X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcBinds.lhs;h=9e60bbd47f29bb61f0bf384a7130be8183ed75be;hb=43a2e4a26175b9dbf29e39b97f7d032ef00f9993;hp=5d9dbb885a0a38badb0312aa31ba3bdf0e345234;hpb=e5ca7e6e5137a2e6081717e5e90ca52a30840f68;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcBinds.lhs b/compiler/typecheck/TcBinds.lhs index 5d9dbb8..9e60bbd 100644 --- a/compiler/typecheck/TcBinds.lhs +++ b/compiler/typecheck/TcBinds.lhs @@ -5,6 +5,13 @@ \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, @@ -30,11 +37,12 @@ import TcPat import TcMType import TcType import {- Kind parts of -} Type +import Coercion import VarEnv import TysPrim import Id import IdInfo -import Var ( TyVar ) +import Var ( TyVar, varType ) import Name import NameSet import NameEnv @@ -162,9 +170,9 @@ 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) } @@ -176,14 +184,14 @@ 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) } ------------------------ @@ -195,15 +203,15 @@ 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) } @@ -241,7 +249,7 @@ 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 @@ -336,15 +344,15 @@ tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req -- BUILD THE POLYMORPHIC RESULT IDs - ; let dict_ids = map instToId dicts - ; 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 + dict_vars exports (dict_binds `unionBags` binds') ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport @@ -352,7 +360,8 @@ tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds -------------- -mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo +mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType] + -> MonoBindInfo -> TcM ([TyVar], Id, Id, [LPrag]) -- mkExport generates exports with -- zonked type variables, @@ -365,20 +374,24 @@ 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) } @@ -411,11 +424,10 @@ 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 @@ -507,7 +519,7 @@ 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 #) @@ -534,15 +546,18 @@ 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', @@ -560,7 +575,7 @@ 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 $ traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id) | (n,id) <- rhs_id_env]) `thenM_` mapM (wrapLocM tcRhs) tc_binds @@ -648,9 +663,13 @@ 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, fun_tick = Nothing }) } @@ -728,9 +747,9 @@ generalise dflags top_lvl bind_list sig_fn mono_infos lie_req 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 @@ -765,7 +784,17 @@ unifyCtxts (sig1 : sigs) -- Argument is always non-empty unify_ctxt sig@(TcSigInfo { sig_theta = theta }) = 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 @@ -946,6 +975,44 @@ 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 @@ -962,7 +1029,7 @@ mkTcSigFun sigs = lookupNameEnv env | 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] --------------- @@ -970,10 +1037,6 @@ 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] @@ -995,17 +1058,6 @@ data TcSigInfo -- only the lexically scoped ones into the environment. --- 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'. --- --- We assume that the scoped ones are at the *front* of sig_tvs, --- and remember the names from the original HsForAllTy in sig_scoped - -- Note [Instantiate sig] -- It's vital to instantiate a type signature with fresh variables. -- For example: @@ -1036,10 +1088,12 @@ 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 @@ -1058,7 +1112,7 @@ 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) @@ -1067,15 +1121,7 @@ tcInstSig use_skols name scoped_names ; 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 @@ -1144,4 +1190,13 @@ 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:") <+> ppr name <+> dcolon <+> ppr ty]] \end{code}