X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=5bd9cae2b8644ef751a63b3728b333daabbe4b95;hb=ebf2c80221ccf11aeb7a0a2be27bfc72529855a5;hp=75b3683a5ac7b05e2c146155668038784843ecc3;hpb=1fb1ab5d53a09607e7f6d2450806760688396387;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index 75b3683..5bd9cae 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -1,66 +1,63 @@ % -% (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, tcTopBinds, + tcSpecSigs, tcBindWithSigs ) where -module TcBinds ( tcBindsAndThen, tcPragmaSigs, checkSigTyVars ) where +#include "HsVersions.h" -IMP_Ubiq() +import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun ) +import {-# SOURCE #-} TcExpr ( tcExpr ) -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 CmdLineOpts ( opt_NoMonomorphismRestriction ) +import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), + Match(..), HsMatchContext(..), + collectMonoBinders, andMonoBinds ) +import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds ) +import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet ) import TcMonad -import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..), - newDicts, tyVarsOfInst, instToId +import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..), + newDicts, instToId ) -import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds, - tcGetGlobalTyVars, tcExtendGlobalTyVars +import TcEnv ( tcExtendLocalValEnv, + newSpecPragmaId, newLocalId + ) +import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyCheck, tcSimplifyRestricted, tcSimplifyToDicts ) +import TcMonoType ( tcHsSigType, checkSigTyVars, + TcSigInfo(..), tcTySig, maybeSig, sigCtxt ) -import SpecEnv ( SpecEnv ) -IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds ) -import TcMatches ( tcMatchesFun ) -import TcSimplify ( tcSimplify, tcSimplifyAndCheck ) -import TcMonoType ( tcHsType ) import TcPat ( tcPat ) 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 TcType ( newTyVarTy, newTyVar, + zonkTcTyVarToTyVar + ) +import TcUnify ( unifyTauTy, unifyTauTyLists ) + +import CoreFVs ( idFreeTyVars ) +import Id ( mkLocalId, setInlinePragma ) +import Var ( idType, idName ) +import IdInfo ( InlinePragInfo(..) ) +import Name ( Name, getOccName, getSrcLoc ) +import NameSet +import Type ( mkTyVarTy, tyVarsOfTypes, + mkForAllTys, mkFunTys, tyVarsOfType, + mkPredTy, mkForAllTy, isUnLiftedType, + unliftedTypeKind, liftedTypeKind, openTypeKind ) -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 Var ( tyVarKind ) +import VarSet +import Bag +import Util ( isIn ) +import ListSetOps ( minusList ) +import Maybes ( maybeToBool ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isNotTopLevel ) +import FiniteMap ( listToFM, lookupFM ) +import Outputable \end{code} @@ -96,251 +93,432 @@ 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} +tcTopBinds :: RenamedHsBinds -> TcM ((TcMonoBinds, TcEnv), LIE) +tcTopBinds binds + = tc_binds_and_then TopLevel glue binds $ + tcGetEnv `thenNF_Tc` \ env -> + returnTc ((EmptyMonoBinds, env), emptyLIE) + where + glue is_rec binds1 (binds2, thing) = (binds1 `AndMonoBinds` binds2, thing) -An aside. The original version of @tcBindsAndThen@ which lacks a -combiner function, appears below. Though it is perfectly well -behaved, it cannot be typed by Haskell, because the recursive call is -at a different type to the definition itself. There aren't too many -examples of this, which is why I thought it worth preserving! [SLPJ] -\begin{pseudocode} tcBindsAndThen - :: RenamedHsBinds - -> TcM s (thing, LIE 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) - -tcBindsAndThen (SingleBind bind) do_next - = tcBindAndThen bind [] do_next - -tcBindsAndThen (BindWith bind sigs) do_next - = tcBindAndThen bind sigs do_next + :: (RecFlag -> TcMonoBinds -> thing -> thing) -- Combinator + -> RenamedHsBinds + -> TcM (thing, LIE) + -> TcM (thing, LIE) + +tcBindsAndThen = tc_binds_and_then NotTopLevel + +tc_binds_and_then top_lvl combiner EmptyBinds do_next + = do_next +tc_binds_and_then top_lvl combiner (MonoBind EmptyMonoBinds sigs is_rec) do_next + = do_next + +tc_binds_and_then top_lvl combiner (ThenBinds b1 b2) do_next + = tc_binds_and_then top_lvl combiner b1 $ + tc_binds_and_then top_lvl combiner b2 $ + do_next + +tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next + = -- TYPECHECK THE SIGNATURES + mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs -> + + tcBindWithSigs top_lvl bind tc_ty_sigs + sigs is_rec `thenTc` \ (poly_binds, poly_lie, poly_ids) -> + + -- Extend the environment to bind the new polymorphic Ids + tcExtendLocalValEnv [(idName poly_id, poly_id) | poly_id <- poly_ids] $ + + -- Build bindings and IdInfos corresponding to user pragmas + tcSpecSigs sigs `thenTc` \ (prag_binds, prag_lie) -> -tcBindsAndThen (ThenBinds binds1 binds2) do_next - = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) - `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> + -- Now do whatever happens next, in the augmented envt + do_next `thenTc` \ (thing, thing_lie) -> - returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) -\end{pseudocode} + -- Create specialisations of functions bound here + -- We want to keep non-recursive things non-recursive + -- so that we desugar unlifted bindings correctly + case (top_lvl, is_rec) of + + -- For the top level don't bother will all this bindInstsOfLocalFuns stuff + -- All the top level things are rec'd together anyway, so it's fine to + -- leave them to the tcSimplifyTop, and quite a bit faster too + (TopLevel, _) + -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing, + thing_lie `plusLIE` prag_lie `plusLIE` poly_lie) + + (NotTopLevel, NonRecursive) + -> bindInstsOfLocalFuns + (thing_lie `plusLIE` prag_lie) + poly_ids `thenTc` \ (thing_lie', lie_binds) -> + + returnTc ( + combiner NonRecursive poly_binds $ + combiner NonRecursive prag_binds $ + combiner Recursive lie_binds $ + -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns + -- aren't guaranteed in dependency order (though we could change + -- that); hence the Recursive marker. + thing, + + thing_lie' `plusLIE` poly_lie + ) + + (NotTopLevel, Recursive) + -> bindInstsOfLocalFuns + (thing_lie `plusLIE` poly_lie `plusLIE` prag_lie) + poly_ids `thenTc` \ (final_lie, lie_binds) -> + + returnTc ( + combiner Recursive ( + poly_binds `andMonoBinds` + lie_binds `andMonoBinds` + prag_binds) thing, + final_lie + ) +\end{code} %************************************************************************ %* * -\subsection{tcBindWithSigsAndThen} +\subsection{tcBindWithSigs} %* * %************************************************************************ -@tcBindAndThen@ deals with one binding group and the thing it scopes over. +@tcBindWithSigs@ deals with a single binding group. It does generalisation, +so all the clever stuff is in here. + +* binder_names and mbind must define the same set of Names + +* The Names in tc_ty_sigs must be a subset of binder_names + +* The Ids in tc_ty_sigs don't necessarily have to have the same name + as the Name in the tc_ty_sig \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 ( +tcBindWithSigs + :: TopLevelFlag + -> RenamedMonoBinds + -> [TcSigInfo] + -> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs + -> RecFlag + -> TcM (TcMonoBinds, LIE, [TcId]) + +tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec + = recoverTc ( -- If typechecking the binds fails, then return with each - -- binder given type (forall a.a), to minimise subsequent + -- signature-less binder given type (forall a.a), to minimise subsequent -- error messages - newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv -> + newTyVar liftedTypeKind `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] + forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) + binder_names = collectMonoBinders mbind + poly_ids = map mk_dummy binder_names + mk_dummy name = case maybeSig tc_ty_sigs name of + Just (TySigInfo _ poly_id _ _ _ _ _ _) -> poly_id -- Signature + Nothing -> mkLocalId name forall_a_a -- No signature in - -- Extend the environment to bind the new polymorphic Ids - -- and do the thing inside - tcExtendLocalValEnv binder_names poly_ids $ - do_next - ) $ + returnTc (EmptyMonoBinds, emptyLIE, poly_ids) + ) $ - 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) -> + -- TYPECHECK THE BINDINGS + tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) -> + let + tau_tvs = varSetElems (foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids) + in - -- Extend the environment to bind the new polymorphic Ids - tcExtendLocalValEnv binder_names poly_ids $ + -- GENERALISE + generalise binder_names mbind tau_tvs lie_req tc_ty_sigs + `thenTc` \ (tc_tyvars_to_gen, lie_free, dict_binds, dict_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) -> + -- 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. + mapNF_Tc zonkTcTyVarToTyVar tc_tyvars_to_gen `thenNF_Tc` \ real_tyvars_to_gen -> - -- Create specialisations of functions bound here - bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie) - poly_ids `thenTc` \ (lie2, inst_mbinds) -> + -- 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 + mapNF_Tc zonkId dict_ids `thenNF_Tc` \ zonked_dict_ids -> + mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids -> + + -- CHECK FOR BOGUS UNLIFTED BINDINGS + checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids `thenTc_` - -- All done + -- BUILD THE POLYMORPHIC RESULT IDs let - final_lie = lie2 `plusLIE` poly_lie - final_binds = poly_binds `ThenBinds` - SingleBind (NonRecBind inst_mbinds) `ThenBinds` - prag_binds + exports = zipWith mk_export binder_names zonked_mono_ids + dict_tys = map idType zonked_dict_ids + + inlines = mkNameSet [name | InlineSig name _ loc <- inline_sigs] + no_inlines = listToFM ([(name, IMustNotBeINLINEd False phase) | NoInlineSig name phase loc <- inline_sigs] ++ + [(name, IMustNotBeINLINEd True phase) | InlineSig name phase loc <- inline_sigs, maybeToBool phase]) + -- "INLINE n foo" means inline foo, but not until at least phase n + -- "NOINLINE n foo" means don't inline foo until at least phase n, and even + -- then only if it is small enough etc. + -- "NOINLINE foo" means don't inline foo ever, which we signal with a (IMustNotBeINLINEd Nothing) + -- See comments in CoreUnfold.blackListed for the Authorised Version + + mk_export binder_name zonked_mono_id + = (tyvars, + attachNoInlinePrag no_inlines poly_id, + zonked_mono_id) + where + (tyvars, poly_id) = + case maybeSig tc_ty_sigs binder_name of + Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) -> + (sig_tyvars, sig_poly_id) + Nothing -> (real_tyvars_to_gen, 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 - returnTc (prag_info_fn, (combiner final_binds thing, final_lie, thing_ty)) - ) `thenTc` \ (_, result) -> - returnTc result + + traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds), + exports, [idType poly_id | (_, poly_id, _) <- exports])) `thenTc_` + + -- BUILD RESULTS + returnTc ( + AbsBinds real_tyvars_to_gen + zonked_dict_ids + exports + inlines + (dict_binds `andMonoBinds` mbind'), + lie_free, + [poly_id | (_, poly_id, _) <- exports] + ) + +attachNoInlinePrag no_inlines bndr + = case lookupFM no_inlines (idName bndr) of + Just prag -> bndr `setInlinePragma` prag + Nothing -> bndr + +checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids + = ASSERT( not (any ((== 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. + -- That's why we just use an ASSERT here. + + -- Check that pattern-bound variables are not unlifted + (if or [ (idName id `elem` pat_binders) && isUnLiftedType (idType id) + | id <- zonked_mono_ids ] then + addErrTc (unliftedBindErr "Pattern" mbind) + else + returnTc () + ) `thenTc_` + + -- Unlifted bindings must be non-recursive, + -- not top level, non-polymorphic, and not pattern bound + if any (isUnLiftedType . idType) zonked_mono_ids then + checkTc (isNotTopLevel top_lvl) + (unliftedBindErr "Top-level" mbind) `thenTc_` + checkTc (isNonRec is_rec) + (unliftedBindErr "Recursive" mbind) `thenTc_` + checkTc (null real_tyvars_to_gen) + (unliftedBindErr "Polymorphic" mbind) + else + returnTc () + where - binder_names = map fst (bagToList (collectBinders bind)) + pat_binders :: [Name] + pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds) + + justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds + justPatBindings (AndMonoBinds b1 b2) binds = + justPatBindings b1 (justPatBindings b2 binds) + justPatBindings other_bind binds = binds \end{code} -%************************************************************************ -%* * -\subsection{tcBindWithSigs} -%* * -%************************************************************************ +Polymorphic recursion +~~~~~~~~~~~~~~~~~~~~~ +The game plan for polymorphic recursion in the code above is -@tcBindWithSigs@ deals with a single binding group. It does generalisation, -so all the clever stuff is in here. + * 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. -\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 +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: - -- TYPECHECK THE SIGNATURES - mapTc tcTySig ty_sigs `thenTc` \ tc_ty_sigs -> + f :: Eq a => [a] -> [a] + f xs = ...f... - -- TYPECHECK THE BINDINGS - tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) -> +If we don't take care, after typechecking we get - -- 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 + 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 - -- 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)) +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. - 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 + ff = f Int dEqInt - -- 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) + = let f' = f Int dEqInt in \ys. ...f'... - ) `thenTc` \ (lie_free, dict_binds, dicts_bound) -> + = let f' = let f' = f Int dEqInt in \ys. ...f'... + in \ys. ...f'... - -- DEAL WITH TYPE VARIABLE KINDS - defaultUncommittedTyVars tyvars_to_gen_list `thenTc_` +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. - -- BUILD THE POLYMORPHIC RESULT IDs + +%************************************************************************ +%* * +\subsection{getTyVarsToGen} +%* * +%************************************************************************ + +\begin{code} +generalise_help doc tau_tvs lie_req sigs + +----------------------- + | null sigs + = -- INFERENCE CASE: Unrestricted group, no type signatures + tcSimplifyInfer doc + tau_tvs lie_req + +----------------------- + | otherwise + = -- CHECKING CASE: Unrestricted group, there are type signatures + -- Check signature contexts are empty + checkSigsCtxts sigs `thenTc` \ (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 `thenTc` \ (forall_tvs, lie_free, dict_binds) -> + + -- Check that signature type variables are OK + checkSigsTyVars sigs `thenTc_` + + returnTc (forall_tvs, lie_free, dict_binds, sig_dicts) + +generalise binder_names mbind tau_tvs lie_req sigs + | is_unrestricted -- UNRESTRICTED CASE + = generalise_help doc tau_tvs lie_req sigs + + | otherwise -- RESTRICTED CASE + = -- Do a simplification to decide what type variables + -- are constrained. We can't just take the free vars + -- of lie_req because that'll have methods that may + -- incidentally mention entirely unconstrained variables + -- e.g. a call to f :: Eq a => a -> b -> b + -- Here, b is unconstrained. A good example would be + -- foo = f (3::Int) + -- We want to infer the polymorphic type + -- foo :: forall b. b -> b + generalise_help doc tau_tvs lie_req sigs `thenTc` \ (forall_tvs, lie_free, dict_binds, dict_ids) -> + + -- Check signature contexts are empty + checkTc (null sigs || null dict_ids) + (restrictedBindCtxtErr binder_names) `thenTc_` + + -- Identify constrained tyvars 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) + constrained_tvs = varSetElems (tyVarsOfTypes (map idType dict_ids)) + -- The dict_ids are fully zonked + final_forall_tvs = forall_tvs `minusList` constrained_tvs 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 = [] + -- Now simplify with exactly that set of tyvars + -- We have to squash those Methods + tcSimplifyRestricted doc final_forall_tvs [] lie_req `thenTc` \ (lie_free, binds) -> + + returnTc (final_forall_tvs, lie_free, binds, []) - 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) - 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 - ) where - no_of_binders = length binder_names + is_unrestricted | opt_NoMonomorphismRestriction = True + | otherwise = isUnRestrictedGroup tysig_names mbind - is_rec_bind = case bind of - NonRecBind _ -> False - RecBind _ -> True + tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- sigs] - mbind = case bind of - NonRecBind mb -> mb - RecBind mb -> mb + doc | null sigs = ptext SLIT("banding(s) for") <+> pprBinders binder_names + | otherwise = ptext SLIT("type signature(s) for") <+> pprBinders binder_names - ty_sigs = [sig | sig@(Sig name _ _) <- sigs] - tysig_names = [name | (Sig name _ _) <- 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 _ id1 sig_tvs theta1 _ _ _ _ : other_sigs) + = mapTc_ check_one other_sigs `thenTc_` + if null theta1 then + returnTc ([], []) -- Non-overloaded type signatures + else + newDicts SignatureOrigin theta1 `thenNF_Tc` \ 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 + returnTc (sig_avails, map instToId sig_dicts) + where + sig1_dict_tys = map mkPredTy theta1 + n_sig1_theta = length theta1 + sig_meths = concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs] - kind | is_rec_bind = mkBoxedTypeKind -- Recursive, so no unboxed types - | otherwise = mkTypeKind -- Non-recursive, so we permit unboxed types + check_one sig@(TySigInfo _ id _ theta _ _ _ src_loc) + = tcAddSrcLoc src_loc $ + tcAddErrCtxt (sigContextsCtxt id1 id) $ + checkTc (length theta == n_sig1_theta) sigContextsErr `thenTc_` + unifyTauTyLists sig1_dict_tys (map mkPredTy theta) - wrap_it mbind | is_rec_bind = RecBind mbind - | otherwise = NonRecBind mbind +checkSigsTyVars sigs = mapTc_ check_one sigs + where + check_one (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc) + = tcAddSrcLoc src_loc $ + tcAddErrCtxtM (sigCtxt (sig_msg id) sig_tyvars sig_theta sig_tau) $ + checkSigTyVars sig_tyvars (idFreeTyVars id) + sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id) \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 @@ -368,6 +546,8 @@ 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 @@ -378,62 +558,22 @@ constrained tyvars. We don't use any of the results, except to find which tyvars are constrained. \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} - - -\begin{code} isUnRestrictedGroup :: [Name] -- Signatures given for these -> RenamedMonoBinds -> Bool is_elem v vs = isIn "isUnResMono" v vs -isUnRestrictedGroup sigs (PatMonoBind (VarPatIn v) _ _) = v `is_elem` sigs -isUnRestrictedGroup sigs (PatMonoBind other _ _) = False +isUnRestrictedGroup sigs (PatMonoBind other _ _) = False isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs -isUnRestrictedGroup sigs (FunMonoBind _ _ _ _) = True +isUnRestrictedGroup sigs (FunMonoBind v _ matches _) = any isUnRestrictedMatch matches || + v `is_elem` sigs isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 && isUnRestrictedGroup sigs mb2 isUnRestrictedGroup sigs EmptyMonoBinds = True -\end{code} - -@defaultUncommittedTyVars@ checks for generalisation over unboxed -types, and defaults any TypeKind TyVars to BoxedTypeKind. -\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 - - box_it tyvar = newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ boxed_ty -> - unifyTauTy boxed_ty (mkTyVarTy tyvar) +isUnRestrictedMatch (Match _ [] Nothing _) = False -- No args, no signature +isUnRestrictedMatch other = True -- Some args or a signature \end{code} @@ -448,180 +588,126 @@ 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 -\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). - -\begin{code} -checkSigMatch binder_names_w_mono_isd [] - = returnTc (error "checkSigMatch") - -checkSigMatch binder_names_w_mono_ids tc_ty_sigs - = - - -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK - -- Doesn't affect substitution - mapTc check_one_sig tc_ty_sigs `thenTc_` + -> [TcSigInfo] + -> RecFlag + -> TcM (TcMonoBinds, + LIE, -- LIE required + [Name], -- Bound names + [TcId]) -- Corresponding monomorphic bound things + +tcMonoBinds mbinds tc_ty_sigs is_rec + = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) -> + let + id_list = bagToList ids + (names, mono_ids) = unzip id_list + + -- This last defn is the key one: + -- extend the val envt with bindings for the + -- things bound in this group, overriding the monomorphic + -- ids with the polymorphic ones from the pattern + extra_val_env = case is_rec of + Recursive -> map mk_bind id_list + NonRecursive -> [] + in + -- Don't know how to deal with pattern-bound existentials yet + checkTc (isEmptyBag tvs && isEmptyBag lie_avail) + (existentialExplode mbinds) `thenTc_` + + -- *Before* checking the RHSs, but *after* checking *all* the patterns, + -- extend the envt with bindings for all the bound ids; + -- and *then* override with the polymorphic Ids from the signatures + -- That is the whole point of the "complete_it" stuff. + -- + -- There's a further wrinkle: we have to delay extending the environment + -- until after we've dealt with any pattern-bound signature type variables + -- Consider f (x::a) = ...f... + -- We're going to check that a isn't unified with anything in the envt, + -- so f itself had better not be! So we pass the envt binding f into + -- complete_it, which extends the actual envt in TcMatches.tcMatch, after + -- dealing with the signature tyvars - -- 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_` + complete_it extra_val_env `thenTc` \ (mbinds', lie_req_rhss) -> - returnTc theta + returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids) 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} - - -@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 () + -- This function is used when dealing with a LHS binder; + -- we make a monomorphic version of the Id. + -- 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 maatches the type of the LHS; then tc_mb_pats + -- ensures the LHS and RHS have the same type + + tc_pat_bndr name pat_ty + = case maybeSig tc_ty_sigs name of + Nothing + -> newLocalId (getOccName name) pat_ty (getSrcLoc name) + + Just (TySigInfo _ _ _ _ _ mono_id _ _) + -> tcAddSrcLoc (getSrcLoc name) $ + unifyTauTy (idType mono_id) pat_ty `thenTc_` + returnTc mono_id + + mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of + Nothing -> (name, mono_id) + Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id) + + tc_mb_pats EmptyMonoBinds + = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE) + + tc_mb_pats (AndMonoBinds mb1 mb2) + = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) -> + tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) -> + let + complete_it xve = complete_it1 xve `thenTc` \ (mb1', lie1) -> + complete_it2 xve `thenTc` \ (mb2', lie2) -> + returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2) + in + returnTc (complete_it, + lie_req1 `plusLIE` lie_req2, + tvs1 `unionBags` tvs2, + ids1 `unionBags` ids2, + lie_avail1 `plusLIE` lie_avail2) + + tc_mb_pats (FunMonoBind name inf matches locn) + = newTyVarTy kind `thenNF_Tc` \ bndr_ty -> + tc_pat_bndr name bndr_ty `thenTc` \ bndr_id -> + let + complete_it xve = tcAddSrcLoc locn $ + tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) -> + returnTc (FunMonoBind bndr_id inf matches' locn, lie) + in + returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE) + + tc_mb_pats bind@(PatMonoBind pat grhss locn) + = tcAddSrcLoc locn $ + newTyVarTy kind `thenNF_Tc` \ pat_ty -> + + -- Now typecheck the pattern + -- We don't support binding fresh type variables in the + -- pattern of a pattern binding. For example, this is illegal: + -- (x::a, y::b) = e + -- whereas this is ok + -- (x::Int, y::Bool) = e + -- + -- We don't check explicitly for this problem. Instead, we simply + -- type check the pattern with tcPat. If the pattern mentions any + -- fresh tyvars we simply get an out-of-scope type variable error + tcPat tc_pat_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) -> + let + complete_it xve = tcAddSrcLoc locn $ + tcAddErrCtxt (patMonoBindsCtxt bind) $ + tcExtendLocalValEnv xve $ + tcGRHSs grhss pat_ty PatBindRhs `thenTc` \ (grhss', lie) -> + returnTc (PatMonoBind pat' grhss' locn, lie) + in + returnTc (complete_it, lie_req, tvs, ids, lie_avail) -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) + -- Figure out the appropriate kind for the pattern, + -- and generate a suitable type variable + kind = case is_rec of + Recursive -> liftedTypeKind -- Recursive, so no unlifted types + NonRecursive -> openTypeKind -- Non-recursive, so we permit unlifted types \end{code} @@ -631,45 +717,13 @@ 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 #-} @@ -692,113 +746,41 @@ 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 (TcMonoBinds, LIE) +tcSpecSigs (SpecSig name poly_ty src_loc : sigs) + = -- SPECIALISE f :: forall b. theta => tau = g + tcAddSrcLoc src_loc $ + tcAddErrCtxt (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 - - -- Check that the SPECIALIZE pragma had an empty context - checkTc (null sig_theta) - (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_` - - -- Get and instantiate the type of the id mentioned - tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id -> - tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty -> - let - (main_tyvars, main_rho) = splitForAllTy main_ty - (main_theta,main_tau) = splitRhoTy main_rho - main_arg_tys = mkTyVarTys main_tyvars - 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) + tcHsSigType poly_ty `thenTc` \ sig_ty -> - Just spec_name -> -- Use spec_name as the specialisation value ... + -- Check that f has a more general type, and build a RHS for + -- the spec-pragma-id at the same time + tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) -> - -- Type check a simple occurrence of the specialised Id - tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) -> + -- Squeeze out any Methods (see comments with tcSimplifyToDicts) + tcSimplifyToDicts spec_lie `thenTc` \ (spec_dicts, spec_binds) -> - -- 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_` + -- Just specialise "f" by building a SpecPragmaId binding + -- It is the thing that makes sure we don't prematurely + -- dead-code-eliminate the binding we are really interested in. + newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_id -> - -- Make a local SpecId to bind to applied spec_id - newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id -> + -- Do the rest and combine + tcSpecSigs sigs `thenTc` \ (binds_rest, lie_rest) -> + returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr), + lie_rest `plusLIE` mkLIE spec_dicts) - 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 [] = returnTc (EmptyMonoBinds, emptyLIE) \end{code} @@ -810,78 +792,40 @@ 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) +patMonoBindsCtxt bind + = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind) ----------------------------------------------- -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") - ]) +sigContextsErr = ptext SLIT("Mismatched contexts") ------------------------------------------------ -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) - ]) +sigContextsCtxt s1 s2 + = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"), + quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)]) + 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)")) ----------------------------------------------- -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")]) +-- Used in error messages +pprBinders bndrs = braces (pprWithCommas ppr bndrs) +\end{code}