From: Ian Lynagh Date: Sun, 18 May 2008 12:56:06 +0000 (+0000) Subject: Detab TcBinds X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=1b68b94fcde73a92a371730b210b5b1c8678a44f Detab TcBinds --- diff --git a/compiler/typecheck/TcBinds.lhs b/compiler/typecheck/TcBinds.lhs index 3b9a496..45e3264 100644 --- a/compiler/typecheck/TcBinds.lhs +++ b/compiler/typecheck/TcBinds.lhs @@ -13,10 +13,10 @@ -- for details module TcBinds ( tcLocalBinds, tcTopBinds, - tcHsBootSigs, tcMonoBinds, - TcPragFun, tcSpecPrag, tcPrags, mkPragFun, - TcSigInfo(..), TcSigFun, mkTcSigFun, - badBootDeclErr ) where + tcHsBootSigs, tcMonoBinds, + TcPragFun, tcSpecPrag, tcPrags, mkPragFun, + TcSigInfo(..), TcSigFun, mkTcSigFun, + badBootDeclErr ) where import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun ) import {-# SOURCE #-} TcExpr ( tcMonoExpr ) @@ -61,9 +61,9 @@ import Control.Monad %************************************************************************ -%* * +%* * \subsection{Type-checking bindings} -%* * +%* * %************************************************************************ @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because @@ -93,26 +93,26 @@ dictionaries, which we resolve at the module level. \begin{code} tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv) - -- Note: returning the TcLclEnv is more than we really - -- want. The bit we care about is the local bindings - -- and the free type variables thereof + -- Note: returning the TcLclEnv is more than we really + -- want. The bit we care about is the local bindings + -- and the free type variables thereof tcTopBinds binds - = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv - ; return (foldr (unionBags . snd) emptyBag prs, env) } - -- The top level bindings are flattened into a giant - -- implicitly-mutually-recursive LHsBinds + = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv + ; return (foldr (unionBags . snd) emptyBag prs, env) } + -- The top level bindings are flattened into a giant + -- implicitly-mutually-recursive LHsBinds tcHsBootSigs :: HsValBinds Name -> TcM [Id] -- A hs-boot file has only one BindGroup, and it only has type -- signatures in it. The renamer checked all this tcHsBootSigs (ValBindsOut binds sigs) - = do { checkTc (null binds) badBootDeclErr - ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) } + = do { checkTc (null binds) badBootDeclErr + ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) } where tc_boot_sig (TypeSig (L _ name) ty) = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty - ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) } - -- Notice that we make GlobalIds, not LocalIds + ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) } + -- Notice that we make GlobalIds, not LocalIds tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups) badBootDeclErr :: Message @@ -120,28 +120,28 @@ badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file") ------------------------ tcLocalBinds :: HsLocalBinds Name -> TcM thing - -> TcM (HsLocalBinds TcId, thing) + -> TcM (HsLocalBinds TcId, thing) tcLocalBinds EmptyLocalBinds thing_inside - = do { thing <- thing_inside - ; return (EmptyLocalBinds, thing) } + = do { thing <- thing_inside + ; return (EmptyLocalBinds, thing) } tcLocalBinds (HsValBinds binds) thing_inside - = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside - ; return (HsValBinds binds', thing) } + = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside + ; return (HsValBinds binds', thing) } tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside - = do { (thing, lie) <- getLIE thing_inside - ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds + = do { (thing, lie) <- getLIE thing_inside + ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds - -- If the binding binds ?x = E, we must now - -- discharge any ?x constraints in expr_lie - ; dict_binds <- tcSimplifyIPs avail_ips lie - ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) } + -- If the binding binds ?x = E, we must now + -- discharge any ?x constraints in expr_lie + ; dict_binds <- tcSimplifyIPs avail_ips lie + ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) } where - -- I wonder if we should do these one at at time - -- Consider ?x = 4 - -- ?y = ?x + 1 + -- I wonder if we should do these one at at time + -- Consider ?x = 4 + -- ?y = ?x + 1 tc_ip_bind (IPBind ip expr) = do ty <- newFlexiTyVarTy argTypeKind (ip', ip_inst) <- newIPDict (IPBindOrigin ip) ip ty @@ -150,90 +150,90 @@ tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside ------------------------ tcValBinds :: TopLevelFlag - -> HsValBinds Name -> TcM thing - -> TcM (HsValBinds TcId, thing) + -> HsValBinds Name -> TcM thing + -> TcM (HsValBinds TcId, thing) tcValBinds top_lvl (ValBindsIn binds sigs) thing_inside = pprPanic "tcValBinds" (ppr binds) tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside - = do { -- Typecheck the signature - ; let { prag_fn = mkPragFun sigs - ; ty_sigs = filter isVanillaLSig sigs - ; sig_fn = mkTcSigFun ty_sigs } - - ; poly_ids <- mapM tcTySig ty_sigs - -- No recovery from bad signatures, because the type sigs - -- may bind type variables, so proceeding without them - -- can lead to a cascade of errors - -- ToDo: this means we fall over immediately if any type sig - -- is wrong, which is over-conservative, see Trac bug #745 - - -- Extend the envt right away with all - -- the Ids declared with type signatures - ; poly_rec <- doptM Opt_RelaxedPolyRec - ; (binds', thing) <- tcExtendIdEnv poly_ids $ - tc_val_binds poly_rec top_lvl sig_fn prag_fn - binds thing_inside - - ; return (ValBindsOut binds' sigs, thing) } + = do { -- Typecheck the signature + ; let { prag_fn = mkPragFun sigs + ; ty_sigs = filter isVanillaLSig sigs + ; sig_fn = mkTcSigFun ty_sigs } + + ; poly_ids <- mapM tcTySig ty_sigs + -- No recovery from bad signatures, because the type sigs + -- may bind type variables, so proceeding without them + -- can lead to a cascade of errors + -- ToDo: this means we fall over immediately if any type sig + -- is wrong, which is over-conservative, see Trac bug #745 + + -- Extend the envt right away with all + -- the Ids declared with type signatures + ; poly_rec <- doptM Opt_RelaxedPolyRec + ; (binds', thing) <- tcExtendIdEnv poly_ids $ + tc_val_binds poly_rec top_lvl sig_fn prag_fn + binds thing_inside + + ; return (ValBindsOut binds' sigs, thing) } ------------------------ tc_val_binds :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun - -> [(RecFlag, LHsBinds Name)] -> TcM thing - -> TcM ([(RecFlag, LHsBinds TcId)], thing) + -> [(RecFlag, LHsBinds Name)] -> TcM thing + -> TcM ([(RecFlag, LHsBinds TcId)], thing) -- Typecheck a whole lot of value bindings, -- one strongly-connected component at a time tc_val_binds poly_rec top_lvl sig_fn prag_fn [] thing_inside - = do { thing <- thing_inside - ; return ([], thing) } + = do { thing <- thing_inside + ; return ([], thing) } tc_val_binds poly_rec top_lvl sig_fn prag_fn (group : groups) thing_inside - = do { (group', (groups', thing)) - <- 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) } + = do { (group', (groups', thing)) + <- 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) } ------------------------ tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun - -> (RecFlag, LHsBinds Name) -> TcM thing - -> TcM ([(RecFlag, LHsBinds TcId)], thing) + -> (RecFlag, LHsBinds Name) -> TcM thing + -> TcM ([(RecFlag, LHsBinds TcId)], thing) -- Typecheck one strongly-connected component of the original program. -- We get a list of groups back, because there may -- be specialisations etc as well 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 + -- 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) } + = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside + ; return ([(NonRecursive, b) | b <- binds], thing) } 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) } - - | otherwise -- Recursive group, with gla-exts - = -- To maximise polymorphism (with -fglasgow-exts), we do a new - -- strongly-connected-component analysis, this time omitting - -- any references to variables with type signatures. - -- - -- Notice that the bindInsts thing covers *all* the bindings in the original - -- group at once; an earlier one may use a later one! - do { traceTc (text "tc_group rec" <+> pprLHsBinds binds) - ; (binds1,thing) <- bindLocalInsts top_lvl $ - go (stronglyConnComp (mkEdges sig_fn binds)) - ; return ([(Recursive, unionManyBags binds1)], thing) } - -- Rec them all together + | 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) } + + | otherwise -- Recursive group, with gla-exts + = -- To maximise polymorphism (with -fglasgow-exts), we do a new + -- strongly-connected-component analysis, this time omitting + -- any references to variables with type signatures. + -- + -- Notice that the bindInsts thing covers *all* the bindings in the original + -- group at once; an earlier one may use a later one! + do { traceTc (text "tc_group rec" <+> pprLHsBinds binds) + ; (binds1,thing) <- bindLocalInsts top_lvl $ + go (stronglyConnComp (mkEdges sig_fn binds)) + ; return ([(Recursive, unionManyBags binds1)], thing) } + -- Rec them all together where -- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], [TcId], thing) - go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc - ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs - ; return (binds1 ++ binds2, ids1 ++ ids2, thing) } - go [] = do { thing <- thing_inside; return ([], [], thing) } + go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc + ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs + ; return (binds1 ++ binds2, ids1 ++ ids2, thing) } + go [] = do { thing <- thing_inside; return ([], [], thing) } tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind) tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds) @@ -250,24 +250,24 @@ 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 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 + -- 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 - | otherwise -- Nested case - = do { ((binds, ids, thing), lie) <- getLIE thing_inside - ; lie_binds <- bindInstsOfLocalFuns lie ids - ; return (binds ++ [lie_binds], thing) } + | otherwise -- Nested case + = do { ((binds, ids, thing), lie) <- getLIE thing_inside + ; lie_binds <- bindInstsOfLocalFuns lie ids + ; return (binds ++ [lie_binds], thing) } ------------------------ mkEdges :: TcSigFun -> LHsBinds Name - -> [(LHsBind Name, BKey, [BKey])] + -> [(LHsBind Name, BKey, [BKey])] type BKey = Int -- Just number off the bindings mkEdges sig_fn binds = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)), - Just key <- [lookupNameEnv key_map n], no_sig n ]) + Just key <- [lookupNameEnv key_map n], no_sig n ]) | (bind, key) <- keyd_binds ] where @@ -276,9 +276,9 @@ mkEdges sig_fn binds keyd_binds = bagToList binds `zip` [0::BKey ..] - key_map :: NameEnv BKey -- Which binding it comes from + key_map :: NameEnv BKey -- Which binding it comes from key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds - , bndr <- bindersOfHsBind bind ] + , bndr <- bindersOfHsBind bind ] bindersOfHsBind :: HsBind Name -> [Name] bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat @@ -286,11 +286,11 @@ bindersOfHsBind (FunBind { fun_id = L _ f }) = [f] ------------------------ tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun - -> RecFlag -- Whether the group is really recursive - -> RecFlag -- Whether it's recursive after breaking - -- dependencies based on type signatures - -> LHsBinds Name - -> TcM ([LHsBinds TcId], [TcId]) + -> RecFlag -- Whether the group is really recursive + -> RecFlag -- Whether it's recursive after breaking + -- dependencies based on type signatures + -> LHsBinds Name + -> TcM ([LHsBinds TcId], [TcId]) -- Typechecks a single bunch of bindings all together, -- and generalises them. The bunch may be only part of a recursive @@ -304,69 +304,69 @@ tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds = let - bind_list = bagToList binds + bind_list = bagToList binds binder_names = collectHsBindBinders binds - loc = getLoc (head bind_list) - -- TODO: location a bit awkward, but the mbinds have been - -- dependency analysed and may no longer be adjacent + loc = getLoc (head bind_list) + -- TODO: location a bit awkward, but the mbinds have been + -- dependency analysed and may no longer be adjacent in - -- SET UP THE MAIN RECOVERY; take advantage of any type sigs - setSrcSpan loc $ - recoverM (recoveryCode binder_names sig_fn) $ do + -- SET UP THE MAIN RECOVERY; take advantage of any type sigs + setSrcSpan loc $ + recoverM (recoveryCode binder_names sig_fn) $ do { traceTc (ptext (sLit "------------------------------------------------")) ; traceTc (ptext (sLit "Bindings for") <+> ppr binder_names) - -- TYPECHECK THE BINDINGS + -- TYPECHECK THE BINDINGS ; ((binds', mono_bind_infos), lie_req) - <- getLIE (tcMonoBinds bind_list sig_fn rec_tc) + <- 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 - -- They desugar to a case expression in the end + -- CHECK FOR UNLIFTED BINDINGS + -- These must be non-recursive etc, and are not generalised + -- They desugar to a case expression in the end ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos) ; is_strict <- checkStrictBinds top_lvl rec_group binds' - zonked_mono_tys mono_bind_infos + zonked_mono_tys mono_bind_infos ; if is_strict then - do { extendLIEs lie_req - ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys - mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, []) - mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, []) - -- ToDo: prags for unlifted bindings + do { extendLIEs lie_req + ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys + mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, []) + mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, []) + -- ToDo: prags for unlifted bindings - ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'], - [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked + ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'], + [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked - else do -- The normal lifted case: GENERALISE + else do -- The normal lifted case: GENERALISE { dflags <- getDOpts ; (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 + <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $ + generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req - -- BUILD THE POLYMORPHIC RESULT IDs - ; let dict_vars = map instToVar dicts -- May include equality constraints + -- BUILD THE POLYMORPHIC RESULT 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 + mono_bind_infos - ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports] + ; 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_vars exports - (dict_binds `unionBags` binds') + dict_vars exports + (dict_binds `unionBags` binds') - ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport + ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport } } -------------- mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType] - -> MonoBindInfo - -> TcM ([TyVar], Id, Id, [LPrag]) + -> MonoBindInfo + -> TcM ([TyVar], Id, Id, [LPrag]) -- mkExport generates exports with --- zonked type variables, --- zonked poly_ids +-- zonked type variables, +-- zonked poly_ids -- The former is just because no further unifications will change -- the quantified type variables, so we can fix their final form -- right now. @@ -376,23 +376,23 @@ mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType] -- Pre-condition: the inferred_tvs are already zonked 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 + = 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 - ; prags <- tcPrags poly_id (prag_fn poly_name) - -- tcPrags requires a zonked poly_id + ; 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 warn Nothing = do { poly_ty' <- zonkTcType poly_ty - ; missingSigWarn warn poly_name poly_ty' - ; return (inferred_tvs, mkLocalId poly_name 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) } + ; return (tvs, sig_id sig) } zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) } @@ -401,17 +401,17 @@ type TcPragFun = Name -> [LSig Name] mkPragFun :: [LSig Name] -> TcPragFun mkPragFun sigs = \n -> lookupNameEnv env n `orElse` [] - where - prs = [(expectJust "mkPragFun" (sigName sig), sig) - | sig <- sigs, isPragLSig sig] - env = foldl add emptyNameEnv prs - add env (n,p) = extendNameEnv_Acc (:) singleton env n p + where + prs = [(expectJust "mkPragFun" (sigName sig), sig) + | sig <- sigs, isPragLSig sig] + env = foldl add emptyNameEnv prs + add env (n,p) = extendNameEnv_Acc (:) singleton env n p tcPrags :: Id -> [LSig Name] -> TcM [LPrag] tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags where tc_prag prag = addErrCtxt (pragSigCtxt prag) $ - tcPrag poly_id prag + tcPrag poly_id prag pragSigCtxt prag = hang (ptext (sLit "In the pragma")) 2 (ppr prag) @@ -419,83 +419,83 @@ tcPrag :: TcId -> Sig Name -> TcM Prag -- Pre-condition: the poly_id is zonked -- Reason: required by tcSubExp tcPrag poly_id (SpecSig orig_name hs_ty inl) = tcSpecPrag poly_id hs_ty inl -tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec +tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl) tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag tcSpecPrag poly_id hs_ty 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 + = 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 -------------- -- If typechecking the binds fails, then return with each -- signature-less binder given type (forall a.a), to minimise -- subsequent error messages recoveryCode binder_names sig_fn - = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) - ; poly_ids <- mapM mk_dummy binder_names - ; return ([], poly_ids) } + = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) + ; poly_ids <- mapM mk_dummy binder_names + ; return ([], poly_ids) } where mk_dummy name - | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up - | otherwise = return (mkLocalId name forall_a_a) -- No signature + | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up + | otherwise = return (mkLocalId name forall_a_a) -- No signature forall_a_a :: TcType forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar) -- Check that non-overloaded unlifted bindings are --- a) non-recursive, --- b) not top level, --- c) not a multiple-binding group (more or less implied by (a)) +-- a) non-recursive, +-- b) not top level, +-- c) not a multiple-binding group (more or less implied by (a)) checkStrictBinds :: TopLevelFlag -> RecFlag - -> LHsBinds TcId -> [TcType] -> [MonoBindInfo] - -> TcM Bool + -> LHsBinds TcId -> [TcType] -> [MonoBindInfo] + -> TcM Bool checkStrictBinds top_lvl rec_group mbind mono_tys infos | unlifted || bang_pat - = do { checkTc (isNotTopLevel top_lvl) - (strictBindErr "Top-level" unlifted mbind) - ; checkTc (isNonRec rec_group) - (strictBindErr "Recursive" unlifted mbind) - ; checkTc (isSingletonBag mbind) - (strictBindErr "Multiple" unlifted mbind) - ; mapM_ check_sig infos - ; return True } + = do { checkTc (isNotTopLevel top_lvl) + (strictBindErr "Top-level" unlifted mbind) + ; checkTc (isNonRec rec_group) + (strictBindErr "Recursive" unlifted mbind) + ; checkTc (isSingletonBag mbind) + (strictBindErr "Multiple" unlifted mbind) + ; mapM_ check_sig infos + ; return True } | otherwise = return False where unlifted = any isUnLiftedType mono_tys bang_pat = anyBag (isBangHsBind . unLoc) mbind check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig)) - (badStrictSig unlifted sig) - check_sig other = return () + (badStrictSig unlifted sig) + check_sig other = return () strictBindErr flavour unlifted mbind = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:")) - 4 (pprLHsBinds mbind) + 4 (pprLHsBinds mbind) where msg | unlifted = ptext (sLit "bindings for unlifted types") - | otherwise = ptext (sLit "bang-pattern bindings") + | otherwise = ptext (sLit "bang-pattern bindings") badStrictSig unlifted sig = hang (ptext (sLit "Illegal polymorphic signature in") <+> msg) - 4 (ppr sig) + 4 (ppr sig) where msg | unlifted = ptext (sLit "an unlifted binding") - | otherwise = ptext (sLit "a bang-pattern binding") + | otherwise = ptext (sLit "a bang-pattern binding") \end{code} %************************************************************************ -%* * +%* * \subsection{tcMonoBind} -%* * +%* * %************************************************************************ @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds. @@ -503,108 +503,108 @@ The signatures have been dealt with already. \begin{code} tcMonoBinds :: [LHsBind Name] - -> TcSigFun - -> RecFlag -- Whether the binding is recursive for typechecking purposes - -- i.e. the binders are mentioned in their RHSs, and - -- we are not resuced by a type signature - -> TcM (LHsBinds TcId, [MonoBindInfo]) + -> TcSigFun + -> RecFlag -- Whether the binding is recursive for typechecking purposes + -- i.e. the binders are mentioned in their RHSs, and + -- we are not resuced by a type signature + -> TcM (LHsBinds TcId, [MonoBindInfo]) tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf, - fun_matches = matches, bind_fvs = fvs })] - sig_fn -- Single function binding, - NonRecursive -- binder isn't mentioned in RHS, - | Nothing <- sig_fn name -- ...with no type signature - = -- In this very special case we infer the type of the - -- right hand side first (it may have a higher-rank type) - -- and *then* make the monomorphic Id for the LHS - -- 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 inf matches) - - -- Check for an unboxed tuple type - -- f = (# True, False #) - -- Zonk first just in case it's hidden inside a meta type variable - -- (This shows up as a (more obscure) kind error - -- in the 'otherwise' case of tcMonoBinds.) - ; zonked_rhs_ty <- zonkTcType rhs_ty - ; checkTc (not (isUnboxedTupleType zonked_rhs_ty)) - (unboxedTupleErr name zonked_rhs_ty) - - ; mono_name <- newLocalName name - ; 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_tick = Nothing })), - [(name, Nothing, mono_id)]) } + fun_matches = matches, bind_fvs = fvs })] + sig_fn -- Single function binding, + NonRecursive -- binder isn't mentioned in RHS, + | Nothing <- sig_fn name -- ...with no type signature + = -- In this very special case we infer the type of the + -- right hand side first (it may have a higher-rank type) + -- and *then* make the monomorphic Id for the LHS + -- 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 inf matches) + + -- Check for an unboxed tuple type + -- f = (# True, False #) + -- Zonk first just in case it's hidden inside a meta type variable + -- (This shows up as a (more obscure) kind error + -- in the 'otherwise' case of tcMonoBinds.) + ; zonked_rhs_ty <- zonkTcType rhs_ty + ; checkTc (not (isUnboxedTupleType zonked_rhs_ty)) + (unboxedTupleErr name zonked_rhs_ty) + + ; mono_name <- newLocalName name + ; 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_tick = Nothing })), + [(name, Nothing, mono_id)]) } tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf, - fun_matches = matches, bind_fvs = fvs })] - sig_fn -- Single function binding - non_rec - | Just scoped_tvs <- sig_fn name -- ...with a type signature - = -- When we have a single function binding, with a type signature - -- 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 - ; 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) <- 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 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, - fun_tick = Nothing } - ; return (unitBag (L b_loc fun_bind'), - [(name, Just tc_sig, mono_id)]) } + fun_matches = matches, bind_fvs = fvs })] + sig_fn -- Single function binding + non_rec + | Just scoped_tvs <- sig_fn name -- ...with a type signature + = -- When we have a single function binding, with a type signature + -- 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 + ; 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) <- 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 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, + fun_tick = Nothing } + ; return (unitBag (L b_loc fun_bind'), + [(name, Just tc_sig, mono_id)]) } tcMonoBinds binds sig_fn non_rec - = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds + = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds - -- Bring the monomorphic Ids, into scope for the RHSs - ; let mono_info = getMonoBindInfo tc_binds - rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info] - -- A monomorphic binding for each term variable that lacks - -- a type sig. (Ones with a sig are already in scope.) + -- Bring the monomorphic Ids, into scope for the RHSs + ; let mono_info = getMonoBindInfo tc_binds + rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info] + -- 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 $ do - traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id) - | (n,id) <- rhs_id_env]) - mapM (wrapLocM tcRhs) tc_binds - ; return (listToBag binds', mono_info) } + ; binds' <- tcExtendIdEnv2 rhs_id_env $ do + traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id) + | (n,id) <- rhs_id_env]) + mapM (wrapLocM tcRhs) tc_binds + ; return (listToBag binds', mono_info) } ------------------------ -- tcLhs typechecks the LHS of the bindings, to construct the environment in which -- we typecheck the RHSs. Basically what we are doing is this: for each binder: --- if there's a signature for it, use the instantiated signature type --- otherwise invent a type variable +-- if there's a signature for it, use the instantiated signature type +-- otherwise invent a type variable -- You see that quite directly in the FunBind case. -- -- But there's a complication for pattern bindings: --- data T = MkT (forall a. a->a) --- MkT f = e +-- data T = MkT (forall a. a->a) +-- MkT f = e -- Here we can guess a type variable for the entire LHS (which will be refined to T) -- but we want to get (f::forall a. a->a) as the RHS environment. -- The simplest way to do this is to typecheck the pattern, and then look up the -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't -data TcMonoBind -- Half completed; LHS done, RHS not done +data TcMonoBind -- Half completed; LHS done, RHS not done = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name) | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType type MonoBindInfo = (Name, Maybe TcSigInfo, TcId) - -- Type signature (if any), and - -- the monomorphic bound things + -- Type signature (if any), and + -- the monomorphic bound things bndrNames :: [MonoBindInfo] -> [Name] bndrNames mbi = [n | (n,_,_) <- mbi] @@ -614,53 +614,53 @@ getMonoType (_,_,mono_id) = idType mono_id tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches }) - = do { mb_sig <- tcInstSig_maybe sig_fn name - ; mono_name <- newLocalName name - ; mono_ty <- mk_mono_ty mb_sig - ; let mono_id = mkLocalId mono_name mono_ty - ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) } + = do { mb_sig <- tcInstSig_maybe sig_fn name + ; mono_name <- newLocalName name + ; mono_ty <- mk_mono_ty mb_sig + ; let mono_id = mkLocalId mono_name mono_ty + ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) } where mk_mono_ty (Just sig) = return (sig_tau sig) mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss }) - = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names - ; mono_pat_binds <- doptM Opt_MonoPatBinds - -- With -fmono-pat-binds, we do no generalisation of pattern bindings - -- But the signature can still be polymoprhic! - -- data T = MkT (forall a. a->a) - -- x :: forall a. a->a - -- MkT x = - -- The function get_sig_ty decides whether the pattern-bound variables - -- should have exactly the type in the type signature (-fmono-pat-binds), - -- or the instantiated version (-fmono-pat-binds) - - ; let nm_sig_prs = names `zip` mb_sigs - get_sig_ty | mono_pat_binds = idType . sig_id - | otherwise = sig_tau - tau_sig_env = mkNameEnv [ (name, get_sig_ty sig) - | (name, Just sig) <- nm_sig_prs] - sig_tau_fn = lookupNameEnv tau_sig_env - - tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $ - mapM lookup_info nm_sig_prs - - -- After typechecking the pattern, look up the binder - -- names, which the pattern has brought into scope. - lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo - lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name - ; return (name, mb_sig, mono_id) } - - ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $ - tcInfer tc_pat - - ; return (TcPatBind infos pat' grhss pat_ty) } + = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names + ; mono_pat_binds <- doptM Opt_MonoPatBinds + -- With -fmono-pat-binds, we do no generalisation of pattern bindings + -- But the signature can still be polymoprhic! + -- data T = MkT (forall a. a->a) + -- x :: forall a. a->a + -- MkT x = + -- The function get_sig_ty decides whether the pattern-bound variables + -- should have exactly the type in the type signature (-fmono-pat-binds), + -- or the instantiated version (-fmono-pat-binds) + + ; let nm_sig_prs = names `zip` mb_sigs + get_sig_ty | mono_pat_binds = idType . sig_id + | otherwise = sig_tau + tau_sig_env = mkNameEnv [ (name, get_sig_ty sig) + | (name, Just sig) <- nm_sig_prs] + sig_tau_fn = lookupNameEnv tau_sig_env + + tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $ + mapM lookup_info nm_sig_prs + + -- After typechecking the pattern, look up the binder + -- names, which the pattern has brought into scope. + lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo + lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name + ; return (name, mb_sig, mono_id) } + + ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $ + tcInfer tc_pat + + ; return (TcPatBind infos pat' grhss pat_ty) } where names = collectPatBinders pat tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind) - -- AbsBind, VarBind impossible + -- AbsBind, VarBind impossible ------------------- tcRhs :: TcMonoBind -> TcM (HsBind TcId) @@ -669,17 +669,17 @@ tcRhs :: TcMonoBind -> TcM (HsBind TcId) -- 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, - fun_tick = Nothing }) } + = 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, + fun_tick = Nothing }) } tcRhs bind@(TcPatBind _ pat' grhss pat_ty) - = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $ - tcGRHSsPat grhss pat_ty - ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty, - bind_fvs = placeHolderNames }) } + = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $ + tcGRHSsPat grhss pat_ty + ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty, + bind_fvs = placeHolderNames }) } --------------------- @@ -693,71 +693,71 @@ getMonoBindInfo tc_binds %************************************************************************ -%* * - Generalisation -%* * +%* * + Generalisation +%* * %************************************************************************ \begin{code} generalise :: DynFlags -> TopLevelFlag - -> [LHsBind Name] -> TcSigFun - -> [MonoBindInfo] -> [Inst] - -> TcM ([TyVar], [Inst], TcDictBinds) + -> [LHsBind Name] -> TcSigFun + -> [MonoBindInfo] -> [Inst] + -> 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 - do { checkTc (all is_mono_sig sigs) - (restrictedBindCtxtErr bndrs) + | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE + = -- Check signature contexts are empty + do { checkTc (all is_mono_sig sigs) + (restrictedBindCtxtErr bndrs) - -- Now simplify with exactly that set of tyvars - -- We have to squash those Methods - ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs - tau_tvs lie_req + -- Now simplify with exactly that set of tyvars + -- We have to squash those Methods + ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs + tau_tvs lie_req - -- Check that signature type variables are OK - ; final_qtvs <- checkSigsTyVars qtvs sigs + -- 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 + | 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; 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 - ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req - - -- Check that signature type variables are OK - ; final_qtvs <- checkSigsTyVars qtvs sigs - - ; return (final_qtvs, sig_lie, binds) } + | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS + = 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 + ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req + + -- Check that signature type variables are OK + ; final_qtvs <- checkSigsTyVars qtvs sigs + + ; return (final_qtvs, sig_lie, binds) } where bndrs = bndrNames mono_infos sigs = [sig | (_, Just sig, _) <- mono_infos] - get_tvs | isTopLevel top_lvl = tyVarsOfType -- See Note [Silly type synonym] in TcType - | otherwise = 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 + sig_theta = theta, sig_loc = loc }) mono_id = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs, - tci_theta = theta, tci_loc = loc} + tci_theta = theta, tci_loc = loc} \end{code} unifyCtxts checks that all the signature contexts are the same @@ -775,86 +775,86 @@ 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 - ; theta <- zonkTcThetaType (sig_theta sig1) - ; newDictBndrs (sig_loc sig1) theta } +unifyCtxts (sig1 : sigs) -- Argument is always non-empty + = do { mapM unify_ctxt sigs + ; 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 (instLocSpan (sig_loc sig)) $ - addErrCtxt (sigContextsCtxt sig1 sig) $ - 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")) - } + = setSrcSpan (instLocSpan (sig_loc sig)) $ + addErrCtxt (sigContextsCtxt sig1 sig) $ + 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 <- 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 - -- going to generalise over. Reason: we occasionally get - -- silly types like - -- type T a = () -> () - -- f :: T a - -- f () = () - -- 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) - ; return all_tvs } + = do { gbl_tvs <- tcGetGlobalTyVars + ; 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 + -- going to generalise over. Reason: we occasionally get + -- silly types like + -- type T a = () -> () + -- f :: T a + -- f () = () + -- 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) + ; 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 - ; when (any (`elemVarSet` gbl_tvs) tvs') - (bleatEscapedTvs gbl_tvs tvs tvs') - ; return 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 + ; when (any (`elemVarSet` gbl_tvs) tvs') + (bleatEscapedTvs gbl_tvs tvs tvs') + ; return tvs' } checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar] -- (checkDistinctTyVars tvs) checks that the tvs from one type signature -- are still all type variables, and all distinct from each other. -- It returns a zonked set of type variables. -- For example, if the type sig is --- f :: forall a b. a -> b -> b +-- f :: forall a b. a -> b -> b -- we want to check that 'a' and 'b' haven't --- (a) been unified with a non-tyvar type --- (b) been unified with each other (all distinct) +-- (a) been unified with a non-tyvar type +-- (b) been unified with each other (all distinct) checkDistinctTyVars sig_tvs - = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs - ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs) - ; return zonked_tvs } + = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs + ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs) + ; return zonked_tvs } where check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar) - -- The TyVarEnv maps each zonked type variable back to its - -- corresponding user-written signature type variable + -- The TyVarEnv maps each zonked type variable back to its + -- corresponding user-written signature type variable check_dup acc (sig_tv, zonked_tv) - = case lookupVarEnv acc zonked_tv of - Just sig_tv' -> bomb_out sig_tv sig_tv' + = case lookupVarEnv acc zonked_tv of + Just sig_tv' -> bomb_out sig_tv sig_tv' - Nothing -> return (extendVarEnv acc zonked_tv sig_tv) + Nothing -> return (extendVarEnv acc zonked_tv sig_tv) bomb_out sig_tv1 sig_tv2 = do { env0 <- tcInitTidyEnv - ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1 - (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2 - msg = ptext (sLit "Quantified type variable") <+> quotes (ppr tidy_tv1) - <+> ptext (sLit "is unified with another quantified type variable") - <+> quotes (ppr tidy_tv2) - ; failWithTcM (env2, msg) } + ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1 + (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2 + msg = ptext (sLit "Quantified type variable") <+> quotes (ppr tidy_tv1) + <+> ptext (sLit "is unified with another quantified type variable") + <+> quotes (ppr tidy_tv2) + ; failWithTcM (env2, msg) } where \end{code} @@ -868,8 +868,8 @@ remove from tyvars_to_gen any constrained type variables *Don't* simplify dicts at this point, because we aren't going to generalise over these dicts. By the time we do simplify them we may well know more. For example (this actually came up) - f :: Array Int Int - f x = array ... xs where xs = [1,2,3,4,5] + f :: Array Int Int + f x = array ... xs where xs = [1,2,3,4,5] We don't want to generate lots of (fromInt Int 1), (fromInt Int 2) stuff. If we simplify only at the f-binding (not the xs-binding) we'll know that the literals are all Ints, and we can just produce @@ -880,19 +880,19 @@ Find all the type variables involved in overloading, the generalise. We must be careful about doing this: (a) If we fail to generalise a tyvar which is not actually - constrained, then it will never, ever get bound, and lands - up printed out in interface files! Notorious example: - instance Eq a => Eq (Foo a b) where .. - Here, b is not constrained, even though it looks as if it is. - Another, more common, example is when there's a Method inst in - the LIE, whose type might very well involve non-overloaded - type variables. + constrained, then it will never, ever get bound, and lands + up printed out in interface files! Notorious example: + instance Eq a => Eq (Foo a b) where .. + Here, b is not constrained, even though it looks as if it is. + Another, more common, example is when there's a Method inst in + the LIE, whose type might very well involve non-overloaded + type variables. [NOTE: Jan 2001: I don't understand the problem here so I'm doing - the simple thing instead] + the simple thing instead] (b) On the other hand, we mustn't generalise tyvars which are constrained, - because we are going to pass on out the unmodified LIE, with those - tyvars in it. They won't be in scope if we've generalised them. + because we are going to pass on out the unmodified LIE, with those + tyvars in it. They won't be in scope if we've generalised them. So we are careful, and do a complete simplification just to find the constrained tyvars. We don't use any of the results, except to @@ -902,21 +902,21 @@ Note [Polymorphic recursion] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The game plan for polymorphic recursion in the code above is - * Bind any variable for which we have a type signature - to an Id with a polymorphic type. Then when type-checking - the RHSs we'll make a full polymorphic call. + * Bind any variable for which we have a type signature + to an Id with a polymorphic type. Then when type-checking + the RHSs we'll make a full polymorphic call. This fine, but if you aren't a bit careful you end up with a horrendous amount of partial application and (worse) a huge space leak. For example: - f :: Eq a => [a] -> [a] - f xs = ...f... + f :: Eq a => [a] -> [a] + f xs = ...f... If we don't take care, after typechecking we get - f = /\a -> \d::Eq a -> let f' = f a d - in - \ys:[a] -> ...f'... + f = /\a -> \d::Eq a -> let f' = f a d + in + \ys:[a] -> ...f'... Notice the the stupid construction of (f a d), which is of course identical to the function we're executing. In this case, the @@ -924,19 +924,19 @@ polymorphic recursion isn't being used (but that's a very common case). This can lead to a massive space leak, from the following top-level defn (post-typechecking) - ff :: [Int] -> [Int] - ff = f Int dEqInt + ff :: [Int] -> [Int] + ff = f Int dEqInt Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but f' is another thunk which evaluates to the same thing... and you end up with a chain of identical values all hung onto by the CAF ff. - ff = f Int dEqInt + ff = f Int dEqInt - = let f' = f Int dEqInt in \ys. ...f'... + = let f' = f Int dEqInt in \ys. ...f'... - = let f' = let f' = f Int dEqInt in \ys. ...f'... - in \ys. ...f'... + = let f' = let f' = f Int dEqInt in \ys. ...f'... + in \ys. ...f'... Etc. @@ -952,17 +952,17 @@ is doing. Then we get - f = /\a -> \d::Eq a -> letrec - fm = \ys:[a] -> ...fm... - in - fm + f = /\a -> \d::Eq a -> letrec + fm = \ys:[a] -> ...fm... + in + fm %************************************************************************ -%* * - Signatures -%* * +%* * + Signatures +%* * %************************************************************************ Type signatures are tricky. See Note [Signature skolems] in TcType @@ -980,20 +980,20 @@ 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 + 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 + 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... + 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. @@ -1005,8 +1005,8 @@ 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 + 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'. @@ -1015,10 +1015,10 @@ 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 - -- by its type signature. - -- Nothing => no type signature +type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of + -- type variables brought into scope + -- by its type signature. + -- Nothing => no type signature mkTcSigFun :: [LSig Name] -> TcSigFun -- Search for a particular type signature @@ -1027,27 +1027,27 @@ mkTcSigFun :: [LSig Name] -> TcSigFun mkTcSigFun sigs = lookupNameEnv env where 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 [More instantiated than scoped].) - -- See Note [Only scoped tyvars are in the TyVarEnv] + | 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 [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_id :: TcId, -- *Polymorphic* binder for this value... - sig_tvs :: [TcTyVar], -- Instantiated type variables - -- See Note [Instantiate sig] + sig_tvs :: [TcTyVar], -- Instantiated type variables + -- See Note [Instantiate sig] - sig_theta :: TcThetaType, -- Instantiated theta - sig_tau :: TcTauType, -- Instantiated tau - sig_loc :: InstLoc -- The location of the signature + sig_theta :: TcThetaType, -- Instantiated theta + sig_tau :: TcTauType, -- Instantiated tau + sig_loc :: InstLoc -- The location of the signature } --- Note [Only scoped tyvars are in the TyVarEnv] +-- 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 @@ -1059,28 +1059,28 @@ data TcSigInfo -- only the lexically scoped ones into the environment. --- Note [Instantiate sig] +-- Note [Instantiate sig] -- It's vital to instantiate a type signature with fresh variables. -- For example: --- type S = forall a. a->a --- f,g :: S --- f = ... --- g = ... +-- type S = forall a. a->a +-- f,g :: S +-- f = ... +-- g = ... -- Here, we must use distinct type variables when checking f,g's right hand sides. -- (Instantiation is only necessary because of type synonyms. Otherwise, -- it's all cool; each signature has distinct type variables from the renamer.) instance Outputable TcSigInfo where ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau}) - = ppr id <+> ptext (sLit "::") <+> ppr tyvars <+> ppr theta <+> ptext (sLit "=>") <+> ppr tau + = ppr id <+> ptext (sLit "::") <+> ppr tyvars <+> ppr theta <+> ptext (sLit "=>") <+> ppr tau \end{code} \begin{code} tcTySig :: LSig Name -> TcM TcId tcTySig (L span (TypeSig (L _ name) ty)) - = setSrcSpan span $ - do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty - ; return (mkLocalId name sigma_ty) } + = setSrcSpan span $ + do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty + ; return (mkLocalId name sigma_ty) } ------------------- tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo) @@ -1088,11 +1088,11 @@ tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo) -- this signature is part of a multi-signature group tcInstSig_maybe sig_fn name = case sig_fn name of - Nothing -> return Nothing - 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]. + Nothing -> return Nothing + 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 -> TcM TcSigInfo -- Instantiate the signature, with either skolems or meta-type variables @@ -1100,29 +1100,29 @@ tcInstSig :: Bool -> Name -> TcM TcSigInfo -- when we are typechecking a single function binding; and False for -- 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. +-- 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 -- separately, even if it's mutually recursive, so use_skols will be True -- -- We always instantiate with fresh uniques, -- although we keep the same print-name --- --- type T = forall a. [a] -> [a] --- f :: T; --- f = g where { g :: T; g = } +-- +-- type T = forall a. [a] -> [a] +-- f :: T; +-- f = g where { g :: T; g = } -- -- We must not use the same 'a' from the defn of T at both places!! 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 = 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_loc = loc }) } + = 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 = 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_loc = loc }) } ------------------- isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool @@ -1131,7 +1131,7 @@ isMonoGroup dflags binds = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds where is_pat_bind (L _ (PatBind {})) = True - is_pat_bind other = False + is_pat_bind other = False ------------------- isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool @@ -1142,22 +1142,22 @@ isRestrictedGroup dflags binds sig_fn all_unrestricted = all (unrestricted . unLoc) binds has_sig n = isJust (sig_fn n) - unrestricted (PatBind {}) = False - unrestricted (VarBind { var_id = v }) = has_sig v + unrestricted (PatBind {}) = False + unrestricted (VarBind { var_id = v }) = has_sig v unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches - || has_sig (unLoc v) + || has_sig (unLoc v) unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False - -- No args => like a pattern binding - unrestricted_match other = True - -- Some args => a function binding + -- No args => like a pattern binding + unrestricted_match other = True + -- Some args => a function binding \end{code} %************************************************************************ -%* * +%* * \subsection[TcBinds-errors]{Error contexts and messages} -%* * +%* * %************************************************************************ @@ -1170,9 +1170,9 @@ patMonoBindsCtxt pat grhss ----------------------------------------------- sigContextsCtxt sig1 sig2 = vcat [ptext (sLit "When matching the contexts of the signatures for"), - nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1), - ppr id2 <+> dcolon <+> ppr (idType id2)]), - ptext (sLit "The signature contexts in a mutually recursive group should all be identical")] + nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1), + ppr id2 <+> dcolon <+> ppr (idType id2)]), + ptext (sLit "The signature contexts in a mutually recursive group should all be identical")] where id1 = sig_id sig1 id2 = sig_id sig2 @@ -1181,23 +1181,23 @@ sigContextsCtxt sig1 sig2 ----------------------------------------------- unboxedTupleErr name ty = hang (ptext (sLit "Illegal binding of unboxed tuple")) - 4 (ppr name <+> dcolon <+> ppr ty) + 4 (ppr name <+> dcolon <+> ppr ty) ----------------------------------------------- restrictedBindCtxtErr binder_names = hang (ptext (sLit "Illegal overloaded type signature(s)")) 4 (vcat [ptext (sLit "in a binding group for") <+> pprBinders binder_names, - ptext (sLit "that falls under the monomorphism restriction")]) + ptext (sLit "that falls under the monomorphism restriction")]) 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) } + = 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]] + sep [ptext (sLit "Inferred type:") <+> pprHsVar name <+> dcolon <+> ppr ty]] \end{code}