X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=6a66814edc5276a0d70229f82563c7f4aa1b78b8;hb=ca0b7c66f2e8e50f15a03c406408d9e86455f8eb;hp=f30b80ae4e5661522cebb2c0df7962780c2091e4;hpb=ee125fd5bea482b303aa78acc4ccdb1636d9ea6a;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index f30b80a..6a66814 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -1,75 +1,54 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcBinds]{TcBinds} \begin{code} +module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds, tcSpecSigs ) where + #include "HsVersions.h" -module TcBinds ( tcBindsAndThen, tcPragmaSigs, checkSigTyVars, tcBindWithSigs, TcSigInfo(..) ) where - -IMP_Ubiq() -#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201 -IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds ) -#else -import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds ) -#endif - -import HsSyn ( HsBinds(..), Sig(..), MonoBinds(..), - Match, HsType, InPat(..), OutPat(..), HsExpr(..), - SYN_IE(RecFlag), nonRecursive, - GRHSsAndBinds, ArithSeqInfo, HsLit, Fake, Stmt, DoOrListComp, Fixity, - collectMonoBinders ) -import RnHsSyn ( SYN_IE(RenamedHsBinds), RenamedSig(..), - SYN_IE(RenamedMonoBinds) - ) -import TcHsSyn ( SYN_IE(TcHsBinds), 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_NoMonomorphismRestriction) ) +import HsSyn ( HsExpr(..), HsBind(..), LHsBind, LHsBinds, Sig(..), + LSig, Match(..), HsBindGroup(..), IPBind(..), + collectSigTysFromHsBinds, collectHsBindBinders, ) -import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds, - tcGetGlobalTyVars, tcExtendGlobalTyVars +import TcHsSyn ( TcId, zonkId, mkHsLet ) + +import TcRnMonad +import Inst ( InstOrigin(..), newDicts, newIPDict, instToId ) +import TcEnv ( tcExtendLocalValEnv, tcExtendLocalValEnv2, newLocalName ) +import TcUnify ( Expected(..), newHole, unifyTauTyLists, checkSigTyVarsWrt, sigCtxt ) +import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted, + tcSimplifyToDicts, tcSimplifyIPs ) +import TcHsType ( tcHsSigType, UserTypeCtxt(..), TcSigInfo(..), + tcTySig, maybeSig, tcAddScopedTyVars ) -import SpecEnv ( SpecEnv ) -import TcMatches ( tcMatchesFun ) -import TcSimplify ( tcSimplify, tcSimplifyAndCheck ) -import TcMonoType ( tcHsType ) -import TcPat ( tcPat ) +import TcPat ( tcPat, tcSubPat, tcMonoPatBndr ) 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 TcMType ( newTyVar, newTyVarTy, zonkTcTyVarToTyVar ) +import TcType ( TcTyVar, mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType, + mkPredTy, mkForAllTy, isUnLiftedType, + unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind ) -import Unify ( unifyTauTy, unifyTauTyLists ) - -import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind ) -import Id ( GenId, idType, mkUserLocal, mkUserId ) -import IdInfo ( noIdInfo ) -import Maybes ( maybeToBool, assocMaybe, catMaybes ) -import Name ( getOccName, getSrcLoc, Name ) -import PragmaInfo ( PragmaInfo(..) ) -import Pretty -import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes, eqSimpleTheta, - mkSigmaTy, splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy, - 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, pprTrace ) -import PprType ( GenClass, GenType, GenTyVar ) -import Unique ( Unique ) -import SrcLoc ( SrcLoc ) - -import Outputable --( interppSP, interpp'SP ) - +import CoreFVs ( idFreeTyVars ) +import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma ) +import Var ( idType, idName ) +import Name ( Name, getSrcLoc ) +import NameSet +import Var ( tyVarKind ) +import VarSet +import SrcLoc ( Located(..), srcLocSpan, unLoc, noLoc ) +import Bag +import Util ( isIn, equalLength ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec, + isNotTopLevel, isAlwaysActive ) +import FiniteMap ( listToFM, lookupFM ) +import Outputable \end{code} @@ -105,85 +84,177 @@ 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) - -> TcM s (thing, LIE s) - -tcBindsAndThen combiner EmptyBinds do_next - = do_next `thenTc` \ (thing, lie) -> - returnTc (combiner EmptyBinds thing, lie) - -tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next - = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next) - -tcBindsAndThen combiner (MonoBind bind sigs is_rec) 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. +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 $ + getLclEnv `thenM` \ env -> + returnM (emptyBag, env) + where + -- The top level bindings are flattened into a giant + -- implicitly-mutually-recursive MonoBinds + glue (HsBindGroup binds1 _ _) (binds2, env) = (binds1 `unionBags` binds2, env) + -- Can't have a HsIPBinds at top level - -- TYPECHECK THE SIGNATURES - mapTc (tcTySig prag_info_fn) ty_sigs `thenTc` \ tc_ty_sigs -> - tcBindWithSigs binder_names bind - tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) -> +tcBindsAndThen + :: (HsBindGroup TcId -> thing -> thing) -- Combinator + -> [HsBindGroup Name] + -> TcM thing + -> TcM thing - -- Extend the environment to bind the new polymorphic Ids - tcExtendLocalValEnv binder_names poly_ids $ +tcBindsAndThen = tc_binds_and_then NotTopLevel - -- Build bindings and IdInfos corresponding to user pragmas - tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) -> +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 - -- Now do whatever happens next, in the augmented envt - do_next `thenTc` \ (thing, thing_lie) -> +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') -> - -- Create specialisations of functions bound here - bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie) - poly_ids `thenTc` \ (lie2, inst_mbinds) -> + -- If the binding binds ?x = E, we must now + -- discharge any ?x constraints in expr_lie + tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds -> - -- All done - let - final_lie = lie2 `plusLIE` poly_lie - final_binds = MonoBind poly_binds [] is_rec `ThenBinds` - MonoBind inst_mbinds [] nonRecursive `ThenBinds` - prag_binds - in - returnTc (prag_info_fn, (combiner final_binds thing, final_lie)) - ) `thenTc` \ (_, result) -> - returnTc result + returnM (combiner (HsIPBinds binds') $ + combiner (HsBindGroup dict_binds [] Recursive) result) where - binder_names = map fst (bagToList (collectMonoBinders bind)) - ty_sigs = [sig | sig@(Sig name _ _) <- sigs] - -\end{code} - -An aside. The original version of @tcBindsAndThen@ which lacks a -combiner function, appears below. Though it is perfectly well -behaved, it cannot be typed by Haskell, because the recursive call is -at a different type to the definition itself. There aren't too many -examples of this, which is why I thought it worth preserving! [SLPJ] - -\begin{pseudocode} -tcBindsAndThen - :: RenamedHsBinds - -> TcM s (thing, LIE s, thing_ty)) - -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty) - -tcBindsAndThen EmptyBinds do_next - = do_next `thenTc` \ (thing, lie, thing_ty) -> - returnTc ((EmptyBinds, thing), lie, thing_ty) + -- I wonder if we should do these one at at time + -- Consider ?x = 4 + -- ?y = ?x + 1 + tc_ip_bind (IPBind ip expr) + = newTyVarTy openTypeKind `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 + | isEmptyBag 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) + tcAddScopedTyVars (collectSigTysFromHsBinds (bagToList binds)) $ + tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) -> + + 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 + -- + -- Subtle (and ugly) point: furthermore at top level we + -- return the TcLclEnv, which contains the LIE var; we + -- don't want to return the wrong one! + -> 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. We must include + -- the LIE from the RHSs too -- polymorphic recursion! + -> getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) -> + + -- Create specialisations of functions bound here + bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds -> + + -- We want to keep non-recursive things non-recursive + -- so that we desugar unlifted bindings correctly + if isRec is_rec then + returnM ( + combiner (HsBindGroup + (poly_binds `unionBags` + lie_binds `unionBags` + prag_binds) + [] Recursive) thing + ) + else + 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) -tcBindsAndThen (ThenBinds binds1 binds2) do_next - = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) - `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> +{- + = -- 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) + tcAddScopedTyVars (collectSigTysFromHsBinds (bagToList binds)) $ + + tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) -> + + 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 + -- + -- Subtle (and ugly) point: furthermore at top level we + -- return the TcLclEnv, which contains the LIE var; we + -- don't want to return the wrong one! + -> 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 teh bindInstsOfLocalFuns thing + -> getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) -> + + -- Create specialisations of functions bound here + bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds -> + + -- We want to keep non-recursive things non-recursive + -- so that we desugar unlifted bindings correctly + if isRec is_rec then + returnM ( + combiner (HsBindGroup ( + poly_binds `unionBags` + lie_binds `unionBags` + prag_binds) + [] Recursive) thing + ) + else + 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) +-} + where + tc_body poly_ids -- Type check the pragmas and "thing inside" + = -- Extend the environment to bind the new polymorphic Ids + tcExtendLocalValEnv poly_ids $ + + -- Build bindings and IdInfos corresponding to user pragmas + tcSpecSigs sigs `thenM` \ prag_binds -> - returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) + -- Now do whatever happens next, in the augmented envt + do_next `thenM` \ thing -> -tcBindsAndThen (MonoBind bind sigs is_rec) do_next - = tcBindAndThen bind sigs do_next -\end{pseudocode} + returnM (prag_binds, thing) +\end{code} %************************************************************************ @@ -203,140 +274,337 @@ so all the clever stuff is in here. as the Name in the tc_ty_sig \begin{code} -tcBindWithSigs - :: [Name] - -> RenamedMonoBinds - -> [TcSigInfo s] - -> RecFlag - -> (Name -> PragmaInfo) - -> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s]) - -tcBindWithSigs binder_names mbind tc_ty_sigs is_rec prag_info_fn - = recoverTc ( +tcBindWithSigs :: TopLevelFlag + -> LHsBinds Name + -> [LSig Name] + -> RecFlag + -> TcM (LHsBinds TcId, [TcId]) + +tcBindWithSigs top_lvl mbind sigs is_rec + = -- TYPECHECK THE SIGNATURES + recoverM (returnM []) ( + mappM tcTySig [sig | sig@(L _(Sig name _)) <- sigs] + ) `thenM` \ tc_ty_sigs -> + + -- SET UP THE MAIN RECOVERY; take advantage of any type sigs + recoverM ( -- If typechecking the binds fails, then return with each -- signature-less binder given type (forall a.a), to minimise subsequent -- error messages - newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv -> + newTyVar liftedTypeKind `thenM` \ alpha_tv -> let - forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) - poly_ids = map mk_dummy binder_names + forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) + binder_names = collectHsBindBinders 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 -> mkUserId name forall_a_a NoPragmaInfo -- No signature + Just sig -> sig_poly_id sig -- Signature + Nothing -> mkLocalId name forall_a_a -- No signature in - returnTc (EmptyMonoBinds, emptyLIE, poly_ids) - ) $ + traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) `thenM_` + returnM (emptyBag, poly_ids) + ) $ - -- 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 -> - mapNF_Tc mk_mono_id_ty binder_names `thenNF_Tc` \ mono_id_tys -> + -- TYPECHECK THE BINDINGS + traceTc (ptext SLIT("--------------------------------------------------------")) `thenM_` + traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind)) `thenM_` + getLIE (tcMonoBinds mbind tc_ty_sigs is_rec) `thenM` \ ((mbind', bndr_names_w_ids), lie_req) -> let - mono_id_tyvars = tyVarsOfTypes mono_id_tys - mono_ids = zipWith3Equal "tcBindAndSigs" mk_id binder_names uniqs mono_id_tys - mk_id name uniq ty = mkUserLocal (getOccName name) uniq ty (getSrcLoc name) + (binder_names, mono_ids) = unzip (bagToList bndr_names_w_ids) + tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids in - -- TYPECHECK THE BINDINGS - tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) -> + -- GENERALISE + -- (it seems a bit crude to have to do getLIE twice, + -- but I can't see a better way just now) + addSrcSpan (srcLocSpan (minimum (map getSrcLoc binder_names))) $ + -- TODO: location wrong + + addErrCtxt (genCtxt binder_names) $ + getLIE (generalise binder_names mbind tau_tvs lie_req tc_ty_sigs) + `thenM` \ ((tc_tyvars_to_gen, dict_binds, dict_ids), lie_free) -> + + + -- ZONK THE GENERALISED TYPE VARIABLES TO REAL TyVars + -- This commits any unbound kind variables to boxed kind, by unification + -- It's important that the final quanfified type variables + -- are fully zonked, *including boxity*, because they'll be + -- included in the forall types of the polymorphic Ids. + -- At calls of these Ids we'll instantiate fresh type variables from + -- them, and we use their boxity then. + mappM zonkTcTyVarToTyVar tc_tyvars_to_gen `thenM` \ real_tyvars_to_gen -> + + -- ZONK THE Ids + -- It's important that the dict Ids are zonked, including the boxity set + -- in the previous step, because they are later used to form the type of + -- the polymorphic thing, and forall-types must be zonked so far as + -- their bound variables are concerned + mappM zonkId dict_ids `thenM` \ zonked_dict_ids -> + mappM zonkId mono_ids `thenM` \ zonked_mono_ids -> + + -- BUILD THE POLYMORPHIC RESULT IDs + let + exports = zipWith mk_export binder_names zonked_mono_ids + poly_ids = [poly_id | (_, poly_id, _) <- exports] + dict_tys = map idType zonked_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 + + mk_export binder_name zonked_mono_id + = (tyvars, + attachInlinePhase inline_phases poly_id, + zonked_mono_id) + where + (tyvars, poly_id) = + case maybeSig tc_ty_sigs binder_name of + Just sig -> (sig_tvs sig, sig_poly_id sig) + Nothing -> (real_tyvars_to_gen, new_poly_id) + + new_poly_id = mkLocalId binder_name poly_ty + poly_ty = mkForAllTys real_tyvars_to_gen + $ 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. + in + + traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds), + exports, map idType poly_ids)) `thenM_` - -- CHECK THAT THE SIGNATURES MATCH - -- (must do this before getTyVarsToGen) - checkSigMatch tc_ty_sigs `thenTc` \ sig_theta -> + -- Check for an unlifted, non-overloaded group + -- In that case we must make extra checks + if any (isUnLiftedType . idType) zonked_mono_ids && null zonked_dict_ids + then -- Some bindings are unlifted + checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind `thenM_` - -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen - -- The tyvars_not_to_gen are free in the environment, and hence - -- candidates for generalisation, but sometimes the monomorphism - -- restriction means we can't generalise them nevertheless - getTyVarsToGen is_unrestricted mono_id_tyvars lie `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen) -> - - -- DEAL WITH TYPE VARIABLE KINDS - mapTc defaultUncommittedTyVar (tyVarSetToList tyvars_to_gen) `thenTc` \ tyvars_to_gen_list -> - -- It's important that the final list (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. - -- - -- This step can do unification => keep other zonking after this - - -- 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)) - - else - zonk_theta 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 - - -- 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) -> - - ASSERT( not (any (isUnboxedTypeKind . tyVarKind) tyvars_to_gen_list) ) + extendLIEs lie_req `thenM_` + returnM ( + unitBag $ noLoc $ + AbsBinds [] [] exports inlines mbind', + -- Do not generate even any x=y bindings + poly_ids + ) + + else -- The normal case + extendLIEs lie_free `thenM_` + returnM ( + unitBag $ noLoc $ + AbsBinds real_tyvars_to_gen + zonked_dict_ids + exports + inlines + (dict_binds `unionBags` mbind'), + poly_ids + ) + +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) non-polymorphic +-- d) not a multiple-binding group (more or less implied by (a)) + +checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind + = ASSERT( not (any ((eqKind unliftedTypeKind) . tyVarKind) real_tyvars_to_gen) ) -- 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. + -- 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 zonkTcType mono_id_tys `thenNF_Tc` \ zonked_mono_id_types -> - let - exports = zipWith3 mk_export binder_names mono_ids zonked_mono_id_types - dict_tys = map tcIdType dicts_bound + checkTc (isNotTopLevel top_lvl) + (unliftedBindErr "Top-level" mbind) `thenM_` + checkTc (isNonRec is_rec) + (unliftedBindErr "Recursive" mbind) `thenM_` + checkTc (isSingletonBag mbind) + (unliftedBindErr "Multiple" mbind) `thenM_` + checkTc (null real_tyvars_to_gen) + (unliftedBindErr "Polymorphic" mbind) +\end{code} - mk_export binder_name mono_id zonked_mono_id_ty - | maybeToBool maybe_sig = (sig_tyvars, TcId sig_poly_id, TcId mono_id) - | otherwise = (tyvars_to_gen_list, TcId poly_id, TcId mono_id) - where - maybe_sig = maybeSig tc_ty_sigs binder_name - Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _) = maybe_sig - poly_id = mkUserId binder_name poly_ty (prag_info_fn binder_name) - poly_ty = mkForAllTys tyvars_to_gen_list $ mkFunTys dict_tys $ zonked_mono_id_ty - -- It's important to build a fully-zonked poly_ty, because - -- we'll slurp out its free type variables when extending the - -- local environment (tcExtendLocalValEnv); if it's not zonked - -- it appears to have free tyvars that aren't actually free at all. - in - -- BUILD RESULTS - returnTc ( - AbsBinds tyvars_to_gen_list - dicts_bound - exports - (dict_binds `AndMonoBinds` mbind'), - lie_free, - [poly_id | (_, TcId poly_id, _) <- exports] - ) +Polymorphic recursion +~~~~~~~~~~~~~~~~~~~~~ +The game plan for polymorphic recursion in the code above is + + * Bind any variable for which we have a type signature + to an Id with a polymorphic type. Then when type-checking + the RHSs we'll make a full polymorphic call. + +This fine, but if you aren't a bit careful you end up with a horrendous +amount of partial application and (worse) a huge space leak. For example: + + f :: Eq a => [a] -> [a] + f xs = ...f... + +If we don't take care, after typechecking we get + + f = /\a -> \d::Eq a -> let f' = f a d + in + \ys:[a] -> ...f'... + +Notice the the stupid construction of (f a d), which is of course +identical to the function we're executing. In this case, the +polymorphic recursion isn't being used (but that's a very common case). +We'd prefer + + f = /\a -> \d::Eq a -> letrec + fm = \ys:[a] -> ...fm... + in + fm + +This can lead to a massive space leak, from the following top-level defn +(post-typechecking) + + ff :: [Int] -> [Int] + ff = f Int dEqInt + +Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but +f' is another thunk which evaluates to the same thing... and you end +up with a chain of identical values all hung onto by the CAF ff. + + ff = f Int dEqInt + + = let f' = f Int dEqInt in \ys. ...f'... + + = let f' = let f' = f Int dEqInt in \ys. ...f'... + in \ys. ...f'... + +Etc. +Solution: when typechecking the RHSs we always have in hand the +*monomorphic* Ids for each binding. So we just need to make sure that +if (Method f a d) shows up in the constraints emerging from (...f...) +we just use the monomorphic Id. We achieve this by adding monomorphic Ids +to the "givens" when simplifying constraints. That's what the "lies_avail" +is doing. + + +%************************************************************************ +%* * +\subsection{getTyVarsToGen} +%* * +%************************************************************************ + +\begin{code} +generalise binder_names mbind tau_tvs lie_req sigs = + + -- check for -fno-monomorphism-restriction + doptM Opt_NoMonomorphismRestriction `thenM` \ no_MR -> + let is_unrestricted | no_MR = True + | otherwise = isUnRestrictedGroup tysig_names mbind + in + + if not is_unrestricted then -- RESTRICTED CASE + -- Check signature contexts are empty + checkTc (all is_mono_sig sigs) + (restrictedBindCtxtErr binder_names) `thenM_` + + -- Now simplify with exactly that set of tyvars + -- We have to squash those Methods + tcSimplifyRestricted doc tau_tvs lie_req `thenM` \ (qtvs, binds) -> + + -- Check that signature type variables are OK + checkSigsTyVars qtvs sigs `thenM` \ final_qtvs -> + + returnM (final_qtvs, binds, []) + + else if null sigs then -- UNRESTRICTED CASE, NO TYPE SIGS + tcSimplifyInfer doc tau_tvs lie_req + + else -- UNRESTRICTED CASE, WITH TYPE SIGS + -- CHECKING CASE: Unrestricted group, there are type signatures + -- Check signature contexts are identical + checkSigsCtxts sigs `thenM` \ (sig_avails, sig_dicts) -> + + -- Check that the needed dicts can be + -- expressed in terms of the signature ones + tcSimplifyInferCheck doc tau_tvs sig_avails lie_req `thenM` \ (forall_tvs, dict_binds) -> + + -- Check that signature type variables are OK + checkSigsTyVars forall_tvs sigs `thenM` \ final_qtvs -> + + returnM (final_qtvs, dict_binds, sig_dicts) + where - no_of_binders = length binder_names + tysig_names = map (idName . sig_poly_id) sigs + is_mono_sig sig = null (sig_theta sig) - mk_mono_id_ty binder_name = case maybeSig tc_ty_sigs binder_name of - Just (TySigInfo name _ _ _ tau_ty _) -> returnNF_Tc tau_ty -- There's a signature - otherwise -> newTyVarTy kind -- No signature + doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names - tysig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs] - is_unrestricted = isUnRestrictedGroup tysig_names mbind +----------------------- + -- 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 +checkSigsCtxts sigs@(TySigInfo { sig_poly_id = id1, sig_tvs = sig_tvs, sig_theta = theta1, sig_loc = span} + : other_sigs) + = addSrcSpan span $ + mappM_ check_one other_sigs `thenM_` + if null theta1 then + returnM ([], []) -- Non-overloaded type signatures + else + newDicts SignatureOrigin theta1 `thenM` \ sig_dicts -> + 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) + sig_avails = sig_dicts ++ sig_meths + in + returnM (sig_avails, map instToId sig_dicts) + where + sig1_dict_tys = map mkPredTy theta1 + sig_meths = concatMap sig_insts sigs - kind | is_rec = mkBoxedTypeKind -- Recursive, so no unboxed types - | otherwise = mkTypeKind -- Non-recursive, so we permit unboxed types + check_one (TySigInfo {sig_poly_id = id, sig_theta = theta}) + = addErrCtxt (sigContextsCtxt id1 id) $ + checkTc (equalLength theta theta1) sigContextsErr `thenM_` + unifyTauTyLists sig1_dict_tys (map mkPredTy theta) -zonk_theta theta = mapNF_Tc zonk theta - where - zonk (c,t) = zonkTcType t `thenNF_Tc` \ t' -> - returnNF_Tc (c,t') +checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar] +checkSigsTyVars qtvs sigs + = mappM check_one sigs `thenM` \ sig_tvs_s -> + 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 = extendVarSetList sig_tvs qtvs + in + returnM (varSetElems all_tvs) + where + check_one (TySigInfo {sig_poly_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) $ + checkSigTyVarsWrt (idFreeTyVars id) tvs \end{code} -@getImplicitStuffToGen@ decides what type variables generalise over. +@getTyVarsToGen@ decides what type variables to generalise over. For a "restricted group" -- see the monomorphism restriction for a definition -- we bind no dictionaries, and @@ -364,6 +632,8 @@ 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 @@ -374,54 +644,22 @@ constrained tyvars. We don't use any of the results, except to find which tyvars are constrained. \begin{code} -getTyVarsToGen is_unrestricted mono_tyvars lie - = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars -> - zonkTcTyVars mono_tyvars `thenNF_Tc` \ mentioned_tyvars -> - let - 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} - - -\begin{code} isUnRestrictedGroup :: [Name] -- Signatures given for these - -> RenamedMonoBinds + -> LHsBinds Name -> Bool +isUnRestrictedGroup sigs binds = all (unrestricted . unLoc) (bagToList binds) + where + unrestricted (PatBind other _) = False + unrestricted (VarBind v _) = v `is_elem` sigs + unrestricted (FunBind v _ matches) = unrestricted_match matches + || unLoc v `is_elem` sigs + + unrestricted_match (L _ (Match [] _ _) : _) = False + -- No args => like a pattern binding + unrestricted_match other = True + -- Some args => a function binding is_elem v vs = isIn "isUnResMono" v vs - -isUnRestrictedGroup sigs (PatMonoBind (VarPatIn v) _ _) = v `is_elem` sigs -isUnRestrictedGroup sigs (PatMonoBind other _ _) = False -isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs -isUnRestrictedGroup sigs (FunMonoBind _ _ _ _) = True -isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 && - isUnRestrictedGroup sigs mb2 -isUnRestrictedGroup sigs EmptyMonoBinds = True -\end{code} - -@defaultUncommittedTyVar@ checks for generalisation over unboxed -types, and defaults any TypeKind TyVars to BoxedTypeKind. - -\begin{code} -defaultUncommittedTyVar tyvar - | isTypeKind (tyVarKind tyvar) - = newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ boxed_tyvar -> - unifyTauTy (mkTyVarTy boxed_tyvar) (mkTyVarTy tyvar) `thenTc_` - returnTc boxed_tyvar - - | otherwise - = returnTc tyvar \end{code} @@ -435,199 +673,140 @@ defaultUncommittedTyVar tyvar The signatures have been dealt with already. \begin{code} -tcMonoBinds :: RenamedMonoBinds - -> [Name] -> [TcIdBndr s] - -> [TcSigInfo s] - -> TcM s (TcMonoBinds s, LIE s) - -tcMonoBinds mbind binder_names mono_ids tc_ty_sigs - = tcExtendLocalValEnv binder_names mono_ids ( - tc_mono_binds mbind - ) - where - sig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs] - sig_ids = [id | (TySigInfo _ id _ _ _ _) <- tc_ty_sigs] - - tc_mono_binds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE) - - tc_mono_binds (AndMonoBinds mb1 mb2) - = tc_mono_binds mb1 `thenTc` \ (mb1a, lie1) -> - tc_mono_binds mb2 `thenTc` \ (mb2a, lie2) -> - returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2) - - tc_mono_binds (FunMonoBind name inf matches locn) - = tcAddSrcLoc locn $ - tcLookupLocalValueOK "tc_mono_binds" name `thenNF_Tc` \ id -> - - -- Before checking the RHS, extend the envt with - -- bindings for the *polymorphic* Ids from any type signatures - tcExtendLocalValEnv sig_names sig_ids $ - tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) -> - - returnTc (FunMonoBind (TcId id) inf matches' locn, lie) - - tc_mono_binds bind@(PatMonoBind pat grhss_and_binds locn) - = tcAddSrcLoc locn $ - 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) -\end{code} - -%************************************************************************ -%* * -\subsection{Signatures} -%* * -%************************************************************************ - -@tcSigs@ checks the signatures for validity, and returns a list of -{\em freshly-instantiated} signatures. That is, the types are already -split up, and have fresh type variables installed. All non-type-signature -"RenamedSigs" are ignored. - -The @TcSigInfo@ contains @TcTypes@ because they are unified with -the variable's type, and after that checked to see whether they've -been instantiated. - -\begin{code} -data TcSigInfo s - = TySigInfo Name - (TcIdBndr s) -- *Polymorphic* binder for this value... - [TcTyVar s] (TcThetaType s) (TcTauType s) - SrcLoc - - -maybeSig :: [TcSigInfo s] -> Name -> Maybe (TcSigInfo s) - -- Search for a particular signature -maybeSig [] name = Nothing -maybeSig (sig@(TySigInfo sig_name _ _ _ _ _) : sigs) name - | name == sig_name = Just sig - | otherwise = maybeSig sigs name -\end{code} - - -\begin{code} -tcTySig :: (Name -> PragmaInfo) - -> RenamedSig - -> TcM s (TcSigInfo s) - -tcTySig prag_info_fn (Sig v ty src_loc) - = tcAddSrcLoc src_loc $ - tcHsType ty `thenTc` \ sigma_ty -> - tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' -> - let - poly_id = mkUserId v sigma_ty' (prag_info_fn v) - (tyvars', theta', tau') = splitSigmaTy sigma_ty' - -- This splitSigmaTy tries hard to make sure that tau' is a type synonym - -- wherever possible, which can improve interface files. - in - returnTc (TySigInfo v poly_id tyvars' theta' tau' src_loc) -\end{code} - -@checkSigMatch@ does the next step in checking signature matching. -The tau-type part has already been unified. What we do here is to -check that this unification has not over-constrained the (polymorphic) -type variables of the original signature type. - -The error message here is somewhat unsatisfactory, but it'll do for -now (ToDo). - -\begin{code} -checkSigMatch [] - = returnTc (error "checkSigMatch") - -checkSigMatch tc_ty_sigs@( sig1@(TySigInfo _ id1 _ theta1 _ _) : all_sigs_but_first ) - = -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK - -- Doesn't affect substitution - mapTc check_one_sig tc_ty_sigs `thenTc_` - - -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE - -- The type signatures on a mutually-recursive group of definitions - -- must all have the same context (or none). - -- - -- We unify them because, with polymorphic recursion, their types - -- might not otherwise be related. This is a rather subtle issue. - -- ToDo: amplify - mapTc check_one_cxt all_sigs_but_first `thenTc_` - - returnTc theta1 - where - sig1_dict_tys = mk_dict_tys theta1 - n_sig1_dict_tys = length sig1_dict_tys - - check_one_cxt sig@(TySigInfo _ id _ theta _ src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (sigContextsCtxt id1 id) $ - checkTc (length this_sig_dict_tys == n_sig1_dict_tys) - sigContextsErr `thenTc_` - unifyTauTyLists sig1_dict_tys this_sig_dict_tys - where - this_sig_dict_tys = mk_dict_tys theta - - check_one_sig (TySigInfo name id sig_tyvars _ sig_tau src_loc) - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (sigCtxt id) $ - checkSigTyVars sig_tyvars sig_tau - - mk_dict_tys theta = [mkDictTy c t | (c,t) <- theta] -\end{code} - - -@checkSigTyVars@ is used after the type in a type signature has been unified with -the actual type found. It then checks that the type variables of the type signature -are - (a) still all type variables - eg matching signature [a] against inferred type [(p,q)] - [then a will be unified to a non-type variable] - - (b) still all distinct - eg matching signature [(a,b)] against inferred type [(p,p)] - [then a and b will be unified together] - -BUT ACTUALLY THESE FIRST TWO ARE FORCED BY USING DontBind TYVARS - - (c) not mentioned in the environment - eg the signature for f in this: - - g x = ... where - f :: a->[a] - f y = [x,y] - - Here, f is forced to be monorphic by the free occurence of x. - -Before doing this, the substitution is applied to the signature type variable. - -\begin{code} -checkSigTyVars :: [TcTyVar s] -- The original signature type variables - -> TcType s -- signature type (for err msg) - -> TcM s () - -checkSigTyVars sig_tyvars sig_tau - = tcGetGlobalTyVars `thenNF_Tc` \ globals -> +tcMonoBinds :: LHsBinds Name + -> [TcSigInfo] -> RecFlag + -> TcM (LHsBinds TcId, + Bag (Name, -- Bound names + TcId)) -- Corresponding monomorphic bound things + +tcMonoBinds mbinds tc_ty_sigs is_rec + -- Three stages: + -- 1. Check the patterns, building up an environment binding + -- the variables in this group (in the recursive case) + -- 2. Extend the environment + -- 3. Check the RHSs + = mapBagM tc_lbind_pats mbinds `thenM` \ bag_of_pairs -> let - mono_tyvars = filter (`elementOfTyVarSet` globals) sig_tyvars + (complete_it, xve) + = foldrBag combine + (returnM (emptyBag, emptyBag), emptyBag) + bag_of_pairs + combine (complete_it1, xve1) (complete_it2, xve2) + = (complete_it, xve1 `unionBags` xve2) + where + complete_it = complete_it1 `thenM` \ (b1, bs1) -> + complete_it2 `thenM` \ (b2, bs2) -> + returnM (b1 `consBag` b2, bs1 `unionBags` bs2) 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) + tcExtendLocalValEnv2 (bagToList xve) complete_it + where + tc_lbind_pats :: LHsBind Name + -> TcM (TcM (LHsBind TcId, Bag (Name,TcId)), -- Completer + Bag (Name,TcId)) + -- wrapper for tc_bind_pats to deal with the location stuff + tc_lbind_pats (L loc bind) + = addSrcSpan loc $ do + (tc, bag) <- tc_bind_pats bind + return (wrap tc, bag) + where + wrap tc = addSrcSpan loc $ do + (bind, stuff) <- tc + return (L loc bind, stuff) + + + tc_bind_pats :: HsBind Name + -> TcM (TcM (HsBind TcId, Bag (Name,TcId)), -- Completer + Bag (Name,TcId)) + tc_bind_pats (FunBind (L nm_loc name) inf matches) + -- Three cases: + -- a) Type sig supplied + -- b) No type sig and recursive + -- c) No type sig and non-recursive + + | Just sig <- maybeSig tc_ty_sigs name + = let -- (a) There is a type signature + -- Use it for the environment extension, and check + -- the RHS has the appropriate type (with outer for-alls stripped off) + mono_id = sig_mono_id sig + mono_ty = idType mono_id + complete_it = tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' -> + returnM (FunBind (L nm_loc mono_id) inf matches', + unitBag (name, mono_id)) + in + returnM (complete_it, if isRec is_rec then unitBag (name, sig_poly_id sig) + else emptyBag) + + | isRec is_rec + = -- (b) No type signature, and recursive + -- So we must use an ordinary H-M type variable + -- which means the variable gets an inferred tau-type + newLocalName name `thenM` \ mono_name -> + newTyVarTy openTypeKind `thenM` \ mono_ty -> + let + mono_id = mkLocalId mono_name mono_ty + complete_it = tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' -> + returnM (FunBind (L nm_loc mono_id) inf matches', + unitBag (name, mono_id)) + in + returnM (complete_it, unitBag (name, mono_id)) + + | otherwise -- (c) No type signature, and non-recursive + = let -- So we can use a 'hole' type to infer a higher-rank type + complete_it + = newHole `thenM` \ hole -> + tcMatchesFun name matches (Infer hole) `thenM` \ matches' -> + readMutVar hole `thenM` \ fun_ty -> + newLocalName name `thenM` \ mono_name -> + let + mono_id = mkLocalId mono_name fun_ty + in + returnM (FunBind (L nm_loc mono_id) inf matches', + unitBag (name, mono_id)) + in + returnM (complete_it, emptyBag) + + tc_bind_pats bind@(PatBind pat grhss) + = -- Now typecheck the pattern + -- We do now support binding fresh (not-already-in-scope) scoped + -- type variables in the pattern of a pattern binding. + -- For example, this is now legal: + -- (x::a, y::b) = e + -- The type variables are brought into scope in tc_binds_and_then, + -- so we don't have to do anything here. + newHole `thenM` \ hole -> + tcPat tc_pat_bndr pat (Infer hole) `thenM` \ (pat', tvs, ids, lie_avail) -> + readMutVar hole `thenM` \ pat_ty -> + + -- Don't know how to deal with pattern-bound existentials yet + checkTc (isEmptyBag tvs && null lie_avail) + (existentialExplode bind) `thenM_` + + let + complete_it = addErrCtxt (patMonoBindsCtxt bind) $ + tcGRHSsPat grhss (Check pat_ty) `thenM` \ grhss' -> + returnM (PatBind pat' grhss', ids) + in + returnM (complete_it, if isRec is_rec then ids else emptyBag) + + -- tc_pat_bndr is used when dealing with a LHS binder in a pattern. + -- If there was a type sig for that Id, we want to make it much + -- as if that type signature had been on the binder as a SigPatIn. + -- We check for a type signature; if there is one, we use the mono_id + -- from the signature. This is how we make sure the tau part of the + -- signature actually matches the type of the LHS; then tc_bind_pats + -- ensures the LHS and RHS have the same type + + tc_pat_bndr name pat_ty + = case maybeSig tc_ty_sigs name of + Nothing -> newLocalName name `thenM` \ bndr_name -> + tcMonoPatBndr bndr_name pat_ty + + Just sig -> addSrcSpan (srcLocSpan (getSrcLoc name)) $ + -- TODO: location wrong + tcSubPat (idType mono_id) pat_ty `thenM` \ co_fn -> + returnM (co_fn, mono_id) + where + mono_id = sig_mono_id sig \end{code} @@ -637,53 +816,13 @@ 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) - --- For now we just deal with INLINE pragmas -tcPragmaSigs sigs = returnTc (prag_fn, EmptyBinds, emptyLIE ) - where - prag_fn name | any has_inline sigs = IWantToBeINLINEd - | otherwise = NoPragmaInfo - where - has_inline (InlineSig n _) = (n == name) - has_inline other = False - - -{- -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} - -Here are the easy cases for tcPragmaSigs +They look like this: -\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 #-} @@ -706,116 +845,46 @@ 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: + {-# SPECIALISE (f:: TcM (LHsBinds TcId) +tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs) + = -- SPECIALISE f :: forall b. theta => tau = g + addSrcSpan 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) -> + -- Do the rest and combine + tcSpecSigs sigs `thenM` \ binds_rest -> + returnM (binds_rest `snocBag` L loc spec_bind) - -- 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) --} +tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs +tcSpecSigs [] = returnM emptyBag \end{code} - %************************************************************************ %* * \subsection[TcBinds-errors]{Error contexts and messages} @@ -824,72 +893,46 @@ tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc) \begin{code} -patMonoBindsCtxt bind sty - = hang (ptext SLIT("In a pattern binding:")) 4 (ppr sty bind) +patMonoBindsCtxt bind + = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind) ----------------------------------------------- -valSpecSigCtxt v ty sty - = hang (ptext SLIT("In a SPECIALIZE pragma for a value:")) - 4 (sep [(<>) (ppr sty v) (ptext 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 - = hang (ptext SLIT("A type signature is more polymorphic than the inferred type")) - 4 (vcat [text "Some type variables in the inferred type can't be forall'd, namely:", - interpp'SP sty mono_tyvars, - ptext SLIT("Possible cause: the RHS mentions something subject to the monomorphism restriction") - ]) +sigContextsErr = ptext SLIT("Mismatched contexts") ------------------------------------------------ -badMatchErr sig_ty inferred_ty sty - = hang (ptext SLIT("Type signature doesn't match inferred type")) - 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sty sig_ty), - hang (ptext SLIT("Inferred :")) 4 (ppr sty inferred_ty) - ]) +sigContextsCtxt s1 s2 + = vcat [ptext SLIT("When matching the contexts of the signatures for"), + nest 2 (vcat [ppr s1 <+> dcolon <+> ppr (idType s1), + ppr s2 <+> dcolon <+> ppr (idType s2)]), + ptext SLIT("The signature contexts in a mutually recursive group should all be identical")] ----------------------------------------------- -sigCtxt id sty - = sep [ptext SLIT("When checking signature for"), ppr sty id] -sigsCtxt ids sty - = sep [ptext 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 sty - = ptext SLIT("Mismatched contexts") -sigContextsCtxt s1 s2 sty - = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"), - ppr sty s1, ptext SLIT("and"), ppr sty s2]) - 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)")) +existentialExplode mbinds + = hang (vcat [text "My brain just exploded.", + text "I can't handle pattern bindings for existentially-quantified constructors.", + text "In the binding group"]) + 4 (ppr mbinds) ----------------------------------------------- -specGroundnessCtxt - = panic "specGroundnessCtxt" - --------------------------------------------- -specContextGroundnessCtxt -- err_ctxt dicts sty - = panic "specContextGroundnessCtxt" -{- - = hang ( - sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr sty name], - hcat [ptext SLIT(" specialised to the type"), ppr sty spec_ty], - pp_spec_id sty, - ptext SLIT("... not all overloaded type variables were instantiated"), - ptext SLIT("to ground types:")]) - 4 (vcat [hsep [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 -> empty) - ValSpecSpecIdCtxt n ty spec loc -> - (n, ty, loc, - \ sty -> hsep [ptext SLIT("... type of explicit id"), ppr sty spec]) --} +restrictedBindCtxtErr binder_names + = hang (ptext SLIT("Illegal overloaded type signature(s)")) + 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names, + ptext SLIT("that falls under the monomorphism restriction")]) + +genCtxt binder_names + = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names + +-- Used in error messages +-- Use quotes for a single one; they look a bit "busy" for several +pprBinders [bndr] = quotes (ppr bndr) +pprBinders bndrs = pprWithCommas ppr bndrs \end{code} - - - -