X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=07a1094d58de98b08937c346db5965a070bac90f;hb=0c88fe0000481527a0a9f6305512ac2f605340d5;hp=05797f5426e333c8a3e9371c9f6628bc125834e4;hpb=f714e6b642fd614a9971717045ae47c3d871275e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 05797f5..07a1094 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -5,53 +5,46 @@ \begin{code} module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, - matchCtxt, - tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig, - tcMatchPats, - TcStmtCtxt(..), TcMatchCtxt(..) + matchCtxt, TcMatchCtxt(..), + tcStmts, tcDoStmts, + tcDoStmt, tcMDoStmt, tcGuardStmt ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcCheckRho, tcMonoExpr ) +import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr ) -import HsSyn ( HsExpr(..), LHsExpr, HsBindGroup(..), +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), Match(..), LMatch, GRHSs(..), GRHS(..), Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), - ReboundNames, LPat, - pprMatch, isDoExpr, - pprMatchContext, pprStmtContext, pprStmtResultContext, - collectSigTysFromPats, glueBindsOnGRHSs - ) -import TcHsSyn ( ExprCoFn, TcDictBinds, isIdCoercion, (<$>), (<.>) ) + pprMatch, isIrrefutableHsPat, mkHsCoerce, + pprMatchContext, pprStmtContext, + noSyntaxExpr, matchGroupArity, pprMatches, + ExprCoFn ) import TcRnMonad -import TcHsType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) -import Inst ( tcSyntaxName, tcInstCall ) -import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 ) -import TcPat ( tcPat, tcMonoPatBndr ) -import TcMType ( newTyVarTy, newTyVarTys, zonkTcType ) -import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, - tyVarsOfTypes, tidyOpenTypes, isSigmaTy, typeKind, - mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind, - mkArrowKind, mkAppTy ) -import TcBinds ( tcBindsAndThen ) -import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedBranches, readExpectedType, - unifyTauTy, subFunTys, unifyPArrTy, unifyListTy, unifyFunTy, - checkSigTyVarsWrt, tcSubExp, tcGen ) -import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +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, mkListTy, mkPArrTy ) +import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy ) +import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName ) import Id ( idType, mkLocalId ) -import CoreFVs ( idFreeTyVars ) -import BasicTypes ( RecFlag(..) ) -import VarSet -import Bag -import Util ( isSingleton, notNull ) +import TyCon ( TyCon ) import Outputable -import SrcLoc ( Located(..), noLoc ) - -import List ( nub ) +import SrcLoc ( Located(..), getLoc ) +import ErrUtils ( Message ) \end{code} %************************************************************************ @@ -67,29 +60,34 @@ same number of arguments before using @tcMatches@ to do the work. \begin{code} tcMatchesFun :: Name - -> [LMatch Name] - -> Expected TcRhoType -- Expected type - -> TcM [LMatch TcId] - -tcMatchesFun fun_name matches@(first_match:_) expected_ty - = -- 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... - checkTc (sameNoOfArgs matches) - (varyingArgsErr fun_name matches) `thenM_` + -> 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 subFunTys does that on the fly - tcMatches match_ctxt 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 - match_ctxt = MC { mc_what = FunRhs fun_name, - mc_body = tcMonoExpr } + 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 @@ -97,64 +95,36 @@ parser guarantees that each equation has exactly one argument. \begin{code} tcMatchesCase :: TcMatchCtxt -- Case context - -> [LMatch Name] -- The case alternatives - -> Expected TcRhoType -- Type of whole case expressions - -> TcM (TcRhoType, -- Inferred type of the scrutinee - [LMatch TcId]) -- Translated alternatives - -tcMatchesCase ctxt matches (Check expr_ty) - = newTyVarTy openTypeKind `thenM` \ scrut_ty -> - -- openTypeKind because the scrutinee can be an unboxed type - tcMatches ctxt matches (Check (mkFunTy scrut_ty expr_ty)) `thenM` \ matches' -> - returnM (scrut_ty, matches') - -tcMatchesCase ctxt matches (Infer hole) - = newHole `thenM` \ fun_hole -> - tcMatches ctxt matches (Infer fun_hole) `thenM` \ matches' -> - readMutVar fun_hole `thenM` \ fun_ty -> - -- The result of tcMatches is bound to be a function type - unifyFunTy fun_ty `thenM` \ (scrut_ty, res_ty) -> - writeMutVar hole res_ty `thenM_` - returnM (scrut_ty, matches') - - -tcMatchLambda :: LMatch Name -> Expected TcRhoType -> TcM (LMatch TcId) -tcMatchLambda match res_ty = tcMatch match_ctxt res_ty match + -> 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 = tcMonoExpr } + mc_body = tcPolyExpr } \end{code} @tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. \begin{code} -tcGRHSsPat :: GRHSs Name - -> Expected TcRhoType - -> TcM (GRHSs TcId) -tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty +tcGRHSsPat :: GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId) +tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty where match_ctxt = MC { mc_what = PatBindRhs, - mc_body = tcMonoExpr } -\end{code} - -\begin{code} -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 - -> Expected TcRhoType - -> TcM (LHsExpr TcId) } - -tcMatches :: TcMatchCtxt - -> [LMatch Name] - -> Expected TcRhoType - -> TcM [LMatch TcId] - -tcMatches ctxt matches exp_ty - = -- If there is more than one branch, and exp_ty is a 'hole', - -- all branches must be types, not type schemes, otherwise the - -- order in which we check them would affect the result. - zapExpectedBranches matches exp_ty `thenM` \ exp_ty' -> - mappM (tcMatch ctxt exp_ty') matches + mc_body = tcPolyExpr } \end{code} @@ -165,225 +135,70 @@ tcMatches ctxt matches exp_ty %************************************************************************ \begin{code} +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 - -> Expected TcRhoType -- 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. + -> [BoxySigmaType] -- Expected pattern types + -> BoxyRhoType -- Expected result-type of the Match. -> LMatch Name -> TcM (LMatch TcId) -tcMatch ctxt exp_ty match = wrapLocM (tc_match ctxt exp_ty) match - -tc_match ctxt expected_ty match@(Match pats maybe_rhs_sig grhss) - = addErrCtxt (matchCtxt (mc_what ctxt) match) $ -- I'm not sure why, so I put it back - subFunTys pats expected_ty $ \ pats_w_tys rhs_ty -> - -- This is the unique place we call subFunTys - -- The point is that if expected_y is a "hole", we want - -- to make arg_ty and rest_ty as "holes" too. - tcMatchPats pats_w_tys rhs_ty (tc_grhss rhs_ty) `thenM` \ (pats', grhss', ex_binds) -> - returnM (Match pats' Nothing (glueBindsOnGRHSs ex_binds grhss')) - - where - tc_grhss rhs_ty - = case maybe_rhs_sig of -- Deal with the result signature - Nothing -> tcGRHSs ctxt grhss rhs_ty - - Just sig -> tcAddScopedTyVars [sig] $ - -- Bring into scope the type variables in the signature - tcHsSigType ResSigCtxt sig `thenM` \ sig_ty -> - tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty `thenM` \ (co_fn, grhss') -> - - -- Pushes the coercion down to the right hand sides, - -- because there is no convenient place to hang it otherwise. - if isIdCoercion co_fn then - returnM grhss' - else - readExpectedType rhs_ty `thenM` \ rhs_ty' -> - returnM (lift_grhss co_fn rhs_ty' grhss') - -lift_grhss co_fn rhs_ty (GRHSs grhss binds ty) - = GRHSs (map (fmap lift_grhs) grhss) binds rhs_ty -- Change the type, since the coercion does +tcMatch ctxt pat_tys rhs_ty match + = wrapLocM (tc_match ctxt pat_tys rhs_ty) match where - lift_grhs (GRHS stmts) = GRHS (map lift_stmt stmts) - - lift_stmt (L loc (ResultStmt e)) = L loc (ResultStmt (fmap (co_fn <$>) e)) - lift_stmt stmt = stmt - -tcGRHSs :: TcMatchCtxt -> GRHSs Name - -> Expected TcRhoType - -> TcM (GRHSs TcId) - - -- Special case when there is just one equation with a degenerate - -- guard; then we pass in the full Expected type, so that we get - -- good inference from simple things like - -- f = \(x::forall a.a->a) -> - -- This is a consequence of the fact that tcStmts takes a TcType, - -- not a Expected TcType, a decision we could revisit if necessary -tcGRHSs ctxt (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs)])] binds _) exp_ty - = tcBindsAndThen glueBindsOnGRHSs binds $ - mc_body ctxt rhs exp_ty `thenM` \ rhs' -> - readExpectedType exp_ty `thenM` \ exp_ty' -> - returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] [] exp_ty') - -tcGRHSs ctxt (GRHSs grhss binds _) exp_ty - = tcBindsAndThen glueBindsOnGRHSs binds $ - zapExpectedType exp_ty openTypeKind `thenM` \ exp_ty' -> - -- Even if there is only one guard, we zap the RHS type to - -- a monotype. Reason: it makes tcStmts much easier, - -- and even a one-armed guard has a notional second arm - let - stmt_ctxt = SC { sc_what = PatGuard (mc_what ctxt), - sc_rhs = tcCheckRho, - sc_body = sc_body, - sc_ty = exp_ty' } - sc_body body = mc_body ctxt body (Check exp_ty') - - tc_grhs (GRHS guarded) - = tcStmts stmt_ctxt guarded `thenM` \ guarded' -> - returnM (GRHS guarded') - in - mappM (wrapLocM tc_grhs) grhss `thenM` \ grhss' -> - returnM (GRHSs grhss' [] exp_ty') -\end{code} - - -\begin{code} -tcThingWithSig :: TcSigmaType -- Type signature - -> (TcRhoType -> TcM r) -- How to type check the thing inside - -> Expected TcRhoType -- Overall expected result type - -> TcM (ExprCoFn, r) --- Used for expressions with a type signature, and for result type signatures - -tcThingWithSig sig_ty thing_inside res_ty - | not (isSigmaTy sig_ty) - = thing_inside sig_ty `thenM` \ result -> - tcSubExp res_ty sig_ty `thenM` \ co_fn -> - returnM (co_fn, result) - - | otherwise -- The signature has some outer foralls - = -- Must instantiate the outer for-alls of sig_tc_ty - -- else we risk instantiating a ? res_ty to a forall-type - -- which breaks the invariant that tcMonoExpr only returns phi-types - tcGen sig_ty emptyVarSet thing_inside `thenM` \ (gen_fn, result) -> - tcInstCall SignatureOrigin sig_ty `thenM` \ (inst_fn, inst_sig_ty) -> - tcSubExp res_ty inst_sig_ty `thenM` \ co_fn -> - returnM (co_fn <.> inst_fn <.> gen_fn, result) - -- Note that we generalise, then instantiate. Ah well. -\end{code} - - -%************************************************************************ -%* * -\subsection{tcMatchPats} -%* * -%************************************************************************ - -\begin{code} -tcMatchPats - :: [(LPat Name, Expected TcRhoType)] - -> Expected TcRhoType - -> TcM a - -> TcM ([LPat TcId], a, HsBindGroup TcId) --- 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_w_tys body_ty thing_inside - = -- STEP 1: Bring pattern-signature type variables into scope - tcAddScopedTyVars (collectSigTysFromPats (map fst pats_w_tys)) ( - - -- STEP 2: Typecheck the patterns themselves, gathering all the stuff - -- then do the thing inside - getLIE (tc_match_pats pats_w_tys thing_inside) - - ) `thenM` \ ((pats', ex_tvs, ex_ids, ex_lie, result), lie_req) -> - - -- 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 ex_tvs ex_ids ex_lie lie_req - pats_w_tys body_ty `thenM` \ ex_binds -> - -- NB: we *must* pass "pats_w_tys" not just "body_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 (C -> a -> Int). - - returnM (pats', result, HsBindGroup ex_binds [] Recursive) - -tc_match_pats [] thing_inside - = thing_inside `thenM` \ answer -> - returnM ([], emptyBag, [], [], answer) - -tc_match_pats ((pat,pat_ty):pats) thing_inside - = tcPat tcMonoPatBndr pat pat_ty `thenM` \ (pat', ex_tvs, pat_bndrs, ex_lie) -> - let - xve = bagToList pat_bndrs - ex_ids = [id | (_, id) <- xve] - -- ex_ids is all the pattern-bound Ids, a superset - -- of the existential Ids used in checkExistentialPat - in - tcExtendLocalValEnv2 xve $ - traceTc (text "tc_match_pats" <+> (ppr xve $$ ppr (map (idType . snd) xve) $$ - ppr (map (typeKind . idType . snd) xve))) `thenM_` - tc_match_pats pats thing_inside `thenM` \ (pats', exs_tvs, exs_ids, exs_lie, answer) -> - returnM ( pat':pats', - ex_tvs `unionBags` exs_tvs, - ex_ids ++ exs_ids, - ex_lie ++ exs_lie, - answer - ) - - -tcCheckExistentialPat :: Bag TcTyVar -- Existentially quantified tyvars bound by pattern - -> [TcId] -- Ids bound by this pattern; used - -- (a) by bindsInstsOfLocalFuns - -- (b) to generate helpful error messages - -> [Inst] -- and context - -> [Inst] -- Required context - -> [(pat,Expected TcRhoType)] -- Types of the patterns - -> Expected TcRhoType -- Type of the body of the match - -- Tyvars in either of these must not escape - -> TcM TcDictBinds -- LIE to float out and dict bindings -tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req pats_w_tys body_ty - | isEmptyBag ex_tvs && all not_overloaded ex_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( null ex_lie ) - extendLIEs lie_req `thenM_` - returnM emptyBag - - | otherwise - = -- Read the by-now-filled-in expected types - mapM readExpectedType (body_ty : map snd pats_w_tys) `thenM` \ tys -> - addErrCtxtM (sigPatCtxt tv_list ex_ids tys) $ - - -- 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 - getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, lie) -> - - -- Deal with overloaded functions bound by the pattern - tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds -> - - -- Check for type variable escape - checkSigTyVarsWrt (tyVarsOfTypes tys) tv_list `thenM_` - - returnM (dict_binds `unionBags` inst_binds) + 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 - doc = text ("existential context of a data constructor") - tv_list = bagToList ex_tvs - not_overloaded id = not (isOverloadedTy (idType id)) + stmt_ctxt = PatGuard (mc_what ctxt) \end{code} @@ -395,49 +210,48 @@ tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req pats_w_tys body_ty \begin{code} tcDoStmts :: HsStmtContext Name - -> [LStmt Name] -> ReboundNames Name - -> TcRhoType -- To keep it simple, we don't have an "expected" type here - -> TcM ([LStmt TcId], ReboundNames TcId) -tcDoStmts PArrComp stmts method_names res_ty - = unifyPArrTy res_ty `thenM` \elt_ty -> - tcComprehension PArrComp mkPArrTy elt_ty stmts `thenM` \ stmts' -> - returnM (stmts', [{- unused -}]) - -tcDoStmts ListComp stmts method_names res_ty - = unifyListTy res_ty ` thenM` \ elt_ty -> - tcComprehension ListComp mkListTy elt_ty stmts `thenM` \ stmts' -> - returnM (stmts', [{- unused -}]) - -tcDoStmts do_or_mdo stmts method_names res_ty - = newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty -> - newTyVarTy liftedTypeKind `thenM` \ elt_ty -> - unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_` - let - ctxt = SC { sc_what = do_or_mdo, - sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mkAppTy m_ty rhs_elt_ty), - sc_body = \ body -> tcCheckRho body res_ty, - sc_ty = res_ty } - in - tcStmts ctxt stmts `thenM` \ stmts' -> - - -- Build the then and zero methods in case we need them - -- It's important that "then" and "return" appear just once in the final LIE, - -- not only for typechecker efficiency, but also because otherwise during - -- simplification we end up with silly stuff like - -- then = case d of (t,r) -> t - -- then = then - -- where the second "then" sees that it already exists in the "available" stuff. - mapM (tcSyntaxName DoOrigin m_ty) method_names `thenM` \ methods -> - - returnM (stmts', methods) - -tcComprehension do_or_lc mk_mty elt_ty stmts - = tcStmts ctxt stmts - where - ctxt = SC { sc_what = do_or_lc, - sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mk_mty rhs_elt_ty), - sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no mk_mty! - sc_ty = mk_mty elt_ty } + -> [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} @@ -447,150 +261,218 @@ tcComprehension do_or_lc mk_mty elt_ty stmts %* * %************************************************************************ -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 ctxt stmts - = ASSERT( notNull stmts ) - tcStmtsAndThen (:) ctxt stmts (returnM []) - -data TcStmtCtxt - = SC { sc_what :: HsStmtContext Name, -- What kind of thing this is - sc_rhs :: LHsExpr Name -> TcType -> TcM (LHsExpr TcId), -- Type checker for RHS computations - sc_body :: LHsExpr Name -> TcM (LHsExpr TcId), -- Type checker for return computation - sc_ty :: TcType } -- Return type; used *only* to check - -- for escape in existential patterns -tcStmtsAndThen - :: (LStmt TcId -> thing -> thing) -- Combiner - -> TcStmtCtxt +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] - -> TcM thing - -> TcM thing - - -- Base case -tcStmtsAndThen combine ctxt [] thing_inside - = thing_inside - -tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside - = tcStmtAndThen combine ctxt stmt $ - tcStmtsAndThen combine ctxt stmts $ - thing_inside - - -- LetStmt -tcStmtAndThen combine ctxt (L _ (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 - - -- BindStmt -tcStmtAndThen combine ctxt (L src_loc stmt@(BindStmt pat exp)) thing_inside - = addSrcSpan src_loc $ - addErrCtxt (stmtCtxt ctxt stmt) $ - newTyVarTy liftedTypeKind `thenM` \ pat_ty -> - sc_rhs ctxt exp pat_ty `thenM` \ exp' -> - tcMatchPats [(pat, Check pat_ty)] (Check (sc_ty ctxt)) ( - popErrCtxt thing_inside - ) `thenM` \ ([pat'], thing, dict_binds) -> - returnM (combine (L src_loc (BindStmt pat' exp')) - (glue_binds combine dict_binds thing)) - - -- ExprStmt -tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside - = addSrcSpan src_loc ( - addErrCtxt (stmtCtxt ctxt stmt) $ - if isDoExpr (sc_what ctxt) - then -- do or mdo; the expression is a computation - newTyVarTy liftedTypeKind `thenM` \ any_ty -> - sc_rhs ctxt exp any_ty `thenM` \ exp' -> - returnM (L src_loc (ExprStmt exp' any_ty)) - else -- List comprehensions, pattern guards; expression is a boolean - tcCheckRho exp boolTy `thenM` \ exp' -> - returnM (L src_loc (ExprStmt exp' boolTy)) - ) `thenM` \ stmt' -> - - thing_inside `thenM` \ thing -> - returnM (combine stmt' thing) - - - -- ParStmt -tcStmtAndThen combine ctxt (L src_loc (ParStmt bndr_stmts_s)) thing_inside - = loop bndr_stmts_s `thenM` \ (pairs', thing) -> - returnM (combine (L src_loc (ParStmt pairs')) thing) + -> 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 `thenM` \ thing -> - returnM ([], thing) - - loop ((stmts, bndrs) : pairs) - = tcStmtsAndThen combine_par ctxt stmts $ - -- Notice we pass on ctxt; the result type is used only - -- to get escaping type variables for checkExistentialPat - tcLookupLocalIds bndrs `thenM` \ bndrs' -> - loop pairs `thenM` \ (pairs', thing) -> - returnM (([], bndrs') : pairs', thing) - - combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing) - - -- RecStmt -tcStmtAndThen combine ctxt (L src_loc (RecStmt stmts laterNames recNames _)) thing_inside - = newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> - let - rec_ids = zipWith mkLocalId recNames recTys - in - tcExtendLocalValEnv rec_ids $ - tcStmtsAndThen combine_rec ctxt stmts ( - mappM tc_ret (recNames `zip` recTys) `thenM` \ rec_rets -> - tcLookupLocalIds laterNames `thenM` \ later_ids -> - returnM ([], (later_ids, rec_rets)) - ) `thenM` \ (stmts', (later_ids, rec_rets)) -> - - tcExtendLocalValEnv later_ids $ - -- NB: The rec_ids for the recursive things - -- already scope over this part - thing_inside `thenM` \ 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 - returnM (combine (L src_loc (RecStmt stmts' later_ids rec_ids rec_rets)) thing) + ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, thing) + }} where - combine_rec stmt (stmts, thing) = (stmt:stmts, thing) - -- Unify the types of the "final" Ids with those of "knot-tied" Ids - tc_ret (rec_name, mono_ty) - = tcLookupId rec_name `thenM` \ poly_id -> + 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 - tcSubExp (Check mono_ty) (idType poly_id) `thenM` \ co_fn -> - returnM (L src_loc (co_fn <$> HsVar poly_id)) - - -- Result statements -tcStmtAndThen combine ctxt (L src_loc stmt@(ResultStmt exp)) thing_inside - = addErrCtxt (stmtCtxt ctxt stmt) (sc_body ctxt exp) `thenM` \ exp' -> - thing_inside `thenM` \ thing -> - returnM (combine (L src_loc (ResultStmt exp')) thing) + ; 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) ------------------------------- -glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing - -- ToDo: fix the noLoc \end{code} @@ -604,43 +486,30 @@ glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing number of args are used in each equation. \begin{code} -sameNoOfArgs :: [LMatch Name] -> 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 + 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} -varyingArgsErr name matches - = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] - -matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) - 4 (pprMatch ctxt match) - -stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pp_ctxt (sc_what ctxt) <> colon) 4 (ppr stmt) - where - pp_ctxt = case stmt of - ResultStmt _ -> pprStmtResultContext - other -> pprStmtContext - -sigPatCtxt bound_tvs bound_ids tys tidy_env - = -- tys is (body_ty : pat_tys) - mapM zonkTcType tys `thenM` \ tys' -> - let - (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) - (_env2, tidy_body_ty : tidy_pat_tys) = tidyOpenTypes env1 tys' - in - returnM (env1, - sep [ptext SLIT("When checking an existential match that binds"), - nest 4 (vcat (zipWith ppr_id show_ids tidy_tys)), - ptext SLIT("The pattern(s) have type(s):") <+> vcat (map ppr tidy_pat_tys), - ptext SLIT("The body has type:") <+> ppr tidy_body_ty - ]) - where - show_ids = filter is_interesting bound_ids - is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs +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) - ppr_id id ty = ppr id <+> dcolon <+> ppr ty - -- Don't zonk the types so we get the separate, un-unified versions +stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon) + 4 (ppr stmt) \end{code}