X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcBinds.lhs;h=d9f55874c07efb3d662d1c52452d53560fdfe1e0;hp=24f98d86e0bdbd711b34a3c0fa6ed5c0e6fd5c38;hb=30c122df62ec75f9ed7f392f24c2925675bf1d06;hpb=e6d057711f4d6d6ff6342c39fa2b9e44d25447f1 diff --git a/compiler/typecheck/TcBinds.lhs b/compiler/typecheck/TcBinds.lhs index 24f98d8..d9f5587 100644 --- a/compiler/typecheck/TcBinds.lhs +++ b/compiler/typecheck/TcBinds.lhs @@ -1,9 +1,17 @@ % +% (c) The University of Glasgow 2006 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcBinds]{TcBinds} \begin{code} +{-# OPTIONS -w #-} +-- The above warning supression flag is a temporary kludge. +-- While working on this module you are encouraged to remove it and fix +-- any warnings in the module. See +-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings +-- for details + module TcBinds ( tcLocalBinds, tcTopBinds, tcHsBootSigs, tcMonoBinds, TcPragFun, tcSpecPrag, tcPrags, mkPragFun, @@ -15,58 +23,42 @@ module TcBinds ( tcLocalBinds, tcTopBinds, import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun ) import {-# SOURCE #-} TcExpr ( tcMonoExpr ) -import DynFlags ( dopt, DynFlags, - DynFlag(Opt_MonomorphismRestriction, Opt_MonoPatBinds, Opt_GlasgowExts) ) -import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, LHsBind, Sig(..), - HsLocalBinds(..), HsValBinds(..), HsIPBinds(..), - LSig, Match(..), IPBind(..), Prag(..), - HsType(..), LHsType, HsExplicitForAll(..), hsLTyVarNames, - isVanillaLSig, sigName, placeHolderNames, isPragLSig, - LPat, GRHSs, MatchGroup(..), pprLHsBinds, mkHsWrap, - collectHsBindBinders, collectPatBinders, pprPatBind, isBangHsBind - ) -import TcHsSyn ( zonkId ) +import DynFlags +import HsSyn +import TcHsSyn import TcRnMonad -import Inst ( newDictBndrs, newIPDict, instToId ) -import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2, - pprBinders, tcLookupId, - tcGetGlobalTyVars ) -import TcUnify ( tcInfer, tcSubExp, unifyTheta, - bleatEscapedTvs, sigCtxt ) -import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, - tcSimplifyRestricted, tcSimplifyIPs ) -import TcHsType ( tcHsSigType, UserTypeCtxt(..) ) -import TcPat ( tcLetPat ) -import TcSimplify ( bindInstsOfLocalFuns ) -import TcMType ( newFlexiTyVarTy, zonkQuantifiedTyVar, zonkSigTyVar, - tcInstSigTyVars, tcInstSkolTyVars, tcInstType, - zonkTcType, zonkTcTypes, zonkTcTyVar ) -import TcType ( TcType, TcTyVar, TcThetaType, - SkolemInfo(SigSkol), UserTypeCtxt(FunSigCtxt), - TcTauType, TcSigmaType, isUnboxedTupleType, - mkTyVarTy, mkForAllTys, mkFunTys, exactTyVarsOfType, - mkForAllTy, isUnLiftedType, tcGetTyVar, - mkTyVarTys, tidyOpenTyVar ) -import {- Kind parts of -} Type ( argTypeKind ) -import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv ) -import TysPrim ( alphaTyVar ) -import Id ( Id, mkLocalId, mkVanillaGlobal ) -import IdInfo ( vanillaIdInfo ) -import Var ( TyVar, idType, idName ) -import Name ( Name ) +import Inst +import TcEnv +import TcUnify +import TcSimplify +import TcHsType +import TcPat +import TcMType +import TcType +import {- Kind parts of -} Type +import Coercion +import VarEnv +import TysPrim +import Id +import IdInfo +import Var ( TyVar, varType ) +import Name import NameSet import NameEnv import VarSet -import SrcLoc ( Located(..), unLoc, getLoc ) +import SrcLoc import Bag -import ErrUtils ( Message ) -import Digraph ( SCC(..), stronglyConnComp ) -import Maybes ( expectJust, isJust, isNothing, orElse ) -import Util ( singleton ) -import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel, - RecFlag(..), isNonRec, InlineSpec, defaultInlineSpec ) +import ErrUtils +import Digraph +import Maybes +import List +import Util +import BasicTypes import Outputable +import FastString + +import Control.Monad \end{code} @@ -152,11 +144,11 @@ tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside -- I wonder if we should do these one at at time -- Consider ?x = 4 -- ?y = ?x + 1 - tc_ip_bind (IPBind ip expr) - = newFlexiTyVarTy argTypeKind `thenM` \ ty -> - newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) -> - tcMonoExpr expr ty `thenM` \ expr' -> - returnM (ip_inst, (IPBind ip' expr')) + tc_ip_bind (IPBind ip expr) = do + ty <- newFlexiTyVarTy argTypeKind + (ip', ip_inst) <- newIPDict (IPBindOrigin ip) ip ty + expr' <- tcMonoExpr expr ty + return (ip_inst, (IPBind ip' expr')) ------------------------ tcValBinds :: TopLevelFlag @@ -181,9 +173,9 @@ tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside -- Extend the envt right away with all -- the Ids declared with type signatures - ; gla_exts <- doptM Opt_GlasgowExts + ; poly_rec <- doptM Opt_RelaxedPolyRec ; (binds', thing) <- tcExtendIdEnv poly_ids $ - tc_val_binds gla_exts top_lvl sig_fn prag_fn + tc_val_binds poly_rec top_lvl sig_fn prag_fn binds thing_inside ; return (ValBindsOut binds' sigs, thing) } @@ -195,14 +187,14 @@ tc_val_binds :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun -- Typecheck a whole lot of value bindings, -- one strongly-connected component at a time -tc_val_binds gla_exts top_lvl sig_fn prag_fn [] thing_inside +tc_val_binds poly_rec top_lvl sig_fn prag_fn [] thing_inside = do { thing <- thing_inside ; return ([], thing) } -tc_val_binds gla_exts top_lvl sig_fn prag_fn (group : groups) thing_inside +tc_val_binds poly_rec top_lvl sig_fn prag_fn (group : groups) thing_inside = do { (group', (groups', thing)) - <- tc_group gla_exts top_lvl sig_fn prag_fn group $ - tc_val_binds gla_exts top_lvl sig_fn prag_fn groups thing_inside + <- tc_group poly_rec top_lvl sig_fn prag_fn group $ + tc_val_binds poly_rec top_lvl sig_fn prag_fn groups thing_inside ; return (group' ++ groups', thing) } ------------------------ @@ -214,15 +206,15 @@ tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun -- We get a list of groups back, because there may -- be specialisations etc as well -tc_group gla_exts top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside +tc_group poly_rec top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside -- A single non-recursive binding -- We want to keep non-recursive things non-recursive -- so that we desugar unlifted bindings correctly = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside ; return ([(NonRecursive, b) | b <- binds], thing) } -tc_group gla_exts top_lvl sig_fn prag_fn (Recursive, binds) thing_inside - | not gla_exts -- Recursive group, normal Haskell 98 route +tc_group poly_rec top_lvl sig_fn prag_fn (Recursive, binds) thing_inside + | not poly_rec -- Recursive group, normal Haskell 98 route = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside ; return ([(Recursive, unionManyBags binds1)], thing) } @@ -260,7 +252,7 @@ tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a) bindLocalInsts top_lvl thing_inside | isTopLevel top_lvl = do { (binds, ids, thing) <- thing_inside; return (binds, thing) } - -- For the top level don't bother will all this bindInstsOfLocalFuns stuff. + -- For the top level don't bother with all this bindInstsOfLocalFuns stuff. -- All the top level things are rec'd together anyway, so it's fine to -- leave them to the tcSimplifyTop, and quite a bit faster too @@ -330,6 +322,7 @@ tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds -- TYPECHECK THE BINDINGS ; ((binds', mono_bind_infos), lie_req) <- getLIE (tcMonoBinds bind_list sig_fn rec_tc) + ; traceTc (text "temp" <+> (ppr binds' $$ ppr lie_req)) -- CHECK FOR UNLIFTED BINDINGS -- These must be non-recursive etc, and are not generalised @@ -349,25 +342,20 @@ tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds else do -- The normal lifted case: GENERALISE { dflags <- getDOpts - ; (tyvars_to_gen, dict_binds, dict_ids) + ; (tyvars_to_gen, dicts, dict_binds) <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $ generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req - -- FINALISE THE QUANTIFIED TYPE VARIABLES - -- The quantified type variables often include meta type variables - -- we want to freeze them into ordinary type variables, and - -- default their kind (e.g. from OpenTypeKind to TypeKind) - ; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen - -- BUILD THE POLYMORPHIC RESULT IDs - ; exports <- mapM (mkExport prag_fn tyvars_to_gen' (map idType dict_ids)) + ; let dict_vars = map instToVar dicts -- May include equality constraints + ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map varType dict_vars)) mono_bind_infos ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports] ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids)) - ; let abs_bind = L loc $ AbsBinds tyvars_to_gen' - dict_ids exports + ; let abs_bind = L loc $ AbsBinds tyvars_to_gen + dict_vars exports (dict_binds `unionBags` binds') ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport @@ -375,8 +363,9 @@ tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds -------------- -mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo - -> TcM ([TyVar], Id, Id, [Prag]) +mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType] + -> MonoBindInfo + -> TcM ([TyVar], Id, Id, [LPrag]) -- mkExport generates exports with -- zonked type variables, -- zonked poly_ids @@ -388,20 +377,24 @@ mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo -- Pre-condition: the inferred_tvs are already zonked -mkExport prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id) - = do { (tvs, poly_id) <- mk_poly_id mb_sig +mkExport top_lvl prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id) + = do { warn_missing_sigs <- doptM Opt_WarnMissingSigs + ; let warn = isTopLevel top_lvl && warn_missing_sigs + ; (tvs, poly_id) <- mk_poly_id warn mb_sig + -- poly_id has a zonked type - ; poly_id' <- zonkId poly_id - ; prags <- tcPrags poly_id' (prag_fn poly_name) + ; prags <- tcPrags poly_id (prag_fn poly_name) -- tcPrags requires a zonked poly_id - ; return (tvs, poly_id', mono_id, prags) } + ; return (tvs, poly_id, mono_id, prags) } where poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id)) - mk_poly_id Nothing = return (inferred_tvs, mkLocalId poly_name poly_ty) - mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig) - ; return (tvs, sig_id sig) } + mk_poly_id warn Nothing = do { poly_ty' <- zonkTcType poly_ty + ; missingSigWarn warn poly_name poly_ty' + ; return (inferred_tvs, mkLocalId poly_name poly_ty') } + mk_poly_id warn (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig) + ; return (tvs, sig_id sig) } zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) } @@ -416,12 +409,11 @@ mkPragFun sigs = \n -> lookupNameEnv env n `orElse` [] env = foldl add emptyNameEnv prs add env (n,p) = extendNameEnv_Acc (:) singleton env n p -tcPrags :: Id -> [LSig Name] -> TcM [Prag] -tcPrags poly_id prags = mapM tc_prag prags +tcPrags :: Id -> [LSig Name] -> TcM [LPrag] +tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags where - tc_prag (L loc prag) = setSrcSpan loc $ - addErrCtxt (pragSigCtxt prag) $ - tcPrag poly_id prag + tc_prag prag = addErrCtxt (pragSigCtxt prag) $ + tcPrag poly_id prag pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag) @@ -435,11 +427,10 @@ tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl) tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag tcSpecPrag poly_id hs_ty inl - = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty - ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty) - ; extendLIEs lie - ; let const_dicts = map instToId lie - ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty const_dicts inl) } + = do { let name = idName poly_id + ; spec_ty <- tcHsSigType (FunSigCtxt name) hs_ty + ; co_fn <- tcSubExp (SpecPragOrigin name) (idType poly_id) spec_ty + ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty inl) } -- Most of the work of specialisation is done by -- the desugarer, guided by the SpecPrag @@ -531,7 +522,7 @@ tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf, -- e.g. f = \(x::forall a. a->a) -> -- We want to infer a higher-rank type for f setSrcSpan b_loc $ - do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name matches) + do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches) -- Check for an unboxed tuple type -- f = (# True, False #) @@ -546,7 +537,7 @@ tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf, ; let mono_id = mkLocalId mono_name zonked_rhs_ty ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf, fun_matches = matches', bind_fvs = fvs, - fun_co_fn = co_fn })), + fun_co_fn = co_fn, fun_tick = Nothing })), [(name, Nothing, mono_id)]) } tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf, @@ -558,19 +549,23 @@ tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf, -- we can (a) use genuine, rigid skolem constants for the type variables -- (b) bring (rigid) scoped type variables into scope setSrcSpan b_loc $ - do { tc_sig <- tcInstSig True name scoped_tvs + do { tc_sig <- tcInstSig True name ; mono_name <- newLocalName name ; let mono_ty = sig_tau tc_sig mono_id = mkLocalId mono_name mono_ty rhs_tvs = [ (name, mkTyVarTy tv) - | (name, tv) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ] + | (name, tv) <- scoped_tvs `zip` sig_tvs tc_sig ] + -- See Note [More instantiated than scoped] + -- Note that the scoped_tvs and the (sig_tvs sig) + -- may have different Names. That's quite ok. - ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $ - tcMatchesFun mono_name matches mono_ty + ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $ + tcMatchesFun mono_name inf matches mono_ty ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id, fun_infix = inf, fun_matches = matches', - bind_fvs = placeHolderNames, fun_co_fn = co_fn } + bind_fvs = placeHolderNames, fun_co_fn = co_fn, + fun_tick = Nothing } ; return (unitBag (L b_loc fun_bind'), [(name, Just tc_sig, mono_id)]) } @@ -583,9 +578,9 @@ tcMonoBinds binds sig_fn non_rec -- A monomorphic binding for each term variable that lacks -- a type sig. (Ones with a sig are already in scope.) - ; binds' <- tcExtendIdEnv2 rhs_id_env $ + ; binds' <- tcExtendIdEnv2 rhs_id_env $ do traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id) - | (n,id) <- rhs_id_env]) `thenM_` + | (n,id) <- rhs_id_env]) mapM (wrapLocM tcRhs) tc_binds ; return (listToBag binds', mono_info) } @@ -671,11 +666,16 @@ tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind) ------------------- tcRhs :: TcMonoBind -> TcM (HsBind TcId) -tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches) - = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) matches - (idType mono_id) +-- When we are doing pattern bindings, or multiple function bindings at a time +-- we *don't* bring any scoped type variables into scope +-- Wny not? They are not completely rigid. +-- That's why we have the special case for a single FunBind in tcMonoBinds +tcRhs (TcFunBind (_,_,mono_id) fun' inf matches) + = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf + matches (idType mono_id) ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches', - bind_fvs = placeHolderNames, fun_co_fn = co_fn }) } + bind_fvs = placeHolderNames, fun_co_fn = co_fn, + fun_tick = Nothing }) } tcRhs bind@(TcPatBind _ pat' grhss pat_ty) = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $ @@ -704,10 +704,13 @@ getMonoBindInfo tc_binds generalise :: DynFlags -> TopLevelFlag -> [LHsBind Name] -> TcSigFun -> [MonoBindInfo] -> [Inst] - -> TcM ([TcTyVar], TcDictBinds, [TcId]) + -> TcM ([TyVar], [Inst], TcDictBinds) +-- The returned [TyVar] are all ready to quantify + generalise dflags top_lvl bind_list sig_fn mono_infos lie_req | isMonoGroup dflags bind_list - = do { extendLIEs lie_req; return ([], emptyBag, []) } + = do { extendLIEs lie_req + ; return ([], [], emptyBag) } | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE = -- Check signature contexts are empty @@ -722,39 +725,41 @@ generalise dflags top_lvl bind_list sig_fn mono_infos lie_req -- Check that signature type variables are OK ; final_qtvs <- checkSigsTyVars qtvs sigs - ; return (final_qtvs, binds, []) } + ; return (final_qtvs, [], binds) } | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS = tcSimplifyInfer doc tau_tvs lie_req | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS - = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty + = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty; sig_lie is zonked ; let -- The "sig_avails" is the stuff available. We get that from -- the context of the type signature, BUT ALSO the lie_avail -- so that polymorphic recursion works right (see Note [Polymorphic recursion]) local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos] sig_avails = sig_lie ++ local_meths + loc = sig_loc (head sigs) -- Check that the needed dicts can be -- expressed in terms of the signature ones - ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req + ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req -- Check that signature type variables are OK - ; final_qtvs <- checkSigsTyVars forall_tvs sigs + ; final_qtvs <- checkSigsTyVars qtvs sigs - ; returnM (final_qtvs, dict_binds, map instToId sig_lie) } + ; return (final_qtvs, sig_lie, binds) } where bndrs = bndrNames mono_infos sigs = [sig | (_, Just sig, _) <- mono_infos] - tau_tvs = foldr (unionVarSet . exactTyVarsOfType . getMonoType) emptyVarSet mono_infos - -- NB: exactTyVarsOfType; see Note [Silly type synonym] - -- near defn of TcType.exactTyVarsOfType + get_tvs | isTopLevel top_lvl = tyVarsOfType -- See Note [Silly type synonym] in TcType + | otherwise = exactTyVarsOfType + tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos is_mono_sig sig = null (sig_theta sig) doc = ptext SLIT("type signature(s) for") <+> pprBinders bndrs mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs, sig_theta = theta, sig_loc = loc }) mono_id - = Method mono_id poly_id (mkTyVarTys tvs) theta loc + = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs, + tci_theta = theta, tci_loc = loc} \end{code} unifyCtxts checks that all the signature contexts are the same @@ -771,21 +776,33 @@ might not otherwise be related. This is a rather subtle issue. \begin{code} unifyCtxts :: [TcSigInfo] -> TcM [Inst] +-- Post-condition: the returned Insts are full zonked unifyCtxts (sig1 : sigs) -- Argument is always non-empty = do { mapM unify_ctxt sigs - ; newDictBndrs (sig_loc sig1) (sig_theta sig1) } + ; theta <- zonkTcThetaType (sig_theta sig1) + ; newDictBndrs (sig_loc sig1) theta } where theta1 = sig_theta sig1 unify_ctxt :: TcSigInfo -> TcM () unify_ctxt sig@(TcSigInfo { sig_theta = theta }) - = setSrcSpan (instLocSrcSpan (sig_loc sig)) $ + = setSrcSpan (instLocSpan (sig_loc sig)) $ addErrCtxt (sigContextsCtxt sig1 sig) $ - unifyTheta theta1 theta + do { cois <- unifyTheta theta1 theta + ; -- Check whether all coercions are identity coercions + -- That can happen if we have, say + -- f :: C [a] => ... + -- g :: C (F a) => ... + -- where F is a type function and (F a ~ [a]) + -- Then unification might succeed with a coercion. But it's much + -- much simpler to require that such signatures have identical contexts + checkTc (all isIdentityCoercion cois) + (ptext SLIT("Mutually dependent functions have syntactically distinct contexts")) + } checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar] checkSigsTyVars qtvs sigs = do { gbl_tvs <- tcGetGlobalTyVars - ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs + ; sig_tvs_s <- mapM (check_sig gbl_tvs) sigs ; let -- Sigh. Make sure that all the tyvars in the type sigs -- appear in the returned ty var list, which is what we are @@ -797,15 +814,15 @@ checkSigsTyVars qtvs sigs -- Here, 'a' won't appear in qtvs, so we have to add it sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s all_tvs = varSetElems (extendVarSetList sig_tvs qtvs) - ; returnM all_tvs } + ; return all_tvs } where check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs, sig_theta = theta, sig_tau = tau}) = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $ addErrCtxtM (sigCtxt id tvs theta tau) $ do { tvs' <- checkDistinctTyVars tvs - ; ifM (any (`elemVarSet` gbl_tvs) tvs') - (bleatEscapedTvs gbl_tvs tvs tvs') + ; when (any (`elemVarSet` gbl_tvs) tvs') + (bleatEscapedTvs gbl_tvs tvs tvs') ; return tvs' } checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar] @@ -841,7 +858,7 @@ checkDistinctTyVars sig_tvs <+> quotes (ppr tidy_tv2) ; failWithTcM (env2, msg) } where -\end{code} +\end{code} @getTyVarsToGen@ decides what type variables to generalise over. @@ -961,6 +978,44 @@ The @TcSigInfo@ contains @TcTypes@ because they are unified with the variable's type, and after that checked to see whether they've been instantiated. +Note [Scoped tyvars] +~~~~~~~~~~~~~~~~~~~~ +The -XScopedTypeVariables flag brings lexically-scoped type variables +into scope for any explicitly forall-quantified type variables: + f :: forall a. a -> a + f x = e +Then 'a' is in scope inside 'e'. + +However, we do *not* support this + - For pattern bindings e.g + f :: forall a. a->a + (f,g) = e + + - For multiple function bindings, unless Opt_RelaxedPolyRec is on + f :: forall a. a -> a + f = g + g :: forall b. b -> b + g = ...f... + Reason: we use mutable variables for 'a' and 'b', since they may + unify to each other, and that means the scoped type variable would + not stand for a completely rigid variable. + + Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec + + +Note [More instantiated than scoped] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +There may be more instantiated type variables than lexically-scoped +ones. For example: + type T a = forall b. b -> (a,b) + f :: forall c. T c +Here, the signature for f will have one scoped type variable, c, +but two instantiated type variables, c' and b'. + +We assume that the scoped ones are at the *front* of sig_tvs, +and remember the names from the original HsForAllTy in the TcSigFun. + + \begin{code} type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of -- type variables brought into scope @@ -973,23 +1028,18 @@ mkTcSigFun :: [LSig Name] -> TcSigFun -- Precondition: no duplicates mkTcSigFun sigs = lookupNameEnv env where - env = mkNameEnv [(name, scoped_tyvars hs_ty) - | L span (TypeSig (L _ name) (L _ hs_ty)) <- sigs] - scoped_tyvars (HsForAllTy Explicit tvs _ _) = hsLTyVarNames tvs - scoped_tyvars other = [] + env = mkNameEnv [(name, hsExplicitTvs lhs_ty) + | L span (TypeSig (L _ name) lhs_ty) <- sigs] -- The scoped names are the ones explicitly mentioned -- in the HsForAll. (There may be more in sigma_ty, because - -- of nested type synonyms. See Note [Scoped] with TcSigInfo.) + -- of nested type synonyms. See Note [More instantiated than scoped].) + -- See Note [Only scoped tyvars are in the TyVarEnv] --------------- data TcSigInfo = TcSigInfo { sig_id :: TcId, -- *Polymorphic* binder for this value... - sig_scoped :: [Name], -- Names for any scoped type variables - -- Invariant: correspond 1-1 with an initial - -- segment of sig_tvs (see Note [Scoped]) - sig_tvs :: [TcTyVar], -- Instantiated type variables -- See Note [Instantiate sig] @@ -998,19 +1048,21 @@ data TcSigInfo sig_loc :: InstLoc -- The location of the signature } --- Note [Scoped] --- There may be more instantiated type variables than scoped --- ones. For example: --- type T a = forall b. b -> (a,b) --- f :: forall c. T c --- Here, the signature for f will have one scoped type variable, c, --- but two instantiated type variables, c' and b'. + +-- Note [Only scoped tyvars are in the TyVarEnv] +-- We are careful to keep only the *lexically scoped* type variables in +-- the type environment. Why? After all, the renamer has ensured +-- that only legal occurrences occur, so we could put all type variables +-- into the type env. -- --- We assume that the scoped ones are at the *front* of sig_tvs, --- and remember the names from the original HsForAllTy in sig_scoped +-- But we want to check that two distinct lexically scoped type variables +-- do not map to the same internal type variable. So we need to know which +-- the lexically-scoped ones are... and at the moment we do that by putting +-- only the lexically scoped ones into the environment. + -- Note [Instantiate sig] --- It's vital to instantiate a type signature with fresh variable. +-- It's vital to instantiate a type signature with fresh variables. -- For example: -- type S = forall a. a->a -- f,g :: S @@ -1039,14 +1091,16 @@ tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo) tcInstSig_maybe sig_fn name = case sig_fn name of Nothing -> return Nothing - Just tvs -> do { tc_sig <- tcInstSig False name tvs - ; return (Just tc_sig) } + Just scoped_tvs -> do { tc_sig <- tcInstSig False name + ; return (Just tc_sig) } + -- NB: the scoped_tvs may be non-empty, but we can + -- just ignore them. See Note [Scoped tyvars]. -tcInstSig :: Bool -> Name -> [Name] -> TcM TcSigInfo +tcInstSig :: Bool -> Name -> TcM TcSigInfo -- Instantiate the signature, with either skolems or meta-type variables -- depending on the use_skols boolean. This variable is set True -- when we are typechecking a single function binding; and False for --- pattern bindigs and a group of several function bindings. +-- pattern bindings and a group of several function bindings. -- Reason: in the latter cases, the "skolems" can be unified together, -- so they aren't properly rigid in the type-refinement sense. -- NB: unless we are doing H98, each function with a sig will be done @@ -1061,25 +1115,16 @@ tcInstSig :: Bool -> Name -> [Name] -> TcM TcSigInfo -- -- We must not use the same 'a' from the defn of T at both places!! -tcInstSig use_skols name scoped_names +tcInstSig use_skols name = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into -- scope when starting the binding group ; let skol_info = SigSkol (FunSigCtxt name) - inst_tyvars | use_skols = tcInstSkolTyVars skol_info - | otherwise = tcInstSigTyVars skol_info + inst_tyvars = tcInstSigTyVars use_skols skol_info ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id) ; loc <- getInstLoc (SigOrigin skol_info) ; return (TcSigInfo { sig_id = poly_id, sig_tvs = tvs, sig_theta = theta, sig_tau = tau, - sig_scoped = final_scoped_names, sig_loc = loc }) } - -- Note that the scoped_names and the sig_tvs will have - -- different Names. That's quite ok; when we bring the - -- scoped_names into scope, we just bind them to the sig_tvs - where - -- We also only have scoped type variables when we are instantiating - -- with true skolems - final_scoped_names | use_skols = scoped_names - | otherwise = [] + sig_loc = loc }) } ------------------- isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool @@ -1148,4 +1193,13 @@ restrictedBindCtxtErr binder_names genCtxt binder_names = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names + +missingSigWarn False name ty = return () +missingSigWarn True name ty + = do { env0 <- tcInitTidyEnv + ; let (env1, tidy_ty) = tidyOpenType env0 ty + ; addWarnTcM (env1, mk_msg tidy_ty) } + where + mk_msg ty = vcat [ptext SLIT("Definition but no type signature for") <+> quotes (ppr name), + sep [ptext SLIT("Inferred type:") <+> pprHsVar name <+> dcolon <+> ppr ty]] \end{code}