X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=8f4d38ffc72aac9d0acc9e628847829c5fe1fe8a;hb=6b29d930b1a8b4fbb5925099e51ecc0a2483bf54;hp=ebd6ba56e2bdb9977e6d5993cffe66794c48e099;hpb=5f3528244ad3ec004bb67a8a2ec086fe90318ce7;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index ebd6ba5..8f4d38f 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,39 +4,53 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where +module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda, + matchCtxt, + tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig, + tcMatchPats, + TcStmtCtxt(..), TcMatchCtxt(..) + ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcExpr ) +import {-# SOURCE #-} TcExpr( tcCheckRho, tcInferRho, tcMonoExpr ) -import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), - MonoBinds(..), StmtCtxt(..), Stmt(..), - pprMatch, getMatchLoc, consLetStmt, - mkMonoBind +import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..), + Match(..), LMatch, GRHSs(..), GRHS(..), + Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..), + ReboundNames, LPat, HsBindGroup(..), + pprMatch, isDoExpr, + pprMatchContext, pprStmtContext, pprStmtResultContext, + collectPatsBinders, glueBindsOnGRHSs ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt ) - -import TcMonad -import TcMonoType ( checkSigTyVars, tcHsTyVar, tcHsSigType, sigPatCtxt ) -import Inst ( Inst, LIE, plusLIE, emptyLIE, plusLIEs ) -import TcEnv ( tcExtendLocalValEnv, tcExtendGlobalTyVars, tcExtendTyVarEnv, tcGetGlobalTyVars ) -import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig ) -import TcType ( TcType, newTyVarTy, newTyVarTy_OpenKind, zonkTcTyVars ) +import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) ) + +import TcRnMonad +import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) ) +import Inst ( tcSyntaxName, tcInstCall ) +import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv, + tcExtendTyVarEnv ) +import TcPat ( PatCtxt(..), tcPats ) +import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType ) +import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys, + tyVarsOfTypes, tidyOpenTypes, isSigmaTy, mkTyConApp, + liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy ) import TcBinds ( tcBindsAndThen ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcUnify ( unifyFunTy, unifyTauTy ) +import TcUnify ( Expected(..), zapExpectedType, readExpectedType, + unifyTauTy, subFunTys, unifyListTy, unifyTyConApp, + checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen, + unifyAppTy ) +import TcSimplify ( bindInstsOfLocalFuns ) import Name ( Name ) -import TysWiredIn ( boolTy ) - -import BasicTypes ( RecFlag(..) ) -import Type ( Kind, tyVarsOfType, isTauTy, mkFunTy, boxedTypeKind ) +import TysWiredIn ( boolTy, parrTyCon, listTyCon ) +import Id ( idType, mkLocalId ) +import CoreFVs ( idFreeTyVars ) import VarSet -import Var ( Id ) -import Util -import Bag +import BasicTypes ( RecFlag(..) ) +import Util ( isSingleton, notNull ) import Outputable +import SrcLoc ( Located(..), noLoc ) + import List ( nub ) \end{code} @@ -52,64 +66,69 @@ 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 s ([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 + -> Expected TcRhoType -- Expected type of function + -> TcM (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... + checkTc (sameNoOfArgs matches) (varyingArgsErr 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 unifyFunTy does that on the fly - tcMatches xve matches expected_ty (FunRhs fun_name) + -- 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. + ; exp_ty' <- zapExpectedBranches matches exp_ty + ; subFunTys matches 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 } \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 s (TcType, -- Inferred type of the scrutinee - [TcMatch], -- Translated alternatives - LIE) - -tcMatchesCase matches expr_ty - = newTyVarTy_OpenKind `thenNF_Tc` \ scrut_ty -> - tcMatches [] matches (mkFunTy scrut_ty expr_ty) CaseAlt `thenTc` \ (matches', lie) -> - returnTc (scrut_ty, matches', lie) - -tcMatchLambda :: RenamedMatch -> TcType -> TcM s (TcMatch, LIE) -tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaBody +tcMatchesCase :: TcMatchCtxt -- Case context + -> TcRhoType -- Type of scrutinee + -> MatchGroup Name -- The case alternatives + -> Expected TcRhoType -- Type of whole case expressions + -> TcM (MatchGroup TcId) -- Translated alternatives + +tcMatchesCase ctxt scrut_ty matches exp_ty + = do { exp_ty' <- zapExpectedBranches matches exp_ty + ; tcMatches ctxt [Check scrut_ty] exp_ty' matches } + +tcMatchLambda :: MatchGroup Name -> Expected TcRhoType -> TcM (MatchGroup TcId) +tcMatchLambda match exp_ty -- One branch so no unifyBranches needed + = subFunTys match exp_ty $ \ pat_tys rhs_ty -> + tcMatches match_ctxt pat_tys rhs_ty match + where + match_ctxt = MC { mc_what = LambdaExpr, + mc_body = tcMonoExpr } \end{code} +@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@. \begin{code} -tcMatches :: [(Name,Id)] - -> [RenamedMatch] - -> TcType - -> StmtCtxt - -> TcM s ([TcMatch], LIE) - -tcMatches xve matches expected_ty fun_or_case - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> - returnTc (matches, plusLIEs lies) +tcGRHSsPat :: GRHSs Name + -> Expected TcRhoType + -> TcM (GRHSs TcId) +tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty where - tc_match match = tcMatch xve match expected_ty fun_or_case + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcMonoExpr } \end{code} @@ -120,116 +139,127 @@ tcMatches xve matches expected_ty fun_or_case %************************************************************************ \begin{code} -tcMatch :: [(Name,Id)] - -> RenamedMatch - -> TcType -- Expected result-type of the Match. - -- Early unification with this guy gives better error messages - -> StmtCtxt - -> TcM s (TcMatch, LIE) - -tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt - = tcAddSrcLoc (getMatchLoc match) $ - tcAddErrCtxt (matchCtxt ctxt match) $ - - if null sig_tvs then -- The common case - tc_match expected_ty `thenTc` \ (_, match_and_lie) -> - returnTc match_and_lie - - else - -- If there are sig tvs we must be careful *not* to use - -- expected_ty right away, else we'll unify with tyvars free - -- in the envt. So invent a fresh tyvar and use that instead - newTyVarTy_OpenKind `thenNF_Tc` \ tyvar_ty -> - - -- Extend the tyvar env and check the match itself - mapNF_Tc tcHsTyVar sig_tvs `thenNF_Tc` \ sig_tyvars -> - tcExtendTyVarEnv sig_tyvars ( - tc_match tyvar_ty - ) `thenTc` \ (pat_ids, match_and_lie) -> - - -- Check that the scoped type variables from the patterns - -- have not been constrained - tcAddErrCtxtM (sigPatCtxt sig_tyvars pat_ids) ( - checkSigTyVars sig_tyvars emptyVarSet - ) `thenTc_` - - -- *Now* we're free to unify with expected_ty - unifyTauTy expected_ty tyvar_ty `thenTc_` - - returnTc match_and_lie - - where - tc_match expected_ty -- Any sig tyvars are in scope by now - = -- STEP 1: Typecheck the patterns - tcMatchPats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> - let - xve2 = bagToList pat_bndrs - pat_ids = map snd xve2 - ex_tv_list = bagToList ex_tvs - in - - -- STEP 2: Check that the remaining "expected type" is not a rank-2 type - -- If it is it'll mess up the unifier when checking the RHS - checkTc (isTauTy rhs_ty) lurkingRank2SigErr `thenTc_` - - -- STEP 3: Unify with the rhs type signature if any - (case maybe_rhs_sig of - Nothing -> returnTc () - Just sig -> tcHsSigType sig `thenTc` \ sig_ty -> - - -- Check that the signature isn't a polymorphic one, which - -- we don't permit (at present, anyway) - checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_` - unifyTauTy rhs_ty sig_ty - ) `thenTc_` - - -- STEP 4: Typecheck the guarded RHSs and the associated where clause - tcExtendLocalValEnv xve1 (tcExtendLocalValEnv xve2 ( - tcGRHSs grhss rhs_ty ctxt - )) `thenTc` \ (grhss', lie_req2) -> - - -- STEP 5: Check for existentially bound type variables - tcExtendGlobalTyVars (tyVarsOfType rhs_ty) ( - tcAddErrCtxtM (sigPatCtxt ex_tv_list pat_ids) $ - checkSigTyVars ex_tv_list emptyVarSet `thenTc` \ zonked_ex_tvs -> - tcSimplifyAndCheck - (text ("the existential context of a data constructor")) - (mkVarSet zonked_ex_tvs) - lie_avail (lie_req1 `plusLIE` lie_req2) - ) `thenTc` \ (lie_req', ex_binds) -> - - -- STEP 6 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' pat_ids `thenTc` \ (lie_req'', inst_binds) -> - - -- Phew! All done. - let - grhss'' = glue_on Recursive ex_binds $ - glue_on Recursive inst_binds grhss' - in - returnTc (pat_ids, (Match [] pats' Nothing grhss'', lie_req'')) - - -- 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 :: RenamedGRHSs - -> TcType -> StmtCtxt - -> TcM s (TcGRHSs, LIE) - -tcGRHSs (GRHSs grhss binds _) expected_ty ctxt - = tcBindsAndThen glue_on binds (tc_grhss grhss) +tcMatches :: TcMatchCtxt + -> [Expected TcRhoType] -- Expected pattern types + -> Expected TcRhoType -- 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 + -> Expected TcRhoType + -> TcM (LHsExpr TcId) } + +tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _) + = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches + ; pat_tys' <- mapM readExpectedType pat_tys + ; rhs_ty' <- readExpectedType rhs_ty + ; return (MatchGroup matches' (mkFunTys pat_tys' rhs_ty')) } + +------------- +tcMatch :: TcMatchCtxt + -> [Expected TcRhoType] -- Expected pattern types + -> Expected TcRhoType -- 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 + +tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss) + = addErrCtxt (matchCtxt (mc_what ctxt) match) $ + do { (pats', grhss') <- tcMatchPats pats pat_tys rhs_ty $ + tc_grhss ctxt maybe_rhs_sig grhss rhs_ty + ; 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 { (sig_tvs, sig_ty) <- tcHsPatSigType ResSigCtxt res_sig + ; traceTc (text "tc_grhss" <+> ppr sig_tvs) + ; (co_fn, grhss') <- tcExtendTyVarEnv sig_tvs $ + tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty + + -- Push the coercion down to the right hand sides, + -- because there is no convenient place to hang it otherwise. + ; if isIdCoercion co_fn then + return grhss' + else + return (lift_grhss co_fn grhss') } + +------------- +lift_grhss co_fn (GRHSs grhss binds) + = GRHSs (map (fmap lift_grhs) grhss) binds where - tc_grhss grhss - = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) -> - returnTc (GRHSs grhss' EmptyBinds (Just expected_ty), plusLIEs lies) - - tc_grhs (GRHS guarded locn) - = tcAddSrcLoc locn $ - tcStmts ctxt (\ty -> ty) guarded expected_ty `thenTc` \ (guarded', lie) -> - returnTc (GRHS guarded' locn, lie) + 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' -> + returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] []) + +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 = tcInferRho, + 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' []) +\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 InstSigOrigin 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} @@ -239,123 +269,261 @@ tcGRHSs (GRHSs grhss binds _) expected_ty ctxt %* * %************************************************************************ -\begin{code} -tcMatchPats [] expected_ty - = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) - -tcMatchPats (pat:pats) expected_ty - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> - tcPat tcPatBndr_NoSigs pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) -> - tcMatchPats 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} +tcMatchPats :: [LPat Name] + -> [Expected TcSigmaType] -- Pattern types + -> Expected TcRhoType -- Result type; + -- used only to check existential escape + -> TcM a + -> TcM ([LPat TcId], a) +-- 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 tys body_ty thing_inside + = do { (pats', ex_tvs, res) <- tcPats LamPat pats tys thing_inside + ; tcCheckExistentialPat pats' ex_tvs tys body_ty + ; returnM (pats', res) } + +tcCheckExistentialPat :: [LPat TcId] -- Patterns (just for error message) + -> [TcTyVar] -- Existentially quantified tyvars bound by pattern + -> [Expected TcSigmaType] -- Types of the patterns + -> Expected TcRhoType -- Type of the body of the match + -- Tyvars in either of these must not escape + -> TcM () + -- NB: we *must* pass "pats_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). + +tcCheckExistentialPat pats [] pat_tys body_ty + = return () -- Short cut for case when there are no existentials + +tcCheckExistentialPat pats ex_tvs pat_tys body_ty + = do { tys <- mapM readExpectedType (body_ty : pat_tys) + ; addErrCtxtM (sigPatCtxt (collectPatsBinders pats) ex_tvs tys) $ + checkSigTyVarsWrt (tyVarsOfTypes tys) ex_tvs } \end{code} %************************************************************************ %* * -\subsection{tcStmts} +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} %* * %************************************************************************ - \begin{code} -tcStmts :: StmtCtxt - -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs - -> [RenamedStmt] - -> TcType -- elt_ty, where type of the comprehension is (m elt_ty) - -> TcM s ([TcStmt], LIE) - -tcStmts do_or_lc m (stmt@(ReturnStmt exp) : stmts) elt_ty - = ASSERT( null stmts ) - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - tcExpr exp elt_ty `thenTc` \ (exp', exp_lie) -> - returnTc ([ReturnStmt exp'], exp_lie) - - -- ExprStmt at the end -tcStmts do_or_lc m [stmt@(ExprStmt exp src_loc)] elt_ty - = tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - tcExpr exp (m elt_ty) `thenTc` \ (exp', exp_lie) -> - returnTc ([ExprStmt exp' src_loc], exp_lie) - - -- ExprStmt not at the end -tcStmts do_or_lc m (stmt@(ExprStmt exp src_loc) : stmts) elt_ty - = ASSERT( isDoStmt do_or_lc ) - tcAddSrcLoc src_loc ( - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - -- exp has type (m tau) for some tau (doesn't matter what) - newTyVarTy_OpenKind `thenNF_Tc` \ any_ty -> - tcExpr exp (m any_ty) - ) `thenTc` \ (exp', exp_lie) -> - tcStmts do_or_lc m stmts elt_ty `thenTc` \ (stmts', stmts_lie) -> - returnTc (ExprStmt exp' src_loc : stmts', - exp_lie `plusLIE` stmts_lie) - -tcStmts do_or_lc m (stmt@(GuardStmt exp src_loc) : stmts) elt_ty - = ASSERT( not (isDoStmt do_or_lc) ) - tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( - tcAddSrcLoc src_loc $ - tcExpr exp boolTy - ) `thenTc` \ (exp', exp_lie) -> - tcStmts do_or_lc m stmts elt_ty `thenTc` \ (stmts', stmts_lie) -> - returnTc (GuardStmt exp' src_loc : stmts', - exp_lie `plusLIE` stmts_lie) - -tcStmts do_or_lc m (stmt@(BindStmt pat exp src_loc) : stmts) elt_ty - = tcAddSrcLoc src_loc ( - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - newTyVarTy boxedTypeKind `thenNF_Tc` \ pat_ty -> - tcPat tcPatBndr_NoSigs pat pat_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail) -> - tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> - returnTc (pat', exp', - pat_lie `plusLIE` exp_lie, - pat_tvs, pat_ids, avail) - ) `thenTc` \ (pat', exp', lie_req, pat_tvs, pat_bndrs, lie_avail) -> +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 + = do { [elt_ty] <- unifyTyConApp parrTyCon res_ty + ; stmts' <- tcComprehension PArrComp parrTyCon elt_ty stmts + ; return (stmts', [{- unused -}]) } + +tcDoStmts ListComp stmts method_names res_ty + = unifyListTy res_ty ` thenM` \ elt_ty -> + tcComprehension ListComp listTyCon elt_ty stmts `thenM` \ stmts' -> + returnM (stmts', [{- unused -}]) + +tcDoStmts do_or_mdo stmts method_names res_ty + = newTyFlexiVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty -> + newTyFlexiVarTy liftedTypeKind `thenM` \ elt_ty -> + unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_` let - new_val_env = bagToList pat_bndrs - pat_ids = map snd new_val_env - pat_tv_list = bagToList pat_tvs - in + ctxt = SC { sc_what = do_or_mdo, + sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs + ; rhs_elt_ty <- unifyAppTy m_ty rhs_ty + ; return (rhs', 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 m_tycon elt_ty stmts + = tcStmts ctxt stmts + where + ctxt = SC { sc_what = do_or_lc, + sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs + ; [rhs_elt_ty] <- unifyTyConApp m_tycon rhs_ty + ; return (rhs', rhs_elt_ty) }, + sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no m_tycon here! + sc_ty = mkTyConApp m_tycon [elt_ty] } +\end{code} - -- Do the rest; we don't need to add the pat_tvs to the envt - -- because they all appear in the pat_ids's types - tcExtendLocalValEnv new_val_env ( - tcStmts do_or_lc m stmts elt_ty - ) `thenTc` \ (stmts', stmts_lie) -> +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ - -- Reinstate context for existential checks - tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ - tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $ - tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $ +Typechecking statements is rendered a bit tricky by parallel list comprehensions: - checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs -> + [ (g x, h x) | ... ; let g v = ... + | ... ; let h v = ... ] - tcSimplifyAndCheck - (text ("the existential context of a data constructor")) - (mkVarSet zonked_pat_tvs) - lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) -> +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: - returnTc (BindStmt pat' exp' src_loc : - consLetStmt (mkMonoBind dict_binds [] Recursive) stmts', - lie_req `plusLIE` final_lie) + data T = forall a. Show a => C a -tcStmts do_or_lc m (LetStmt binds : stmts) elt_ty - = tcBindsAndThen -- No error context, but a binding group is - combine -- rather a large thing for an error context anyway - binds - (tcStmts do_or_lc m stmts elt_ty) - where - combine is_rec binds' stmts' = consLetStmt (mkMonoBind binds' [] is_rec) stmts' + [ (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. -isDoStmt DoStmt = True -isDoStmt other = False +\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 -> TcM (LHsExpr TcId, TcType), -- Type inference 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 + -- We 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. + +tcStmtsAndThen + :: (LStmt TcId -> thing -> thing) -- Combiner + -> TcStmtCtxt + -> [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 + = setSrcSpan src_loc $ + addErrCtxt (stmtCtxt ctxt stmt) $ + do { (exp', pat_ty) <- sc_rhs ctxt exp + ; ([pat'], thing) <- tcMatchPats [pat] [Check pat_ty] (Check (sc_ty ctxt)) $ + popErrCtxt thing_inside + ; return (combine (L src_loc (BindStmt pat' exp')) thing) } + + -- ExprStmt +tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside + = setSrcSpan src_loc ( + addErrCtxt (stmtCtxt ctxt stmt) $ + if isDoExpr (sc_what ctxt) + then -- do or mdo; the expression is a computation + sc_rhs ctxt exp `thenM` \ (exp', exp_ty) -> + returnM (L src_loc (ExprStmt exp' exp_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) + 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 + = newTyFlexiVarTys (length recNames) liftedTypeKind `thenM` \ recTys -> + let + rec_ids = zipWith mkLocalId recNames recTys + in + tcExtendIdEnv rec_ids $ + tcStmtsAndThen combine_rec ctxt stmts ( + zipWithM tc_ret recNames recTys `thenM` \ rec_rets -> + tcLookupLocalIds laterNames `thenM` \ later_ids -> + returnM ([], (later_ids, rec_rets)) + ) `thenM` \ (stmts', (later_ids, rec_rets)) -> + + tcExtendIdEnv later_ids $ + -- 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) + getLIE thing_inside `thenM` \ (thing, lie) -> + bindInstsOfLocalFuns lie later_ids `thenM` \ lie_binds -> + + returnM (combine (L src_loc (RecStmt stmts' later_ids rec_ids rec_rets)) $ + combine (L src_loc (LetStmt [HsBindGroup lie_binds [] Recursive])) $ + 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 -> + -- 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) + + +------------------------------ +glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing + -- ToDo: fix the noLoc \end{code} @@ -369,47 +537,44 @@ isDoStmt other = False number of args are used in each equation. \begin{code} -sameNoOfArgs :: [RenamedMatch] -> Bool -sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1 +sameNoOfArgs :: MatchGroup Name -> Bool +sameNoOfArgs (MatchGroup matches _) + = isSingleton (nub (map args_in_match matches)) where - args_in_match :: RenamedMatch -> Int - args_in_match (Match _ pats _ _) = length pats + args_in_match :: LMatch Name -> Int + args_in_match (L _ (Match pats _ _)) = length pats \end{code} \begin{code} -matchCtxt CaseAlt match - = hang (ptext SLIT("In a case alternative:")) - 4 (pprMatch (True,empty) {-is_case-} match) - -matchCtxt (FunRhs fun) match - = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr_fun), char ':']) - 4 (pprMatch (False, ppr_fun) {-not case-} match) - where - ppr_fun = ppr fun - -matchCtxt LambdaBody match - = hang (ptext SLIT("In the lambda expression")) - 4 (pprMatch (True, empty) match) - varyingArgsErr name matches = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)] -lurkingRank2SigErr - = ptext SLIT("Too few explicit arguments when defining a function with a rank-2 type") - -stmtCtxt do_or_lc stmt - = hang (ptext SLIT("In") <+> what <> colon) - 4 (ppr stmt) +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_ids bound_tvs 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 - what = case do_or_lc of - ListComp -> ptext SLIT("a list-comprehension qualifier") - DoStmt -> ptext SLIT("a do statement") - PatBindRhs -> thing <+> ptext SLIT("a pattern binding") - FunRhs f -> thing <+> ptext SLIT("an equation for") <+> quotes (ppr f) - CaseAlt -> thing <+> ptext SLIT("a case alternative") - LambdaBody -> thing <+> ptext SLIT("a lambda abstraction") - thing = case stmt of - BindStmt _ _ _ -> ptext SLIT("a pattern guard for") - GuardStmt _ _ -> ptext SLIT("a guard for") - ExprStmt _ _ -> ptext SLIT("the right-hand side of") + show_ids = filter is_interesting bound_ids + is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs + + ppr_id id ty = ppr id <+> dcolon <+> ppr ty + -- Don't zonk the types so we get the separate, un-unified versions \end{code}