X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcInstDcls.lhs;h=26616bc550215e7da341609ff184ac19fb81b311;hb=1cdafe99abae1628f34ca8c064e3a8c0fcdbd079;hp=2f75b9d0c4893d2dcd07472c30728a0bf7cc9aa6;hpb=6c381e873e222417d9a67aeec77b9555eca7b7a8;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs index 2f75b9d..3fec58d 100644 --- a/ghc/compiler/typecheck/TcInstDcls.lhs +++ b/ghc/compiler/typecheck/TcInstDcls.lhs @@ -1,82 +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} +module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where + #include "HsVersions.h" -module TcInstDcls ( - tcInstDecls1, - tcInstDecls2, - processInstBinds - ) where - - -import Ubiq - -import HsSyn ( InstDecl(..), FixityDecl, Sig(..), - SpecInstSig(..), HsBinds(..), Bind(..), - MonoBinds(..), GRHSsAndBinds, Match, - InPat(..), OutPat(..), HsExpr(..), HsLit(..), - Stmt, Qual, ArithSeqInfo, Fake, - PolyType(..), MonoType ) -import RnHsSyn ( RenamedHsBinds(..), RenamedMonoBinds(..), - RenamedInstDecl(..), RenamedFixityDecl(..), - RenamedSig(..), RenamedSpecInstSig(..) ) -import TcHsSyn ( TcIdOcc(..), TcHsBinds(..), - TcMonoBinds(..), TcExpr(..), - mkHsTyLam, mkHsTyApp, - mkHsDictLam, mkHsDictApp ) - - -import TcMonad -import GenSpecEtc ( checkSigTyVars, specTy ) -import Inst ( Inst, InstOrigin(..), InstanceMapper(..), - newDicts, newMethod, LIE(..), emptyLIE, plusLIE ) -import TcBinds ( tcPragmaSigs ) +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, tcTyVarScope, newLocalIds ) -import TcGRHSs ( tcGRHSsAndBinds ) -import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs ) -import TcKind ( TcKind, unifyKind ) -import TcMatches ( tcMatchesFun ) -import TcMonoType ( tcContext, tcMonoTypeKind ) -import TcSimplify ( tcSimplifyAndCheck, tcSimplifyThetas ) -import TcType ( TcType(..), TcTyVar(..), - tcInstTyVar, tcInstType, tcInstTheta ) -import Unify ( unifyTauTy ) - - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, - concatBag, foldBag, bagToList ) -import CmdLineOpts ( opt_GlasgowExts, opt_CompilingPrelude, - opt_OmitDefaultInstanceMethods, - opt_SpecialiseOverloaded ) -import Class ( GenClass, GenClassOp, - isCcallishClass, getClassBigSig, - getClassOps, getClassOpLocalType ) -import CoreUtils ( escErrorMsg ) -import Id ( idType, isDefaultMethodId_maybe ) +import TcEnv ( InstInfo(..), InstBindings(..), + newDFunName, tcExtendIdEnv + ) +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 ) -import Name ( Name, getTagFromClassOpName ) import Outputable -import PrelInfo ( pAT_ERROR_ID ) -import PprType ( GenType, GenTyVar, GenClass, GenClassOp, TyCon, - pprParendType ) -import PprStyle -import Pretty -import RnUtils ( GlobalNameMappers(..), GlobalNameMapper(..) ) -import TyCon ( derivedFor ) -import Type ( GenType(..), ThetaType(..), mkTyVarTy, - splitSigmaTy, splitAppTy, isTyVarTy, matchTy, - getTyCon_maybe, maybeBoxedPrimType ) -import TyVar ( GenTyVar, tyVarListToSet ) -import TysWiredIn ( stringTy ) -import Unique ( Unique ) -import Util ( panic ) - +import Bag +import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) ) +import FastString \end{code} Typechecking instance declarations is done in two passes. The first @@ -152,95 +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 :: Bag RenamedInstDecl - -> [RenamedSpecInstSig] - -> FAST_STRING -- module name for deriving - -> GlobalNameMappers -- renamer fns for deriving - -> [RenamedFixityDecl] -- fixities for deriving - -> TcM s (Bag InstInfo, - RenamedHsBinds, - PprStyle -> Pretty) - -tcInstDecls1 inst_decls specinst_sigs mod_name renamer_name_funs fixities - = -- Do the ordinary instance declarations - mapBagNF_Tc (tcInstDecl1 mod_name) inst_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 = concatBag 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 renamer_name_funs decl_inst_info fixities - `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 - inst_info = deriv_inst_info `unionBags` decl_inst_info + (tyvars, theta, tau) = tcSplitSigmaTy poly_ty' in -{- LATER - -- Handle specialise instance pragmas - tcSpecInstSigs inst_info specinst_sigs - `thenTc` \ spec_inst_info -> --} - let - spec_inst_info = emptyBag -- For now - - full_inst_info = inst_info `unionBags` spec_inst_info + 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 :: FAST_STRING -> RenamedInstDecl -> NF_TcM s (Bag InstInfo) - -tcInstDecl1 mod_name - (InstDecl class_name - poly_ty@(HsForAllTy tyvar_names context inst_ty) - binds - from_here inst_mod uprags pragmas src_loc) - = -- Prime error recovery, set source location - recoverNF_Tc (returnNF_Tc emptyBag) $ - tcAddSrcLoc src_loc $ - - -- Look things up - tcLookupClass class_name `thenNF_Tc` \ (clas_kind, clas) -> - - -- Typecheck the context and instance type - tcTyVarScope tyvar_names (\ tyvars -> - tcContext context `thenTc` \ theta -> - tcMonoTypeKind 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 from_here clas inst_tau - `thenTc` \ (inst_tycon,arg_tys) -> - - -- Deal with the case where we are deriving - -- and importing the same instance - if (not from_here && (clas `derivedFor` inst_tycon) - && all isTyVarTy arg_tys) - then - if mod_name == inst_mod then - -- Imported instance came from this module; - -- discard and derive fresh instance - returnTc emptyBag - else - -- Imported instance declared in another module; - -- report duplicate instance error - failTc (derivingWhenInstanceImportedErr inst_mod clas inst_tycon) - else - - -- Make the dfun id and constant-method ids - mkInstanceRelatedIds from_here inst_mod pragmas - clas inst_tyvars inst_tau inst_theta uprags - `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) -> - - returnTc (unitBag (InstInfo clas inst_tyvars inst_tau inst_theta - dfun_theta dfun_id const_meth_ids - binds from_here inst_mod src_loc uprags)) + + tcIsHsBoot `thenM` \ is_boot -> + checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags)) + badBootDeclErr `thenM_` + + returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags })) + where + 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 %************************************************************************ \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 @@ -330,607 +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 _ _ _ _ _ _ _ _ False{-import-} _ _ _) - = returnNF_Tc (emptyLIE, EmptyBinds) - -tcInstDecl2 (InstInfo clas inst_tyvars inst_ty - inst_decl_theta dfun_theta - dfun_id const_meth_ids monobinds - True{-here-} inst_mod locn uprags) - = -- Prime error recovery - recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $ - tcAddSrcLoc locn $ - - -- Get the class signature - mapNF_Tc tcInstTyVar inst_tyvars `thenNF_Tc` \ inst_tyvars' -> - let - tenv = inst_tyvars `zip` (map mkTyVarTy inst_tyvars') - - (class_tyvar, - super_classes, sc_sel_ids, - class_ops, op_sel_ids, defm_ids) = getClassBigSig clas - in - tcInstType tenv inst_ty `thenNF_Tc` \ inst_ty' -> - tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' -> - tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' -> - let - sc_theta' = super_classes `zip` (repeat inst_ty') - origin = InstanceDeclOrigin - mk_method sel_id = newMethod origin (RealId sel_id) [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]) -> - -- Create method variables - mapAndUnzipNF_Tc mk_method op_sel_ids `thenNF_Tc` \ (meth_insts_s, meth_ids) -> +\begin{code} +tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id) - -- Collect available Insts - let - avail_insts -- These insts are in scope; quite a few, eh? - = unionManyBags (this_dict : dfun_arg_dicts : meth_insts_s) - - mk_method_expr - = if opt_OmitDefaultInstanceMethods then - makeInstanceDeclNoDefaultExpr origin clas meth_ids defm_ids inst_mod inst_ty' - else - makeInstanceDeclDefaultMethodExpr origin this_dict_id class_ops defm_ids inst_ty' +tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds }) + = let + dfun_id = instanceDFunId ispec + rigid_info = InstSkol dfun_id + inst_ty = idType dfun_id in - processInstBinds mk_method_expr inst_tyvars' avail_insts meth_ids monobinds - `thenTc` \ (insts_needed, method_mbinds) -> + -- 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 - -- Create the dict and method binds - dict_bind - = VarMonoBind this_dict_id (Dictionary sc_dict_ids meth_ids) - - dict_and_method_binds - = dict_bind `AndMonoBinds` method_mbinds + (clas, inst_tys') = tcSplitDFunHead inst_head' + (class_tyvars, sc_theta, _, op_items) = classBigSig clas - inst_tyvars_set' = tyVarListToSet inst_tyvars' + -- Instantiate the super-class context with inst_tys + sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta + origin = SigOrigin rigid_info in - -- Check the overloading constraints of the methods and superclasses - tcAddErrCtxt (bindSigCtxt meth_ids) ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars - avail_insts - (sc_dicts `unionBags` insts_needed) -- Need to get defns for all these - ) `thenTc` \ (const_lie, super_binds) -> - - -- Check that we *could* construct the superclass dictionaries, - -- even though we are *actually* going to pass the superclass dicts in; - -- the check ensures that the caller will never have a problem building - -- them. - tcAddErrCtxt superClassSigCtxt ( - tcSimplifyAndCheck - inst_tyvars_set' -- Local tyvars - inst_decl_dicts -- The instance dictionaries available - sc_dicts -- The superclass dicationaries reqd - ) `thenTc_` - -- Ignore the result; we're only doing - -- this to make sure it can be done. - - -- Now process any SPECIALIZE pragmas for the methods - let - spec_sigs = [ s | s@(SpecSig _ _ _ _) <- uprags ] - in - tcPragmaSigs spec_sigs `thenTc` \ (_, spec_binds, spec_lie) -> - let - -- Complete the binding group, adding any spec_binds - inst_binds - = AbsBinds - inst_tyvars' - dfun_arg_dicts_ids - ((this_dict_id, RealId dfun_id) - : (meth_ids `zip` (map RealId const_meth_ids))) - -- const_meth_ids will often be empty - super_binds - (RecBind dict_and_method_binds) - - `ThenBinds` - spec_binds - in - - returnTc (const_lie `plusLIE` spec_lie, inst_binds) -\end{code} - -This function makes a default method which calls the global default method, at -the appropriate instance type. - -See the notes under default decls in TcClassDcl.lhs. - -\begin{code} -makeInstanceDeclDefaultMethodExpr - :: InstOrigin s - -> TcIdOcc s - -> [ClassOp] - -> [Id] - -> TcType s - -> Int - -> NF_TcM s (TcExpr s) - -makeInstanceDeclDefaultMethodExpr origin this_dict class_ops defm_ids inst_ty tag - = specTy origin (getClassOpLocalType class_op) - `thenNF_Tc` \ (op_tyvars, op_lie, op_tau, op_dicts) -> - - -- def_op_id = /\ op_tyvars -> \ op_dicts -> - -- defm_id inst_ty op_tyvars this_dict op_dicts - - returnNF_Tc ( - mkHsTyLam op_tyvars ( - mkHsDictLam op_dicts ( - mkHsDictApp (mkHsTyApp (HsVar (RealId defm_id)) - (inst_ty : map mkTyVarTy op_tyvars)) - (this_dict : op_dicts) - ))) - where - idx = tag - 1 - class_op = class_ops !! idx - defm_id = defm_ids !! idx - -makeInstanceDeclNoDefaultExpr - :: InstOrigin s - -> Class - -> [TcIdOcc s] - -> [Id] - -> FAST_STRING - -> TcType s - -> Int - -> NF_TcM s (TcExpr s) - -makeInstanceDeclNoDefaultExpr origin clas method_occs defm_ids inst_mod inst_ty tag - = let - (op_tyvars,op_theta,op_tau) = splitSigmaTy (idType method_id) + -- 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 - newDicts origin op_theta `thenNF_Tc` \ (op_lie,op_dicts) -> - - -- Produce a warning if the default instance method - -- has been omitted when one exists in the class - warnTc (not err_defm_ok) - (omitDefaultMethodWarn clas_op clas_name inst_ty) - `thenNF_Tc_` - returnNF_Tc (mkHsTyLam op_tyvars ( - mkHsDictLam op_dicts ( - HsApp (mkHsTyApp (HsVar (RealId pAT_ERROR_ID)) [op_tau]) - (HsLitOut (HsString (_PK_ error_msg)) stringTy)))) - where - idx = tag - 1 - method_occ = method_occs !! idx - clas_op = (getClassOps clas) !! idx - defm_id = defm_ids !! idx - - TcId method_id = method_occ - Just (_, _, err_defm_ok) = isDefaultMethodId_maybe defm_id - - error_msg = "%E" -- => No explicit method for \" - ++ escErrorMsg error_str - - error_str = _UNPK_ inst_mod ++ "." ++ _UNPK_ clas_name ++ "." - ++ (ppShow 80 (ppr PprForUser inst_ty)) ++ "." - ++ (ppShow 80 (ppr PprForUser clas_op)) ++ "\"" - - (_, clas_name) = getOrigName clas -\end{code} - - -%************************************************************************ -%* * -\subsection{Processing each method} -%* * -%************************************************************************ - -@processInstBinds@ returns a @MonoBinds@ which binds -all the method ids (which are passed in). It is used - - both for instance decls, - - and to compile the default-method declarations in a class decl. - -Any method ids which don't have a binding have a suitable default -binding created for them. The actual right-hand side used is -created using a function which is passed in, because the right thing to -do differs between instance and class decls. - -\begin{code} -processInstBinds - :: (Int -> NF_TcM s (TcExpr s)) -- Function to make default method - -> [TcTyVar s] -- Tyvars for this instance decl - -> LIE s -- available Insts - -> [TcIdOcc s] -- Local method ids in tag order - -- (instance tyvars are free in their types) - -> RenamedMonoBinds - -> TcM s (LIE s, -- These are required - TcMonoBinds s) - -processInstBinds mk_default_method_rhs inst_tyvars avail_insts method_ids monobinds - = - -- Process the explicitly-given method bindings - processInstBinds1 inst_tyvars avail_insts method_ids monobinds - `thenTc` \ (tags, insts_needed_in_methods, method_binds) -> - - -- Find the methods not handled, and make default method bindings for them. + 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 - unmentioned_tags = [1.. length method_ids] `minusList` tags + specs = case binds of + VanillaInst _ prags -> filter isSpecInstLSig prags + other -> [] in - mapNF_Tc mk_default_method unmentioned_tags - `thenNF_Tc` \ default_bind_list -> - - returnTc (insts_needed_in_methods, - foldr AndMonoBinds method_binds default_bind_list) - where - -- From a tag construct us the passed-in function to construct - -- the binding for the default method - mk_default_method tag = mk_default_method_rhs tag `thenNF_Tc` \ rhs -> - returnNF_Tc (VarMonoBind (method_ids !! (tag-1)) rhs) -\end{code} - -\begin{code} -processInstBinds1 - :: [TcTyVar s] -- Tyvars for this instance decl - -> LIE s -- available Insts - -> [TcIdOcc s] -- Local method ids in tag order (instance tyvars are free), - -> RenamedMonoBinds - -> TcM s ([Int], -- Class-op tags accounted for - LIE s, -- These are required - TcMonoBinds s) - -processInstBinds1 inst_tyvars avail_insts method_ids EmptyMonoBinds - = returnTc ([], emptyLIE, EmptyMonoBinds) - -processInstBinds1 inst_tyvars avail_insts method_ids (AndMonoBinds mb1 mb2) - = processInstBinds1 inst_tyvars avail_insts method_ids mb1 - `thenTc` \ (op_tags1,dicts1,method_binds1) -> - processInstBinds1 inst_tyvars avail_insts method_ids mb2 - `thenTc` \ (op_tags2,dicts2,method_binds2) -> - returnTc (op_tags1 ++ op_tags2, - dicts1 `unionBags` dicts2, - AndMonoBinds method_binds1 method_binds2) -\end{code} - -\begin{code} -processInstBinds1 inst_tyvars avail_insts method_ids mbind - = - -- Find what class op is being defined here. The complication is - -- that we could have a PatMonoBind or a FunMonoBind. If the - -- former, it should only bind a single variable, or else we're in - -- trouble (I'm not sure what the static semantics of methods - -- defined in a pattern binding with multiple patterns is!) - -- Renamer has reduced us to these two cases. + tcPrags dfun_id specs `thenM` \ prags -> + + -- Create the result bindings let - (op,locn) = case mbind of - FunMonoBind op _ locn -> (op, locn) - PatMonoBind (VarPatIn op) _ locn -> (op, locn) - - occ = getOccurrenceName op - origin = InstanceDeclOrigin - in - tcAddSrcLoc locn $ - - -- Make a method id for the method - let tag = getTagFromClassOpName op - method_id = method_ids !! (tag-1) - - TcId method_bndr = method_id - method_ty = idType method_bndr - (method_tyvars, method_theta, method_tau) = splitSigmaTy method_ty - in - newDicts origin method_theta `thenNF_Tc` \ (method_dicts,method_dict_ids) -> - - case (method_tyvars, method_dict_ids) of - - ([],[]) -> -- The simple case; no local polymorphism or overloading in the method - - -- Type check the method itself - tcMethodBind method_id method_tau mbind `thenTc` \ (mbind', lieIop) -> - - -- Make sure that the instance tyvars havn't been - -- unified with each other or with the method tyvars. - tcSetErrCtxt (methodSigCtxt op method_tau) ( - checkSigTyVars inst_tyvars method_tau method_tau - ) `thenTc_` - returnTc ([tag], lieIop, mbind') - - other -> -- It's a locally-polymorphic and/or overloaded method; UGH! - - -- Make a new id for (a) the local, non-overloaded method - -- and (b) the locally-overloaded method - -- The latter is needed just so we can return an AbsBinds wrapped - -- up inside a MonoBinds. - - newLocalIds [occ,occ] [method_tau,method_ty] `thenNF_Tc` \ new_ids -> - let - [local_id, copy_id] = map TcId new_ids - inst_method_tyvars = inst_tyvars ++ method_tyvars - in - -- Typecheck the method - tcMethodBind local_id method_tau mbind `thenTc` \ (mbind', lieIop) -> - - -- Make sure that the instance tyvars haven't been - -- unified with each other or with the method tyvars. - tcAddErrCtxt (methodSigCtxt op method_tau) ( - checkSigTyVars inst_method_tyvars method_tau method_tau - ) `thenTc_` - - -- Check the overloading part of the signature. - -- Simplify everything fully, even though some - -- constraints could "really" be left to the next - -- level out. The case which forces this is + 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. -- - -- class Foo a where { op :: Bar a => a -> a } + -- 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 -- - -- Here we must simplify constraints on "a" to catch all - -- the Bar-ish things. - tcAddErrCtxt (methodSigCtxt op method_ty) ( - tcSimplifyAndCheck - (tyVarListToSet inst_method_tyvars) - (method_dicts `plusLIE` avail_insts) - lieIop - ) `thenTc` \ (f_dicts, dict_binds) -> - - returnTc ([tag], - f_dicts, - VarMonoBind method_id - (HsLet - (AbsBinds - method_tyvars - method_dict_ids - [(local_id, copy_id)] - dict_binds - (NonRecBind mbind')) - (HsVar copy_id))) -\end{code} - -\begin{code} -tcMethodBind :: TcIdOcc s -> TcType s -> RenamedMonoBinds - -> TcM s (TcMonoBinds s, LIE s) - -tcMethodBind meth_id meth_ty (FunMonoBind name matches locn) - = tcMatchesFun name meth_ty matches `thenTc` \ (rhs', lie) -> - returnTc (FunMonoBind meth_id rhs' locn, lie) - -tcMethodBind meth_id meth_ty pbind@(PatMonoBind pat grhss_and_binds locn) - -- pat is sure to be a (VarPatIn op) - = tcAddErrCtxt (patMonoBindsCtxt pbind) $ - tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, rhs_ty) -> - unifyTauTy meth_ty rhs_ty `thenTc_` - returnTc (PatMonoBind (VarPat meth_id) grhss_and_binds' locn, lie) -\end{code} - - -%************************************************************************ -%* * -\subsection{Type-checking specialise instance pragmas} -%* * -%************************************************************************ + -- 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 + showLIE (text "instance") `thenM_` + returnM (unitBag main_bind) -\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 = extractMonoTyNames (==) 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 -> +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 - maybe_tycon = case maybeDataTyCon inst_ty of - Just (tc,_,_) -> Just tc - Nothing -> Nothing - - maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos + sel_names = [idName sel_id | (sel_id, _) <- op_items] + bad_bndrs = collectHsBindBinders monobinds `minusList` sel_names in - -- Check that we have a local instance declaration to specialise - checkMaybeTc maybe_unspec_inst - (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_` + mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_` - -- Create tvs to substitute for tmpls while simplifying the context - copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) -> + -- Make the method bindings let - Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta - _ _ _ binds True{-from here-} mod _ 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 + mk_method_bind = mkMethodBind origin clas inst_tys' monobinds in - tcSimplifyThetas mk_spec_origin subst_tv_theta - `thenTc` \ simpl_tv_theta -> + 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 - simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ] - - tv_tmpl_map = inst_tv_tys `zipEqual` inst_tmpl_tys - tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv + 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 - mkInstanceRelatedIds e True{-from here-} mod NoInstancePragmas src_loc - clas inst_tmpls inst_ty simpl_theta uprag - `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) -> - - getSwitchCheckerTc `thenNF_Tc` \ sw_chkr -> - (if sw_chkr SpecialiseTrace then - pprTrace "Specialised Instance: " - (ppAboves [ppCat [if null simpl_theta then ppNil else ppr PprDebug simpl_theta, - if null simpl_theta then ppNil else ppStr "=>", - ppr PprDebug clas, - pprParendType PprDebug inst_ty], - ppCat [ppStr " derived from:", - if null unspec_theta then ppNil else ppr PprDebug unspec_theta, - if null unspec_theta then ppNil else ppStr "=>", - ppr PprDebug clas, - pprParendType PprDebug unspec_inst_ty]]) - else id) ( - - returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta - dfun_theta dfun_id const_meth_ids - binds True{-from here-} mod 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 - match_inst_ty = case maybe_tycon of - Just tycon -> match_tycon tycon - Nothing -> match_fun + mapM tc_method_bind meth_infos `thenM` \ meth_binds_s -> + + returnM (meth_ids, unionManyBags meth_binds_s) - match_tycon tycon inst_ty = case (maybeDataTyCon inst_ty) of - Just (inst_tc,_,_) -> tycon == inst_tc - Nothing -> False - match_fun inst_ty = isFunType inst_ty +-- Derived newtype instances +tcMethods origin clas inst_tyvars' dfun_theta' inst_tys' + avail_insts op_items (NewTypeDerived rep_tys) + = getInstLoc origin `thenM` \ inst_loc -> + mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) -> + + tcSimplifyCheck + (ptext SLIT("newtype derived instance")) + inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds -> + -- I don't think we have to do the checkSigTyVars thing -is_plain_instance inst_ty - = case (maybeDataTyCon 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" --} -\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. - -We can also have instances for functions: @instance Foo (a -> b) ...@. - -\begin{code} -scrutiniseInstanceType from_here clas inst_tau - -- TYCON CHECK - | not (maybeToBool inst_tycon_maybe) - = failTc (instTypeErr inst_tau) - - -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1) - | from_here - = returnTc (inst_tycon,arg_tys) - - -- TYVARS CHECK - | not (all isTyVarTy arg_tys || - not from_here || - 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. - isCcallishClass clas - && not opt_CompilingPrelude -- which allows anything - && maybeToBool (maybeBoxedPrimType inst_tau) - = failTc (nonBoxedPrimCCallErr clas inst_tau) - - | otherwise - = returnTc (inst_tycon,arg_tys) + returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds) where - (possible_tycon, arg_tys) = splitAppTy inst_tau - inst_tycon_maybe = getTyCon_maybe possible_tycon - inst_tycon = expectJust "tcInstDecls1:inst_tycon" inst_tycon_maybe + 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} -\begin{code} - -instTypeErr ty sty - = case ty of - SynTy tc _ _ -> ppBesides [ppStr "The type synonym `", ppr sty tc, rest_of_msg] - TyVarTy tv -> ppBesides [ppStr "The type variable `", ppr sty tv, rest_of_msg] - other -> ppBesides [ppStr "The type `", ppr sty ty, rest_of_msg] - where - rest_of_msg = ppStr "' cannot be used as an instance type." - -derivingWhenInstanceExistsErr clas tycon sty - = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"]) - 4 (ppStr "when an explicit instance exists") - -derivingWhenInstanceImportedErr inst_mod clas tycon sty - = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"]) - 4 (ppBesides [ppStr "when an instance declared in module `", ppPStr inst_mod, ppStr "' has been imported"]) - -nonBoxedPrimCCallErr clas inst_ty sty - = ppHang (ppStr "Instance isn't for a `boxed-primitive' type") - 4 (ppBesides [ ppStr "class `", ppr sty clas, ppStr "' type `", - ppr sty inst_ty, ppStr "'"]) - -omitDefaultMethodWarn clas_op clas_name inst_ty sty - = ppCat [ppStr "Warning: Omitted default method for", - ppr sty clas_op, ppStr "in instance", - ppPStr clas_name, pprParendType sty inst_ty] + ------------------------------ + [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. -patMonoBindsCtxt pbind sty - = ppHang (ppStr "In a pattern binding:") - 4 (ppr sty pbind) -methodSigCtxt name ty sty - = ppHang (ppBesides [ppStr "When matching the definition of class method `", - ppr sty name, ppStr "' to its signature :" ]) - 4 (ppr sty ty) +%************************************************************************ +%* * +\subsection{Error messages} +%* * +%************************************************************************ -bindSigCtxt method_ids sty - = ppHang (ppStr "When checking type signatures for: ") - 4 (ppInterleave (ppStr ", ") (map (ppr sty) method_ids)) +\begin{code} +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 + (_,_,cls,tys) = tcSplitDFunTy dfun_ty -superClassSigCtxt sty - = ppStr "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}