X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=c4e1b92f6c981640dce050094c6cfaeafa1b4d51;hb=ff818166a0a06e77becad9e28ed116f3b7f5cc8b;hp=f0679f3a4d30931e2d7fb4cf72fca7bdf16f82e7;hpb=c2b053f3228a8e32cf4d4909c2e97b338e3ac3c1;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index f0679f3..c4e1b92 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -4,65 +4,57 @@ \section[TcBinds]{TcBinds} \begin{code} -module TcBinds ( tcBindsAndThen, tcTopBindsAndThen, - tcSpecSigs, tcBindWithSigs ) where +module TcBinds ( tcBindsAndThen, tcTopBinds, tcHsBootSigs, tcMonoBinds, tcSpecSigs ) where #include "HsVersions.h" -import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun ) -import {-# SOURCE #-} TcExpr ( tcExpr ) +import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun ) +import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho ) -import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), InPat(..), StmtCtxt(..), - collectMonoBinders, andMonoBindList, 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, TcId, zonkId, mkHsLet ) - -import TcMonad -import Inst ( Inst, LIE, emptyLIE, mkLIE, plusLIE, plusLIEs, InstOrigin(..), - newDicts, tyVarsOfInst, instToId, getFunDepsOfLIE, - zonkFunDeps - ) -import TcEnv ( tcExtendLocalValEnv, - newSpecPragmaId, newLocalId, - tcLookupTyCon, - tcGetGlobalTyVars, tcExtendGlobalTyVars - ) -import TcSimplify ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts ) -import TcImprove ( tcImprove ) -import TcMonoType ( tcHsType, checkSigTyVars, - TcSigInfo(..), tcTySig, maybeSig, sigCtxt +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 TcPat ( tcPat ) +import TcPat ( tcPat, PatCtxt(..) ) import TcSimplify ( bindInstsOfLocalFuns ) -import TcType ( TcType, TcThetaType, - TcTyVar, - newTyVarTy, newTyVar, newTyVarTy_OpenKind, tcInstTcType, - zonkTcType, zonkTcTypes, zonkTcThetaType, zonkTcTyVarToTyVar - ) -import TcUnify ( unifyTauTy, unifyTauTyLists ) - -import PrelInfo ( main_NAME, ioTyCon_NAME ) - -import Id ( Id, mkVanillaId, setInlinePragma ) +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 IdInfo ( IdInfo, vanillaIdInfo, setInlinePragInfo, InlinePragInfo(..) ) -import Name ( Name, getName, getOccName, getSrcLoc ) +import Name ( Name ) import NameSet -import Type ( mkTyVarTy, tyVarsOfTypes, mkTyConApp, - splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, - mkDictTy, splitRhoTy, mkForAllTy, isUnLiftedType, - isUnboxedType, unboxedTypeKind, boxedTypeKind - ) -import FunDeps ( tyVarFunDep, oclose ) -import Var ( TyVar, tyVarKind ) import VarSet +import SrcLoc ( Located(..), unLoc, noLoc, getLoc ) import Bag import Util ( isIn ) -import Maybes ( maybeToBool ) -import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNotTopLevel ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec, + isNotTopLevel, isAlwaysActive ) import FiniteMap ( listToFM, lookupFM ) -import SrcLoc ( SrcLoc ) import Outputable \end{code} @@ -99,109 +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 -> thing -> thing) -- Combinator - -> RenamedHsBinds - -> TcM s (thing, LIE) - -> TcM s (thing, LIE) +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 + -- 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) } -tcTopBindsAndThen = tc_binds_and_then TopLevel -tcBindsAndThen = tc_binds_and_then NotTopLevel +tcBindsAndThen + :: (HsBindGroup TcId -> thing -> thing) -- Combinator + -> [HsBindGroup Name] + -> TcM thing + -> TcM thing -tc_binds_and_then top_lvl combiner EmptyBinds do_next - = do_next -tc_binds_and_then top_lvl combiner (MonoBind EmptyMonoBinds sigs is_rec) do_next +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_binds_and_then top_lvl combiner (ThenBinds b1 b2) do_next - = tc_binds_and_then top_lvl combiner b1 $ - tc_binds_and_then top_lvl combiner b2 $ - 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') -> -tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next - = -- TYPECHECK THE SIGNATURES - mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs -> - - tcBindWithSigs top_lvl bind tc_ty_sigs - sigs is_rec `thenTc` \ (poly_binds, poly_lie, poly_ids) -> - - -- Extend the environment to bind the new polymorphic Ids - tcExtendLocalValEnv [(idName poly_id, poly_id) | poly_id <- poly_ids] $ + -- If the binding binds ?x = E, we must now + -- discharge any ?x constraints in expr_lie + tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds -> + + 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 `thenTc` \ (prag_binds, prag_lie) -> - - -- Now do whatever happens next, in the augmented envt - do_next `thenTc` \ (thing, thing_lie) -> - - -- Create specialisations of functions bound here - -- We want to keep non-recursive things non-recursive - -- so that we desugar unboxed bindings correctly - case (top_lvl, is_rec) of - - -- 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 - (TopLevel, _) - -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing, - thing_lie `plusLIE` prag_lie `plusLIE` poly_lie) - - (NotTopLevel, NonRecursive) - -> bindInstsOfLocalFuns - (thing_lie `plusLIE` prag_lie) - poly_ids `thenTc` \ (thing_lie', lie_binds) -> - - returnTc ( - combiner NonRecursive poly_binds $ - combiner NonRecursive prag_binds $ - combiner Recursive lie_binds $ - -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns - -- aren't guaranteed in dependency order (though we could change - -- that); hence the Recursive marker. - thing, - - thing_lie' `plusLIE` poly_lie - ) + tcSpecSigs sigs `thenM` \ prag_binds -> - (NotTopLevel, Recursive) - -> bindInstsOfLocalFuns - (thing_lie `plusLIE` poly_lie `plusLIE` prag_lie) - poly_ids `thenTc` \ (final_lie, lie_binds) -> - - returnTc ( - combiner Recursive ( - poly_binds `andMonoBinds` - lie_binds `andMonoBinds` - prag_binds) thing, - final_lie - ) -\end{code} + -- Now do whatever happens next, in the augmented envt + do_next `thenM` \ thing -> -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] - -\begin{pseudocode} -% tcBindsAndThen -% :: RenamedHsBinds -% -> TcM s (thing, LIE, thing_ty)) -% -> TcM s ((TcHsBinds, thing), LIE, thing_ty) -% -% tcBindsAndThen EmptyBinds do_next -% = do_next `thenTc` \ (thing, lie, thing_ty) -> -% returnTc ((EmptyBinds, thing), lie, thing_ty) -% -% tcBindsAndThen (ThenBinds binds1 binds2) do_next -% = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) -% `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> -% -% returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) -% -% tcBindsAndThen (MonoBind bind sigs is_rec) do_next -% = tcBindAndThen bind sigs do_next -\end{pseudocode} + returnM (prag_binds, thing) +\end{code} %************************************************************************ @@ -221,216 +247,138 @@ so all the clever stuff is in here. as the Name in the tc_ty_sig \begin{code} -tcBindWithSigs - :: TopLevelFlag - -> RenamedMonoBinds - -> [TcSigInfo] - -> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs - -> RecFlag - -> TcM s (TcMonoBinds, LIE, [TcId]) - -tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec - = recoverTc ( - -- If typechecking the binds fails, then return with each - -- signature-less binder given type (forall a.a), to minimise subsequent - -- error messages - newTyVar boxedTypeKind `thenNF_Tc` \ alpha_tv -> - let - forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) - binder_names = map fst (bagToList (collectMonoBinders mbind)) - 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 -> mkVanillaId name forall_a_a -- No signature - in - returnTc (EmptyMonoBinds, emptyLIE, poly_ids) - ) $ - - -- TYPECHECK THE BINDINGS - tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) -> - - -- CHECK THAT THE SIGNATURES MATCH - -- (must do this before getTyVarsToGen) - checkSigMatch top_lvl binder_names mono_ids tc_ty_sigs `thenTc` \ maybe_sig_theta -> - - -- IMPROVE the LIE - -- Force any unifications dictated by functional dependencies. - -- Because unification may happen, it's important that this step - -- come before: - -- - computing vars over which to quantify - -- - zonking the generalized type vars - tcImprove lie_req `thenTc_` - - -- 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 - let - mono_id_tys = map idType mono_ids - in - getTyVarsToGen is_unrestricted mono_id_tys lie_req `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) -> - - -- Finally, zonk the generalised type variables to real TyVars - -- This commits any unbound kind variables to boxed kind - -- I'm a little worried that such a kind variable might be - -- free in the environment, but I don't think it's possible for - -- this to happen when the type variable is not free in the envt - -- (which it isn't). SLPJ Nov 98 - mapTc zonkTcTyVarToTyVar (varSetElems tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list -> - let - real_tyvars_to_gen = mkVarSet 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 tyvars_not_to_gen ( - if null real_tyvars_to_gen_list then - -- No polymorphism, so no need to simplify context - returnTc (lie_req, EmptyMonoBinds, []) - else - case maybe_sig_theta of - Nothing -> - -- No signatures, so just simplify the lie - -- NB: no signatures => no polymorphic recursion, so no - -- need to use lie_avail (which will be empty anyway) - tcSimplify (text "tcBinds1" <+> ppr binder_names) - top_lvl real_tyvars_to_gen lie_req `thenTc` \ (lie_free, dict_binds, lie_bound) -> - returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound)) - - Just (sig_theta, lie_avail) -> - -- There are signatures, and their context is sig_theta - -- Furthermore, lie_avail is an LIE containing the 'method insts' - -- for the things bound here - - 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 lie_avail - -- so that polymorphic recursion works right (see comments at end of fn) - givens = dicts_sig `plusLIE` lie_avail - 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") <+> pprQuotedList binder_names) - real_tyvars_to_gen givens lie_req `thenTc` \ (lie_free, dict_binds) -> - - returnTc (lie_free, dict_binds, dict_ids) - - ) `thenTc` \ (lie_free, dict_binds, dicts_bound) -> - - -- GET THE FINAL MONO_ID_TYS - zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types -> - - - -- CHECK FOR BOGUS UNPOINTED BINDINGS - (if any isUnLiftedType zonked_mono_id_types then - -- Unlifted bindings must be non-recursive, - -- not top level, and non-polymorphic - checkTc (isNotTopLevel top_lvl) - (unliftedBindErr "Top-level" mbind) `thenTc_` - checkTc (case is_rec of {Recursive -> False; NonRecursive -> True}) - (unliftedBindErr "Recursive" mbind) `thenTc_` - checkTc (null real_tyvars_to_gen_list) - (unliftedBindErr "Polymorphic" mbind) - else - returnTc () - ) `thenTc_` - - ASSERT( not (any ((== unboxedTypeKind) . 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 - mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids -> - let - exports = zipWith mk_export binder_names zonked_mono_ids - dict_tys = map idType dicts_bound - - inlines = mkNameSet [name | InlineSig name _ loc <- inline_sigs] - no_inlines = listToFM ([(name, IMustNotBeINLINEd False phase) | NoInlineSig name phase loc <- inline_sigs] ++ - [(name, IMustNotBeINLINEd True phase) | InlineSig name phase loc <- inline_sigs, maybeToBool phase]) - -- "INLINE n foo" means inline foo, but not until at least phase n - -- "NOINLINE n foo" means don't inline foo until at least phase n, and even - -- then only if it is small enough etc. - -- "NOINLINE foo" means don't inline foo ever, which we signal with a (IMustNotBeINLINEd Nothing) - -- See comments in CoreUnfold.blackListed for the Authorised Version - - mk_export binder_name zonked_mono_id - = (tyvars, - attachNoInlinePrag no_inlines poly_id, - zonked_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 = mkVanillaId binder_name poly_ty - poly_ty = mkForAllTys real_tyvars_to_gen_list - $ mkFunTys dict_tys - $ idType (zonked_mono_id) - -- 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. - - pat_binders :: [Name] - pat_binders = map fst $ bagToList $ collectMonoBinders $ - (justPatBindings mbind EmptyMonoBinds) - in - -- CHECK FOR UNBOXED BINDERS IN PATTERN BINDINGS - mapTc (\id -> checkTc (not (idName id `elem` pat_binders - && isUnboxedType (idType id))) - (unboxedPatBindErr id)) zonked_mono_ids - `thenTc_` - - -- BUILD RESULTS - returnTc ( - AbsBinds real_tyvars_to_gen_list - dicts_bound - exports - inlines - (dict_binds `andMonoBinds` mbind'), - lie_free, - [poly_id | (_, 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 - tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- tc_ty_sigs] - is_unrestricted = isUnRestrictedGroup tysig_names mbind - -justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds -justPatBindings (AndMonoBinds b1 b2) binds = - justPatBindings b1 (justPatBindings b2 binds) -justPatBindings other_bind binds = binds - -attachNoInlinePrag no_inlines bndr - = case lookupFM no_inlines (idName bndr) of + 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 @@ -489,10 +437,294 @@ 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} %* * %************************************************************************ +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 @@ -521,6 +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 @@ -531,278 +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 - body_tyvars = tyVarsOfTypes zonked_mono_id_tys `minusVarSet` free_tyvars - in - if is_unrestricted - then - let fds = concatMap snd (getFunDepsOfLIE lie) in - zonkFunDeps fds `thenNF_Tc` \ fds' -> - let tvFundep = tyVarFunDep fds' - extended_tyvars = oclose tvFundep body_tyvars in - -- pprTrace "gTVTG" (ppr (lie, body_tyvars, extended_tyvars)) $ - returnNF_Tc (emptyVarSet, extended_tyvars) - else - -- This recover and discard-errs is to avoid duplicate error - -- messages; this, after all, is an "extra" call to tcSimplify - recoverNF_Tc (returnNF_Tc (emptyVarSet, body_tyvars)) $ - discardErrsTc $ - - tcSimplify (text "getTVG") NotTopLevel body_tyvars lie `thenTc` \ (_, _, constrained_dicts) -> - let - -- ASSERT: dicts_sig is already zonked! - constrained_tyvars = foldrBag (unionVarSet . tyVarsOfInst) emptyVarSet constrained_dicts - reduced_tyvars_to_gen = body_tyvars `minusVarSet` 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} - - -%************************************************************************ -%* * -\subsection{tcMonoBind} -%* * -%************************************************************************ - -@tcMonoBinds@ deals with a single @MonoBind@. -The signatures have been dealt with already. - -\begin{code} -tcMonoBinds :: RenamedMonoBinds - -> [TcSigInfo] - -> RecFlag - -> TcM s (TcMonoBinds, - LIE, -- LIE required - [Name], -- Bound names - [TcId]) -- Corresponding monomorphic bound things - -tcMonoBinds mbinds tc_ty_sigs is_rec - = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) -> - let - tv_list = bagToList tvs - id_list = bagToList ids - (names, mono_ids) = unzip id_list - - -- This last defn is the key one: - -- extend the val envt with bindings for the - -- things bound in this group, overriding the monomorphic - -- ids with the polymorphic ones from the pattern - extra_val_env = case is_rec of - Recursive -> map mk_bind id_list - NonRecursive -> [] - in - -- Don't know how to deal with pattern-bound existentials yet - checkTc (isEmptyBag tvs && isEmptyBag lie_avail) - (existentialExplode mbinds) `thenTc_` - - -- *Before* checking the RHSs, but *after* checking *all* the patterns, - -- extend the envt with bindings for all the bound ids; - -- and *then* override with the polymorphic Ids from the signatures - -- That is the whole point of the "complete_it" stuff. - -- - -- There's a further wrinkle: we have to delay extending the environment - -- until after we've dealt with any pattern-bound signature type variables - -- Consider f (x::a) = ...f... - -- We're going to check that a isn't unified with anything in the envt, - -- so f itself had better not be! So we pass the envt binding f into - -- complete_it, which extends the actual envt in TcMatches.tcMatch, after - -- dealing with the signature tyvars - - complete_it extra_val_env `thenTc` \ (mbinds', lie_req_rhss) -> - - returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids) - where - - -- This function is used when dealing with a LHS binder; we make a monomorphic - -- version of the Id. We check for type signatures - tc_pat_bndr name pat_ty - = case maybeSig tc_ty_sigs name of - Nothing - -> newLocalId (getOccName name) pat_ty (getSrcLoc name) - - Just (TySigInfo _ _ _ _ _ mono_id _ _) - -> tcAddSrcLoc (getSrcLoc name) $ - unifyTauTy (idType mono_id) pat_ty `thenTc_` - returnTc mono_id - - mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of - Nothing -> (name, mono_id) - Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id) - - tc_mb_pats EmptyMonoBinds - = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE) - - tc_mb_pats (AndMonoBinds mb1 mb2) - = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) -> - tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) -> - let - complete_it xve = complete_it1 xve `thenTc` \ (mb1', lie1) -> - complete_it2 xve `thenTc` \ (mb2', lie2) -> - returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2) - in - returnTc (complete_it, - lie_req1 `plusLIE` lie_req2, - tvs1 `unionBags` tvs2, - ids1 `unionBags` ids2, - lie_avail1 `plusLIE` lie_avail2) - - tc_mb_pats (FunMonoBind name inf matches locn) - = newTyVarTy boxedTypeKind `thenNF_Tc` \ bndr_ty -> - tc_pat_bndr name bndr_ty `thenTc` \ bndr_id -> - let - complete_it xve = tcAddSrcLoc locn $ - tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) -> - returnTc (FunMonoBind bndr_id inf matches' locn, lie) - in - returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE) - - tc_mb_pats bind@(PatMonoBind pat grhss locn) - = tcAddSrcLoc locn $ - - -- Figure out the appropriate kind for the pattern, - -- and generate a suitable type variable - (case is_rec of - Recursive -> newTyVarTy boxedTypeKind -- Recursive, so no unboxed types - NonRecursive -> newTyVarTy_OpenKind -- Non-recursive, so we permit unboxed types - ) `thenNF_Tc` \ pat_ty -> - - -- Now typecheck the pattern - -- We don't support binding fresh type variables in the - -- pattern of a pattern binding. For example, this is illegal: - -- (x::a, y::b) = e - -- whereas this is ok - -- (x::Int, y::Bool) = e - -- - -- We don't check explicitly for this problem. Instead, we simply - -- type check the pattern with tcPat. If the pattern mentions any - -- fresh tyvars we simply get an out-of-scope type variable error - tcPat tc_pat_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) -> - let - complete_it xve = tcAddSrcLoc locn $ - tcAddErrCtxt (patMonoBindsCtxt bind) $ - tcExtendLocalValEnv xve $ - tcGRHSs grhss pat_ty PatBindRhs `thenTc` \ (grhss', lie) -> - returnTc (PatMonoBind pat' grhss' locn, lie) - in - returnTc (complete_it, lie_req, tvs, ids, lie_avail) -\end{code} - -%************************************************************************ -%* * -\subsection{Signatures} -%* * -%************************************************************************ - -@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 top_lvl binder_names mono_ids sigs - | main_bound_here - = -- First unify the main_id with IO t, for any old t - tcSetErrCtxt mainTyCheckCtxt ( - tcLookupTyCon ioTyCon_NAME `thenTc` \ ioTyCon -> - newTyVarTy boxedTypeKind `thenNF_Tc` \ t_tv -> - unifyTauTy ((mkTyConApp ioTyCon [t_tv])) - (idType main_mono_id) - ) `thenTc_` - - -- Now check the signatures - -- Must do this after the unification with IO t, - -- in case of a silly signature like - -- main :: forall a. a - -- The unification to IO t will bind the type variable 'a', - -- which is just waht check_one_sig looks for - mapTc check_one_sig sigs `thenTc_` - mapTc check_main_ctxt sigs `thenTc_` - - returnTc (Just ([], emptyLIE)) - - | not (null sigs) - = mapTc check_one_sig sigs `thenTc_` - mapTc check_one_ctxt all_sigs_but_first `thenTc_` - returnTc (Just (theta1, sig_lie)) - - | otherwise - = returnTc Nothing -- No constraints from type sigs - - where - (TySigInfo _ id1 _ theta1 _ _ _ _ : all_sigs_but_first) = sigs - - sig1_dict_tys = mk_dict_tys theta1 - n_sig1_dict_tys = length sig1_dict_tys - sig_lie = mkLIE [inst | TySigInfo _ _ _ _ _ _ inst _ <- sigs] - - maybe_main = find_main top_lvl binder_names mono_ids - main_bound_here = maybeToBool maybe_main - Just main_mono_id = maybe_main - - -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK - -- Doesn't affect substitution - check_one_sig (TySigInfo _ id sig_tyvars _ sig_tau _ _ src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxtM (sigCtxt (sig_msg id) (idType id)) $ - checkSigTyVars sig_tyvars - - - -- 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 - check_one_ctxt 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 THAT FOR A GROUP INVOLVING Main.main, all - -- the signature contexts are empty (what a bore) - check_main_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc) - = tcAddSrcLoc src_loc $ - checkTc (null theta) (mainContextsErr id) - - mk_dict_tys theta = [mkDictTy c ts | (c,ts) <- theta] - - sig_msg id tidy_ty = sep [ptext SLIT("When checking the type signature"), - nest 4 (ppr id <+> dcolon <+> ppr tidy_ty)] - - -- Search for Main.main in the binder_names, return corresponding mono_id - find_main NotTopLevel binder_names mono_ids = Nothing - find_main TopLevel binder_names mono_ids = go binder_names mono_ids - go [] [] = Nothing - go (n:ns) (m:ms) | n == main_NAME = Just m - | otherwise = go ns ms \end{code} @@ -845,40 +826,42 @@ We used to have a form {-# SPECIALISE f :: = g #-} which promised that g implemented f at , but we do that with a RULE now: - {-# SPECIALISE (f::) = g #-} \begin{code} -tcSpecSigs :: [RenamedSig] -> TcM s (TcMonoBinds, LIE) -tcSpecSigs (SpecSig name poly_ty src_loc : sigs) +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_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) -> + 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 `thenTc` \ (spec_lie1, spec_binds) -> + 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. - newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_id -> + 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 `thenTc` \ (binds_rest, lie_rest) -> - returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr), - lie_rest `plusLIE` spec_lie1) + tcSpecSigs sigs `thenM` \ binds_rest -> + returnM (binds_rest `snocBag` L loc spec_bind) tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs -tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE) +tcSpecSigs [] = returnM emptyLHsBinds \end{code} - %************************************************************************ %* * \subsection[TcBinds-errors]{Error contexts and messages} @@ -887,8 +870,10 @@ tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE) \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 @@ -896,56 +881,34 @@ valSpecSigCtxt v 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) - ]) - ------------------------------------------------ -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) - ]) - ------------------------------------------------ -unboxedPatBindErr id - = ptext SLIT("variable in a lazy pattern binding has unboxed type: ") - <+> quotes (ppr id) - ------------------------------------------------ -bindSigsCtxt ids - = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids - ------------------------------------------------ -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)")) - -mainContextsErr id - | getName id == main_NAME = ptext SLIT("Main.main cannot be overloaded") - | otherwise - = quotes (ppr id) <+> ptext SLIT("cannot be overloaded") <> char ',' <> -- sigh; workaround for cpp's inability to deal - ptext SLIT("because it is mutually recursive with Main.main") -- with commas inside SLIT strings. +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 -mainTyCheckCtxt - = hsep [ptext SLIT("When checking that"), quotes (ppr main_NAME), - ptext SLIT("has the required type")] ----------------------------------------------- unliftedBindErr flavour mbind - = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed")) + = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:")) 4 (ppr mbind) +----------------------------------------------- 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) + +----------------------------------------------- +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}