts) bad_groups `thenM_` - - -- Check that there is an InstInfo for each generic type constructor - let - missing = genericTyCons `minusList` [tc | (tc,_) <- tc_inst_infos] + 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 - checkTc (null missing) (missingGenericInstances missing) `thenM_` - returnM 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 (foldl add emptyAssoc matches) - -- Using foldl not foldr is vital, else - -- we reverse the order of the bindings! - where - add env match = case maybeGenericMatch match of - Nothing -> env - Just (ty, match') -> extendAssoc_C (++) env (ty, [match']) - - wrap ms = FunMonoBind id infixop ms loc - ---------------------------------- -mkGenericInstance :: Class -> SrcLoc - -> (RenamedHsType, RenamedMonoBinds) - -> TcM InstInfo - -mkGenericInstance clas loc (hs_ty, binds) - -- Make a generic instance declaration - -- For example: instance (C a, C b) => C (a+b) where { binds } - - = -- Extract the universally quantified type variables - let - sig_tvs = map UserTyVar (nameSetToList (extractHsTyVars hs_ty)) - in - tcHsTyVars sig_tvs (kcHsSigType hs_ty) $ \ tyvars -> - - -- Type-check the instance type, and check its form - tcHsSigType GenPatCtxt hs_ty `thenM` \ inst_ty -> - checkTc (validGenericInstanceType inst_ty) - (badGenericInstanceType binds) `thenM_` - - -- Make the dictionary function. - newDFunName clas [inst_ty] loc `thenM` \ dfun_name -> - let - inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars] - dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty] - in - - returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] }) + msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class")) \end{code} @@ -408,10 +222,27 @@ mkGenericInstance clas loc (hs_ty, binds) %************************************************************************ \begin{code} -tcInstDecls2 :: [InstInfo] -> TcM TcMonoBinds -tcInstDecls2 inst_decls - = mappM tcInstDecl2 inst_decls `thenM` \ binds_s -> - returnM (andMonoBindList binds_s) +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) ============== @@ -482,74 +313,74 @@ First comes the easy case of a non-local instance decl. \begin{code} -tcInstDecl2 :: InstInfo -> TcM TcMonoBinds +tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) -tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) - = -- Prime error recovery - recoverM (returnM EmptyMonoBinds) $ - addSrcLoc (getSrcLoc dfun_id) $ - addErrCtxt (instDeclCtxt (toHsType (idType dfun_id))) $ - let - inst_ty = idType dfun_id - (inst_tyvars, _) = tcSplitForAllTys inst_ty - -- The tyvars of the instance decl scope over the 'where' part +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! - in - - -- Instantiate the instance decl with tc-style type variables - tcInstType InstTv inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') -> let - Just pred = tcSplitPredTy_maybe inst_head' - (clas, inst_tys') = getClassPredTys pred + (clas, inst_tys') = tcSplitDFunHead inst_head' (class_tyvars, sc_theta, _, op_items) = classBigSig clas -- Instantiate the super-class context with inst_tys - sc_theta' = substTheta (mkTyVarSubst class_tyvars inst_tys') sc_theta - origin = InstanceDeclOrigin + sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta + origin = SigOrigin rigid_info in -- 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] -> + 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 - tcMethods clas inst_tyvars 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 - tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts - `thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) -> - - -- Deal with 'SPECIALISE instance' pragmas by making them - -- look like SPECIALISE pragmas for the dfun + -- 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 - 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' + specs = case binds of + VanillaInst _ prags -> filter isSpecInstLSig prags + other -> [] in - tcExtendGlobalValEnv [dfun_id] ( - tcExtendTyVarEnv2 xtve $ - tcSpecSigs spec_prags - ) `thenM` \ prag_binds -> - + tcPrags dfun_id specs `thenM` \ prags -> + -- Create the result bindings let 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) + 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 @@ -562,17 +393,6 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) -- 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 @@ -584,33 +404,34 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds }) 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 + dict_bind = noLoc (VarBind this_dict_id dict_rhs) + all_binds = dict_bind `consBag` (sc_binds `unionBags` meth_binds) - main_bind = AbsBinds - zonked_inst_tyvars - (map instToId dfun_arg_dicts) - [(inst_tyvars', dfun_id, this_dict_id)] - inlines all_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 - showLIE "instance" `thenM_` - returnM (main_bind `AndMonoBinds` prag_binds `AndMonoBinds` sc_binds_outer) + showLIE (text "instance") `thenM_` + returnM (unitBag main_bind) -tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' +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 = collectMonoBinders monobinds `minusList` sel_names + bad_bndrs = collectHsBindBinders monobinds `minusList` sel_names in mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` -- Make the method bindings let - mk_method_bind = mkMethodBind InstanceDeclOrigin clas inst_tys' monobinds + mk_method_bind = mkMethodBind origin clas inst_tys' monobinds in - mapAndUnzipM mk_method_bind op_items `thenM` \ (meth_insts, meth_infos) -> + 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 @@ -629,20 +450,34 @@ tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' -- -- 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 - all_insts = avail_insts ++ meth_insts - xtve = inst_tyvars `zip` inst_tyvars' - tc_method_bind = tcMethodBind xtve inst_tyvars' dfun_theta' all_insts uprags + 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 + mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> - returnM (map instToId meth_insts, andMonoBindList meth_binds_s) + returnM (meth_ids, unionManyBags meth_binds_s) -- Derived newtype instances -tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' +tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' avail_insts op_items (NewTypeDerived rep_tys) - = getInstLoc InstanceDeclOrigin `thenM` \ inst_loc -> + = getInstLoc origin `thenM` \ inst_loc -> mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) -> tcSimplifyCheck @@ -651,7 +486,7 @@ tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' -- I don't think we have to do the checkSigTyVars thing - returnM (meth_ids, lie_binds `AndMonoBinds` andMonoBindList meth_binds) + returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds) where do_one inst_loc (sel_id, _) @@ -664,73 +499,14 @@ tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys' let meth_id = instToId meth_inst in - return (meth_id, VarMonoBind meth_id (HsVar (instToId rhs_inst)), rhs_inst) + return (meth_id, noLoc (VarBind meth_id (nlHsVar (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: - - 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 - = addErrCtxt superClassCtxt $ - getLIE (tcSimplifyCheck doc inst_tyvars' - dfun_arg_dicts - sc_dicts) `thenM` \ (sc_binds1, sc_lie) -> - - -- It's possible that the superclass stuff might have done unification - checkSigTyVars inst_tyvars' `thenM` \ zonked_inst_tyvars -> - - -- We must simplify this all the way down - -- lest we build superclass loops - -- See Note [Superclass loops] above - tcSimplifyTop sc_lie `thenM` \ sc_binds2 -> - - returnM (zonked_inst_tyvars, sc_binds1, sc_binds2) - - where - doc = ptext SLIT("instance declaration superclass context") + -- 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} @@ -832,44 +608,17 @@ simplified: only zeze2 is extracted and its body is simplified. %************************************************************************ \begin{code} -tcAddDeclCtxt decl thing_inside - = addSrcLoc (tcdLoc decl) $ - addErrCtxt 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 - 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} + (_,_,cls,tys) = tcSplitDFunTy dfun_ty + +inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc -\begin{code} -badGenericInstanceType binds - = vcat [ptext SLIT("Illegal type pattern in the generic bindings"), - nest 4 (ppr binds)] - -missingGenericInstances missing - = ptext SLIT("Missing type patterns for") <+> pprQuotedList missing - -dupGenericInsts tc_inst_infos - = vcat [ptext SLIT("More than one type pattern for a single generic type constructor:"), - nest 4 (vcat (map ppr_inst_ty tc_inst_infos)), - ptext SLIT("All the type patterns for a generic type constructor must be identical") - ] - where - ppr_inst_ty (tc,inst) = ppr (simpleInstInfoTy inst) - -methodCtxt = ptext SLIT("When checking the methods of an instance declaration") superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration") \end{code}