X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=5ab2d1d9212632d5680c6c00e1561e199b10cfbd;hb=ff818166a0a06e77becad9e28ed116f3b7f5cc8b;hp=75b3683a5ac7b05e2c146155668038784843ecc3;hpb=1fb1ab5d53a09607e7f6d2450806760688396387;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index 75b3683..c4e1b92 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -1,66 +1,61 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcBinds]{TcBinds} \begin{code} -#include "HsVersions.h" - -module TcBinds ( tcBindsAndThen, tcPragmaSigs, checkSigTyVars ) where +module TcBinds ( tcBindsAndThen, tcTopBinds, tcHsBootSigs, tcMonoBinds, tcSpecSigs ) where -IMP_Ubiq() +#include "HsVersions.h" -import HsSyn ( HsBinds(..), Bind(..), Sig(..), MonoBinds(..), - Match, HsType, InPat(..), OutPat(..), HsExpr(..), - GRHSsAndBinds, ArithSeqInfo, HsLit, Fake, Stmt, DoOrListComp, Fixity, - collectBinders ) -import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedBind), RenamedSig(..), - SYN_IE(RenamedMonoBinds) - ) -import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcBind), SYN_IE(TcMonoBinds), - TcIdOcc(..), SYN_IE(TcIdBndr), SYN_IE(TcExpr), - tcIdType - ) +import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun ) +import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho ) -import TcMonad -import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..), - newDicts, tyVarsOfInst, instToId +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 TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds, - tcGetGlobalTyVars, tcExtendGlobalTyVars +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 SpecEnv ( SpecEnv ) -IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds ) -import TcMatches ( tcMatchesFun ) -import TcSimplify ( tcSimplify, tcSimplifyAndCheck ) -import TcMonoType ( tcHsType ) -import TcPat ( tcPat ) +import TcPat ( tcPat, PatCtxt(..) ) import TcSimplify ( bindInstsOfLocalFuns ) -import TcType ( SYN_IE(TcType), SYN_IE(TcThetaType), SYN_IE(TcTauType), - SYN_IE(TcTyVarSet), SYN_IE(TcTyVar), - newTyVarTy, zonkTcType, zonkTcTyVar, zonkTcTyVars, - newTcTyVar, tcInstSigType, newTyVarTys - ) -import Unify ( unifyTauTy ) - -import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind ) -import Id ( GenId, idType, mkUserLocal, mkUserId ) -import IdInfo ( noIdInfo ) -import Maybes ( assocMaybe, catMaybes ) -import Name ( pprNonSym, getOccName, getSrcLoc, Name ) -import PragmaInfo ( PragmaInfo(..) ) -import Pretty -import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes, eqSimpleTheta, - mkSigmaTy, splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, - splitRhoTy, mkForAllTy, splitForAllTy ) -import TyVar ( GenTyVar, SYN_IE(TyVar), tyVarKind, minusTyVarSet, emptyTyVarSet, - elementOfTyVarSet, unionTyVarSets, tyVarSetToList ) -import Bag ( bagToList, foldrBag, isEmptyBag ) -import Util ( isIn, zipEqual, zipWithEqual, zipWith3Equal, hasNoDups, assoc, - assertPanic, panic ) -import PprType ( GenClass, GenType, GenTyVar ) -import Unique ( Unique ) -import Outputable ( interppSP, interpp'SP ) +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} @@ -96,123 +91,142 @@ At the top-level the LIE is sure to contain nothing but constant dictionaries, which we resolve at the module level. \begin{code} -tcBindsAndThen - :: (TcHsBinds s -> thing -> thing) -- Combinator - -> RenamedHsBinds - -> TcM s (thing, LIE s, thing_ty) - -> TcM s (thing, LIE s, thing_ty) - -tcBindsAndThen combiner EmptyBinds do_next - = do_next `thenTc` \ (thing, lie, thing_ty) -> - returnTc (combiner EmptyBinds thing, lie, thing_ty) - -tcBindsAndThen combiner (SingleBind bind) do_next - = tcBindWithSigsAndThen combiner bind [] do_next - -tcBindsAndThen combiner (BindWith bind sigs) do_next - = tcBindWithSigsAndThen combiner bind sigs do_next - -tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next - = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next) -\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] +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) } -\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 EmptyBinds do_next - = do_next `thenTc` \ (thing, lie, thing_ty) -> - returnTc ((EmptyBinds, thing), lie, thing_ty) +tcBindsAndThen = tc_binds_and_then NotTopLevel -tcBindsAndThen (SingleBind bind) do_next - = tcBindAndThen bind [] do_next +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 -tcBindsAndThen (BindWith bind sigs) do_next - = tcBindAndThen bind sigs 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 (ThenBinds binds1 binds2) do_next - = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) - `thenTc` \ ((binds1', (binds2', thing')), lie1, 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 -> - returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) -\end{pseudocode} - - -%************************************************************************ -%* * -\subsection{tcBindWithSigsAndThen} -%* * -%************************************************************************ + 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 -> -@tcBindAndThen@ deals with one binding group and the thing it scopes over. + -- Now do whatever happens next, in the augmented envt + do_next `thenM` \ thing -> -\begin{code} -tcBindWithSigsAndThen - :: (TcHsBinds s -> thing -> thing) -- Combinator - -> RenamedBind -- The Bind to typecheck - -> [RenamedSig] -- ...and its signatures - -> TcM s (thing, LIE s, thing_ty) -- Thing to type check in - -- augmented envt - -> TcM s (thing, LIE s, thing_ty) -- Results, incl the - -tcBindWithSigsAndThen combiner bind sigs do_next - = - recoverTc ( - -- If typechecking the binds fails, then return with each - -- 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 = [ mkUserId name forall_a_a NoPragmaInfo - | name <- binder_names] - in - -- Extend the environment to bind the new polymorphic Ids - -- and do the thing inside - tcExtendLocalValEnv binder_names poly_ids $ - do_next - ) $ - - 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. - tcBindWithSigs binder_names bind - sigs 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) -> - - -- Now do whatever happens next, in the augmented envt - do_next `thenTc` \ (thing, thing_lie, thing_ty) -> - - -- Create specialisations of functions bound here - bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie) - poly_ids `thenTc` \ (lie2, inst_mbinds) -> - - -- All done - let - final_lie = lie2 `plusLIE` poly_lie - final_binds = poly_binds `ThenBinds` - SingleBind (NonRecBind inst_mbinds) `ThenBinds` - prag_binds - in - returnTc (prag_info_fn, (combiner final_binds thing, final_lie, thing_ty)) - ) `thenTc` \ (_, result) -> - returnTc result - where - binder_names = map fst (bagToList (collectBinders bind)) + returnM (prag_binds, thing) \end{code} @@ -225,216 +239,200 @@ tcBindWithSigsAndThen combiner bind sigs do_next @tcBindWithSigs@ deals with a single binding group. It does generalisation, so all the clever stuff is in here. -\begin{code} -tcBindWithSigs binder_names bind sigs prag_info_fn - = -- Create a new identifier for each binder, with each being given - -- a fresh unique, and a type-variable type. - tcGetUniques no_of_binders `thenNF_Tc` \ uniqs -> - newTyVarTys no_of_binders kind `thenNF_Tc` \ tys -> - let - mono_ids = zipWith3Equal "tcBindAndSigs" mk_id binder_names uniqs tys - mk_id name uniq ty = mkUserLocal (getOccName name) uniq ty (getSrcLoc name) - in - - -- TYPECHECK THE SIGNATURES - mapTc tcTySig ty_sigs `thenTc` \ tc_ty_sigs -> - - -- TYPECHECK THE BINDINGS - tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) -> +* binder_names and mbind must define the same set of Names - -- CHECK THAT THE SIGNATURES MATCH - -- (must do this before getTyVarsToGen) - checkSigMatch (binder_names `zip` mono_ids) 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 - mapNF_Tc (zonkTcType . idType) mono_ids `thenNF_Tc` \ mono_id_types -> - getTyVarsToGen is_unrestricted mono_id_types lie `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen) -> - let - tyvars_to_gen_list = tyVarSetToList tyvars_to_gen -- Commit to a particular order - in +* The Names in tc_ty_sigs must be a subset of binder_names - -- SIMPLIFY THE LIE - tcExtendGlobalTyVars tyvars_not_to_gen ( - if null tc_ty_sigs then - -- No signatures, so just simplify the lie - tcSimplify tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) -> - returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound)) +* The Ids in tc_ty_sigs don't necessarily have to have the same name + as the Name in the tc_ty_sig - else - 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 - - -- Check that the needed dicts can be expressed in - -- terms of the signature ones - tcAddErrCtxt (sigsCtxt tysig_names) $ - tcSimplifyAndCheck tyvars_to_gen dicts_sig lie `thenTc` \ (lie_free, dict_binds) -> - returnTc (lie_free, dict_binds, dict_ids) - - ) `thenTc` \ (lie_free, dict_binds, dicts_bound) -> - - -- DEAL WITH TYPE VARIABLE KINDS - defaultUncommittedTyVars tyvars_to_gen_list `thenTc_` - - -- BUILD THE POLYMORPHIC RESULT IDs - let - dict_tys = map tcIdType dicts_bound - poly_tys = map (mkForAllTys tyvars_to_gen_list . mkFunTys dict_tys) mono_id_types - poly_ids = zipWithEqual "genspecetc" mk_poly binder_names poly_tys - mk_poly name ty = mkUserId name ty (prag_info_fn name) - in - - -- MAKE EXTRA BINDS FOR THE TYPE-SIG POLYMORPHIC VARIABLES - -- These are only needed to scope over the right-hand sides of the group, - -- and hence aren't needed at all for non-recursive definitions. - -- - -- Alas, the polymorphic variables from the type signature can't coincide - -- with the poly_ids because the order of their type variables may not be - -- the same. These bindings just swizzle the type variables. - let - poly_binds | is_rec_bind = map mk_poly_bind tc_ty_sigs - | otherwise = [] - - mk_poly_bind (TySigInfo name rhs_poly_id rhs_tyvars _ _ _) - = (TcId rhs_poly_id, TyLam rhs_tyvars $ - TyApp (HsVar (TcId main_poly_id)) $ - mkTyVarTys tyvars_to_gen_list) +\begin{code} +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 - main_poly_id = head (filter ((== name) . getName) poly_ids) - in - -- BUILD RESULTS - returnTc ( - AbsBinds tyvars_to_gen_list - dicts_bound - (zipEqual "genBinds" (map TcId mono_ids) (map TcId poly_ids)) - (poly_binds ++ dict_binds) - (wrap_it mbind'), - lie_free, - poly_ids - ) + 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 - - is_rec_bind = case bind of - NonRecBind _ -> False - RecBind _ -> True - - mbind = case bind of - NonRecBind mb -> mb - RecBind mb -> mb - - ty_sigs = [sig | sig@(Sig name _ _) <- sigs] - tysig_names = [name | (Sig name _ _) <- ty_sigs] - is_unrestricted = isUnRestrictedGroup tysig_names mbind - - kind | is_rec_bind = mkBoxedTypeKind -- Recursive, so no unboxed types - | otherwise = mkTypeKind -- Non-recursive, so we permit unboxed types - - wrap_it mbind | is_rec_bind = RecBind mbind - | otherwise = NonRecBind mbind - + 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} -@getImplicitStuffToGen@ decides what type variables generalise over. -For a "restricted group" -- see the monomorphism restriction -for a definition -- we bind no dictionaries, and -remove from tyvars_to_gen any constrained type variables +Polymorphic recursion +~~~~~~~~~~~~~~~~~~~~~ +The game plan for polymorphic recursion in the code above is -*Don't* simplify dicts at this point, because we aren't going -to generalise over these dicts. By the time we do simplify them -we may well know more. For example (this actually came up) - f :: Array Int Int - f x = array ... xs where xs = [1,2,3,4,5] -We don't want to generate lots of (fromInt Int 1), (fromInt Int 2) -stuff. If we simplify only at the f-binding (not the xs-binding) -we'll know that the literals are all Ints, and we can just produce -Int literals! + * Bind any variable for which we have a type signature + to an Id with a polymorphic type. Then when type-checking + the RHSs we'll make a full polymorphic call. -Find all the type variables involved in overloading, the -"constrained_tyvars". These are the ones we *aren't* going to -generalise. We must be careful about doing this: +This fine, but if you aren't a bit careful you end up with a horrendous +amount of partial application and (worse) a huge space leak. For example: - (a) If we fail to generalise a tyvar which is not actually - constrained, then it will never, ever get bound, and lands - up printed out in interface files! Notorious example: - instance Eq a => Eq (Foo a b) where .. - Here, b is not constrained, even though it looks as if it is. - Another, more common, example is when there's a Method inst in - the LIE, whose type might very well involve non-overloaded - type variables. + f :: Eq a => [a] -> [a] + f xs = ...f... - (b) On the other hand, we mustn't generalise tyvars which are constrained, - because we are going to pass on out the unmodified LIE, with those - tyvars in it. They won't be in scope if we've generalised them. +If we don't take care, after typechecking we get -So we are careful, and do a complete simplification just to find the -constrained tyvars. We don't use any of the results, except to -find which tyvars are constrained. + f = /\a -> \d::Eq a -> let f' = f a d + in + \ys:[a] -> ...f'... -\begin{code} -getTyVarsToGen is_unrestricted mono_id_types lie - = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars -> - let - mentioned_tyvars = tyVarsOfTypes mono_id_types - tyvars_to_gen = mentioned_tyvars `minusTyVarSet` free_tyvars - in - if is_unrestricted - then - returnTc (emptyTyVarSet, tyvars_to_gen) - else - tcSimplify 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} +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 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 -\begin{code} -isUnRestrictedGroup :: [Name] -- Signatures given for these - -> RenamedMonoBinds - -> Bool +This can lead to a massive space leak, from the following top-level defn +(post-typechecking) -is_elem v vs = isIn "isUnResMono" v vs + ff :: [Int] -> [Int] + ff = f Int dEqInt -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} +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. -@defaultUncommittedTyVars@ checks for generalisation over unboxed -types, and defaults any TypeKind TyVars to BoxedTypeKind. + ff = f Int dEqInt -\begin{code} -defaultUncommittedTyVars tyvars - = ASSERT( null unboxed_kind_tyvars ) -- The instCantBeGeneralised stuff in tcSimplify - -- should have dealt with unboxed type variables; - -- and it's better done there because we have more - -- precise origin information. - -- That's why we call this *after* simplifying. - -- (NB: unboxed tyvars are always introduced along - -- with a class constraint.) - - mapTc box_it unresolved_kind_tyvars - where - unboxed_kind_tyvars = filter (isUnboxedTypeKind . tyVarKind) tyvars - unresolved_kind_tyvars = filter (isTypeKind . tyVarKind) tyvars + = let f' = f Int dEqInt in \ys. ...f'... - box_it tyvar = newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ boxed_ty -> - unifyTauTy boxed_ty (mkTyVarTy tyvar) -\end{code} + = 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. That's what the "lies_avail" +is doing. %************************************************************************ @@ -447,181 +445,345 @@ defaultUncommittedTyVars tyvars 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 - ) +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 - 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 $ - tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) -> - tcExtendLocalValEnv sig_names sig_ids $ - tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds2, lie, grhss_ty) -> - tcAddErrCtxt (patMonoBindsCtxt bind) $ - unifyTauTy pat_ty grhss_ty `thenTc_` - returnTc (PatMonoBind pat2 grhss_and_binds2 locn, - plusLIE lie_pat lie) + get_info (TcFunBind info _ _ _) rest = info : rest + get_info (TcPatBind infos _ _ _) rest = infos ++ rest \end{code} + %************************************************************************ %* * -\subsection{Signatures} +\subsection{getTyVarsToGen} %* * %************************************************************************ -@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. +Type signatures are tricky. See Note [Signature skolems] in TcType \begin{code} -data TcSigInfo s - = TySigInfo Name - (TcIdBndr s) -- *Polymorphic* binder for this value... - [TcTyVar s] (TcThetaType s) (TcTauType s) - SrcLoc +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} -tcTySig :: RenamedSig -> TcM s (TcSigInfo s) - -tcTySig (Sig v ty src_loc) - = tcAddSrcLoc src_loc $ - tcHsType ty `thenTc` \ sigma_ty -> - tcGetUnique `thenNF_Tc` \ uniq -> - tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' -> - let - poly_id = mkUserLocal (getOccName v) uniq sigma_ty' src_loc - (tyvars', theta', tau') = splitSigmaTy sigma_ty' - 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). +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 -\begin{code} -checkSigMatch binder_names_w_mono_isd [] - = returnTc (error "checkSigMatch") + ; returnM (final_qtvs, dict_binds, map instToId sig_lie) } -checkSigMatch binder_names_w_mono_ids tc_ty_sigs - = + 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 THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK - -- Doesn't affect substitution - mapTc check_one_sig tc_ty_sigs `thenTc_` + 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' - -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE IDENTICAL - -- The type signatures on a mutually-recursive group of definitions - -- must all have the same context (or none). - -- We have to zonk them first to make their type variables line up - mapNF_Tc get_zonked_theta tc_ty_sigs `thenNF_Tc` \ (theta:thetas) -> - checkTc (all (eqSimpleTheta theta) thetas) - (sigContextsErr tc_ty_sigs) `thenTc_` + Nothing -> return (extendVarEnv acc zonked_tv sig_tv) - returnTc theta - where - check_one_sig (TySigInfo name id sig_tyvars _ sig_tau src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (sigCtxt id) $ - unifyTauTy sig_tau mono_id_ty `thenTc_` - checkSigTyVars sig_tyvars sig_tau - where - mono_id_ty = idType (assoc "checkSigMatch" binder_names_w_mono_ids name) - - get_zonked_theta (TySigInfo _ _ _ theta _ _) - = mapNF_Tc (\ (c,t) -> zonkTcType t `thenNF_Tc` \ t' -> returnNF_Tc (c,t')) theta -\end{code} + 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} -@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] +@getTyVarsToGen@ decides what type variables to generalise over. - (b) still all distinct - eg matching signature [(a,b)] against inferred type [(p,p)] - [then a and b will be unified together] +For a "restricted group" -- see the monomorphism restriction +for a definition -- we bind no dictionaries, and +remove from tyvars_to_gen any constrained type variables -BUT ACTUALLY THESE FIRST TWO ARE FORCED BY USING DontBind TYVARS +*Don't* simplify dicts at this point, because we aren't going +to generalise over these dicts. By the time we do simplify them +we may well know more. For example (this actually came up) + f :: Array Int Int + f x = array ... xs where xs = [1,2,3,4,5] +We don't want to generate lots of (fromInt Int 1), (fromInt Int 2) +stuff. If we simplify only at the f-binding (not the xs-binding) +we'll know that the literals are all Ints, and we can just produce +Int literals! - (c) not mentioned in the environment - eg the signature for f in this: +Find all the type variables involved in overloading, the +"constrained_tyvars". These are the ones we *aren't* going to +generalise. We must be careful about doing this: - g x = ... where - f :: a->[a] - f y = [x,y] + (a) If we fail to generalise a tyvar which is not actually + constrained, then it will never, ever get bound, and lands + up printed out in interface files! Notorious example: + instance Eq a => Eq (Foo a b) where .. + Here, b is not constrained, even though it looks as if it is. + Another, more common, example is when there's a Method inst in + the LIE, whose type might very well involve non-overloaded + type variables. + [NOTE: Jan 2001: I don't understand the problem here so I'm doing + the simple thing instead] - Here, f is forced to be monorphic by the free occurence of x. + (b) On the other hand, we mustn't generalise tyvars which are constrained, + because we are going to pass on out the unmodified LIE, with those + tyvars in it. They won't be in scope if we've generalised them. -Before doing this, the substitution is applied to the signature type variable. +So we are careful, and do a complete simplification just to find the +constrained tyvars. We don't use any of the results, except to +find which tyvars are constrained. \begin{code} -checkSigTyVars :: [TcTyVar s] -- The original signature type variables - -> TcType s -- signature type (for err msg) - -> TcM s () +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 -checkSigTyVars sig_tyvars sig_tau - = tcGetGlobalTyVars `thenNF_Tc` \ globals -> - let - mono_tyvars = filter (`elementOfTyVarSet` globals) sig_tyvars - in - -- TEMPORARY FIX - -- Until the final Bind-handling stuff is in, several type signatures in the same - -- bindings group can cause the signature type variable from the different - -- signatures to be unified. So we still need to zonk and check point (b). - -- Remove when activating the new binding code - mapNF_Tc zonkTcTyVar sig_tyvars `thenNF_Tc` \ sig_tys -> - checkTcM (hasNoDups (map (getTyVar "checkSigTyVars") sig_tys)) - (zonkTcType sig_tau `thenNF_Tc` \ sig_tau' -> - failTc (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_tys and sig_tyvars' correspond - -- 1-1 with sig_tyvars, so we can just map back. - checkTc (null mono_tyvars) - (notAsPolyAsSigErr sig_tau mono_tyvars) +is_elem v vs = isIn "isUnResMono" v vs \end{code} @@ -631,45 +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 -> PragmaInfo, -- Maps name to the appropriate PragmaInfo - TcHsBinds s, - LIE s) - -tcPragmaSigs sigs = returnTc ( \name -> NoPragmaInfo, EmptyBinds, emptyLIE ) - -{- -tcPragmaSigs sigs - = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) -> - let - name_to_info name = foldr ($) noIdInfo - [info_fn | (n,info_fn) <- names_w_id_infos, n==name] - in - returnTc (name_to_info, - foldr ThenBinds EmptyBinds binds, - foldr plusLIE emptyLIE lies) -\end{code} +They look like this: -Here are the easy cases for tcPragmaSigs - -\begin{code} -tcPragmaSig (DeforestSig name loc) - = returnTc ((name, addDeforestInfo DoDeforest),EmptyBinds,emptyLIE) -tcPragmaSig (InlineSig name loc) - = returnTc ((name, addUnfoldInfo (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE) -tcPragmaSig (MagicUnfoldingSig name string loc) - = returnTc ((name, addUnfoldInfo (mkMagicUnfolding string)), EmptyBinds, emptyLIE) -\end{code} - -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 #-} @@ -692,115 +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 (SpecSig name poly_ty maybe_spec_name src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (valSpecSigCtxt name spec_ty) $ +tcSpecSigs :: [LSig Name] -> TcM (LHsBinds TcId) +tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs) + = -- SPECIALISE f :: forall b. theta => tau = g + 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 -> - let - (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty - origin = ValSpecOrigin name - in + tcHsSigType (FunSigCtxt name) poly_ty `thenM` \ sig_ty -> - -- Check that the SPECIALIZE pragma had an empty context - checkTc (null sig_theta) - (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_` + -- Check that f has a more general type, and build a RHS for + -- the spec-pragma-id at the same time + getLIE (tcCheckSigma (L nm_loc (HsVar name)) sig_ty) `thenM` \ (spec_expr, spec_lie) -> - -- Get and instantiate the type of the id mentioned - tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id -> - tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty -> + -- 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 - (main_tyvars, main_rho) = splitForAllTy main_ty - (main_theta,main_tau) = splitRhoTy main_rho - main_arg_tys = mkTyVarTys main_tyvars + spec_bind = VarBind (mkSpecPragmaId spec_name sig_ty) + (mkHsLet spec_binds spec_expr) in - -- Check that the specialised type is indeed an instance of - -- the type of the main function. - unifyTauTy sig_tau main_tau `thenTc_` - checkSigTyVars sig_tyvars sig_tau `thenTc_` - - -- Check that the type variables of the polymorphic function are - -- either left polymorphic, or instantiate to ground type. - -- Also check that the overloaded type variables are instantiated to - -- ground type; or equivalently that all dictionaries have ground type - mapTc zonkTcType main_arg_tys `thenNF_Tc` \ main_arg_tys' -> - zonkTcThetaType main_theta `thenNF_Tc` \ main_theta' -> - tcAddErrCtxt (specGroundnessCtxt main_arg_tys') - (checkTc (all isGroundOrTyVarTy main_arg_tys')) `thenTc_` - tcAddErrCtxt (specContextGroundnessCtxt main_theta') - (checkTc (and [isGroundTy ty | (_,ty) <- theta'])) `thenTc_` - - -- Build the SpecPragmaId; 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_pragma_id -> - - -- Build a suitable binding; depending on whether we were given - -- a value (Maybe Name) to be used as the specialisation. - case using of - Nothing -> -- No implementation function specified - - -- Make a Method inst for the occurrence of the overloaded function - newMethodWithGivenTy (OccurrenceOf name) - (TcId main_id) main_arg_tys main_rho `thenNF_Tc` \ (lie, meth_id) -> - - let - pseudo_bind = VarMonoBind spec_pragma_id pseudo_rhs - pseudo_rhs = mkHsTyLam sig_tyvars (HsVar (TcId meth_id)) - in - returnTc (pseudo_bind, lie, \ info -> info) - - Just spec_name -> -- Use spec_name as the specialisation value ... - - -- Type check a simple occurrence of the specialised Id - tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) -> - - -- Check that it has the correct type, and doesn't constrain the - -- signature variables at all - unifyTauTy sig_tau spec_tau `thenTc_` - checkSigTyVars sig_tyvars sig_tau `thenTc_` - - -- Make a local SpecId to bind to applied spec_id - newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id -> - - let - spec_rhs = mkHsTyLam sig_tyvars spec_body - spec_binds = VarMonoBind local_spec_id spec_rhs - `AndMonoBinds` - VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id)) - spec_info = SpecInfo spec_tys (length main_theta) local_spec_id - in - returnTc ((name, addSpecInfo spec_info), spec_binds, spec_lie) --} -\end{code} + -- 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} %************************************************************************ %* * @@ -810,78 +870,45 @@ tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc) \begin{code} -patMonoBindsCtxt bind sty - = ppHang (ppPStr SLIT("In a pattern binding:")) 4 (ppr sty 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 sty - = ppHang (ppPStr SLIT("In a SPECIALIZE pragma for a value:")) - 4 (ppSep [ppBeside (pprNonSym sty v) (ppPStr SLIT(" ::")), - ppr sty ty]) - - +valSpecSigCtxt v ty + = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"), + nest 4 (ppr v <+> dcolon <+> ppr ty)] ----------------------------------------------- -notAsPolyAsSigErr sig_tau mono_tyvars sty - = ppHang (ppPStr SLIT("A type signature is more polymorphic than the inferred type")) - 4 (ppAboves [ppStr "Some type variables in the inferred type can't be forall'd, namely:", - interpp'SP sty mono_tyvars, - ppPStr SLIT("Possible cause: the RHS mentions something subject to the monomorphism restriction") - ]) +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 sty - = ppHang (ppPStr SLIT("Type signature doesn't match inferred type")) - 4 (ppAboves [ppHang (ppPStr SLIT("Signature:")) 4 (ppr sty sig_ty), - ppHang (ppPStr SLIT("Inferred :")) 4 (ppr sty inferred_ty) - ]) ----------------------------------------------- -sigCtxt id sty - = ppSep [ppPStr SLIT("When checking signature for"), ppr sty id] -sigsCtxt ids sty - = ppSep [ppPStr SLIT("When checking signature(s) for:"), interpp'SP sty ids] +unliftedBindErr flavour mbind + = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:")) + 4 (ppr mbind) ----------------------------------------------- -sigContextsErr ty_sigs sty - = ppHang (ppPStr SLIT("A group of type signatures have mismatched contexts")) - 4 (ppAboves (map ppr_tc_ty_sig ty_sigs)) - where - ppr_tc_ty_sig (TySigInfo val _ tyvars theta tau_ty _) - = ppHang (ppBeside (ppr sty val) (ppPStr SLIT(" :: "))) - 4 (if null theta - then ppNil - else ppBesides [ppChar '(', - ppIntersperse (ppStr ", ") (map (ppr_inst sty) theta), - ppStr ") => ..."]) - ppr_inst sty (clas, ty) = ppCat [ppr sty clas, ppr sty ty] +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 sty - = panic "specContextGroundnessCtxt" -{- - = ppHang ( - ppSep [ppBesides [ppPStr SLIT("In the SPECIALIZE pragma for `"), ppr sty name, ppChar '\''], - ppBesides [ppPStr SLIT(" specialised to the type `"), ppr sty spec_ty, ppChar '\''], - pp_spec_id sty, - ppPStr SLIT("... not all overloaded type variables were instantiated"), - ppPStr SLIT("to ground types:")]) - 4 (ppAboves [ppCat [ppr sty c, ppr sty 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 -> ppNil) - ValSpecSpecIdCtxt n ty spec loc -> - (n, ty, loc, - \ sty -> ppBesides [ppPStr SLIT("... type of explicit id `"), ppr sty spec, ppChar '\'']) --} -\end{code} - - - +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}