X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=c4e1b92f6c981640dce050094c6cfaeafa1b4d51;hb=ff818166a0a06e77becad9e28ed116f3b7f5cc8b;hp=f711ef7207d787ce3c1d6f64612eb94cd0a74fb1;hpb=2c3d6429e4080b179b3fd9227691c2ee69360065;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index f711ef7..c4e1b92 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -1,66 +1,60 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcBinds]{TcBinds} \begin{code} -module TcBinds ( tcBindsAndThen, tcTopBindsAndThen, bindInstsOfLocalFuns, - tcPragmaSigs, checkSigTyVars, tcBindWithSigs, - sigCtxt, TcSigInfo(..) ) where +module TcBinds ( tcBindsAndThen, tcTopBinds, tcHsBootSigs, tcMonoBinds, tcSpecSigs ) where #include "HsVersions.h" -import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds ) -import {-# SOURCE #-} TcExpr ( tcExpr ) +import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun ) +import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho ) -import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), InPat(..), - collectMonoBinders, andMonoBinds +import CmdLineOpts ( DynFlag(Opt_MonomorphismRestriction) ) +import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, Sig(..), + LSig, Match(..), HsBindGroup(..), IPBind(..), + HsType(..), hsLTyVarNames, isVanillaLSig, + LPat, GRHSs, MatchGroup(..), emptyLHsBinds, isEmptyLHsBinds, + collectHsBindBinders, collectPatBinders, pprPatBind ) -import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds ) -import TcHsSyn ( TcHsBinds, TcMonoBinds, - TcIdOcc(..), TcIdBndr, - tcIdType +import TcHsSyn ( TcId, TcDictBinds, zonkId, mkHsLet ) + +import TcRnMonad +import Inst ( InstOrigin(..), newDictsAtLoc, newIPDict, instToId ) +import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2, + newLocalName, tcLookupLocalIds, pprBinders, + tcGetGlobalTyVars ) +import TcUnify ( Expected(..), tcInfer, unifyTheta, + bleatEscapedTvs, sigCtxt ) +import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted, + tcSimplifyToDicts, tcSimplifyIPs ) +import TcHsType ( tcHsSigType, UserTypeCtxt(..), tcAddLetBoundTyVars, + TcSigInfo(..), TcSigFun, lookupSig ) - -import TcMonad -import Inst ( Inst, LIE, emptyLIE, plusLIE, plusLIEs, InstOrigin(..), - newDicts, tyVarsOfInst, instToId, newMethodWithGivenTy, - zonkInst, pprInsts - ) -import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, - newLocalId, newSpecPragmaId, - tcGetGlobalTyVars, tcExtendGlobalTyVars - ) -import TcMatches ( tcMatchesFun ) -import TcSimplify ( tcSimplify, tcSimplifyAndCheck ) -import TcMonoType ( tcHsType ) -import TcPat ( tcPat ) +import TcPat ( tcPat, PatCtxt(..) ) import TcSimplify ( bindInstsOfLocalFuns ) -import TcType ( TcType, TcThetaType, TcTauType, - TcTyVarSet, TcTyVar, - newTyVarTy, newTcTyVar, tcInstSigType, tcInstSigTcType, - zonkTcType, zonkTcTypes, zonkTcThetaType, zonkTcTyVar - ) -import Unify ( unifyTauTy, unifyTauTyLists ) - -import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind ) -import MkId ( mkUserId ) -import Id ( idType, idName, idInfo, replaceIdInfo ) -import IdInfo ( IdInfo, noIdInfo, setInlinePragInfo, InlinePragInfo(..) ) -import Maybes ( maybeToBool, assocMaybe ) -import Name ( getOccName, getSrcLoc, Name ) -import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes, - splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy, - splitRhoTy, mkForAllTy, splitForAllTys - ) -import TyVar ( TyVar, tyVarKind, mkTyVarSet, minusTyVarSet, emptyTyVarSet, - elementOfTyVarSet, unionTyVarSets, tyVarSetToList - ) -import Bag ( bagToList, foldrBag, ) -import Util ( isIn, hasNoDups, assoc ) -import Unique ( Unique ) -import BasicTypes ( TopLevelFlag(..), RecFlag(..) ) -import SrcLoc ( SrcLoc ) +import TcMType ( newTyFlexiVarTy, zonkQuantifiedTyVar, + tcInstSigType, zonkTcTypes, zonkTcTyVar ) +import TcType ( TcTyVar, SkolemInfo(SigSkol), + TcTauType, TcSigmaType, + mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType, + mkForAllTy, isUnLiftedType, tcGetTyVar, + mkTyVarTys, tidyOpenTyVar, tidyOpenType ) +import Kind ( argTypeKind ) +import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv, emptyTidyEnv ) +import TysPrim ( alphaTyVar ) +import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma ) +import Var ( idType, idName ) +import Name ( Name ) +import NameSet +import VarSet +import SrcLoc ( Located(..), unLoc, noLoc, getLoc ) +import Bag +import Util ( isIn ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec, + isNotTopLevel, isAlwaysActive ) +import FiniteMap ( listToFM, lookupFM ) import Outputable \end{code} @@ -97,112 +91,143 @@ At the top-level the LIE is sure to contain nothing but constant dictionaries, which we resolve at the module level. \begin{code} -tcTopBindsAndThen, tcBindsAndThen - :: (RecFlag -> TcMonoBinds s -> this -> that) -- Combinator - -> RenamedHsBinds - -> TcM s (this, LIE s) - -> TcM s (that, LIE s) - -tcTopBindsAndThen = tc_binds_and_then TopLevel -tcBindsAndThen = tc_binds_and_then NotTopLevel - -tc_binds_and_then top_lvl combiner binds do_next - = tcBinds top_lvl binds `thenTc` \ (mbinds1, binds_lie, env, ids) -> - tcSetEnv env $ - - -- Now do whatever happens next, in the augmented envt - do_next `thenTc` \ (thing, thing_lie) -> - - -- Create specialisations of functions bound here - -- Nota Bene: we glom the bindings all together in a single - -- recursive group ("recursive" passed to combiner, below) - -- so that we can do thsi bindInsts thing once for all the bindings - -- and the thing inside. This saves a quadratic-cost algorithm - -- when there's a long sequence of bindings. - bindInstsOfLocalFuns (binds_lie `plusLIE` thing_lie) ids `thenTc` \ (final_lie, mbinds2) -> - - -- All done - let - final_mbinds = mbinds1 `AndMonoBinds` mbinds2 - in - returnTc (combiner Recursive final_mbinds thing, final_lie) - -tcBinds :: TopLevelFlag - -> RenamedHsBinds - -> TcM s (TcMonoBinds s, LIE s, TcEnv s, [TcIdBndr s]) - -- The envt is the envt with binders in scope - -- The binders are those bound by this group of bindings - -tcBinds top_lvl EmptyBinds - = tcGetEnv `thenNF_Tc` \ env -> - returnTc (EmptyMonoBinds, emptyLIE, env, []) - - -- Short-cut for the rather common case of an empty bunch of bindings -tcBinds top_lvl (MonoBind EmptyMonoBinds sigs is_rec) - = tcGetEnv `thenNF_Tc` \ env -> - returnTc (EmptyMonoBinds, emptyLIE, env, []) - -tcBinds top_lvl (ThenBinds binds1 binds2) - = tcBinds top_lvl binds1 `thenTc` \ (mbinds1, lie1, env1, ids1) -> - tcSetEnv env1 $ - tcBinds top_lvl binds2 `thenTc` \ (mbinds2, lie2, env2, ids2) -> - returnTc (mbinds1 `AndMonoBinds` mbinds2, lie1 `plusLIE` lie2, env2, ids1++ids2) - -tcBinds top_lvl (MonoBind bind sigs is_rec) - = fixTc (\ ~(prag_info_fn, _) -> - -- This is the usual prag_info fix; the PragmaInfo field of an Id - -- is not inspected till ages later in the compiler, so there - -- should be no black-hole problems here. - - -- TYPECHECK THE SIGNATURES - mapTc tcTySig ty_sigs `thenTc` \ tc_ty_sigs -> - - tcBindWithSigs top_lvl binder_names bind - tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) -> - - -- Extend the environment to bind the new polymorphic Ids - tcExtendLocalValEnv binder_names poly_ids $ - - -- Build bindings and IdInfos corresponding to user pragmas - tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) -> - - -- Catch the environment and return - tcGetEnv `thenNF_Tc` \ env -> - returnTc (prag_info_fn, (poly_binds `AndMonoBinds` prag_binds, - poly_lie `plusLIE` prag_lie, - env, poly_ids) - ) ) `thenTc` \ (_, result) -> - returnTc result +tcTopBinds :: [HsBindGroup 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 +tcTopBinds binds + = tc_binds_and_then TopLevel glue binds $ + do { env <- getLclEnv + ; return (emptyLHsBinds, env) } where - binder_names = map fst (bagToList (collectMonoBinders bind)) - ty_sigs = [sig | sig@(Sig name _ _) <- sigs] -\end{code} - -An aside. The original version of @tcBindsAndThen@ which lacks a -combiner function, appears below. Though it is perfectly well -behaved, it cannot be typed by Haskell, because the recursive call is -at a different type to the definition itself. There aren't too many -examples of this, which is why I thought it worth preserving! [SLPJ] + -- The top level bindings are flattened into a giant + -- implicitly-mutually-recursive MonoBinds + glue (HsBindGroup binds1 _ _) (binds2, env) = (binds1 `unionBags` binds2, env) + glue (HsIPBinds _) _ = panic "Top-level HsIpBinds" + -- Can't have a HsIPBinds at top level + +tcHsBootSigs :: [HsBindGroup Name] -> TcM (LHsBinds TcId, TcLclEnv) +-- A hs-boot file has only one BindGroup, and it only has type +-- signatures in it. The renamer checked all this +tcHsBootSigs [HsBindGroup _ sigs _] + = do { ids <- mapM (addLocM tc_sig) (filter isVanillaLSig sigs) + ; tcExtendIdEnv ids $ do + { env <- getLclEnv + ; return (emptyLHsBinds, env) }} + where + tc_sig (Sig (L _ name) ty) + = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty + ; return (mkLocalId name sigma_ty) } -\begin{pseudocode} tcBindsAndThen - :: RenamedHsBinds - -> TcM s (thing, LIE s, thing_ty)) - -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty) + :: (HsBindGroup TcId -> thing -> thing) -- Combinator + -> [HsBindGroup Name] + -> TcM thing + -> TcM thing + +tcBindsAndThen = tc_binds_and_then NotTopLevel + +tc_binds_and_then top_lvl combiner [] do_next + = do_next +tc_binds_and_then top_lvl combiner (group : groups) do_next + = tc_bind_and_then top_lvl combiner group $ + tc_binds_and_then top_lvl combiner groups do_next + +tc_bind_and_then top_lvl combiner (HsIPBinds binds) do_next + = getLIE do_next `thenM` \ (result, expr_lie) -> + mapAndUnzipM (wrapLocSndM tc_ip_bind) binds `thenM` \ (avail_ips, binds') -> -tcBindsAndThen EmptyBinds do_next - = do_next `thenTc` \ (thing, lie, thing_ty) -> - returnTc ((EmptyBinds, thing), lie, thing_ty) + -- If the binding binds ?x = E, we must now + -- discharge any ?x constraints in expr_lie + tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds -> -tcBindsAndThen (ThenBinds binds1 binds2) do_next - = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) - `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> + returnM (combiner (HsIPBinds binds') $ + combiner (HsBindGroup dict_binds [] Recursive) result) + where + -- I wonder if we should do these one at at time + -- Consider ?x = 4 + -- ?y = ?x + 1 + tc_ip_bind (IPBind ip expr) + = newTyFlexiVarTy argTypeKind `thenM` \ ty -> + newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) -> + tcCheckRho expr ty `thenM` \ expr' -> + returnM (ip_inst, (IPBind ip' expr')) + +tc_bind_and_then top_lvl combiner (HsBindGroup binds sigs is_rec) do_next + | isEmptyLHsBinds binds + = do_next + | otherwise + = -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE + -- Notice that they scope over + -- a) the type signatures in the binding group + -- b) the bindings in the group + -- c) the scope of the binding group (the "in" part) + tcAddLetBoundTyVars binds $ + + case top_lvl of + TopLevel -- For the top level don't bother will 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 + -> tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) -> + tc_body poly_ids `thenM` \ (prag_binds, thing) -> + returnM (combiner (HsBindGroup + (poly_binds `unionBags` prag_binds) + [] -- no sigs + Recursive) + thing) + + NotTopLevel -- For nested bindings we must do the bindInstsOfLocalFuns thing. + | not (isRec is_rec) -- Non-recursive group + -> -- We want to keep non-recursive things non-recursive + -- so that we desugar unlifted bindings correctly + tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) -> + getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) -> + + -- Create specialisations of functions bound here + bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds -> + + returnM ( + combiner (HsBindGroup poly_binds [] NonRecursive) $ + combiner (HsBindGroup prag_binds [] NonRecursive) $ + combiner (HsBindGroup lie_binds [] Recursive) $ + -- NB: the binds returned by tcSimplify and + -- bindInstsOfLocalFuns aren't guaranteed in + -- dependency order (though we could change that); + -- hence the Recursive marker. + thing) + + | otherwise + -> -- NB: polymorphic recursion means that a function + -- may use an instance of itself, we must look at the LIE arising + -- from the function's own right hand side. Hence the getLIE + -- encloses the tcBindWithSigs. + + getLIE ( + tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) -> + tc_body poly_ids `thenM` \ (prag_binds, thing) -> + returnM (poly_ids, poly_binds `unionBags` prag_binds, thing) + ) `thenM` \ ((poly_ids, extra_binds, thing), lie) -> + + bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds -> + + returnM (combiner (HsBindGroup + (extra_binds `unionBags` lie_binds) + [] Recursive) thing + ) + where + tc_body poly_ids -- Type check the pragmas and "thing inside" + = -- Extend the environment to bind the new polymorphic Ids + tcExtendIdEnv poly_ids $ + + -- Build bindings and IdInfos corresponding to user pragmas + tcSpecSigs sigs `thenM` \ prag_binds -> - returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) + -- Now do whatever happens next, in the augmented envt + do_next `thenM` \ thing -> -tcBindsAndThen (MonoBind bind sigs is_rec) do_next - = tcBindAndThen bind sigs do_next -\end{pseudocode} + returnM (prag_binds, thing) +\end{code} %************************************************************************ @@ -222,178 +247,138 @@ so all the clever stuff is in here. as the Name in the tc_ty_sig \begin{code} -tcBindWithSigs - :: TopLevelFlag - -> [Name] - -> RenamedMonoBinds - -> [TcSigInfo s] - -> RecFlag - -> (Name -> IdInfo) - -> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s]) - -tcBindWithSigs top_lvl binder_names mbind tc_ty_sigs is_rec prag_info_fn - = recoverTc ( - -- If typechecking the binds fails, then return with each - -- signature-less binder given type (forall a.a), to minimise subsequent - -- error messages - newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv -> - let - forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) - poly_ids = map mk_dummy binder_names - mk_dummy name = case maybeSig tc_ty_sigs name of - Just (TySigInfo _ poly_id _ _ _ _) -> poly_id -- Signature - Nothing -> mkUserId name forall_a_a -- No signature - in - returnTc (EmptyMonoBinds, emptyLIE, poly_ids) - ) $ - - -- Create a new identifier for each binder, with each being given - -- a fresh unique, and a type-variable type. - -- For "mono_lies" see comments about polymorphic recursion at the - -- end of the function. - mapAndUnzipNF_Tc mk_mono_id binder_names `thenNF_Tc` \ (mono_lies, mono_ids) -> - let - mono_lie = plusLIEs mono_lies - mono_id_tys = map idType mono_ids - in - - -- TYPECHECK THE BINDINGS - tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) -> - - -- CHECK THAT THE SIGNATURES MATCH - -- (must do this before getTyVarsToGen) - checkSigMatch tc_ty_sigs `thenTc` \ sig_theta -> - - -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen - -- The tyvars_not_to_gen are free in the environment, and hence - -- candidates for generalisation, but sometimes the monomorphism - -- restriction means we can't generalise them nevertheless - getTyVarsToGen is_unrestricted mono_id_tys lie `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen) -> - - -- DEAL WITH TYPE VARIABLE KINDS - -- **** This step can do unification => keep other zonking after this **** - mapTc defaultUncommittedTyVar (tyVarSetToList tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list -> - let - real_tyvars_to_gen = mkTyVarSet real_tyvars_to_gen_list - -- It's important that the final list - -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully - -- zonked, *including boxity*, because they'll be included in the forall types of - -- the polymorphic Ids, and instances of these Ids will be generated from them. - -- - -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass - -- real_tyvars_to_gen - in - - -- SIMPLIFY THE LIE - tcExtendGlobalTyVars (tyVarSetToList tyvars_not_to_gen) ( - if null tc_ty_sigs then - -- No signatures, so just simplify the lie - -- NB: no signatures => no polymorphic recursion, so no - -- need to use mono_lies (which will be empty anyway) - tcSimplify (text "tcBinds1" <+> ppr binder_names) - top_lvl real_tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) -> - returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound)) - - else - zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' -> - newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) -> - -- It's important that sig_theta is zonked, because - -- dict_id is later used to form the type of the polymorphic thing, - -- and forall-types must be zonked so far as their bound variables - -- are concerned - - let - -- The "givens" is the stuff available. We get that from - -- the context of the type signature, BUT ALSO the mono_lie - -- so that polymorphic recursion works right (see comments at end of fn) - givens = dicts_sig `plusLIE` mono_lie - in - - -- Check that the needed dicts can be expressed in - -- terms of the signature ones - tcAddErrCtxt (bindSigsCtxt tysig_names) $ - tcSimplifyAndCheck - (ptext SLIT("type signature for") <+> - hsep (punctuate comma (map (quotes . ppr) binder_names))) - real_tyvars_to_gen givens lie `thenTc` \ (lie_free, dict_binds) -> - - returnTc (lie_free, dict_binds, dict_ids) - - ) `thenTc` \ (lie_free, dict_binds, dicts_bound) -> - - ASSERT( not (any (isUnboxedTypeKind . tyVarKind) real_tyvars_to_gen_list) ) - -- The instCantBeGeneralised stuff in tcSimplify should have - -- already raised an error if we're trying to generalise an unboxed tyvar - -- (NB: unboxed tyvars are always introduced along with a class constraint) - -- and it's better done there because we have more precise origin information. - -- That's why we just use an ASSERT here. - - -- BUILD THE POLYMORPHIC RESULT IDs - zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types -> - let - exports = zipWith3 mk_export binder_names mono_ids zonked_mono_id_types - dict_tys = map tcIdType dicts_bound - - mk_export binder_name mono_id zonked_mono_id_ty - = (tyvars, TcId (replaceIdInfo poly_id (prag_info_fn binder_name)), TcId mono_id) +tcBindWithSigs :: TopLevelFlag + -> LHsBinds Name + -> [LSig Name] + -> RecFlag + -> TcM (LHsBinds TcId, [TcId]) + -- The returned TcIds are guaranteed zonked + +tcBindWithSigs top_lvl mbind sigs is_rec = do + { -- TYPECHECK THE SIGNATURES + tc_ty_sigs <- recoverM (returnM []) $ + tcTySigs (filter isVanillaLSig sigs) + ; let lookup_sig = lookupSig tc_ty_sigs + + -- SET UP THE MAIN RECOVERY; take advantage of any type sigs + ; recoverM (recoveryCode mbind lookup_sig) $ do + + { traceTc (ptext SLIT("--------------------------------------------------------")) + ; traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind)) + + -- TYPECHECK THE BINDINGS + ; ((mbind', mono_bind_infos), lie_req) + <- getLIE (tcMonoBinds mbind lookup_sig is_rec) + + -- 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) + ; if any isUnLiftedType zonked_mono_tys then + do { -- Unlifted bindings + checkUnliftedBinds top_lvl is_rec mbind + ; 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) + + ; return ( unitBag $ noLoc $ AbsBinds [] [] exports emptyNameSet mbind', + [poly_id | (_, poly_id, _) <- exports]) } -- Guaranteed zonked + + else do -- The normal lifted case: GENERALISE + { is_unres <- isUnRestrictedGroup mbind tc_ty_sigs + ; (tyvars_to_gen, dict_binds, dict_ids) + <- setSrcSpan (getLoc (head (bagToList mbind))) $ + -- TODO: location a bit awkward, but the mbinds have been + -- dependency analysed and may no longer be adjacent + addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $ + generalise top_lvl is_unres mono_bind_infos tc_ty_sigs 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 + ; let + exports = map mk_export mono_bind_infos + poly_ids = [poly_id | (_, poly_id, _) <- exports] + dict_tys = map idType dict_ids + + inlines = mkNameSet [ name + | L _ (InlineSig True (L _ name) _) <- sigs] + -- Any INLINE sig (regardless of phase control) + -- makes the RHS look small + inline_phases = listToFM [ (name, phase) + | L _ (InlineSig _ (L _ name) phase) <- sigs, + not (isAlwaysActive phase)] + -- Set the IdInfo field to control the inline phase + -- AlwaysActive is the default, so don't bother with them + add_inlines id = attachInlinePhase inline_phases id + + mk_export (binder_name, mb_sig, mono_id) + = case mb_sig of + Just sig -> (sig_tvs sig, add_inlines (sig_id sig), mono_id) + Nothing -> (tyvars_to_gen', add_inlines new_poly_id, mono_id) where - (tyvars, poly_id) = case maybeSig tc_ty_sigs binder_name of - Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _) -> (sig_tyvars, sig_poly_id) - Nothing -> (real_tyvars_to_gen_list, new_poly_id) - - new_poly_id = mkUserId binder_name poly_ty - poly_ty = mkForAllTys real_tyvars_to_gen_list $ mkFunTys dict_tys $ zonked_mono_id_ty - -- It's important to build a fully-zonked poly_ty, because - -- we'll slurp out its free type variables when extending the - -- local environment (tcExtendLocalValEnv); if it's not zonked - -- it appears to have free tyvars that aren't actually free at all. - in - - -- BUILD RESULTS - returnTc ( - AbsBinds real_tyvars_to_gen_list - dicts_bound - exports - (dict_binds `AndMonoBinds` mbind'), - lie_free, - [poly_id | (_, TcId poly_id, _) <- exports] - ) + new_poly_id = mkLocalId binder_name poly_ty + poly_ty = mkForAllTys tyvars_to_gen' + $ mkFunTys dict_tys + $ idType mono_id + + -- ZONK THE poly_ids, because they are used to extend the type + -- environment; see the invariant on TcEnv.tcExtendIdEnv + ; zonked_poly_ids <- mappM zonkId poly_ids + + ; traceTc (text "binding:" <+> ppr ((dict_ids, dict_binds), + exports, map idType zonked_poly_ids)) + + ; return ( + unitBag $ noLoc $ + AbsBinds tyvars_to_gen' + dict_ids + exports + inlines + (dict_binds `unionBags` mbind'), + zonked_poly_ids + ) + } } } + +-- If typechecking the binds fails, then return with each +-- signature-less binder given type (forall a.a), to minimise +-- subsequent error messages +recoveryCode mbind lookup_sig + = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) + ; return (emptyLHsBinds, poly_ids) } where - no_of_binders = length binder_names - - mk_mono_id binder_name - | theres_a_signature -- There's a signature; and it's overloaded, - && not (null sig_theta) -- so make a Method - = tcAddSrcLoc sig_loc $ - newMethodWithGivenTy SignatureOrigin - (TcId poly_id) (mkTyVarTys sig_tyvars) - sig_theta sig_tau `thenNF_Tc` \ (mono_lie, TcId mono_id) -> - -- A bit turgid to have to strip the TcId - returnNF_Tc (mono_lie, mono_id) - - | otherwise -- No signature or not overloaded; - = tcAddSrcLoc (getSrcLoc binder_name) $ - (if theres_a_signature then - returnNF_Tc sig_tau -- Non-overloaded signature; use its type - else - newTyVarTy kind -- No signature; use a new type variable - ) `thenNF_Tc` \ mono_id_ty -> - - newLocalId (getOccName binder_name) mono_id_ty `thenNF_Tc` \ mono_id -> - returnNF_Tc (emptyLIE, mono_id) - where - maybe_sig = maybeSig tc_ty_sigs binder_name - theres_a_signature = maybeToBool maybe_sig - Just (TySigInfo name poly_id sig_tyvars sig_theta sig_tau sig_loc) = maybe_sig - - tysig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs] - is_unrestricted = isUnRestrictedGroup tysig_names mbind - - kind = case is_rec of - Recursive -> mkBoxedTypeKind -- Recursive, so no unboxed types - NonRecursive -> mkTypeKind -- Non-recursive, so we permit unboxed types + forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar) + binder_names = collectHsBindBinders mbind + poly_ids = map mk_dummy binder_names + mk_dummy name = case lookup_sig name of + Just sig -> sig_id sig -- Signature + Nothing -> mkLocalId name forall_a_a -- No signature + +attachInlinePhase inline_phases bndr + = case lookupFM inline_phases (idName bndr) of + Just prag -> bndr `setInlinePragma` prag + Nothing -> bndr + +-- 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)) + +checkUnliftedBinds top_lvl is_rec mbind + = checkTc (isNotTopLevel top_lvl) + (unliftedBindErr "Top-level" mbind) `thenM_` + checkTc (isNonRec is_rec) + (unliftedBindErr "Recursive" mbind) `thenM_` + checkTc (isSingletonBag mbind) + (unliftedBindErr "Multiple" mbind) \end{code} + Polymorphic recursion ~~~~~~~~~~~~~~~~~~~~~ The game plan for polymorphic recursion in the code above is @@ -416,32 +401,331 @@ If we don't take care, after typechecking we get Notice the the stupid construction of (f a d), which is of course identical to the function we're executing. In this case, the -polymorphic recursion ins't being used (but that's a very common case). +polymorphic recursion isn't being used (but that's a very common case). +We'd prefer + + f = /\a -> \d::Eq a -> letrec + fm = \ys:[a] -> ...fm... + in + fm -This can lead to a massive space leak, from the following top-level defn: +This can lead to a massive space leak, from the following top-level defn +(post-typechecking) ff :: [Int] -> [Int] - ff = f dEqInt + 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 + + = let f' = f Int dEqInt in \ys. ...f'... + + = let f' = let f' = f Int dEqInt in \ys. ...f'... + in \ys. ...f'... + +Etc. Solution: when typechecking the RHSs we always have in hand the *monomorphic* Ids for each binding. So we just need to make sure that if (Method f a d) shows up in the constraints emerging from (...f...) we just use the monomorphic Id. We achieve this by adding monomorphic Ids -to the "givens" when simplifying constraints. Thats' what the "mono_lies" +to the "givens" when simplifying constraints. That's what the "lies_avail" is doing. %************************************************************************ %* * +\subsection{tcMonoBind} +%* * +%************************************************************************ + +@tcMonoBinds@ deals with a single @MonoBind@. +The signatures have been dealt with already. + +\begin{code} +tcMonoBinds :: LHsBinds Name + -> TcSigFun -> RecFlag + -> TcM (LHsBinds TcId, [MonoBindInfo]) + +tcMonoBinds binds lookup_sig is_rec + = do { tc_binds <- mapBagM (wrapLocM (tcLhs lookup_sig)) binds + + -- Bring (a) the scoped type variables, and (b) the Ids, into scope for the RHSs + -- For (a) it's ok to bring them all into scope at once, even + -- though each type sig should scope only over its own RHS, + -- because the renamer has sorted all that out. + ; let mono_info = getMonoBindInfo tc_binds + rhs_tvs = [ (name, mkTyVarTy tv) + | (_, Just sig, _) <- mono_info, + (name, tv) <- sig_scoped sig `zip` sig_tvs sig ] + rhs_id_env = map mk mono_info -- A binding for each term variable + + ; binds' <- tcExtendTyVarEnv2 rhs_tvs $ + tcExtendIdEnv2 rhs_id_env $ + traceTc (text "tcMonoBinds" <+> vcat [ppr n <+> ppr id <+> ppr (idType id) | (n,id) <- rhs_id_env]) `thenM_` + mapBagM (wrapLocM tcRhs) tc_binds + ; return (binds', mono_info) } + where + mk (name, Just sig, _) = (name, sig_id sig) -- Use the type sig if there is one + mk (name, Nothing, mono_id) = (name, mono_id) -- otherwise use a monomorphic version + +------------------------ +-- 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 +-- 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 +-- 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 + = 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 + +bndrNames :: [MonoBindInfo] -> [Name] +bndrNames mbi = [n | (n,_,_) <- mbi] + +getMonoType :: MonoBindInfo -> TcTauType +getMonoType (_,_,mono_id) = idType mono_id + +tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind +tcLhs lookup_sig (FunBind (L nm_loc name) inf matches) + = do { let mb_sig = lookup_sig 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 = newTyFlexiVarTy argTypeKind + +tcLhs lookup_sig bind@(PatBind pat grhss _) + = do { let tc_pat exp_ty = tcPat (LetPat lookup_sig) pat exp_ty lookup_infos + ; ((pat', ex_tvs, infos), pat_ty) + <- addErrCtxt (patMonoBindsCtxt pat grhss) + (tcInfer tc_pat) + + -- Don't know how to deal with pattern-bound existentials yet + ; checkTc (null ex_tvs) (existentialExplode bind) + + ; return (TcPatBind infos pat' grhss pat_ty) } + where + names = collectPatBinders pat + + -- After typechecking the pattern, look up the binder + -- names, which the pattern has brought into scope. + lookup_infos :: TcM [MonoBindInfo] + lookup_infos = do { mono_ids <- tcLookupLocalIds names + ; return [ (name, lookup_sig name, mono_id) + | (name, mono_id) <- names `zip` mono_ids] } + +------------------- +tcRhs :: TcMonoBind -> TcM (HsBind TcId) +tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches) + = do { matches' <- tcMatchesFun (idName mono_id) matches + (Check (idType mono_id)) + ; return (FunBind fun' inf matches') } + +tcRhs bind@(TcPatBind _ pat' grhss pat_ty) + = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $ + tcGRHSsPat grhss (Check pat_ty) + ; return (PatBind pat' grhss' pat_ty) } + + +--------------------- +getMonoBindInfo :: Bag (Located TcMonoBind) -> [MonoBindInfo] +getMonoBindInfo tc_binds + = foldrBag (get_info . unLoc) [] tc_binds + where + get_info (TcFunBind info _ _ _) rest = info : rest + get_info (TcPatBind infos _ _ _) rest = infos ++ rest +\end{code} + + +%************************************************************************ +%* * \subsection{getTyVarsToGen} %* * %************************************************************************ -@getTyVarsToGen@ decides what type variables generalise over. +Type signatures are tricky. See Note [Signature skolems] in TcType + +\begin{code} +tcTySigs :: [LSig Name] -> TcM [TcSigInfo] +-- The trick here is that all the signatures should have the same +-- context, and we want to share type variables for that context, so that +-- all the right hand sides agree a common vocabulary for their type +-- constraints +tcTySigs [] = return [] + +tcTySigs sigs + = do { (tc_sig1 : tc_sigs) <- mappM tcTySig sigs + ; mapM (check_ctxt tc_sig1) tc_sigs + ; return (tc_sig1 : tc_sigs) } + where + -- Check tha all the signature contexts are the same + -- The type signatures on a mutually-recursive group of definitions + -- must all have the same context (or none). + -- + -- We unify them because, with polymorphic recursion, their types + -- might not otherwise be related. This is a rather subtle issue. + check_ctxt :: TcSigInfo -> TcSigInfo -> TcM () + check_ctxt sig1@(TcSigInfo { sig_theta = theta1 }) sig@(TcSigInfo { sig_theta = theta }) + = setSrcSpan (instLocSrcSpan (sig_loc sig)) $ + addErrCtxt (sigContextsCtxt sig1 sig) $ + unifyTheta theta1 theta + + +tcTySig :: LSig Name -> TcM TcSigInfo +tcTySig (L span (Sig (L _ name) ty)) + = setSrcSpan span $ + do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty + ; (tvs, theta, tau) <- tcInstSigType name sigma_ty + ; loc <- getInstLoc (SigOrigin (SigSkol name)) + + ; let poly_id = mkLocalId name sigma_ty + + -- 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.) + scoped_names = case ty of + L _ (HsForAllTy _ tvs _ _) -> hsLTyVarNames tvs + other -> [] + + ; return (TcSigInfo { sig_id = poly_id, sig_scoped = scoped_names, + sig_tvs = tvs, sig_theta = theta, sig_tau = tau, + sig_loc = loc }) } +\end{code} + +\begin{code} +generalise :: TopLevelFlag -> Bool -> [MonoBindInfo] -> [TcSigInfo] -> [Inst] + -> TcM ([TcTyVar], TcDictBinds, [TcId]) +generalise top_lvl is_unrestricted mono_infos sigs lie_req + | not is_unrestricted -- RESTRICTED CASE + = -- Check signature contexts are empty + do { checkTc (all is_mono_sig sigs) + (restrictedBindCtxtErr bndr_names) + + -- Now simplify with exactly that set of tyvars + -- We have to squash those Methods + ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndr_names + tau_tvs lie_req + + -- Check that signature type variables are OK + ; final_qtvs <- checkSigsTyVars qtvs sigs + + ; return (final_qtvs, binds, []) } + + | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS + = tcSimplifyInfer doc tau_tvs lie_req + + | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS + = do { let sig1 = head sigs + ; sig_lie <- newDictsAtLoc (sig_loc sig1) (sig_theta sig1) + ; 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 comments at end of fn) + local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos] + sig_avails = sig_lie ++ local_meths + + -- 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 + + -- Check that signature type variables are OK + ; final_qtvs <- checkSigsTyVars forall_tvs sigs + + ; returnM (final_qtvs, dict_binds, map instToId sig_lie) } + + where + bndr_names = bndrNames mono_infos + tau_tvs = foldr (unionVarSet . tyVarsOfType . getMonoType) emptyVarSet mono_infos + is_mono_sig sig = null (sig_theta sig) + doc = ptext SLIT("type signature(s) for") <+> pprBinders bndr_names + + mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs, + sig_theta = theta, sig_tau = tau, sig_loc = loc }) mono_id + = Method mono_id poly_id (mkTyVarTys tvs) theta tau loc + +checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar] +checkSigsTyVars qtvs sigs + = do { gbl_tvs <- tcGetGlobalTyVars + ; sig_tvs_s <- mappM (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) + ; returnM 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') + ; 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 +-- 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) + +checkDistinctTyVars sig_tvs + = do { zonked_tvs <- mapM zonk_one sig_tvs + ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs) + ; return zonked_tvs } + where + zonk_one sig_tv = do { ty <- zonkTcTyVar sig_tv + ; return (tcGetTyVar "checkDistinctTyVars" ty) } + -- 'ty' is bound to be a type variable, because SigSkolTvs + -- can only be unified with type variables + + 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 + check_dup acc (sig_tv, zonked_tv) + = case lookupVarEnv acc zonked_tv of + Just sig_tv' -> bomb_out sig_tv sig_tv' + + Nothing -> return (extendVarEnv acc zonked_tv sig_tv) + + bomb_out sig_tv1 sig_tv2 + = failWithTc (ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1) + <+> ptext SLIT("is unified with another quantified type variable") + <+> ppr tidy_tv2) + where + (env1, tidy_tv1) = tidyOpenTyVar emptyTidyEnv sig_tv1 + (_env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2 +\end{code} + + +@getTyVarsToGen@ decides what type variables to generalise over. For a "restricted group" -- see the monomorphism restriction for a definition -- we bind no dictionaries, and @@ -469,6 +753,8 @@ generalise. We must be careful about doing this: 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] (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 @@ -479,301 +765,25 @@ constrained tyvars. We don't use any of the results, except to find which tyvars are constrained. \begin{code} -getTyVarsToGen is_unrestricted mono_id_tys lie - = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars -> - zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys -> - let - tyvars_to_gen = tyVarsOfTypes zonked_mono_id_tys `minusTyVarSet` free_tyvars - in - if is_unrestricted - then - returnTc (emptyTyVarSet, tyvars_to_gen) - else - tcSimplify (text "getTVG") NotTopLevel tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) -> - let - -- ASSERT: dicts_sig is already zonked! - constrained_tyvars = foldrBag (unionTyVarSets . tyVarsOfInst) emptyTyVarSet constrained_dicts - reduced_tyvars_to_gen = tyvars_to_gen `minusTyVarSet` constrained_tyvars - in - returnTc (constrained_tyvars, reduced_tyvars_to_gen) -\end{code} - - -\begin{code} -isUnRestrictedGroup :: [Name] -- Signatures given for these - -> RenamedMonoBinds - -> Bool +isUnRestrictedGroup :: LHsBinds Name -> [TcSigInfo] -> TcM Bool +isUnRestrictedGroup binds sigs + = do { mono_restriction <- doptM Opt_MonomorphismRestriction + ; return (not mono_restriction || all_unrestricted) } + where + all_unrestricted = all (unrestricted . unLoc) (bagToList binds) + tysig_names = map (idName . sig_id) sigs + + unrestricted (PatBind other _ _) = False + unrestricted (VarBind v _) = v `is_elem` tysig_names + unrestricted (FunBind v _ matches) = unrestricted_match matches + || unLoc v `is_elem` tysig_names + + unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False + -- No args => like a pattern binding + unrestricted_match other = True + -- Some args => a function binding is_elem v vs = isIn "isUnResMono" v vs - -isUnRestrictedGroup sigs (PatMonoBind (VarPatIn v) _ _) = v `is_elem` sigs -isUnRestrictedGroup sigs (PatMonoBind other _ _) = False -isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs -isUnRestrictedGroup sigs (FunMonoBind _ _ _ _) = True -isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 && - isUnRestrictedGroup sigs mb2 -isUnRestrictedGroup sigs EmptyMonoBinds = True -\end{code} - -@defaultUncommittedTyVar@ checks for generalisation over unboxed -types, and defaults any TypeKind TyVars to BoxedTypeKind. - -\begin{code} -defaultUncommittedTyVar tyvar - | isTypeKind (tyVarKind tyvar) - = newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ boxed_tyvar -> - unifyTauTy (mkTyVarTy boxed_tyvar) (mkTyVarTy tyvar) `thenTc_` - returnTc boxed_tyvar - - | otherwise - = returnTc tyvar -\end{code} - - -%************************************************************************ -%* * -\subsection{tcMonoBind} -%* * -%************************************************************************ - -@tcMonoBinds@ deals with a single @MonoBind@. -The signatures have been dealt with already. - -\begin{code} -tcMonoBinds :: RenamedMonoBinds - -> [Name] -> [TcIdBndr s] - -> [TcSigInfo s] - -> TcM s (TcMonoBinds s, LIE s) - -tcMonoBinds mbind binder_names mono_ids tc_ty_sigs - = tcExtendLocalValEnv binder_names mono_ids ( - tc_mono_binds mbind - ) - where - sig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs] - sig_ids = [id | (TySigInfo _ id _ _ _ _) <- tc_ty_sigs] - - tc_mono_binds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE) - - tc_mono_binds (AndMonoBinds mb1 mb2) - = tc_mono_binds mb1 `thenTc` \ (mb1a, lie1) -> - tc_mono_binds mb2 `thenTc` \ (mb2a, lie2) -> - returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2) - - tc_mono_binds (FunMonoBind name inf matches locn) - = tcAddSrcLoc locn $ - tcLookupLocalValueOK "tc_mono_binds" name `thenNF_Tc` \ id -> - - -- Before checking the RHS, extend the envt with - -- bindings for the *polymorphic* Ids from any type signatures - tcExtendLocalValEnv sig_names sig_ids $ - tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) -> - - returnTc (FunMonoBind (TcId id) inf matches' locn, lie) - - tc_mono_binds bind@(PatMonoBind pat grhss_and_binds locn) - = tcAddSrcLoc locn $ - tcAddErrCtxt (patMonoBindsCtxt bind) $ - tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) -> - - -- Before checking the RHS, but after the pattern, extend the envt with - -- bindings for the *polymorphic* Ids from any type signatures - tcExtendLocalValEnv sig_names sig_ids $ - tcGRHSsAndBinds pat_ty grhss_and_binds `thenTc` \ (grhss_and_binds2, lie) -> - returnTc (PatMonoBind pat2 grhss_and_binds2 locn, - plusLIE lie_pat lie) -\end{code} - -%************************************************************************ -%* * -\subsection{Signatures} -%* * -%************************************************************************ - -@tcSigs@ checks the signatures for validity, and returns a list of -{\em freshly-instantiated} signatures. That is, the types are already -split up, and have fresh type variables installed. All non-type-signature -"RenamedSigs" are ignored. - -The @TcSigInfo@ contains @TcTypes@ because they are unified with -the variable's type, and after that checked to see whether they've -been instantiated. - -\begin{code} -data TcSigInfo s - = TySigInfo - Name -- N, the Name in corresponding binding - (TcIdBndr s) -- *Polymorphic* binder for this value... - -- Usually has name = N, but doesn't have to. - [TcTyVar s] - (TcThetaType s) - (TcTauType s) - SrcLoc - - -maybeSig :: [TcSigInfo s] -> Name -> Maybe (TcSigInfo s) - -- Search for a particular signature -maybeSig [] name = Nothing -maybeSig (sig@(TySigInfo sig_name _ _ _ _ _) : sigs) name - | name == sig_name = Just sig - | otherwise = maybeSig sigs name -\end{code} - - -\begin{code} -tcTySig :: RenamedSig - -> TcM s (TcSigInfo s) - -tcTySig (Sig v ty src_loc) - = tcAddSrcLoc src_loc $ - tcHsType ty `thenTc` \ sigma_ty -> - - -- Convert from Type to TcType - tcInstSigType sigma_ty `thenNF_Tc` \ sigma_tc_ty -> - let - poly_id = mkUserId v sigma_tc_ty - in - -- Instantiate this type - -- It's important to do this even though in the error-free case - -- we could just split the sigma_tc_ty (since the tyvars don't - -- unified with anything). But in the case of an error, when - -- the tyvars *do* get unified with something, we want to carry on - -- typechecking the rest of the program with the function bound - -- to a pristine type, namely sigma_tc_ty - tcInstSigTcType sigma_tc_ty `thenNF_Tc` \ (tyvars, rho) -> - let - (theta, tau) = splitRhoTy rho - -- This splitSigmaTy tries hard to make sure that tau' is a type synonym - -- wherever possible, which can improve interface files. - in - returnTc (TySigInfo v poly_id tyvars theta tau src_loc) -\end{code} - -@checkSigMatch@ does the next step in checking signature matching. -The tau-type part has already been unified. What we do here is to -check that this unification has not over-constrained the (polymorphic) -type variables of the original signature type. - -The error message here is somewhat unsatisfactory, but it'll do for -now (ToDo). - -\begin{code} -checkSigMatch [] - = returnTc (error "checkSigMatch") - -checkSigMatch tc_ty_sigs@( sig1@(TySigInfo _ id1 _ theta1 _ _) : all_sigs_but_first ) - = -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK - -- Doesn't affect substitution - mapTc check_one_sig tc_ty_sigs `thenTc_` - - -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE - -- The type signatures on a mutually-recursive group of definitions - -- must all have the same context (or none). - -- - -- We unify them because, with polymorphic recursion, their types - -- might not otherwise be related. This is a rather subtle issue. - -- ToDo: amplify - mapTc check_one_cxt all_sigs_but_first `thenTc_` - - returnTc theta1 - where - sig1_dict_tys = mk_dict_tys theta1 - n_sig1_dict_tys = length sig1_dict_tys - - check_one_cxt sig@(TySigInfo _ id _ theta _ src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (sigContextsCtxt id1 id) $ - checkTc (length this_sig_dict_tys == n_sig1_dict_tys) - sigContextsErr `thenTc_` - unifyTauTyLists sig1_dict_tys this_sig_dict_tys - where - this_sig_dict_tys = mk_dict_tys theta - - check_one_sig (TySigInfo name id sig_tyvars _ sig_tau src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (sigCtxt id) $ - checkSigTyVars sig_tyvars sig_tau - - mk_dict_tys theta = [mkDictTy c ts | (c,ts) <- theta] -\end{code} - - -@checkSigTyVars@ is used after the type in a type signature has been unified with -the actual type found. It then checks that the type variables of the type signature -are - (a) still all type variables - eg matching signature [a] against inferred type [(p,q)] - [then a will be unified to a non-type variable] - - (b) still all distinct - eg matching signature [(a,b)] against inferred type [(p,p)] - [then a and b will be unified together] - - (c) not mentioned in the environment - eg the signature for f in this: - - g x = ... where - f :: a->[a] - f y = [x,y] - - Here, f is forced to be monorphic by the free occurence of x. - -Before doing this, the substitution is applied to the signature type variable. - -We used to have the notion of a "DontBind" type variable, which would -only be bound to itself or nothing. Then points (a) and (b) were -self-checking. But it gave rise to bogus consequential error messages. -For example: - - f = (*) -- Monomorphic - - g :: Num a => a -> a - g x = f x x - -Here, we get a complaint when checking the type signature for g, -that g isn't polymorphic enough; but then we get another one when -dealing with the (Num x) context arising from f's definition; -we try to unify x with Int (to default it), but find that x has already -been unified with the DontBind variable "a" from g's signature. -This is really a problem with side-effecting unification; we'd like to -undo g's effects when its type signature fails, but unification is done -by side effect, so we can't (easily). - -So we revert to ordinary type variables for signatures, and try to -give a helpful message in checkSigTyVars. - -\begin{code} -checkSigTyVars :: [TcTyVar s] -- The original signature type variables - -> TcType s -- signature type (for err msg) - -> TcM s [TcTyVar s] -- Zonked signature type variables - -checkSigTyVars sig_tyvars sig_tau - = mapNF_Tc zonkTcTyVar sig_tyvars `thenNF_Tc` \ sig_tys -> - let - sig_tyvars' = map (getTyVar "checkSigTyVars") sig_tys - in - - -- Check points (a) and (b) - checkTcM (all isTyVarTy sig_tys && hasNoDups sig_tyvars') - (zonkTcType sig_tau `thenNF_Tc` \ sig_tau' -> - failWithTc (badMatchErr sig_tau sig_tau') - ) `thenTc_` - - -- Check point (c) - -- We want to report errors in terms of the original signature tyvars, - -- ie sig_tyvars, NOT sig_tyvars'. sig_tyvars' correspond - -- 1-1 with sig_tyvars, so we can just map back. - tcGetGlobalTyVars `thenNF_Tc` \ globals -> - let - mono_tyvars' = [sig_tv' | sig_tv' <- sig_tyvars', - sig_tv' `elementOfTyVarSet` globals] - - mono_tyvars = map (assoc "checkSigTyVars" (sig_tyvars' `zip` sig_tyvars)) mono_tyvars' - in - checkTcM (null mono_tyvars') - (failWithTc (notAsPolyAsSigErr sig_tau mono_tyvars)) `thenTc_` - - returnTc sig_tyvars' \end{code} @@ -783,28 +793,13 @@ checkSigTyVars sig_tyvars sig_tau %* * %************************************************************************ - -@tcPragmaSigs@ munches up the "signatures" that arise through *user* +@tcSpecSigs@ munches up the specialisation "signatures" that arise through *user* pragmas. It is convenient for them to appear in the @[RenamedSig]@ part of a binding because then the same machinery can be used for moving them into place as is done for type signatures. -\begin{code} -tcPragmaSigs :: [RenamedSig] -- The pragma signatures - -> TcM s (Name -> IdInfo, -- Maps name to the appropriate IdInfo - TcMonoBinds s, - LIE s) - -tcPragmaSigs sigs - = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (maybe_info_modifiers, binds, lies) -> - let - prag_fn name = foldr ($) noIdInfo [f | Just (n,f) <- maybe_info_modifiers, n==name] - in - returnTc (prag_fn, andMonoBinds binds, plusLIEs lies) -\end{code} +They look like this: -The interesting case is for SPECIALISE pragmas. There are two forms. -Here's the first form: \begin{verbatim} f :: Ord a => [a] -> b -> b {-# SPECIALIZE f :: [Int] -> b -> b #-} @@ -827,88 +822,45 @@ specialiser will subsequently discover that there's a call of @f@ at Int, and will create a specialisation for @f@. After that, the binding for @f*@ can be discarded. -The second form is this: -\begin{verbatim} - f :: Ord a => [a] -> b -> b - {-# SPECIALIZE f :: [Int] -> b -> b = g #-} -\end{verbatim} - -Here @g@ is specified as a function that implements the specialised -version of @f@. Suppose that g has type (a->b->b); that is, g's type -is more general than that required. For this we generate -\begin{verbatim} - f@Int = /\b -> g Int b - f* = f@Int -\end{verbatim} - -Here @f@@Int@ is a SpecId, the specialised version of @f@. It inherits -f's export status etc. @f*@ is a SpecPragmaId, as before, which just serves -to prevent @f@@Int@ from being discarded prematurely. After specialisation, -if @f@@Int@ is going to be used at all it will be used explicitly, so the simplifier can -discard the f* binding. - -Actually, there is really only point in giving a SPECIALISE pragma on exported things, -and the simplifer won't discard SpecIds for exporte things anyway, so maybe this is -a bit of overkill. +We used to have a form + {-# SPECIALISE f :: = g #-} +which promised that g implemented f at , but we do that with +a RULE now: + {-# RULES (f::) = g #-} \begin{code} -tcPragmaSig :: RenamedSig -> TcM s (Maybe (Name, IdInfo -> IdInfo), TcMonoBinds s, LIE s) -tcPragmaSig (Sig _ _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE) -tcPragmaSig (SpecInstSig _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE) - -tcPragmaSig (InlineSig name loc) - = returnTc (Just (name, setInlinePragInfo IWantToBeINLINEd), EmptyMonoBinds, emptyLIE) - -tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc) +tcSpecSigs :: [LSig Name] -> TcM (LHsBinds TcId) +tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs) = -- SPECIALISE f :: forall b. theta => tau = g - tcAddSrcLoc src_loc $ - tcAddErrCtxt (valSpecSigCtxt name poly_ty) $ + setSrcSpan loc $ + addErrCtxt (valSpecSigCtxt name poly_ty) $ -- Get and instantiate its alleged specialised type - tcHsType poly_ty `thenTc` \ sig_sigma -> - tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty -> + tcHsSigType (FunSigCtxt name) poly_ty `thenM` \ sig_ty -> -- Check that f has a more general type, and build a RHS for -- the spec-pragma-id at the same time - tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) -> - - case maybe_spec_name of - Nothing -> -- Just specialise "f" by building a SpecPragmaId binding - -- It is the thing that makes sure we don't prematurely - -- dead-code-eliminate the binding we are really interested in. - newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_id -> - returnTc (Nothing, VarMonoBind (TcId spec_id) spec_expr, spec_lie) - - Just g_name -> -- Don't create a SpecPragmaId. Instead add some suitable IdIfo - - panic "Can't handle SPECIALISE with a '= g' part" - - {- Not yet. Because we're still in the TcType world we - can't really add to the SpecEnv of the Id. Instead we have to - record the information in a different sort of Sig, and add it to - the IdInfo after zonking. - - For now we just leave out this case - - -- Get the type of f, and find out what types - -- f has to be instantiated at to give the signature type - tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ f_id -> - tcInstSigTcType (idType f_id) `thenNF_Tc` \ (f_tyvars, f_rho) -> - - let - (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty - (f_theta, f_tau) = splitRhoTy f_rho - sig_tyvar_set = mkTyVarSet sig_tyvars - in - unifyTauTy sig_tau f_tau `thenTc_` - - tcPolyExpr str (HsVar g_name) (mkSigmaTy sig_tyvars f_theta sig_tau) `thenTc` \ (_, _, - -} - -tcPragmaSig other = pprTrace "tcPragmaSig: ignoring" (ppr other) $ - returnTc (Nothing, EmptyMonoBinds, emptyLIE) -\end{code} + getLIE (tcCheckSigma (L nm_loc (HsVar name)) sig_ty) `thenM` \ (spec_expr, spec_lie) -> + + -- Squeeze out any Methods (see comments with tcSimplifyToDicts) + tcSimplifyToDicts spec_lie `thenM` \ spec_binds -> + + -- Just specialise "f" by building a SpecPragmaId binding + -- It is the thing that makes sure we don't prematurely + -- dead-code-eliminate the binding we are really interested in. + newLocalName name `thenM` \ spec_name -> + let + spec_bind = VarBind (mkSpecPragmaId spec_name sig_ty) + (mkHsLet spec_binds spec_expr) + in + + -- Do the rest and combine + tcSpecSigs sigs `thenM` \ binds_rest -> + returnM (binds_rest `snocBag` L loc spec_bind) +tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs +tcSpecSigs [] = returnM emptyLHsBinds +\end{code} %************************************************************************ %* * @@ -918,66 +870,45 @@ tcPragmaSig other = pprTrace "tcPragmaSig: ignoring" (ppr other) $ \begin{code} -patMonoBindsCtxt bind - = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind) +-- This one is called on LHS, when pat and grhss are both Name +-- and on RHS, when pat is TcId and grhss is still Name +patMonoBindsCtxt pat grhss + = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss) ----------------------------------------------- valSpecSigCtxt v ty = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"), - nest 4 (ppr v <+> ptext SLIT(" ::") <+> ppr ty)] + nest 4 (ppr v <+> dcolon <+> ppr ty)] ----------------------------------------------- -notAsPolyAsSigErr sig_tau mono_tyvars - = hang (ptext SLIT("A type signature is more polymorphic than the inferred type")) - 4 (vcat [text "Can't for-all the type variable(s)" <+> - pprQuotedList mono_tyvars, - text "in the type" <+> quotes (ppr sig_tau) - ]) +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")] + where + id1 = sig_id sig1 + id2 = sig_id sig2 ------------------------------------------------ -badMatchErr sig_ty inferred_ty - = hang (ptext SLIT("Type signature doesn't match inferred type")) - 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sig_ty), - hang (ptext SLIT("Inferred :")) 4 (ppr inferred_ty) - ]) ----------------------------------------------- -sigCtxt id - = sep [ptext SLIT("When checking the type signature for"), quotes (ppr id)] - -bindSigsCtxt ids - = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids +unliftedBindErr flavour mbind + = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:")) + 4 (ppr mbind) ----------------------------------------------- -sigContextsErr - = ptext SLIT("Mismatched contexts") -sigContextsCtxt s1 s2 - = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"), - quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)]) - 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)")) +existentialExplode mbinds + = hang (vcat [text "My brain just exploded.", + text "I can't handle pattern bindings for existentially-quantified constructors.", + text "In the binding group"]) + 4 (ppr mbinds) ----------------------------------------------- -specGroundnessCtxt - = panic "specGroundnessCtxt" - --------------------------------------------- -specContextGroundnessCtxt -- err_ctxt dicts - = panic "specContextGroundnessCtxt" -{- - = hang ( - sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr name], - hcat [ptext SLIT(" specialised to the type"), ppr spec_ty], - pp_spec_id, - ptext SLIT("... not all overloaded type variables were instantiated"), - ptext SLIT("to ground types:")]) - 4 (vcat [hsep [ppr c, ppr t] - | (c,t) <- map getDictClassAndType dicts]) - where - (name, spec_ty, locn, pp_spec_id) - = case err_ctxt of - ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> empty) - ValSpecSpecIdCtxt n ty spec loc -> - (n, ty, loc, - hsep [ptext SLIT("... type of explicit id"), ppr spec]) --} +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")]) + +genCtxt binder_names + = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names \end{code}