X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcBinds.lhs;h=f308e330eefc7afeb6f48f087a87b155d01be95b;hb=1c3601593186639f1086bc402582ff56fd3fe9f8;hp=1631365ed65dbc81e30f82cc50d64e98aaf910df;hpb=e7d21ee4f8ac907665a7e170c71d59e13a01da09;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs index 1631365..f308e33 100644 --- a/ghc/compiler/typecheck/TcBinds.lhs +++ b/ghc/compiler/typecheck/TcBinds.lhs @@ -1,75 +1,67 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcBinds]{TcBinds} \begin{code} -#include "HsVersions.h" +module TcBinds ( tcBindsAndThen, tcTopBindsAndThen, + tcSpecSigs, tcBindWithSigs ) where -module TcBinds ( - tcTopBindsAndThen, tcLocalBindsAndThen - ) where +#include "HsVersions.h" ---IMPORT_Trace -- ToDo:rm (debugging) +import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun ) +import {-# SOURCE #-} TcExpr ( tcExpr ) -import TcMonad -- typechecking monad machinery -import TcMonadFns ( newLocalsWithOpenTyVarTys, - newLocalsWithPolyTyVarTys, - newSpecPragmaId, newSpecId, - applyTcSubstAndCollectTyVars +import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), StmtCtxt(..), + Match(..), collectMonoBinders, andMonoBinds ) -import AbsSyn -- the stuff being typechecked +import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds ) +import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet ) -import AbsUniType ( isTyVarTy, isGroundTy, isUnboxedDataType, - isGroundOrTyVarTy, extractTyVarsFromTy, - UniType +import TcMonad +import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..), + newDicts, tyVarsOfInst, instToId, + getAllFunDepsOfLIE, getIPsOfLIE, zonkFunDeps ) -import BackSubst ( applyTcSubstToBinds ) -import E -import Errors ( topLevelUnboxedDeclErr, specGroundnessErr, - specCtxtGroundnessErr, Error(..), UnifyErrContext(..) +import TcEnv ( tcExtendLocalValEnv, + newSpecPragmaId, newLocalId, + tcLookupTyCon, + tcGetGlobalTyVars, tcExtendGlobalTyVars ) -import GenSpecEtc ( checkSigTyVars, genBinds, SignatureInfo(..) ) -import Id ( getIdUniType, mkInstId ) -import IdInfo ( SpecInfo(..) ) -import Inst -import LIE ( nullLIE, mkLIE, plusLIE, LIE ) -import Maybes ( assocMaybe, catMaybes, Maybe(..) ) -import Spec ( specTy ) -import TVE ( nullTVE, TVE(..), UniqFM ) -import TcMonoBnds ( tcMonoBinds ) -import TcPolyType ( tcPolyType ) +import TcSimplify ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts ) +import TcImprove ( tcImprove ) +import TcMonoType ( tcHsSigType, checkSigTyVars, + TcSigInfo(..), tcTySig, maybeSig, sigCtxt + ) +import TcPat ( tcPat ) import TcSimplify ( bindInstsOfLocalFuns ) -import Unify ( unifyTauTy ) -import UniqFM ( emptyUFM ) -- profiling, pragmas only -import Util +import TcType ( TcThetaType, newTyVarTy, newTyVar, + zonkTcTypes, zonkTcThetaType, zonkTcTyVarToTyVar + ) +import TcUnify ( unifyTauTy, unifyTauTyLists ) + +import Id ( mkVanillaId, setInlinePragma, idFreeTyVars ) +import Var ( idType, idName ) +import IdInfo ( InlinePragInfo(..) ) +import Name ( Name, getOccName, getSrcLoc ) +import NameSet +import Type ( mkTyVarTy, tyVarsOfTypes, mkTyConApp, + mkForAllTys, mkFunTys, + mkPredTy, mkForAllTy, isUnLiftedType, + isUnboxedType, unboxedTypeKind, boxedTypeKind, openTypeKind + ) +import FunDeps ( tyVarFunDep, oclose ) +import Var ( tyVarKind ) +import VarSet +import Bag +import Util ( isIn ) +import Maybes ( maybeToBool ) +import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNotTopLevel ) +import FiniteMap ( listToFM, lookupFM ) +import PrelNames ( ioTyConKey, mainKey, hasKey ) +import Outputable \end{code} -%************************************************************************ -%* * -\subsection{Type-checking top-level bindings} -%* * -%************************************************************************ - -@tcBindsAndThen@ takes a boolean which indicates whether the binding -group is at top level or not. The difference from inner bindings is -that -\begin{enumerate} -\item -we zero the substitution before each group -\item -we back-substitute after each group. -\end{enumerate} -We still return an LIE, but it is sure to contain nothing but constant -dictionaries, which we resolve at the module level. - -@tcTopBinds@ returns an LVE, not, as you might expect, a GVE. Why? -Because the monomorphism restriction means that is might return some -monomorphic things, with free type variables. Hence it must be an LVE. - -The LIE returned by @tcTopBinds@ may constrain some type variables, -but they are guaranteed to be a subset of those free in the -corresponding returned LVE. %************************************************************************ %* * @@ -77,7 +69,7 @@ corresponding returned LVE. %* * %************************************************************************ -@tcBindsAndThen@ typechecks a @Binds@. The "and then" part is because +@tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because it needs to know something about the {\em usage} of the things bound, so that it can create specialisations of them. So @tcBindsAndThen@ takes a function which, given an extended environment, E, typechecks @@ -88,7 +80,7 @@ specialising the things bound. @tcBindsAndThen@ also takes a "combiner" which glues together the bindings and the "thing" to make a new "thing". -The real work is done by @tcBindAndThen@. +The real work is done by @tcBindWithSigsAndThen@. Recursive and non-recursive binds are handled in essentially the same way: because of uniques there are no scoping issues left. The only @@ -99,55 +91,86 @@ to the LVE for the following reason. When each individual binding is checked the type of its LHS is unified with that of its RHS; and type-checking the LHS of course requires that the binder is in scope. -\begin{code} -tcBindsAndThen - :: Bool - -> E - -> (TypecheckedBinds -> thing -> thing) -- Combinator - -> RenamedBinds - -> (E -> TcM (thing, LIE, thing_ty)) - -> TcM (thing, LIE, thing_ty) - -tcBindsAndThen top_level e combiner EmptyBinds do_next - = do_next e `thenTc` \ (thing, lie, thing_ty) -> - returnTc (combiner EmptyBinds thing, lie, thing_ty) - -tcBindsAndThen top_level e combiner (SingleBind bind) do_next - = tcBindAndThen top_level e combiner bind [] do_next - -tcBindsAndThen top_level e combiner (BindWith bind sigs) do_next - = tcBindAndThen top_level e combiner bind sigs do_next - -tcBindsAndThen top_level e combiner (ThenBinds binds1 binds2) do_next - = tcBindsAndThen top_level e combiner binds1 new_after - where - -- new_after :: E -> TcM (thing, LIE, thing_ty) - -- Can't write this signature, cos it's monomorphic in thing and - -- thing_ty. - new_after e = tcBindsAndThen top_level e combiner binds2 do_next -\end{code} +At the top-level the LIE is sure to contain nothing but constant +dictionaries, which we resolve at the module level. -Simple wrappers for export: \begin{code} -tcTopBindsAndThen - :: E - -> (TypecheckedBinds -> thing -> thing) -- Combinator - -> RenamedBinds - -> (E -> TcM (thing, LIE, anything)) - -> TcM (thing, LIE, anything) - -tcTopBindsAndThen e combiner binds do_next - = tcBindsAndThen True e combiner binds do_next - -tcLocalBindsAndThen - :: E - -> (TypecheckedBinds -> thing -> thing) -- Combinator - -> RenamedBinds - -> (E -> TcM (thing, LIE, thing_ty)) - -> TcM (thing, LIE, thing_ty) - -tcLocalBindsAndThen e combiner binds do_next - = tcBindsAndThen False e combiner binds do_next +tcTopBindsAndThen, tcBindsAndThen + :: (RecFlag -> TcMonoBinds -> thing -> thing) -- Combinator + -> RenamedHsBinds + -> TcM (thing, LIE) + -> TcM (thing, LIE) + +tcTopBindsAndThen = tc_binds_and_then TopLevel +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) -> + + -- Now do whatever happens next, in the augmented envt + do_next `thenTc` \ (thing, thing_lie) -> + + -- Create specialisations of functions bound here + -- We want to keep non-recursive things non-recursive + -- so that we desugar unboxed bindings correctly + case (top_lvl, is_rec) of + + -- For the top level don't bother will all this bindInstsOfLocalFuns stuff + -- All the top level things are rec'd together anyway, so it's fine to + -- leave them to the tcSimplifyTop, and quite a bit faster too + (TopLevel, _) + -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing, + thing_lie `plusLIE` prag_lie `plusLIE` poly_lie) + + (NotTopLevel, NonRecursive) + -> bindInstsOfLocalFuns + (thing_lie `plusLIE` prag_lie) + poly_ids `thenTc` \ (thing_lie', lie_binds) -> + + returnTc ( + combiner NonRecursive poly_binds $ + combiner NonRecursive prag_binds $ + combiner Recursive lie_binds $ + -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns + -- aren't guaranteed in dependency order (though we could change + -- that); hence the Recursive marker. + thing, + + thing_lie' `plusLIE` poly_lie + ) + + (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} An aside. The original version of @tcBindsAndThen@ which lacks a @@ -157,385 +180,766 @@ 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 - :: Bool -> E -> RenamedBinds - -> (E -> TcM (thing, LIE, thing_ty)) - -> TcM ((TypecheckedBinds, thing), LIE, thing_ty) - -tcBindsAndThen top_level e EmptyBinds do_next - = do_next e `thenTc` \ (thing, lie, thing_ty) -> - returnTc ((EmptyBinds, thing), lie, thing_ty) - -tcBindsAndThen top_level e (SingleBind bind) do_next - = tcBindAndThen top_level e bind [] do_next - -tcBindsAndThen top_level e (BindWith bind sigs) do_next - = tcBindAndThen top_level e bind sigs do_next - -tcBindsAndThen top_level e (ThenBinds binds1 binds2) do_next - = tcBindsAndThen top_level e binds1 new_after - `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> - - returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) - - where - -- new_after :: E -> TcM ((TypecheckedBinds, thing), LIE, thing_ty) - -- Can't write this signature, cos it's monomorphic in thing and thing_ty - new_after e = tcBindsAndThen top_level e binds2 do_next +% tcBindsAndThen +% :: RenamedHsBinds +% -> TcM (thing, LIE, thing_ty)) +% -> TcM ((TcHsBinds, thing), LIE, thing_ty) +% +% tcBindsAndThen EmptyBinds do_next +% = do_next `thenTc` \ (thing, lie, thing_ty) -> +% returnTc ((EmptyBinds, thing), lie, thing_ty) +% +% tcBindsAndThen (ThenBinds binds1 binds2) do_next +% = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next) +% `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) -> +% +% returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty) +% +% tcBindsAndThen (MonoBind bind sigs is_rec) do_next +% = tcBindAndThen bind sigs do_next \end{pseudocode} + %************************************************************************ %* * -\subsection{Bind} +\subsection{tcBindWithSigs} %* * %************************************************************************ +@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} -tcBindAndThen - :: Bool -- At top level - -> E - -> (TypecheckedBinds -> thing -> thing) -- Combinator - -> RenamedBind -- The Bind to typecheck - -> [RenamedSig] -- ...and its signatures - -> (E -> TcM (thing, LIE, thing_ty)) -- Thing to type check in - -- augmented envt - -> TcM (thing, LIE, thing_ty) -- Results, incl the - -tcBindAndThen top_level e combiner bind sigs do_next - = -- Deal with the bind - tcBind top_level e bind sigs `thenTc` \ (poly_binds, poly_lie, poly_lve) -> +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 + -- signature-less binder given type (forall a.a), to minimise subsequent + -- error messages + newTyVar boxedTypeKind `thenNF_Tc` \ alpha_tv -> + let + forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv) + binder_names = collectMonoBinders mbind + poly_ids = map mk_dummy binder_names + mk_dummy name = case maybeSig tc_ty_sigs name of + Just (TySigInfo _ poly_id _ _ _ _ _ _) -> poly_id -- Signature + Nothing -> mkVanillaId name forall_a_a -- No signature + in + returnTc (EmptyMonoBinds, emptyLIE, poly_ids) + ) $ + + -- TYPECHECK THE BINDINGS + tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) -> + + -- CHECK THAT THE SIGNATURES MATCH + -- (must do this before getTyVarsToGen) + checkSigMatch top_lvl binder_names mono_ids tc_ty_sigs `thenTc` \ maybe_sig_theta -> + + -- IMPROVE the LIE + -- Force any unifications dictated by functional dependencies. + -- Because unification may happen, it's important that this step + -- come before: + -- - computing vars over which to quantify + -- - zonking the generalized type vars + let lie_avail = case maybe_sig_theta of + Nothing -> emptyLIE + Just (_, la) -> la + lie_avail_req = lie_avail `plusLIE` lie_req in + tcImprove lie_avail_req `thenTc_` + + -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen + -- The tyvars_not_to_gen are free in the environment, and hence + -- candidates for generalisation, but sometimes the monomorphism + -- restriction means we can't generalise them nevertheless + let + mono_id_tys = map idType mono_ids + in + getTyVarsToGen is_unrestricted mono_id_tys lie_req `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) -> + + -- Finally, zonk the generalised type variables to real TyVars + -- This commits any unbound kind variables to boxed kind + -- I'm a little worried that such a kind variable might be + -- free in the environment, but I don't think it's possible for + -- this to happen when the type variable is not free in the envt + -- (which it isn't). SLPJ Nov 98 + mapTc zonkTcTyVarToTyVar (varSetElems tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list -> + let + real_tyvars_to_gen = mkVarSet real_tyvars_to_gen_list + -- It's important that the final list + -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully + -- zonked, *including boxity*, because they'll be included in the forall types of + -- the polymorphic Ids, and instances of these Ids will be generated from them. + -- + -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass + -- real_tyvars_to_gen + in - -- Now do whatever happens next, in the augmented envt - do_next (growE_LVE e poly_lve) `thenTc` \ (thing, thing_lie, thing_ty) -> + -- SIMPLIFY THE LIE + tcExtendGlobalTyVars tyvars_not_to_gen ( + let ips = getIPsOfLIE lie_avail_req in + if null real_tyvars_to_gen_list && (null ips || not is_unrestricted) then + -- No polymorphism, and no IPs, so no need to simplify context + returnTc (lie_req, EmptyMonoBinds, []) + else + case maybe_sig_theta of + Nothing -> + -- No signatures, so just simplify the lie + -- NB: no signatures => no polymorphic recursion, so no + -- need to use lie_avail (which will be empty anyway) + tcSimplify (text "tcBinds1" <+> ppr binder_names) + real_tyvars_to_gen lie_req `thenTc` \ (lie_free, dict_binds, lie_bound) -> + returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound)) + + Just (sig_theta, lie_avail) -> + -- There are signatures, and their context is sig_theta + -- Furthermore, lie_avail is an LIE containing the 'method insts' + -- for the things bound here + + zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' -> + newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) -> + -- It's important that sig_theta is zonked, because + -- dict_id is later used to form the type of the polymorphic thing, + -- and forall-types must be zonked so far as their bound variables + -- are concerned + + let + -- The "givens" is the stuff available. We get that from + -- the context of the type signature, BUT ALSO the lie_avail + -- so that polymorphic recursion works right (see comments at end of fn) + givens = dicts_sig `plusLIE` lie_avail + in + + -- Check that the needed dicts can be expressed in + -- terms of the signature ones + tcAddErrCtxt (bindSigsCtxt tysig_names) $ + tcSimplifyAndCheck + (ptext SLIT("type signature for") <+> pprQuotedList binder_names) + real_tyvars_to_gen givens lie_req `thenTc` \ (lie_free, dict_binds) -> + + returnTc (lie_free, dict_binds, dict_ids) + + ) `thenTc` \ (lie_free, dict_binds, dicts_bound) -> + + -- GET THE FINAL MONO_ID_TYS + zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types -> + + + -- CHECK FOR BOGUS UNPOINTED BINDINGS + (if any isUnLiftedType zonked_mono_id_types then + -- Unlifted bindings must be non-recursive, + -- not top level, and non-polymorphic + checkTc (isNotTopLevel top_lvl) + (unliftedBindErr "Top-level" mbind) `thenTc_` + checkTc (case is_rec of {Recursive -> False; NonRecursive -> True}) + (unliftedBindErr "Recursive" mbind) `thenTc_` + checkTc (null real_tyvars_to_gen_list) + (unliftedBindErr "Polymorphic" mbind) + else + returnTc () + ) `thenTc_` + + ASSERT( not (any ((== unboxedTypeKind) . tyVarKind) real_tyvars_to_gen_list) ) + -- The instCantBeGeneralised stuff in tcSimplify should have + -- already raised an error if we're trying to generalise an + -- unboxed tyvar (NB: unboxed tyvars are always introduced + -- along with a class constraint) and it's better done there + -- because we have more precise origin information. + -- That's why we just use an ASSERT here. + + + -- BUILD THE POLYMORPHIC RESULT IDs + mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids -> let - bound_ids = map snd poly_lve + exports = zipWith mk_export binder_names zonked_mono_ids + dict_tys = map idType dicts_bound + + inlines = mkNameSet [name | InlineSig name _ loc <- inline_sigs] + no_inlines = listToFM ([(name, IMustNotBeINLINEd False phase) | NoInlineSig name phase loc <- inline_sigs] ++ + [(name, IMustNotBeINLINEd True phase) | InlineSig name phase loc <- inline_sigs, maybeToBool phase]) + -- "INLINE n foo" means inline foo, but not until at least phase n + -- "NOINLINE n foo" means don't inline foo until at least phase n, and even + -- then only if it is small enough etc. + -- "NOINLINE foo" means don't inline foo ever, which we signal with a (IMustNotBeINLINEd Nothing) + -- See comments in CoreUnfold.blackListed for the Authorised Version + + mk_export binder_name zonked_mono_id + = (tyvars, + attachNoInlinePrag no_inlines poly_id, + zonked_mono_id) + where + (tyvars, poly_id) = + case maybeSig tc_ty_sigs binder_name of + Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) -> + (sig_tyvars, sig_poly_id) + Nothing -> (real_tyvars_to_gen_list, new_poly_id) + + new_poly_id = mkVanillaId binder_name poly_ty + poly_ty = mkForAllTys real_tyvars_to_gen_list + $ mkFunTys dict_tys + $ idType (zonked_mono_id) + -- It's important to build a fully-zonked poly_ty, because + -- we'll slurp out its free type variables when extending the + -- local environment (tcExtendLocalValEnv); if it's not zonked + -- it appears to have free tyvars that aren't actually free + -- at all. + + pat_binders :: [Name] + pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds) in - -- Create specialisations - specialiseBinds bound_ids thing_lie poly_binds poly_lie - `thenNF_Tc` \ (final_binds, final_lie) -> - -- All done - returnTc (combiner final_binds thing, final_lie, thing_ty) + -- CHECK FOR UNBOXED BINDERS IN PATTERN BINDINGS + mapTc (\id -> checkTc (not (idName id `elem` pat_binders + && isUnboxedType (idType id))) + (unboxedPatBindErr id)) zonked_mono_ids + `thenTc_` + + -- BUILD RESULTS + returnTc ( + -- pprTrace "binding.." (ppr ((dicts_bound, dict_binds), exports, [idType poly_id | (_, poly_id, _) <- exports])) $ + AbsBinds real_tyvars_to_gen_list + dicts_bound + exports + inlines + (dict_binds `andMonoBinds` mbind'), + lie_free, + [poly_id | (_, poly_id, _) <- exports] + ) + where + tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- tc_ty_sigs] + is_unrestricted = isUnRestrictedGroup tysig_names mbind + +justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds +justPatBindings (AndMonoBinds b1 b2) binds = + justPatBindings b1 (justPatBindings b2 binds) +justPatBindings other_bind binds = binds + +attachNoInlinePrag no_inlines bndr + = case lookupFM no_inlines (idName bndr) of + Just prag -> bndr `setInlinePragma` prag + Nothing -> bndr \end{code} -\begin{code} -tcBind :: Bool -> E - -> RenamedBind -> [RenamedSig] - -> TcM (TypecheckedBinds, LIE, LVE) -- LIE is a fixed point of substitution +Polymorphic recursion +~~~~~~~~~~~~~~~~~~~~~ +The game plan for polymorphic recursion in the code above is -tcBind False e bind sigs -- Not top level - = tcBind_help False e bind sigs + * 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. -tcBind True e bind sigs -- Top level! - = pruneSubstTc (tvOfE e) ( +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: - -- DO THE WORK - tcBind_help True e bind sigs `thenTc` \ (new_binds, lie, lve) -> + f :: Eq a => [a] -> [a] + f xs = ...f... -{- Top-level unboxed values are now allowed - They will be lifted by the Desugarer (see CoreLift.lhs) +If we don't take care, after typechecking we get - -- CHECK FOR PRIMITIVE TOP-LEVEL BINDS - listTc [ checkTc (isUnboxedDataType (getIdUniType id)) - (topLevelUnboxedDeclErr id (getSrcLoc id)) - | (_,id) <- lve ] `thenTc_` --} + f = /\a -> \d::Eq a -> let f' = f a d + in + \ys:[a] -> ...f'... - -- Back-substitute over the binds, since we are about to discard - -- a good chunk of the substitution. - applyTcSubstToBinds new_binds `thenNF_Tc` \ final_binds -> +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 - -- The lie is already a fixed point of the substitution; it just turns out - -- that almost always this happens automatically, and so we made it part of - -- the specification of genBinds. - returnTc (final_binds, lie, lve) - ) -\end{code} + f = /\a -> \d::Eq a -> letrec + fm = \ys:[a] -> ...fm... + in + fm -\begin{code} -tcBind_help top_level e bind sigs - = -- Create an LVE binding each identifier to an appropriate type variable - new_locals binders `thenNF_Tc` \ bound_ids -> - let lve = binders `zip` bound_ids in - - -- Now deal with type signatures, if any - tcSigs e lve sigs `thenTc` \ sig_info -> - - -- Check the bindings: this is the point at which we can use - -- error recovery. If checking the bind fails we just - -- return the empty bindings. The variables will still be in - -- scope, but bound to completely free type variables, which - -- is just what we want to minimise subsequent error messages. - recoverTc (NonRecBind EmptyMonoBinds, nullLIE) - (tc_bind (growE_LVE e lve) bind) `thenNF_Tc` \ (bind', lie) -> - - -- Notice that genBinds gets the old (non-extended) environment - genBinds top_level e bind' lie lve sig_info `thenTc` \ (binds', lie, lve) -> - - -- Add bindings corresponding to SPECIALIZE pragmas in the code - mapAndUnzipTc (doSpecPragma e lve) (get_spec_pragmas sig_info) - `thenTc` \ (spec_binds_s, spec_lie_s) -> - - returnTc (binds' `ThenBinds` (SingleBind (NonRecBind ( - foldr AndMonoBinds EmptyMonoBinds spec_binds_s))), - lie `plusLIE` (foldr plusLIE nullLIE spec_lie_s), - lve) - where - binders = collectBinders bind +This can lead to a massive space leak, from the following top-level defn +(post-typechecking) - new_locals binders - = case bind of - NonRecBind _ -> -- Recursive, so no unboxed types - newLocalsWithOpenTyVarTys binders + ff :: [Int] -> [Int] + ff = f Int dEqInt - RecBind _ -> -- Non-recursive, so we permit unboxed types - newLocalsWithPolyTyVarTys binders +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. - get_spec_pragmas sig_info - = catMaybes (map get_pragma_maybe sig_info) - where - get_pragma_maybe s@(ValSpecInfo _ _ _ _) = Just s - get_pragma_maybe _ = Nothing -\end{code} + ff = f Int dEqInt -\begin{verbatim} - f :: Ord a => [a] -> b -> b - {-# SPECIALIZE f :: [Int] -> b -> b #-} -\end{verbatim} -We generate: -\begin{verbatim} - f@Int = /\ b -> let d1 = ... - in f Int b d1 + = let f' = f Int dEqInt in \ys. ...f'... + = let f' = let f' = f Int dEqInt in \ys. ...f'... + in \ys. ...f'... - h :: Ord a => [a] -> b -> b - {-# SPECIALIZE h :: [Int] -> b -> b #-} +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. - spec_h = /\b -> h [Int] b dListOfInt - ^^^^^^^^^^^^^^^^^^^^ This bit created by specId -\end{verbatim} + +%************************************************************************ +%* * +\subsection{getTyVarsToGen} +%* * +%************************************************************************ + +@getTyVarsToGen@ decides what type variables to generalise over. + +For a "restricted group" -- see the monomorphism restriction +for a definition -- we bind no dictionaries, and +remove from tyvars_to_gen any constrained type variables + +*Don't* simplify dicts at this point, because we aren't going +to generalise over these dicts. By the time we do simplify them +we may well know more. For example (this actually came up) + f :: Array Int Int + f x = array ... xs where xs = [1,2,3,4,5] +We don't want to generate lots of (fromInt Int 1), (fromInt Int 2) +stuff. If we simplify only at the f-binding (not the xs-binding) +we'll know that the literals are all Ints, and we can just produce +Int literals! + +Find all the type variables involved in overloading, the +"constrained_tyvars". These are the ones we *aren't* going to +generalise. We must be careful about doing this: + + (a) If we fail to generalise a tyvar which is not actually + constrained, then it will never, ever get bound, and lands + up printed out in interface files! Notorious example: + instance Eq a => Eq (Foo a b) where .. + Here, b is not constrained, even though it looks as if it is. + Another, more common, example is when there's a Method inst in + the LIE, whose type might very well involve non-overloaded + type variables. + + (b) On the other hand, we mustn't generalise tyvars which are constrained, + because we are going to pass on out the unmodified LIE, with those + tyvars in it. They won't be in scope if we've generalised them. + +So we are careful, and do a complete simplification just to find the +constrained tyvars. We don't use any of the results, except to +find which tyvars are constrained. \begin{code} -doSpecPragma :: E -> LVE - -> SignatureInfo - -> TcM (TypecheckedMonoBinds, LIE) - -doSpecPragma e lve (ValSpecInfo name spec_ty using src_loc) - = let - main_id = assoc "doSpecPragma" lve name - -- Get the parent Id; it should exist (renamer promises...). - - main_id_ty = getIdUniType main_id - main_id_free_tyvars = extractTyVarsFromTy main_id_ty - origin = ValSpecOrigin name src_loc - err_ctxt = ValSpecSigCtxt name spec_ty src_loc +getTyVarsToGen is_unrestricted mono_id_tys lie + = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars -> + zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys -> + let + body_tyvars = tyVarsOfTypes zonked_mono_id_tys `minusVarSet` free_tyvars + fds = getAllFunDepsOfLIE lie in - addSrcLocTc src_loc ( - specTy origin spec_ty `thenNF_Tc` \ (spec_tyvars, spec_dicts, spec_tau) -> - - -- Check that the SPECIALIZE pragma had an empty context - checkTc (not (null spec_dicts)) - (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_` - - -- Make an instance of this id - specTy origin main_id_ty `thenNF_Tc` \ (main_tyvars, main_dicts, main_tau) -> - - -- Check that the specialised type is indeed an instance of - -- the inferred type. - -- The unification should leave all type vars which are - -- currently free in the environment still free, and likewise - -- the signature type vars. - -- The only way type vars free in the envt could possibly be affected - -- is if main_id_ty has free type variables. So we just extract them, - -- and check that they are not constrained in any way by the unification. - applyTcSubstAndCollectTyVars main_id_free_tyvars `thenNF_Tc` \ free_tyvars' -> - unifyTauTy spec_tau main_tau err_ctxt `thenTc_` - checkSigTyVars [] (spec_tyvars ++ free_tyvars') - spec_tau main_tau err_ctxt `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 - applyTcSubstToTyVars main_tyvars `thenNF_Tc` \ main_arg_tys -> - applyTcSubstToInsts main_dicts `thenNF_Tc` \ main_dicts' -> - - checkTc (not (all isGroundOrTyVarTy main_arg_tys)) - (specGroundnessErr err_ctxt main_arg_tys) - `thenTc_` - - checkTc (not (and [isGroundTy ty | (_,ty) <- map getDictClassAndType main_dicts'])) - (specCtxtGroundnessErr err_ctxt main_dicts') - `thenTc_` - - -- Build a suitable binding; depending on whether we were given - -- a value (Maybe Name) to be used as the specialisation. - case using of - Nothing -> - - -- Make a specPragmaId to which to bind the new call-instance - newSpecPragmaId name spec_ty Nothing - `thenNF_Tc` \ pseudo_spec_id -> + if is_unrestricted + then + -- We need to augment the type variables that appear explicitly in + -- the type by those that are determined by the functional dependencies. + -- e.g. suppose our type is C a b => a -> a + -- with the fun-dep a->b + -- Then we should generalise over b too; otherwise it will be + -- reported as ambiguous. + zonkFunDeps fds `thenNF_Tc` \ fds' -> + let tvFundep = tyVarFunDep fds' + extended_tyvars = oclose tvFundep body_tyvars + in + returnNF_Tc (emptyVarSet, extended_tyvars) + else + -- This recover and discard-errs is to avoid duplicate error + -- messages; this, after all, is an "extra" call to tcSimplify + recoverNF_Tc (returnNF_Tc (emptyVarSet, body_tyvars)) $ + discardErrsTc $ + + tcSimplify (text "getTVG") body_tyvars lie `thenTc` \ (_, _, constrained_dicts) -> let - pseudo_bind = VarMonoBind pseudo_spec_id pseudo_rhs - pseudo_rhs = mkTyLam spec_tyvars (mkDictApp (mkTyApp (Var main_id) main_arg_tys) - (map mkInstId main_dicts')) - in - returnTc (pseudo_bind, mkLIE main_dicts') + -- ASSERT: dicts_sig is already zonked! + constrained_tyvars = foldrBag (unionVarSet . tyVarsOfInst) emptyVarSet constrained_dicts + reduced_tyvars_to_gen = body_tyvars `minusVarSet` constrained_tyvars + in + returnTc (constrained_tyvars, reduced_tyvars_to_gen) +\end{code} - Just spec_name -> -- use spec_name as the specialisation value ... - let - spec_id = lookupE_Value e spec_name - spec_id_ty = getIdUniType spec_id - spec_id_free_tyvars = extractTyVarsFromTy spec_id_ty - spec_id_ctxt = ValSpecSpecIdCtxt name spec_ty spec_name src_loc +\begin{code} +isUnRestrictedGroup :: [Name] -- Signatures given for these + -> RenamedMonoBinds + -> Bool + +is_elem v vs = isIn "isUnResMono" v vs + +isUnRestrictedGroup sigs (PatMonoBind other _ _) = False +isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs +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 + +isUnRestrictedMatch (Match _ [] Nothing _) = False -- No args, no signature +isUnRestrictedMatch other = True -- Some args or a signature +\end{code} - spec_tys = map maybe_ty main_arg_tys - maybe_ty ty | isTyVarTy ty = Nothing - | otherwise = Just ty + +%************************************************************************ +%* * +\subsection{tcMonoBind} +%* * +%************************************************************************ + +@tcMonoBinds@ deals with a single @MonoBind@. +The signatures have been dealt with already. + +\begin{code} +tcMonoBinds :: RenamedMonoBinds + -> [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 + + complete_it extra_val_env `thenTc` \ (mbinds', lie_req_rhss) -> + + returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids) + where + + -- This function is used when dealing with a LHS binder; we make a monomorphic + -- version of the Id. We check for type signatures + tc_pat_bndr name pat_ty + = case maybeSig tc_ty_sigs name of + Nothing + -> newLocalId (getOccName name) pat_ty (getSrcLoc name) + + Just (TySigInfo _ _ _ _ _ mono_id _ _) + -> tcAddSrcLoc (getSrcLoc name) $ + unifyTauTy (idType mono_id) pat_ty `thenTc_` + returnTc mono_id + + mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of + Nothing -> (name, mono_id) + Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id) + + tc_mb_pats EmptyMonoBinds + = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE) + + tc_mb_pats (AndMonoBinds mb1 mb2) + = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) -> + tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) -> + let + complete_it xve = complete_it1 xve `thenTc` \ (mb1', lie1) -> + complete_it2 xve `thenTc` \ (mb2', lie2) -> + returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2) in - -- Make an instance of the spec_id - specTy origin spec_id_ty `thenNF_Tc` \ (spec_id_tyvars, spec_id_dicts, spec_id_tau) -> - - -- Check that the specialised type is indeed an instance of - -- the type inferred for spec_id - -- The unification should leave all type vars which are - -- currently free in the environment still free, and likewise - -- the signature type vars. - -- The only way type vars free in the envt could possibly be affected - -- is if spec_id_ty has free type variables. So we just extract them, - -- and check that they are not constrained in any way by the unification. - applyTcSubstAndCollectTyVars spec_id_free_tyvars `thenNF_Tc` \ spec_id_free_tyvars' -> - unifyTauTy spec_tau spec_id_tau spec_id_ctxt `thenTc_` - checkSigTyVars [] (spec_tyvars ++ spec_id_free_tyvars') - spec_tau spec_id_tau spec_id_ctxt `thenTc_` - - -- Check that the type variables of the explicit spec_id 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 - applyTcSubstToTyVars spec_id_tyvars `thenNF_Tc` \ spec_id_arg_tys -> - applyTcSubstToInsts spec_id_dicts `thenNF_Tc` \ spec_id_dicts' -> - - checkTc (not (all isGroundOrTyVarTy spec_id_arg_tys)) - (specGroundnessErr spec_id_ctxt spec_id_arg_tys) - `thenTc_` - - checkTc (not (and [isGroundTy ty | (_,ty) <- map getDictClassAndType spec_id_dicts'])) - (specCtxtGroundnessErr spec_id_ctxt spec_id_dicts') - `thenTc_` - - -- Make a local SpecId to bind to applied spec_id - newSpecId main_id spec_tys spec_ty `thenNF_Tc` \ local_spec_id -> - - -- Make a specPragmaId id with a spec_info for local_spec_id - -- This is bound to local_spec_id - -- The SpecInfo will be extracted by the specialiser and - -- used to create a call instance for main_id (which is - -- extracted from the spec_id) - -- NB: the pseudo_local_id must stay in the scope of main_id !!! + 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 - spec_info = SpecInfo spec_tys (length main_dicts') local_spec_id + complete_it xve = tcAddSrcLoc locn $ + tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) -> + returnTc (FunMonoBind bndr_id inf matches' locn, lie) in - newSpecPragmaId name spec_ty (Just spec_info) `thenNF_Tc` \ pseudo_spec_id -> + 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 - spec_bind = VarMonoBind local_spec_id spec_rhs - spec_rhs = mkTyLam spec_tyvars (mkDictApp (mkTyApp (Var spec_id) spec_id_arg_tys) - (map mkInstId spec_id_dicts')) - pseudo_bind = VarMonoBind pseudo_spec_id (Var local_spec_id) + 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 (spec_bind `AndMonoBinds` pseudo_bind, mkLIE spec_id_dicts') - ) + returnTc (complete_it, lie_req, tvs, ids, lie_avail) + + -- Figure out the appropriate kind for the pattern, + -- and generate a suitable type variable + kind = case is_rec of + Recursive -> boxedTypeKind -- Recursive, so no unboxed types + NonRecursive -> openTypeKind -- Non-recursive, so we permit unboxed types \end{code} -\begin{code} -tc_bind :: E - -> RenamedBind - -> TcM (TypecheckedBind, LIE) +%************************************************************************ +%* * +\subsection{Signatures} +%* * +%************************************************************************ -tc_bind e (NonRecBind mono_binds) - = tcMonoBinds e mono_binds `thenTc` \ (mono_binds2, lie) -> - returnTc (NonRecBind mono_binds2, lie) +@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. -tc_bind e (RecBind mono_binds) - = tcMonoBinds e mono_binds `thenTc` \ (mono_binds2, lie) -> - returnTc (RecBind mono_binds2, lie) -\end{code} +The error message here is somewhat unsatisfactory, but it'll do for +now (ToDo). \begin{code} -specialiseBinds - :: [Id] -- Ids bound in this group - -> LIE -- LIE of scope of these bindings - -> TypecheckedBinds - -> LIE - -> NF_TcM (TypecheckedBinds, LIE) - -specialiseBinds bound_ids lie_of_scope poly_binds poly_lie - = bindInstsOfLocalFuns lie_of_scope bound_ids - `thenNF_Tc` \ (lie2, inst_mbinds) -> - - returnNF_Tc (poly_binds `ThenBinds` (SingleBind (NonRecBind inst_mbinds)), - lie2 `plusLIE` poly_lie) +checkSigMatch :: TopLevelFlag -> [Name] -> [TcId] -> [TcSigInfo] -> TcM (Maybe (TcThetaType, LIE)) +checkSigMatch top_lvl binder_names mono_ids sigs + | main_bound_here + = -- First unify the main_id with IO t, for any old t + tcSetErrCtxt mainTyCheckCtxt ( + tcLookupTyCon ioTyConName `thenTc` \ ioTyCon -> + newTyVarTy boxedTypeKind `thenNF_Tc` \ t_tv -> + unifyTauTy ((mkTyConApp ioTyCon [t_tv])) + (idType main_mono_id) + ) `thenTc_` + + -- Now check the signatures + -- Must do this after the unification with IO t, + -- in case of a silly signature like + -- main :: forall a. a + -- The unification to IO t will bind the type variable 'a', + -- which is just waht check_one_sig looks for + mapTc check_one_sig sigs `thenTc_` + mapTc check_main_ctxt sigs `thenTc_` + + returnTc (Just ([], emptyLIE)) + + | not (null sigs) + = mapTc check_one_sig sigs `thenTc_` + mapTc check_one_ctxt all_sigs_but_first `thenTc_` + returnTc (Just (theta1, sig_lie)) + + | otherwise + = returnTc Nothing -- No constraints from type sigs + + where + (TySigInfo _ id1 _ theta1 _ _ _ _ : all_sigs_but_first) = sigs + + sig1_dict_tys = mk_dict_tys theta1 + n_sig1_dict_tys = length sig1_dict_tys + sig_lie = mkLIE (concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs]) + + maybe_main = find_main top_lvl binder_names mono_ids + main_bound_here = maybeToBool maybe_main + Just main_mono_id = maybe_main + + -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK + -- Doesn't affect substitution + check_one_sig (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc) + = tcAddSrcLoc src_loc $ + tcAddErrCtxtM (sigCtxt (sig_msg id) sig_tyvars sig_theta sig_tau) $ + checkSigTyVars sig_tyvars (idFreeTyVars id) + + + -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE + -- The type signatures on a mutually-recursive group of definitions + -- must all have the same context (or none). + -- + -- We unify them because, with polymorphic recursion, their types + -- might not otherwise be related. This is a rather subtle issue. + -- ToDo: amplify + check_one_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc) + = tcAddSrcLoc src_loc $ + tcAddErrCtxt (sigContextsCtxt id1 id) $ + checkTc (length this_sig_dict_tys == n_sig1_dict_tys) + sigContextsErr `thenTc_` + unifyTauTyLists sig1_dict_tys this_sig_dict_tys + where + this_sig_dict_tys = mk_dict_tys theta + + -- CHECK THAT FOR A GROUP INVOLVING Main.main, all + -- the signature contexts are empty (what a bore) + check_main_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc) + = tcAddSrcLoc src_loc $ + checkTc (null theta) (mainContextsErr id) + + mk_dict_tys theta = map mkPredTy theta + + sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id) + + -- Search for Main.main in the binder_names, return corresponding mono_id + find_main NotTopLevel binder_names mono_ids = Nothing + find_main TopLevel binder_names mono_ids = go binder_names mono_ids + go [] [] = Nothing + go (n:ns) (m:ms) | n `hasKey` mainKey = Just m + | otherwise = go ns ms \end{code} + %************************************************************************ %* * -\subsection{Signatures} +\subsection{SPECIALIZE pragmas} %* * %************************************************************************ -@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 (not @TyVarTemplate@s) -installed. +@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} -tcSigs :: E -> LVE - -> [RenamedSig] - -> TcM [SignatureInfo] - -tcSigs e lve [] = returnTc [] +They look like this: -tcSigs e lve (s:ss) - = tc_sig s `thenTc` \ sig_info1 -> - tcSigs e lve ss `thenTc` \ sig_info2 -> - returnTc (sig_info1 : sig_info2) - where - tc_sig (Sig v ty _ src_loc) -- no interesting pragmas on non-iface sigs - = addSrcLocTc src_loc ( - - babyTcMtoTcM - (tcPolyType (getE_CE e) (getE_TCE e) nullTVE ty) `thenTc` \ sigma_ty -> +\begin{verbatim} + f :: Ord a => [a] -> b -> b + {-# SPECIALIZE f :: [Int] -> b -> b #-} +\end{verbatim} - let val = assoc "tcSigs" lve v in - -- (The renamer/dependency-analyser should have ensured - -- that there are only signatures for which there is a - -- corresponding binding.) +For this we generate: +\begin{verbatim} + f* = /\ b -> let d1 = ... + in f Int b d1 +\end{verbatim} - -- Instantiate the type, and unify with the type variable - -- found in the Id. - specTy SignatureOrigin sigma_ty `thenNF_Tc` \ (tyvars, dicts, tau_ty) -> - unifyTauTy (getIdUniType val) tau_ty - (panic "ToDo: unifyTauTy(tcSigs)") `thenTc_` +where f* is a SpecPragmaId. The **sole** purpose of SpecPragmaIds is to +retain a right-hand-side that the simplifier will otherwise discard as +dead code... the simplifier has a flag that tells it not to discard +SpecPragmaId bindings. - returnTc (TySigInfo val tyvars dicts tau_ty src_loc) - ) +In this case the f* retains a call-instance of the overloaded +function, f, (including appropriate dictionaries) so that the +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. - tc_sig (SpecSig v ty using src_loc) - = addSrcLocTc src_loc ( +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:: +\begin{code} +tcSpecSigs :: [RenamedSig] -> 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 + tcHsSigType poly_ty `thenTc` \ sig_ty -> + + -- Check that f has a more general type, and build a RHS for + -- the spec-pragma-id at the same time + tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) -> + + -- Squeeze out any Methods (see comments with tcSimplifyToDicts) + tcSimplifyToDicts spec_lie `thenTc` \ (spec_lie1, spec_binds) -> + + -- Just specialise "f" by building a SpecPragmaId binding + -- It is the thing that makes sure we don't prematurely + -- dead-code-eliminate the binding we are really interested in. + newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_id -> + + -- Do the rest and combine + tcSpecSigs sigs `thenTc` \ (binds_rest, lie_rest) -> + returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr), + lie_rest `plusLIE` spec_lie1) + +tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs +tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE) +\end{code} - returnTc (ValSpecInfo v sigma_ty using src_loc) - ) - tc_sig (InlineSig v guide locn) - = returnTc (ValInlineInfo v guide locn) +%************************************************************************ +%* * +\subsection[TcBinds-errors]{Error contexts and messages} +%* * +%************************************************************************ - tc_sig (DeforestSig v locn) - = returnTc (ValDeforestInfo v locn) - tc_sig (MagicUnfoldingSig v str locn) - = returnTc (ValMagicUnfoldingInfo v str locn) +\begin{code} +patMonoBindsCtxt bind + = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind) + +----------------------------------------------- +valSpecSigCtxt v ty + = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"), + nest 4 (ppr v <+> dcolon <+> ppr ty)] + +----------------------------------------------- +unboxedPatBindErr id + = ptext SLIT("variable in a lazy pattern binding has unboxed type: ") + <+> quotes (ppr id) + +----------------------------------------------- +bindSigsCtxt ids + = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids + +----------------------------------------------- +sigContextsErr + = ptext SLIT("Mismatched contexts") + +sigContextsCtxt s1 s2 + = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"), + quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)]) + 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)")) + +mainContextsErr id + | id `hasKey` mainKey = ptext SLIT("Main.main cannot be overloaded") + | otherwise + = quotes (ppr id) <+> ptext SLIT("cannot be overloaded") <> char ',' <> -- sigh; workaround for cpp's inability to deal + ptext SLIT("because it is mutually recursive with Main.main") -- with commas inside SLIT strings. + +mainTyCheckCtxt + = hsep [ptext SLIT("When checking that"), quotes (ptext SLIT("main")), + ptext SLIT("has the required type")] + +----------------------------------------------- +unliftedBindErr flavour mbind + = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed")) + 4 (ppr mbind) + +existentialExplode mbinds + = hang (vcat [text "My brain just exploded.", + text "I can't handle pattern bindings for existentially-quantified constructors.", + text "In the binding group"]) + 4 (ppr mbinds) \end{code}