X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=26616bc550215e7da341609ff184ac19fb81b311;hb=1cdafe99abae1628f34ca8c064e3a8c0fcdbd079;hp=012b723b590c77f64c36b9aca64b32d829204654;hpb=6954d21089c19939e9632ffd5a183a2eb053b558;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 012b723..3fec58d 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -1,106 +1,48 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcInstDecls]{Typechecking instance declarations} \begin{code} -#include "HsVersions.h" - -module TcInstDcls ( - tcInstDecls1, - tcInstDecls2, - tcMethodBind - ) where +module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where +#include "HsVersions.h" -IMP_Ubiq() - -import HsSyn ( HsDecl(..), InstDecl(..), TyDecl, ClassDecl, DefaultDecl, - FixityDecl, IfaceSig, Sig(..), - SpecInstSig(..), HsBinds(..), - MonoBinds(..), GRHSsAndBinds(..), GRHS(..), Match, - InPat(..), OutPat(..), HsExpr(..), HsLit(..), - Stmt, DoOrListComp, ArithSeqInfo, Fake, Fixity, - HsType(..), HsTyVar, - SYN_IE(RecFlag), recursive, nonRecursive, collectMonoBinders, - andMonoBinds - ) -import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedMonoBinds), - SYN_IE(RenamedInstDecl), SYN_IE(RenamedFixityDecl), SYN_IE(RenamedHsExpr), - SYN_IE(RenamedSig), SYN_IE(RenamedSpecInstSig), SYN_IE(RenamedHsDecl) - ) -import TcHsSyn ( TcIdOcc(..), SYN_IE(TcIdBndr), SYN_IE(TcHsBinds), - SYN_IE(TcMonoBinds), SYN_IE(TcExpr), tcIdType, - mkHsTyLam, mkHsTyApp, - mkHsDictLam, mkHsDictApp ) - -import TcBinds ( tcBindWithSigs, TcSigInfo(..) ) -import TcMonad -import RnMonad ( SYN_IE(RnNameSupply) ) -import Inst ( Inst, InstOrigin(..), SYN_IE(InstanceMapper), - instToId, newDicts, newMethod, SYN_IE(LIE), emptyLIE, plusLIE ) -import TcBinds ( tcPragmaSigs, checkSigTyVars ) -import PragmaInfo ( PragmaInfo(..) ) +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 ( tcLookupClass, newLocalId, tcExtendGlobalTyVars, tcGetGlobalTyVars ) -import SpecEnv ( SpecEnv ) -import TcGRHSs ( tcGRHSsAndBinds ) -import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs ) -import TcKind ( TcKind, unifyKind ) -import TcMatches ( tcMatchesFun ) -import TcMonoType ( tcTyVarScope, tcContext, tcHsTypeKind ) -import TcSimplify ( tcSimplifyAndCheck ) -import TcType ( SYN_IE(TcType), SYN_IE(TcTyVar), SYN_IE(TcTyVarSet), - tcInstSigTyVars, tcInstType, tcInstSigTcType, - tcInstTheta, tcInstTcType, tcInstSigType +import TcEnv ( InstInfo(..), InstBindings(..), + newDFunName, tcExtendIdEnv ) -import Unify ( unifyTauTy, unifyTauTyLists ) - - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, - concatBag, foldBag, bagToList, listToBag, - Bag ) -import CmdLineOpts ( opt_GlasgowExts, opt_CompilingGhcInternals, - opt_OmitDefaultInstanceMethods, - opt_SpecialiseOverloaded - ) -import Class ( GenClass, GenClassOp, - classBigSig, classOps, classOpLocalType, - classDefaultMethodId, SYN_IE(Class) - ) -import Id ( GenId, idType, isDefaultMethodId_maybe, - isNullaryDataCon, dataConArgTys, SYN_IE(Id) ) +import TcHsType ( kcHsSigType, tcHsKindedType ) +import TcUnify ( checkSigTyVars ) +import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses ) +import Type ( zipOpenTvSubst, substTheta, substTys ) +import DataCon ( classDataCon ) +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 Maybes ( maybeToBool, expectJust, seqMaybe ) -import Name ( nameOccName, getOccString, occNameString, moduleString, getOccName, - isLocallyDefined, OccName, Name{--O only-}, SYN_IE(Module), - NamedThing(..) - ) -import PrelVals ( nO_EXPLICIT_METHOD_ERROR_ID ) -import PprType ( GenType, GenTyVar, GenClass, GenClassOp, TyCon, - pprParendGenType - ) -import PprStyle import Outputable -import SrcLoc ( SrcLoc, noSrcLoc ) -import Pretty -import TyCon ( isSynTyCon, derivedFor ) -import Type ( GenType(..), SYN_IE(ThetaType), mkTyVarTys, isPrimType, - splitSigmaTy, splitAppTys, isTyVarTy, matchTy, mkSigmaTy, - getTyCon_maybe, maybeAppTyCon, SYN_IE(Type), - maybeBoxedPrimType, maybeAppDataTyCon, splitRhoTy, eqTy - ) -import TyVar ( GenTyVar, SYN_IE(GenTyVarSet), tyVarSetToList, - mkTyVarSet, unionTyVarSets, SYN_IE(TyVar) ) -import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon ) -import TysWiredIn ( stringTy ) -import Unique ( Unique, cCallableClassKey, cReturnableClassKey ) -import UniqFM ( Uniquable(..) ) -import Util ( zipEqual, panic, pprPanic, pprTrace -#if __GLASGOW_HASKELL__ < 202 - , trace -#endif - ) +import Bag +import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) ) +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -176,71 +118,100 @@ Here, Bop1 \ldots Bopn bind the methods op1 \ldots opn, and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm. \end{enumerate} + +%************************************************************************ +%* * +\subsection{Extracting instance decls} +%* * +%************************************************************************ + +Gather up the instance declarations from their various sources + \begin{code} -tcInstDecls1 :: [RenamedHsDecl] - -> Module -- module name for deriving - -> RnNameSupply -- for renaming derivings - -> TcM s (Bag InstInfo, - RenamedHsBinds, - PprStyle -> Doc) - -tcInstDecls1 decls mod_name rn_name_supply - = -- Do the ordinary instance declarations - mapNF_Tc (tcInstDecl1 mod_name) - [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags -> +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 + mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos -> + let - decl_inst_info = unionManyBags inst_info_bags + local_inst_info = catMaybes local_inst_infos + clas_decls = filter (isClassDecl.unLoc) tycl_decls in - -- Handle "derived" instances; note that we only do derivings - -- for things in this module; we ignore deriving decls from - -- interfaces! We pass fixities, because they may be used - -- in deriving Read and Show. - tcDeriving mod_name rn_name_supply decl_inst_info - `thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) -> + -- (2) Instances from generic class declarations + getGenericInstances clas_decls `thenM` \ generic_inst_info -> + + -- Next, construct the instance environment so far, consisting of + -- a) local instance decls + -- b) generic instances + addInsts local_inst_info $ + addInsts generic_inst_info $ + + -- (3) Compute instances from "deriving" clauses; + -- 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) -> + 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} +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 +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 - full_inst_info = deriv_inst_info `unionBags` decl_inst_info + (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 (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 - returnTc (full_inst_info, deriv_binds, ddump_deriv) - - -tcInstDecl1 :: Module -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) - -tcInstDecl1 mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc) - = -- Prime error recovery, set source location - recoverNF_Tc (returnNF_Tc emptyBag) $ - tcAddSrcLoc src_loc $ - - -- Look things up - tcLookupClass class_name `thenTc` \ (clas_kind, clas) -> - - -- Typecheck the context and instance type - tcTyVarScope tyvar_names (\ tyvars -> - tcContext context `thenTc` \ theta -> - tcHsTypeKind inst_ty `thenTc` \ (tau_kind, tau) -> - unifyKind clas_kind tau_kind `thenTc_` - returnTc (tyvars, theta, tau) - ) `thenTc` \ (inst_tyvars, inst_theta, inst_tau) -> - - -- Check for respectable instance type - scrutiniseInstanceType dfun_name clas inst_tau - `thenTc` \ (inst_tycon,arg_tys) -> - -- Make the dfun id and constant-method ids - mkInstanceRelatedIds dfun_name - clas inst_tyvars inst_tau inst_theta - `thenNF_Tc` \ (dfun_id, dfun_theta) -> + tcIsHsBoot `thenM` \ is_boot -> + checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags)) + badBootDeclErr `thenM_` - returnTc (unitBag (InstInfo clas inst_tyvars inst_tau inst_theta - dfun_theta dfun_id - binds src_loc uprags)) + returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags })) where - (tyvar_names, context, dict_ty) = case poly_ty of - HsForAllTy tvs cxt dict_ty -> (tvs, cxt, dict_ty) - other -> ([], [], poly_ty) - (class_name, inst_ty) = case dict_ty of - MonoDictTy cls ty -> (cls,ty) - other -> pprPanic "Malformed intance decl" (ppr PprDebug poly_ty) + msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class")) \end{code} @@ -251,19 +222,29 @@ tcInstDecl1 mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc) %************************************************************************ \begin{code} -tcInstDecls2 :: Bag InstInfo - -> NF_TcM s (LIE s, TcHsBinds s) - -tcInstDecls2 inst_decls - = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyBinds)) inst_decls - where - combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) -> - tc2 `thenNF_Tc` \ (lie2, binds2) -> - returnNF_Tc (lie1 `plusLIE` lie2, - binds1 `ThenBinds` binds2) +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) ============== The main purpose of @tcInstDecl2@ is to return a @HsBinds@ which defines @@ -330,461 +311,314 @@ is the @dfun_theta@ below. First comes the easy case of a non-local instance decl. + \begin{code} -tcInstDecl2 :: InstInfo -> NF_TcM s (LIE s, TcHsBinds s) - -tcInstDecl2 (InstInfo clas inst_tyvars inst_ty - inst_decl_theta dfun_theta - dfun_id monobinds - locn uprags) - | not (isLocallyDefined dfun_id) - = returnNF_Tc (emptyLIE, EmptyBinds) - -{- - -- I deleted this "optimisation" because when importing these - -- instance decls the renamer would look for the dfun bindings and they weren't there. - -- This would be fixable, but it seems simpler just to produce a tiny void binding instead, - -- even though it's never used. - - -- This case deals with CCallable etc, which don't need any bindings - | isNoDictClass clas - = returnNF_Tc (emptyLIE, EmptyBinds) --} - - | otherwise - = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc locn $ - - -- Get the class signature - tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) -> - let - origin = InstanceDeclOrigin - (class_tyvar, - super_classes, sc_sel_ids, - class_ops, op_sel_ids, defm_ids) = classBigSig clas +tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) + +tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds }) + = let + dfun_id = instanceDFunId ispec + rigid_info = InstSkol dfun_id + inst_ty = idType dfun_id in - tcInstType tenv inst_ty `thenNF_Tc` \ inst_ty' -> - tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' -> - tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' -> + -- 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 - sc_theta' = super_classes `zip` repeat inst_ty' - in - -- Create dictionary Ids from the specified instance contexts. - newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) -> - newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) -> - newDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) -> - newDicts origin [(clas,inst_ty')] `thenNF_Tc` \ (this_dict, [this_dict_id]) -> + (clas, inst_tys') = tcSplitDFunHead inst_head' + (class_tyvars, sc_theta, _, op_items) = classBigSig clas - -- Check the method bindings - let - inst_tyvars_set' = mkTyVarSet inst_tyvars' - check_from_this_class (bndr, loc) - | nameOccName bndr `elem` sel_names = returnTc () - | otherwise = recoverTc (returnTc ()) $ - tcAddSrcLoc loc $ - failTc (instBndrErr bndr clas) - sel_names = map getOccName op_sel_ids + -- Instantiate the super-class context with inst_tys + sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta + origin = SigOrigin rigid_info in - mapTc check_from_this_class (bagToList (collectMonoBinders monobinds)) `thenTc_` - tcExtendGlobalTyVars inst_tyvars_set' ( - mapAndUnzip3Tc (tcMethodBind (getDefmRhs clas) inst_ty' monobinds) - (op_sel_ids `zip` [0..]) - ) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) -> - - -- Check the overloading constraints of the methods and superclasses - let - (meth_lies, meth_ids) = unzip meth_lies_w_ids - avail_insts -- These insts are in scope; quite a few, eh? - = this_dict `plusLIE` dfun_arg_dicts `plusLIE` unionManyBags meth_lies + -- Create dictionary Ids from the specified instance contexts. + 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 - tcAddErrCtxt (bindSigCtxt meth_ids) ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars - avail_insts - (sc_dicts `unionBags` - unionManyBags insts_needed_s) -- Need to get defns for all these - ) `thenTc` \ (const_lie, super_binds) -> - - -- Check that we *could* construct the superclass dictionaries, - -- even though we are *actually* going to pass the superclass dicts in; - -- the check ensures that the caller will never have a problem building - -- them. - tcAddErrCtxt superClassSigCtxt ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars - inst_decl_dicts -- The instance dictionaries available - sc_dicts -- The superclass dicationaries reqd - ) `thenTc_` - -- Ignore the result; we're only doing - -- this to make sure it can be done. - - -- Now process any SPECIALIZE pragmas for the methods + 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 - spec_sigs = [ s | s@(SpecSig _ _ _ _) <- uprags ] + specs = case binds of + VanillaInst _ prags -> filter isSpecInstLSig prags + other -> [] in - tcPragmaSigs spec_sigs `thenTc` \ (_, spec_binds, spec_lie) -> - + tcPrags dfun_id specs `thenM` \ prags -> + -- Create the result bindings let - dict_bind = VarMonoBind this_dict_id (Dictionary sc_dict_ids meth_ids) - method_binds = andMonoBinds method_binds_s - - main_bind - = MonoBind ( - AbsBinds - inst_tyvars' - dfun_arg_dicts_ids - [(inst_tyvars', RealId dfun_id, this_dict_id)] - (super_binds `AndMonoBinds` - method_binds `AndMonoBinds` - dict_bind)) - [] recursive -- Recursive to play safe + dict_constr = classDataCon clas + 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 + = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths) + -- We don't produce a binding for the dict_constr; instead we + -- rely on the simplifier to unfold this saturated application + -- We do this rather than generate an HsCon directly, because + -- it means that the special cases (e.g. dictionary with only one + -- member) are dealt with by the common MkId.mkDataConWrapId code rather + -- than needing to be repeated here. + + where + msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas) + + dict_bind = 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_lie `plusLIE` spec_lie, - main_bind `ThenBinds` spec_binds) -\end{code} - -The next function looks for a method binding; if there isn't one it -manufactures one that just calls the global default method. - -See the notes under default decls in TcClassDcl.lhs. - -\begin{code} -getDefmRhs :: Class -> Int -> RenamedHsExpr -getDefmRhs clas idx = HsVar (getName (classDefaultMethodId clas idx)) -\end{code} + showLIE (text "instance") `thenM_` + returnM (unitBag main_bind) -%************************************************************************ -%* * -\subsection{Processing each method} -%* * -%************************************************************************ - -\begin{code} -tcMethodBind - :: (Int -> RenamedHsExpr) -- Function mapping a tag to default RHS - -> TcType s -- Instance type - -> RenamedMonoBinds -- Method binding - -> (Id, Int) -- Selector ID (and its 0-indexed tag) - -- for which binding is wanted - -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s)) - -tcMethodBind deflt_fn inst_ty meth_binds (sel_id, idx) - = newMethod origin (RealId sel_id) [inst_ty] `thenNF_Tc` \ meth@(_, TcId meth_id) -> - tcInstSigTcType (idType meth_id) `thenNF_Tc` \ (tyvars', rho_ty') -> +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 - meth_name = getName meth_id - default_bind = PatMonoBind (VarPatIn meth_name) - (GRHSsAndBindsIn [OtherwiseGRHS (deflt_fn idx) noSrcLoc] EmptyBinds) - noSrcLoc - - (op_name, op_bind) = case go (getOccName sel_id) meth_binds of - Just stuff -> stuff - Nothing -> (meth_name, default_bind) - - (theta', tau') = splitRhoTy rho_ty' - sig_info = TySigInfo op_name meth_id tyvars' theta' tau' noSrcLoc + sel_names = [idName sel_id | (sel_id, _) <- op_items] + bad_bndrs = collectHsBindBinders monobinds `minusList` sel_names in - tcBindWithSigs [op_name] op_bind [sig_info] - nonRecursive (\_ -> NoPragmaInfo) `thenTc` \ (binds, insts, _) -> - - returnTc (binds, insts, meth) - where - origin = InstanceDeclOrigin -- Poor - - go occ EmptyMonoBinds = Nothing - go occ (AndMonoBinds b1 b2) = go occ b1 `seqMaybe` go occ b2 + mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` - go occ b@(FunMonoBind op_name _ _ locn) | nameOccName op_name == occ = Just (op_name, b) - | otherwise = Nothing - go occ b@(PatMonoBind (VarPatIn op_name) _ locn) | nameOccName op_name == occ = Just (op_name, b) - | otherwise = Nothing - go occ other = panic "Urk! Bad instance method binding" -\end{code} - - - -%************************************************************************ -%* * -\subsection{Type-checking specialise instance pragmas} -%* * -%************************************************************************ - -\begin{code} -{- LATER -tcSpecInstSigs :: E -> CE -> TCE - -> Bag InstInfo -- inst decls seen (declared and derived) - -> [RenamedSpecInstSig] -- specialise instance upragmas - -> TcM (Bag InstInfo) -- new, overlapped, inst decls - -tcSpecInstSigs e ce tce inst_infos [] - = returnTc emptyBag - -tcSpecInstSigs e ce tce inst_infos sigs - = buildInstanceEnvs inst_infos `thenTc` \ inst_mapper -> - tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ spec_inst_infos -> - returnTc spec_inst_infos - where - tc_inst_spec_sigs inst_mapper [] - = returnNF_Tc emptyBag - tc_inst_spec_sigs inst_mapper (sig:sigs) - = tcSpecInstSig e ce tce inst_infos inst_mapper sig `thenNF_Tc` \ info_sig -> - tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ info_sigs -> - returnNF_Tc (info_sig `unionBags` info_sigs) - -tcSpecInstSig :: E -> CE -> TCE - -> Bag InstInfo - -> InstanceMapper - -> RenamedSpecInstSig - -> NF_TcM (Bag InstInfo) - -tcSpecInstSig e ce tce inst_infos inst_mapper (SpecInstSig class_name ty src_loc) - = recoverTc emptyBag ( - tcAddSrcLoc src_loc ( - let - clas = lookupCE ce class_name -- Renamer ensures this can't fail - - -- Make some new type variables, named as in the specialised instance type - ty_names = extractHsTyNames ???is_tyvarish_name??? ty - (tmpl_e,inst_tmpls,inst_tmpl_tys) = mkTVE ty_names - in - babyTcMtoTcM (tcInstanceType ce tce tmpl_e True src_loc ty) - `thenTc` \ inst_ty -> + -- Make the method bindings let - maybe_tycon = case maybeAppDataTyCon inst_ty of - Just (tc,_,_) -> Just tc - Nothing -> Nothing - - maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos + mk_method_bind = mkMethodBind origin clas inst_tys' monobinds in - -- Check that we have a local instance declaration to specialise - checkMaybeTc maybe_unspec_inst - (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_` - - -- Create tvs to substitute for tmpls while simplifying the context - copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) -> + 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 - Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta - _ _ binds _ uprag) = maybe_unspec_inst - - subst = case matchTy unspec_inst_ty inst_ty of - Just subst -> subst - Nothing -> panic "tcSpecInstSig:matchTy" - - subst_theta = instantiateThetaTy subst unspec_theta - subst_tv_theta = instantiateThetaTy tv_e subst_theta - - mk_spec_origin clas ty - = InstanceSpecOrigin inst_mapper clas ty src_loc - -- I'm VERY SUSPICIOUS ABOUT THIS - -- the inst-mapper is in a knot at this point so it's no good - -- looking at it in tcSimplify... + 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 - tcSimplifyThetas mk_spec_origin subst_tv_theta - `thenTc` \ simpl_tv_theta -> - let - simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ] - tv_tmpl_map = zipEqual "tcSpecInstSig" inst_tv_tys inst_tmpl_tys - tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv - in - mkInstanceRelatedIds - clas inst_tmpls inst_ty simpl_theta uprag - `thenNF_Tc` \ (dfun_id, dfun_theta, const_meth_ids) -> - - getSwitchCheckerTc `thenNF_Tc` \ sw_chkr -> - (if sw_chkr SpecialiseTrace then - pprTrace "Specialised Instance: " - (vcat [hsep [if null simpl_theta then empty else ppr PprDebug simpl_theta, - if null simpl_theta then empty else ptext SLIT("=>"), - ppr PprDebug clas, - pprParendGenType PprDebug inst_ty], - hsep [ptext SLIT(" derived from:"), - if null unspec_theta then empty else ppr PprDebug unspec_theta, - if null unspec_theta then empty else ptext SLIT("=>"), - ppr PprDebug clas, - pprParendGenType PprDebug unspec_inst_ty]]) - else id) ( - - returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta - dfun_theta dfun_id - binds src_loc uprag)) - ))) - - -lookup_unspec_inst clas maybe_tycon inst_infos - = case filter (match_info match_inst_ty) (bagToList inst_infos) of - [] -> Nothing - (info:_) -> Just info - where - match_info match_ty (InstInfo inst_clas _ inst_ty _ _ _ _ _ from_here _ _ _) - = from_here && clas == inst_clas && - match_ty inst_ty && is_plain_instance inst_ty + mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> + + returnM (meth_ids, unionManyBags meth_binds_s) - match_inst_ty = case maybe_tycon of - Just tycon -> match_tycon tycon - Nothing -> match_fun - match_tycon tycon inst_ty = case (maybeAppDataTyCon inst_ty) of - Just (inst_tc,_,_) -> tycon == inst_tc - Nothing -> False +-- 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 -> - match_fun inst_ty = isFunType inst_ty + -- I don't think we have to do the checkSigTyVars thing + returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds) -is_plain_instance inst_ty - = case (maybeAppDataTyCon inst_ty) of - Just (_,tys,_) -> all isTyVarTemplateTy tys - Nothing -> case maybeUnpackFunTy inst_ty of - Just (arg, res) -> isTyVarTemplateTy arg && isTyVarTemplateTy res - Nothing -> error "TcInstDecls:is_plain_instance" --} + where + 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} -Checking for a decent instance type -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -@scrutiniseInstanceType@ checks the type {\em and} its syntactic constraints: -it must normally look like: @instance Foo (Tycon a b c ...) ...@ - -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. + ------------------------------ + [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. -We can also have instances for functions: @instance Foo (a -> b) ...@. -\begin{code} -scrutiniseInstanceType dfun_name clas inst_tau - -- TYCON CHECK - | not (maybeToBool inst_tycon_maybe) || isSynTyCon inst_tycon - = failTc (instTypeErr inst_tau) - - -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1) - | not (isLocallyDefined dfun_name) - = returnTc (inst_tycon,arg_tys) - - -- TYVARS CHECK - | not (all isTyVarTy arg_tys || - opt_GlasgowExts) - = failTc (instTypeErr inst_tau) - - -- DERIVING CHECK - -- It is obviously illegal to have an explicit instance - -- for something that we are also planning to `derive' - -- Though we can have an explicit instance which is more - -- specific than the derived instance - | clas `derivedFor` inst_tycon - && all isTyVarTy arg_tys - = failTc (derivingWhenInstanceExistsErr clas inst_tycon) - - | -- CCALL CHECK - -- A user declaration of a CCallable/CReturnable instance - -- must be for a "boxed primitive" type. - (uniqueOf clas == cCallableClassKey && not (ccallable_type inst_tau)) || - (uniqueOf clas == cReturnableClassKey && not (creturnable_type inst_tau)) - = failTc (nonBoxedPrimCCallErr clas inst_tau) - - | otherwise - = returnTc (inst_tycon,arg_tys) - - where - (possible_tycon, arg_tys) = splitAppTys inst_tau - inst_tycon_maybe = getTyCon_maybe possible_tycon - inst_tycon = expectJust "tcInstDecls1:inst_tycon" inst_tycon_maybe - --- These conditions come directly from what the DsCCall is capable of. --- Totally grotesque. Green card should solve this. - -ccallable_type ty = isPrimType ty || -- Allow CCallable Int# etc - maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc - ty `eqTy` stringTy || - byte_arr_thing - where - byte_arr_thing = case maybeAppDataTyCon ty of - Just (tycon, ty_args, [data_con]) -> --- pprTrace "cc1" (sep [ppr PprDebug tycon, ppr PprDebug data_con, --- sep (map (ppr PprDebug) data_con_arg_tys)])( - length data_con_arg_tys == 2 && - maybeToBool maybe_arg2_tycon && --- pprTrace "cc2" (sep [ppr PprDebug arg2_tycon]) ( - (arg2_tycon == byteArrayPrimTyCon || - arg2_tycon == mutableByteArrayPrimTyCon) --- )) - where - data_con_arg_tys = dataConArgTys data_con ty_args - (data_con_arg_ty1 : data_con_arg_ty2 : _) = data_con_arg_tys - maybe_arg2_tycon = maybeAppTyCon data_con_arg_ty2 - Just (arg2_tycon,_) = maybe_arg2_tycon - - other -> False - -creturnable_type ty = maybeToBool (maybeBoxedPrimType ty) || - -- Or, a data type with a single nullary constructor - case (maybeAppDataTyCon ty) of - Just (tycon, tys_applied, [data_con]) - -> isNullaryDataCon data_con - other -> False -\end{code} +%************************************************************************ +%* * +\subsection{Error messages} +%* * +%************************************************************************ \begin{code} - -instTypeErr ty sty - = case ty of - SynTy tc _ _ -> hcat [ptext SLIT("The type synonym `"), ppr sty tc, rest_of_msg] - TyVarTy tv -> hcat [ptext SLIT("The type variable `"), ppr sty tv, rest_of_msg] - other -> hcat [ptext SLIT("The type `"), ppr sty ty, rest_of_msg] - where - rest_of_msg = ptext SLIT("' cannot be used as an instance type.") - -instBndrErr bndr clas sty - = hsep [ptext SLIT("Class"), ppr sty clas, ptext SLIT("does not have a method"), ppr sty bndr] - -derivingWhenInstanceExistsErr clas tycon sty - = hang (hsep [ptext SLIT("Deriving class"), - ppr sty clas, - ptext SLIT("type"), ppr sty tycon]) - 4 (ptext SLIT("when an explicit instance exists")) - -derivingWhenInstanceImportedErr inst_mod clas tycon sty - = hang (hsep [ptext SLIT("Deriving class"), - ppr sty clas, - ptext SLIT("type"), ppr sty tycon]) - 4 (hsep [ptext SLIT("when an instance declared in module"), - pp_mod, ptext SLIT("has been imported")]) +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 - pp_mod = hsep [ptext SLIT("module"), ptext inst_mod] - -nonBoxedPrimCCallErr clas inst_ty sty - = hang (ptext SLIT("Unacceptable instance type for ccall-ish class")) - 4 (hsep [ ptext SLIT("class"), ppr sty clas, ptext SLIT("type"), - ppr sty inst_ty]) - -omitDefaultMethodWarn clas_op clas_name inst_ty sty - = hsep [ptext SLIT("Warning: Omitted default method for"), - ppr sty clas_op, ptext SLIT("in instance"), - text clas_name, pprParendGenType sty inst_ty] - -instMethodNotInClassErr occ clas sty - = hang (ptext SLIT("Instance mentions a method not in the class")) - 4 (hsep [ptext SLIT("class"), ppr sty clas, ptext SLIT("method"), - ppr sty occ]) - -patMonoBindsCtxt pbind sty - = hang (ptext SLIT("In a pattern binding:")) - 4 (ppr sty pbind) - -methodSigCtxt name ty sty - = hang (hsep [ptext SLIT("When matching the definition of class method"), - ppr sty name, ptext SLIT("to its signature :") ]) - 4 (ppr sty ty) - -bindSigCtxt method_ids sty - = hang (ptext SLIT("When checking type signatures for: ")) - 4 (hsep (punctuate comma (map (ppr sty) method_ids))) + (_,_,cls,tys) = tcSplitDFunTy dfun_ty -superClassSigCtxt sty - = ptext SLIT("When checking superclass constraints on instance declaration") +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}