X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=07a1094d58de98b08937c346db5965a070bac90f;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=ffee33901d7d71281e798534a7197629cfb47980;hpb=246dab8d62eaeb3e239c49b69ab3ad95299c1b38;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index ffee339..07a1094 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,44 +4,47 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, - tcStmts, tcStmtsAndThen, tcGRHSs +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + matchCtxt, TcMatchCtxt(..), + tcStmts, tcDoStmts, + tcDoStmt, tcMDoStmt, tcGuardStmt ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcExpr ) - -import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), - MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..), - pprMatch, getMatchLoc, pprMatchContext, isDoExpr, - mkMonoBind, nullMonoBinds, collectSigTysFromPats - ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedMatchContext ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat ) - -import TcMonad -import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) -import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) -import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars ) -import TcPat ( tcPat, tcMonoPatBndr, polyPatSig ) -import TcMType ( newTyVarTy ) -import TcType ( TcType, TcTyVar, tyVarsOfType, - mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind ) -import TcBinds ( tcBindsAndThen ) -import TcUnify ( subFunTy, checkSigTyVars, tcSub, isIdCoercion, (<$>), sigPatCtxt ) -import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr ) + +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), + Match(..), LMatch, GRHSs(..), GRHS(..), + Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), + pprMatch, isIrrefutableHsPat, mkHsCoerce, + pprMatchContext, pprStmtContext, + noSyntaxExpr, matchGroupArity, pprMatches, + ExprCoFn ) + +import TcRnMonad +import TcHsType ( tcPatSig, UserTypeCtxt(..) ) +import Inst ( newMethodFromName ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv, + tcExtendTyVarEnv2 ) +import TcPat ( PatCtxt(..), tcPats, tcPat ) +import TcMType ( newFlexiTyVarTy, newFlexiTyVarTys ) +import TcType ( TcType, TcRhoType, + BoxySigmaType, BoxyRhoType, + mkFunTys, mkFunTy, mkAppTy, mkTyConApp, + liftedTypeKind ) +import TcBinds ( tcLocalBinds ) +import TcUnify ( boxySplitAppTy, boxySplitTyConApp, boxySplitListTy, + subFunTys, tcSubExp, withBox ) +import TcSimplify ( bindInstsOfLocalFuns ) import Name ( Name ) -import TysWiredIn ( boolTy ) -import Id ( idType ) -import BasicTypes ( RecFlag(..) ) -import VarSet -import Var ( Id ) -import Bag -import Util ( isSingleton ) +import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy ) +import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName ) +import Id ( idType, mkLocalId ) +import TyCon ( TyCon ) import Outputable - -import List ( nub ) +import SrcLoc ( Located(..), getLoc ) +import ErrUtils ( Message ) \end{code} %************************************************************************ @@ -56,64 +59,72 @@ is used in error messages. It checks that all the equations have the same number of arguments before using @tcMatches@ to do the work. \begin{code} -tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group - -> Name - -> TcType -- Expected type - -> [RenamedMatch] - -> TcM ([TcMatch], LIE) - -tcMatchesFun xve fun_name expected_ty matches@(first_match:_) - = -- Check that they all have the same no of arguments - -- Set the location to that of the first equation, so that - -- any inter-equation error messages get some vaguely - -- sensible location. Note: we have to do this odd - -- ann-grabbing, because we don't always have annotations in - -- hand when we call tcMatchesFun... - tcAddSrcLoc (getMatchLoc first_match) ( - checkTc (sameNoOfArgs matches) - (varyingArgsErr fun_name matches) - ) `thenTc_` +tcMatchesFun :: Name + -> MatchGroup Name + -> BoxyRhoType -- Expected type of function + -> TcM (ExprCoFn, MatchGroup TcId) -- Returns type of body + +tcMatchesFun fun_name matches exp_ty + = do { -- Check that they all have the same no of arguments + -- Location is in the monad, set the caller so that + -- any inter-equation error messages get some vaguely + -- sensible location. Note: we have to do this odd + -- ann-grabbing, because we don't always have annotations in + -- hand when we call tcMatchesFun... + checkArgs fun_name matches -- ToDo: Don't use "expected" stuff if there ain't a type signature -- because inconsistency between branches -- may show up as something wrong with the (non-existent) type signature - -- No need to zonk expected_ty, because subFunTy does that on the fly - tcMatches xve (FunRhs fun_name) matches expected_ty + -- This is one of two places places we call subFunTys + -- The point is that if expected_y is a "hole", we want + -- to make pat_tys and rhs_ty as "holes" too. + ; subFunTys doc n_pats exp_ty $ \ pat_tys rhs_ty -> + tcMatches match_ctxt pat_tys rhs_ty matches + } + where + doc = ptext SLIT("The equation(s) for") <+> quotes (ppr fun_name) + <+> ptext SLIT("have") <+> speakNOf n_pats (ptext SLIT("argument")) + n_pats = matchGroupArity matches + match_ctxt = MC { mc_what = FunRhs fun_name, mc_body = tcPolyExpr } \end{code} @tcMatchesCase@ doesn't do the argument-count check because the parser guarantees that each equation has exactly one argument. \begin{code} -tcMatchesCase :: [RenamedMatch] -- The case alternatives - -> TcType -- Type of whole case expressions - -> TcM (TcType, -- Inferred type of the scrutinee - [TcMatch], -- Translated alternatives - LIE) - -tcMatchesCase matches expr_ty - = newTyVarTy openTypeKind `thenNF_Tc` \ scrut_ty -> - tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenTc` \ (matches', lie) -> - returnTc (scrut_ty, matches', lie) - -tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE) -tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty +tcMatchesCase :: TcMatchCtxt -- Case context + -> TcRhoType -- Type of scrutinee + -> MatchGroup Name -- The case alternatives + -> BoxyRhoType -- Type of whole case expressions + -> TcM (MatchGroup TcId) -- Translated alternatives + +tcMatchesCase ctxt scrut_ty matches res_ty + = tcMatches ctxt [scrut_ty] res_ty matches + +tcMatchLambda :: MatchGroup Name -> BoxyRhoType -> TcM (ExprCoFn, MatchGroup TcId) +tcMatchLambda match res_ty + = subFunTys doc n_pats res_ty $ \ pat_tys rhs_ty -> + tcMatches match_ctxt pat_tys rhs_ty match + where + n_pats = matchGroupArity match + doc = sep [ ptext SLIT("The lambda expression") + <+> quotes (pprSetDepth 1 $ pprMatches LambdaExpr match), + -- The pprSetDepth makes the abstraction print briefly + ptext SLIT("has") <+> speakNOf n_pats (ptext SLIT("argument"))] + match_ctxt = MC { mc_what = LambdaExpr, + mc_body = tcPolyExpr } \end{code} +@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. \begin{code} -tcMatches :: [(Name,Id)] - -> RenamedMatchContext - -> [RenamedMatch] - -> TcType - -> TcM ([TcMatch], LIE) - -tcMatches xve fun_or_case matches expected_ty - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> - returnTc (matches, plusLIEs lies) +tcGRHSsPat :: GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId) +tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty where - tc_match match = tcMatch xve fun_or_case match expected_ty + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcPolyExpr } \end{code} @@ -124,177 +135,123 @@ tcMatches xve fun_or_case matches expected_ty %************************************************************************ \begin{code} -tcMatch :: [(Name,Id)] - -> RenamedMatchContext - -> RenamedMatch - -> TcType -- Expected result-type of the Match. - -- Early unification with this guy gives better error messages - -- We regard the Match as having type - -- (ty1 -> ... -> tyn -> result_ty) - -- where there are n patterns. - -> TcM (TcMatch, LIE) - -tcMatch xve1 ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty - = tcAddSrcLoc (getMatchLoc match) $ -- At one stage I removed this; - tcAddErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back - - tcMatchPats pats expected_ty tc_grhss `thenTc` \ ((pats', grhss'), lie, ex_binds) -> - returnTc (Match pats' Nothing (glue_on Recursive ex_binds grhss'), lie) - - where - tc_grhss pats' rhs_ty - = tcExtendLocalValEnv xve1 $ - - -- Deal with the result signature - case maybe_rhs_sig of - Nothing -> tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) -> - returnTc ((pats', grhss'), lie) - - Just sig -> tcAddScopedTyVars [sig] $ - -- Bring into scope the type variables in the signature - tcHsSigType ResSigCtxt sig `thenTc` \ sig_ty -> - tcGRHSs ctxt grhss sig_ty `thenTc` \ (grhss', lie1) -> - tcSub rhs_ty sig_ty `thenTc` \ (co_fn, lie2) -> - returnTc ((pats', lift_grhss co_fn rhs_ty grhss'), - lie1 `plusLIE` lie2) - --- lift_grhss pushes the coercion down to the right hand sides, --- because there is no convenient place to hang it otherwise. -lift_grhss co_fn rhs_ty grhss - | isIdCoercion co_fn = grhss -lift_grhss co_fn rhs_ty (GRHSs grhss binds ty) - = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we +tcMatches :: TcMatchCtxt + -> [BoxySigmaType] -- Expected pattern types + -> BoxyRhoType -- Expected result-type of the Match. + -> MatchGroup Name + -> TcM (MatchGroup TcId) + +data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module + = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is + mc_body :: LHsExpr Name -- Type checker for a body of an alternative + -> BoxyRhoType + -> TcM (LHsExpr TcId) } + +tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _) + = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches + ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) } + +------------- +tcMatch :: TcMatchCtxt + -> [BoxySigmaType] -- Expected pattern types + -> BoxyRhoType -- Expected result-type of the Match. + -> LMatch Name + -> TcM (LMatch TcId) + +tcMatch ctxt pat_tys rhs_ty match + = wrapLocM (tc_match ctxt pat_tys rhs_ty) match where - lift_grhs (GRHS stmts loc) = GRHS (map lift_stmt stmts) loc - - lift_stmt (ResultStmt e l) = ResultStmt (co_fn <$> e) l - lift_stmt stmt = stmt - --- glue_on just avoids stupid dross -glue_on _ EmptyMonoBinds grhss = grhss -- The common case -glue_on is_rec mbinds (GRHSs grhss binds ty) - = GRHSs grhss (mkMonoBind mbinds [] is_rec `ThenBinds` binds) ty - - -tcGRHSs :: RenamedMatchContext -> RenamedGRHSs - -> TcType - -> TcM (TcGRHSs, LIE) - -tcGRHSs ctxt (GRHSs grhss binds _) expected_ty - = tcBindsAndThen glue_on binds (tc_grhss grhss) + tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss) + = addErrCtxt (matchCtxt (mc_what ctxt) match) $ + do { (pats', grhss') <- tcPats LamPat pats pat_tys rhs_ty $ + tc_grhss ctxt maybe_rhs_sig grhss + ; returnM (Match pats' Nothing grhss') } + + tc_grhss ctxt Nothing grhss rhs_ty + = tcGRHSs ctxt grhss rhs_ty -- No result signature + + tc_grhss ctxt (Just res_sig) grhss rhs_ty + = do { (inner_ty, sig_tvs) <- tcPatSig ResSigCtxt res_sig rhs_ty + ; tcExtendTyVarEnv2 sig_tvs $ + tcGRHSs ctxt grhss inner_ty } + +------------- +tcGRHSs :: TcMatchCtxt -> GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId) + +-- Notice that we pass in the full res_ty, so that we get +-- good inference from simple things like +-- f = \(x::forall a.a->a) -> +-- We used to force it to be a monotype when there was more than one guard +-- but we don't need to do that any more + +tcGRHSs ctxt (GRHSs grhss binds) res_ty + = do { (binds', grhss') <- tcLocalBinds binds $ + mappM (wrapLocM (tcGRHS ctxt res_ty)) grhss + + ; returnM (GRHSs grhss' binds') } + +------------- +tcGRHS :: TcMatchCtxt -> BoxyRhoType -> GRHS Name -> TcM (GRHS TcId) + +tcGRHS ctxt res_ty (GRHS guards rhs) + = do { (guards', rhs') <- tcStmts stmt_ctxt tcGuardStmt guards res_ty $ + mc_body ctxt rhs + ; return (GRHS guards' rhs') } where - tc_grhss grhss - = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) -> - returnTc (GRHSs grhss' EmptyBinds expected_ty, plusLIEs lies) - - tc_grhs (GRHS guarded locn) - = tcAddSrcLoc locn $ - tcStmts ctxt (\ty -> ty, expected_ty) guarded `thenTc` \ (guarded', lie) -> - returnTc (GRHS guarded' locn, lie) + stmt_ctxt = PatGuard (mc_what ctxt) \end{code} %************************************************************************ %* * -\subsection{tcMatchPats} +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} %* * %************************************************************************ -\begin{code} -tcMatchPats - :: [RenamedPat] -> TcType - -> ([TypecheckedPat] -> TcType -> TcM (a, LIE)) - -> TcM (a, LIE, TcDictBinds) --- Typecheck the patterns, extend the environment to bind the variables, --- do the thing inside, use any existentially-bound dictionaries to --- discharge parts of the returning LIE, and deal with pattern type --- signatures - -tcMatchPats pats expected_ty thing_inside - = -- STEP 1: Bring pattern-signature type variables into scope - tcAddScopedTyVars (collectSigTysFromPats pats) ( - - -- STEP 2: Typecheck the patterns themselves, gathering all the stuff - tc_match_pats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> - - -- STEP 3: Extend the environment, and do the thing inside - let - xve = bagToList pat_bndrs - pat_ids = map snd xve - in - tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) -> - - returnTc (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) - ) `thenTc` \ (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) -> - - -- STEP 4: Check for existentially bound type variables - -- Do this *outside* the scope of the tcAddScopedTyVars, else checkSigTyVars - -- complains that 'a' is captured by the inscope 'a'! (Test (d) in checkSigTyVars.) - -- - -- I'm a bit concerned that lie_req1 from an 'inner' pattern in the list - -- might need (via lie_req2) something made available from an 'outer' - -- pattern. But it's inconvenient to deal with, and I can't find an example - tcCheckExistentialPat pat_ids ex_tvs lie_avail lie_req2 expected_ty `thenTc` \ (lie_req2', ex_binds) -> - -- NB: we *must* pass "expected_ty" not "result_ty" to tcCheckExistentialPat - -- For example, we must reject this program: - -- data C = forall a. C (a -> Int) - -- f (C g) x = g x - -- Here, result_ty will be simply Int, but expected_ty is (a -> Int). - - returnTc (result, lie_req1 `plusLIE` lie_req2', ex_binds) - -tcCheckExistentialPat :: [TcId] -- Ids bound by this pattern - -> Bag TcTyVar -- Existentially quantified tyvars bound by pattern - -> LIE -- and context - -> LIE -- Required context - -> TcType -- and type of the Match; vars in here must not escape - -> TcM (LIE, TcDictBinds) -- LIE to float out and dict bindings -tcCheckExistentialPat ids ex_tvs lie_avail lie_req match_ty - | isEmptyBag ex_tvs && all not_overloaded ids - -- Short cut for case when there are no existentials - -- and no polymorphic overloaded variables - -- e.g. f :: (forall a. Ord a => a -> a) -> Int -> Int - -- f op x = .... - -- Here we must discharge op Methods - = ASSERT( isEmptyLIE lie_avail ) - returnTc (lie_req, EmptyMonoBinds) - - | otherwise - = tcExtendGlobalTyVars (tyVarsOfType match_ty) $ - tcAddErrCtxtM (sigPatCtxt tv_list ids) $ - - -- In case there are any polymorpic, overloaded binders in the pattern - -- (which can happen in the case of rank-2 type signatures, or data constructors - -- with polymorphic arguments), we must do a bindInstsOfLocalFns here - bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) -> - - -- Deal with overloaded functions bound by the pattern - tcSimplifyCheck doc tv_list (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) -> - checkSigTyVars tv_list emptyVarSet `thenTc_` - - returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) - where - doc = text ("the existential context of a data constructor") - tv_list = bagToList ex_tvs - not_overloaded id = not (isOverloadedTy (idType id)) - -tc_match_pats [] expected_ty - = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) - -tc_match_pats (pat:pats) expected_ty - = subFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> - -- This is the unique place we call subFunTy - -- The point is that if expected_y is a "hole", we want - -- to make arg_ty and rest_ty as "holes" too. - tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) -> - tc_match_pats pats rest_ty `thenTc` \ (rhs_ty, pats', lie_reqs, pats_tvs, pats_ids, lie_avails) -> - returnTc ( rhs_ty, - pat':pats', - lie_req `plusLIE` lie_reqs, - pat_tvs `unionBags` pats_tvs, - pat_ids `unionBags` pats_ids, - lie_avail `plusLIE` lie_avails - ) +\begin{code} +tcDoStmts :: HsStmtContext Name + -> [LStmt Name] + -> LHsExpr Name + -> BoxyRhoType + -> TcM (HsExpr TcId) -- Returns a HsDo +tcDoStmts ListComp stmts body res_ty + = do { elt_ty <- boxySplitListTy res_ty + ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty $ + tcBody (doBodyCtxt ListComp body) body + ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) } + +tcDoStmts PArrComp stmts body res_ty + = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty + ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty $ + tcBody (doBodyCtxt PArrComp body) body + ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) } + +tcDoStmts DoExpr stmts body res_ty + = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty + ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty + ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty) stmts res_ty' $ + tcBody (doBodyCtxt DoExpr body) body + ; return (HsDo DoExpr stmts' body' res_ty') } + +tcDoStmts ctxt@(MDoExpr _) stmts body res_ty + = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty + ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty + tc_rhs rhs = withBox liftedTypeKind $ \ pat_ty -> + tcMonoExpr rhs (mkAppTy m_ty pat_ty) + + ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty' $ + tcBody (doBodyCtxt ctxt body) body + + ; let names = [mfixName, bindMName, thenMName, returnMName, failMName] + ; insts <- mapM (newMethodFromName DoOrigin m_ty) names + ; return (HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty') } + +tcDoStmts ctxt stmts body res_ty = pprPanic "tcDoStmts" (pprStmtContext ctxt) + +tcBody :: Message -> LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr TcId) +tcBody ctxt body res_ty + = -- addErrCtxt ctxt $ -- This context adds little that is useful + tcPolyExpr body res_ty \end{code} @@ -304,128 +261,218 @@ tc_match_pats (pat:pats) expected_ty %* * %************************************************************************ -Typechecking statements is rendered a bit tricky by parallel list comprehensions: - - [ (g x, h x) | ... ; let g v = ... - | ... ; let h v = ... ] - -It's possible that g,h are overloaded, so we need to feed the LIE from the -(g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns). -Similarly if we had an existential pattern match: - - data T = forall a. Show a => C a - - [ (show x, show y) | ... ; C x <- ... - | ... ; C y <- ... ] - -Then we need the LIE from (show x, show y) to be simplified against -the bindings for x and y. - -It's difficult to do this in parallel, so we rely on the renamer to -ensure that g,h and x,y don't duplicate, and simply grow the environment. -So the binders of the first parallel group will be in scope in the second -group. But that's fine; there's no shadowing to worry about. - \begin{code} -tcStmts do_or_lc m_ty stmts - = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE)) - -tcStmtsAndThen - :: (TcStmt -> thing -> thing) -- Combiner - -> RenamedMatchContext - -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs - -- elt_ty, where type of the comprehension is (m elt_ty) - -> [RenamedStmt] - -> TcM (thing, LIE) - -> TcM (thing, LIE) - - -- Base case -tcStmtsAndThen combine do_or_lc m_ty [] do_next - = do_next - -tcStmtsAndThen combine do_or_lc m_ty (stmt:stmts) do_next - = tcStmtAndThen combine do_or_lc m_ty stmt - (tcStmtsAndThen combine do_or_lc m_ty stmts do_next) - - -- LetStmt -tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside - = tcBindsAndThen -- No error context, but a binding group is - (glue_binds combine) -- rather a large thing for an error context anyway - binds - thing_inside - -tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) thing_inside - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (stmtCtxt do_or_lc stmt) $ - newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> - tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> - tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ [pat'] _ -> - tcPopErrCtxt $ - thing_inside `thenTc` \ (thing, lie) -> - returnTc ((BindStmt pat' exp' src_loc, thing), lie) - ) `thenTc` \ ((stmt', thing), lie, dict_binds) -> - returnTc (combine stmt' (glue_binds combine Recursive dict_binds thing), - lie `plusLIE` exp_lie) - - - -- ParStmt -tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside - = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) -> - returnTc (combine (ParStmtOut pairs') thing, lie) +type TcStmtChecker + = forall thing. HsStmtContext Name + -> Stmt Name + -> BoxyRhoType -- Result type for comprehension + -> (BoxyRhoType -> TcM thing) -- Checker for what follows the stmt + -> TcM (Stmt TcId, thing) + + -- The incoming BoxyRhoType may be refined by type refinements + -- before being passed to the thing_inside + +tcStmts :: HsStmtContext Name + -> TcStmtChecker -- NB: higher-rank type + -> [LStmt Name] + -> BoxyRhoType + -> (BoxyRhoType -> TcM thing) + -> TcM ([LStmt TcId], thing) + +-- Note the higher-rank type. stmt_chk is applied at different +-- types in the equations for tcStmts + +tcStmts ctxt stmt_chk [] res_ty thing_inside + = do { thing <- thing_inside res_ty + ; return ([], thing) } + +-- LetStmts are handled uniformly, regardless of context +tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside + = do { (binds', (stmts',thing)) <- tcLocalBinds binds $ + tcStmts ctxt stmt_chk stmts res_ty thing_inside + ; return (L loc (LetStmt binds') : stmts', thing) } + +-- For the vanilla case, handle the location-setting part +tcStmts ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside + = do { (stmt', (stmts', thing)) <- + setSrcSpan loc $ + addErrCtxt (stmtCtxt ctxt stmt) $ + stmt_chk ctxt stmt res_ty $ \ res_ty' -> + popErrCtxt $ + tcStmts ctxt stmt_chk stmts res_ty' $ + thing_inside + ; return (L loc stmt' : stmts', thing) } + +-------------------------------- +-- Pattern guards +tcGuardStmt :: TcStmtChecker +tcGuardStmt ctxt (ExprStmt guard _ _) res_ty thing_inside + = do { guard' <- tcMonoExpr guard boolTy + ; thing <- thing_inside res_ty + ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) } + +tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside + = do { (rhs', rhs_ty) <- tcInferRho rhs + ; (pat', thing) <- tcPat LamPat pat rhs_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcGuardStmt ctxt stmt res_ty thing_inside + = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt) + + +-------------------------------- +-- List comprehensions and PArrays + +tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray) + -> TcStmtChecker + +-- A generator, pat <- rhs +tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) res_ty thing_inside + = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ ty -> + tcMonoExpr rhs (mkTyConApp m_tc [ty]) + ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +-- A boolean guard +tcLcStmt m_tc ctxt (ExprStmt rhs _ _) res_ty thing_inside + = do { rhs' <- tcMonoExpr rhs boolTy + ; thing <- thing_inside res_ty + ; return (ExprStmt rhs' noSyntaxExpr boolTy, thing) } + +-- A parallel set of comprehensions +-- [ (g x, h x) | ... ; let g v = ... +-- | ... ; let h v = ... ] +-- +-- It's possible that g,h are overloaded, so we need to feed the LIE from the +-- (g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns). +-- Similarly if we had an existential pattern match: +-- +-- data T = forall a. Show a => C a +-- +-- [ (show x, show y) | ... ; C x <- ... +-- | ... ; C y <- ... ] +-- +-- Then we need the LIE from (show x, show y) to be simplified against +-- the bindings for x and y. +-- +-- It's difficult to do this in parallel, so we rely on the renamer to +-- ensure that g,h and x,y don't duplicate, and simply grow the environment. +-- So the binders of the first parallel group will be in scope in the second +-- group. But that's fine; there's no shadowing to worry about. + +tcLcStmt m_tc ctxt (ParStmt bndr_stmts_s) elt_ty thing_inside + = do { (pairs', thing) <- loop bndr_stmts_s + ; return (ParStmt pairs', thing) } where - loop [] - = thing_inside `thenTc` \ (thing, stmts_lie) -> - returnTc (([], thing), stmts_lie) - - loop ((bndrs,stmts) : pairs) - = tcStmtsAndThen - combine_par (DoCtxt ListComp) m_ty stmts - -- Notice we pass on m_ty; the result type is used only - -- to get escaping type variables for checkExistentialPat - (tcLookupLocalIds bndrs `thenNF_Tc` \ bndrs' -> - loop pairs `thenTc` \ ((pairs', thing), lie) -> - returnTc (([], (bndrs', pairs', thing)), lie)) `thenTc` \ ((stmts', (bndrs', pairs', thing)), lie) -> - - returnTc ( ((bndrs',stmts') : pairs', thing), lie) - - combine_par stmt (stmts, thing) = (stmt:stmts, thing) - - -- ExprStmt -tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) thing_inside - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( - if isDoExpr do_or_lc then - newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> - tcExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) -> - returnTc (ExprStmt exp' any_ty locn, lie) - else - tcExpr exp boolTy `thenNF_Tc` \ (exp', lie) -> - returnTc (ExprStmt exp' boolTy locn, lie) - ) `thenTc` \ (stmt', stmt_lie) -> - - thing_inside `thenTc` \ (thing, stmts_lie) -> - - returnTc (combine stmt' thing, stmt_lie `plusLIE` stmts_lie) - - - -- Result statements -tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( - if isDoExpr do_or_lc then - tcExpr exp (m res_elt_ty) - else - tcExpr exp res_elt_ty - ) `thenTc` \ (exp', stmt_lie) -> - - thing_inside `thenTc` \ (thing, stmts_lie) -> - - returnTc (combine (ResultStmt exp' locn) thing, - stmt_lie `plusLIE` stmts_lie) - - ------------------------------- -glue_binds combine is_rec binds thing - | nullMonoBinds binds = thing - | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing + -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing) + loop [] = do { thing <- thing_inside elt_ty -- No refinement from pattern + ; return ([], thing) } -- matching in the branches + + loop ((stmts, names) : pairs) + = do { (stmts', (ids, pairs', thing)) + <- tcStmts ctxt (tcLcStmt m_tc) stmts elt_ty $ \ elt_ty' -> + do { ids <- tcLookupLocalIds names + ; (pairs', thing) <- loop pairs + ; return (ids, pairs', thing) } + ; return ( (stmts', ids) : pairs', thing ) } + +tcLcStmt m_tc ctxt stmt elt_ty thing_inside + = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt) + +-------------------------------- +-- Do-notation +-- The main excitement here is dealing with rebindable syntax + +tcDoStmt :: TcType -- Monad type, m + -> TcStmtChecker + +tcDoStmt m_ty ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside + = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ pat_ty -> + tcMonoExpr rhs (mkAppTy m_ty pat_ty) + -- We should use type *inference* for the RHS computations, becuase of GADTs. + -- do { pat <- rhs; } + -- is rather like + -- case rhs of { pat -> } + -- We do inference on rhs, so that information about its type can be refined + -- when type-checking the pattern. + + ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside + + -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b + ; let bind_ty = mkFunTys [mkAppTy m_ty pat_ty, + mkFunTy pat_ty res_ty] res_ty + ; bind_op' <- tcSyntaxOp DoOrigin bind_op bind_ty + -- If (but only if) the pattern can fail, + -- typecheck the 'fail' operator + ; fail_op' <- if isIrrefutableHsPat pat' + then return noSyntaxExpr + else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy res_ty) + ; return (BindStmt pat' rhs' bind_op' fail_op', thing) } + + +tcDoStmt m_ty ctxt (ExprStmt rhs then_op _) res_ty thing_inside + = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b + a_ty <- newFlexiTyVarTy liftedTypeKind + ; let rhs_ty = mkAppTy m_ty a_ty + then_ty = mkFunTys [rhs_ty, res_ty] res_ty + ; then_op' <- tcSyntaxOp DoOrigin then_op then_ty + ; rhs' <- tcPolyExpr rhs rhs_ty + ; thing <- thing_inside res_ty + ; return (ExprStmt rhs' then_op' rhs_ty, thing) } + +tcDoStmt m_ty ctxt stmt res_ty thing_inside + = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt) + +-------------------------------- +-- Mdo-notation +-- The distinctive features here are +-- (a) RecStmts, and +-- (b) no rebindable syntax + +tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference + -> TcStmtChecker +tcMDoStmt tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside + = do { (rhs', pat_ty) <- tc_rhs rhs + ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside + ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcMDoStmt tc_rhs ctxt (ExprStmt rhs then_op _) res_ty thing_inside + = do { (rhs', elt_ty) <- tc_rhs rhs + ; thing <- thing_inside res_ty + ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) } + +tcMDoStmt tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) res_ty thing_inside + = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind + ; let rec_ids = zipWith mkLocalId recNames rec_tys + ; tcExtendIdEnv rec_ids $ do + { (stmts', (later_ids, rec_rets)) + <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ res_ty' -> + -- ToDo: res_ty not really right + do { rec_rets <- zipWithM tc_ret recNames rec_tys + ; later_ids <- tcLookupLocalIds laterNames + ; return (later_ids, rec_rets) } + + ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE (thing_inside res_ty)) + -- NB: The rec_ids for the recursive things + -- already scope over this part. This binding may shadow + -- some of them with polymorphic things with the same Name + -- (see note [RecStmt] in HsExpr) + ; lie_binds <- bindInstsOfLocalFuns lie later_ids + + ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, thing) + }} + where + -- Unify the types of the "final" Ids with those of "knot-tied" Ids + tc_ret rec_name mono_ty + = do { poly_id <- tcLookupId rec_name + -- poly_id may have a polymorphic type + -- but mono_ty is just a monomorphic type variable + ; co_fn <- tcSubExp (idType poly_id) mono_ty + ; return (mkHsCoerce co_fn (HsVar poly_id)) } + +tcMDoStmt tc_rhs ctxt stmt res_ty thing_inside + = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt) + \end{code} @@ -439,17 +486,30 @@ glue_binds combine is_rec binds thing number of args are used in each equation. \begin{code} -sameNoOfArgs :: [RenamedMatch] -> Bool -sameNoOfArgs matches = isSingleton (nub (map args_in_match matches)) +checkArgs :: Name -> MatchGroup Name -> TcM () +checkArgs fun (MatchGroup (match1:matches) _) + | null bad_matches = return () + | otherwise + = failWithTc (vcat [ptext SLIT("Equations for") <+> quotes (ppr fun) <+> + ptext SLIT("have different numbers of arguments"), + nest 2 (ppr (getLoc match1)), + nest 2 (ppr (getLoc (head bad_matches)))]) where - args_in_match :: RenamedMatch -> Int - args_in_match (Match pats _ _) = length pats + n_args1 = args_in_match match1 + bad_matches = [m | m <- matches, args_in_match m /= n_args1] + + args_in_match :: LMatch Name -> Int + args_in_match (L _ (Match pats _ _)) = length pats \end{code} \begin{code} -matchCtxt ctxt match = hang (pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match) -stmtCtxt do_or_lc stmt = hang (pprMatchContext do_or_lc <> colon) 4 (ppr stmt) +matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) + 4 (pprMatch ctxt match) + +doBodyCtxt :: HsStmtContext Name -> LHsExpr Name -> SDoc +doBodyCtxt ctxt body = hang (ptext SLIT("In the result of") <+> pprStmtContext ctxt <> colon) + 4 (ppr body) -varyingArgsErr name matches - = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] +stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon) + 4 (ppr stmt) \end{code}