X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=21c74dcce4ca3162ed6b2740d31d13929049a31c;hb=4e5d22a241b6347c462cf7748e13effde0f02720;hp=4bbcc5a5ffcffd0b22c239b8d57eb72a437c146b;hpb=9e93335020e64a811dbbb223e1727c76933a93ae;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 4bbcc5a..21c74dc 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,43 +4,53 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, - tcStmts, tcStmtsAndThen, tcGRHSs +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, tcMonoExpr ) -import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), - MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..), - pprMatch, getMatchLoc, pprMatchContext, isDoExpr, - mkMonoBind, nullMonoBinds, collectSigTysFromPats +import HsSyn ( HsExpr(..), HsBinds(..), Match(..), GRHSs(..), GRHS(..), + MonoBinds(..), Stmt(..), HsMatchContext(..), HsStmtContext(..), + ReboundNames, + pprMatch, getMatchLoc, isDoExpr, + pprMatchContext, pprStmtContext, pprStmtResultContext, + mkMonoBind, collectSigTysFromPats, glueBindsOnGRHSs ) -import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedHsType, - RenamedMatchContext, extractHsTyVars ) -import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat ) - -import TcMonad -import TcMonoType ( kcHsSigTypes, tcScopedTyVars, checkSigTyVars, tcHsSigType, UserTypeCtxt(..), sigPatCtxt ) -import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) -import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars, - tcInLocalScope ) -import TcPat ( tcPat, tcMonoPatBndr, polyPatSig ) -import TcMType ( newTyVarTy, unifyFunTy, unifyTauTy ) -import TcType ( tyVarsOfType, isTauTy, mkFunTy, isOverloadedTy, - liftedTypeKind, openTypeKind ) +import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedHsExpr, + RenamedPat, RenamedMatchContext ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds, TcExpr, + TcPat, TcStmt, ExprCoFn, + isIdCoercion, (<$>), (<.>) ) + +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, + 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 Name ( Name ) -import TysWiredIn ( boolTy ) -import Id ( idType ) +import TysWiredIn ( boolTy, mkListTy, mkPArrTy ) +import Id ( idType, mkLocalId ) +import CoreFVs ( idFreeTyVars ) import BasicTypes ( RecFlag(..) ) -import NameSet import VarSet -import Var ( Id ) import Bag -import Util ( isSingleton ) +import Util ( isSingleton, notNull ) import Outputable import List ( nub ) @@ -58,64 +68,101 @@ 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 +tcMatchesFun :: Name -> [RenamedMatch] - -> TcM ([TcMatch], LIE) + -> Expected TcRhoType -- Expected type + -> TcM [TcMatch] -tcMatchesFun xve fun_name expected_ty matches@(first_match:_) +tcMatchesFun fun_name matches@(first_match:_) expected_ty = -- 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) ( + addSrcLoc (getMatchLoc first_match) ( checkTc (sameNoOfArgs matches) (varyingArgsErr fun_name matches) - ) `thenTc_` + ) `thenM_` -- 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 (FunRhs fun_name) matches expected_ty + -- No need to zonk expected_ty, because subFunTys does that on the fly + tcMatches match_ctxt matches expected_ty + 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 (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 + -> [RenamedMatch] -- The case alternatives + -> Expected TcRhoType -- Type of whole case expressions + -> TcM (TcRhoType, -- Inferred type of the scrutinee + [TcMatch]) -- Translated alternatives + +tcMatchesCase ctxt matches (Check expr_ty) + = -- This case is a bit yukky, because it prevents the + -- scrutinee being higher-ranked, which might just possible + -- matter if we were seq'ing on it. But it's awkward to fix. + newTyVarTy openTypeKind `thenM` \ scrut_ty -> + 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 :: RenamedMatch -> Expected TcRhoType -> TcM TcMatch +tcMatchLambda match res_ty = tcMatch match_ctxt match res_ty + 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)] - -> RenamedMatchContext - -> [RenamedMatch] - -> TcType - -> TcM ([TcMatch], LIE) +tcGRHSsPat :: RenamedGRHSs + -> Expected TcRhoType + -> TcM TcGRHSs +tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty + where + match_ctxt = MC { mc_what = PatBindRhs, + mc_body = tcMonoExpr } +\end{code} -tcMatches xve fun_or_case matches expected_ty - = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> - returnTc (matches, plusLIEs lies) +\begin{code} +data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module + = MC { mc_what :: RenamedMatchContext, -- What kind of thing this is + mc_body :: RenamedHsExpr -- Type checker for a body of an alternative + -> Expected TcRhoType + -> TcM TcExpr } + +tcMatches :: TcMatchCtxt + -> [RenamedMatch] + -> Expected TcRhoType + -> TcM [TcMatch] + +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 (tc_match exp_ty') matches where - tc_match match = tcMatch xve fun_or_case match expected_ty + tc_match exp_ty match = tcMatch ctxt match exp_ty \end{code} @@ -126,72 +173,112 @@ tcMatches xve fun_or_case matches expected_ty %************************************************************************ \begin{code} -tcMatch :: [(Name,Id)] - -> RenamedMatchContext +tcMatch :: TcMatchCtxt -> RenamedMatch - -> TcType -- Expected result-type of the Match. + -> 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. - -> TcM (TcMatch, LIE) - -tcMatch xve1 ctxt match@(Match sig_tvs 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) + -> TcM TcMatch + +tcMatch ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty + = addSrcLoc (getMatchLoc match) $ -- At one stage I removed this; + 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 pats' rhs_ty - = -- 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` \_ -> - - -- Deal with the result signature - -- It "wraps" the rest of the body typecheck because it may - -- bring into scope the type variables in the signature - tc_result_sig maybe_rhs_sig rhs_ty $ - - -- Typecheck the body - tcExtendLocalValEnv xve1 $ - tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) -> - returnTc ((pats', grhss'), lie) - - tc_result_sig Nothing rhs_ty thing_inside - = thing_inside - tc_result_sig (Just sig) rhs_ty thing_inside - = tcAddScopedTyVars [sig] $ - tcHsSigType ResSigCtxt 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 sig_ty rhs_ty `thenTc_` - thing_inside - - - -- 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_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 lift_grhs grhss) binds rhs_ty -- Change the type, since the coercion does 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) + 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 + +tcGRHSs :: TcMatchCtxt -> RenamedGRHSs + -> Expected TcRhoType + -> TcM TcGRHSs + + -- 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 [GRHS [ResultStmt rhs loc1] loc2] binds _) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + mc_body ctxt rhs exp_ty `thenM` \ rhs' -> + readExpectedType exp_ty `thenM` \ exp_ty' -> + returnM (GRHSs [GRHS [ResultStmt rhs' loc1] loc2] EmptyBinds exp_ty') + +tcGRHSs ctxt (GRHSs grhss binds _) exp_ty + = tcBindsAndThen glueBindsOnGRHSs binds $ + zapExpectedType exp_ty `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 locn) + = addSrcLoc locn $ + tcStmts stmt_ctxt guarded `thenM` \ guarded' -> + returnM (GRHS guarded' locn) + in + mappM tc_grhs grhss `thenM` \ grhss' -> + returnM (GRHSs grhss' EmptyBinds 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} @@ -203,30 +290,24 @@ tcGRHSs ctxt (GRHSs grhss binds _) expected_ty \begin{code} tcMatchPats - :: [RenamedPat] -> TcType - -> ([TypecheckedPat] -> TcType -> TcM (a, LIE)) - -> TcM (a, LIE, TcDictBinds) + :: [(RenamedPat, Expected TcRhoType)] + -> Expected TcRhoType + -> TcM a + -> TcM ([TcPat], a, TcHsBinds) -- 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 +tcMatchPats pats_w_tys body_ty thing_inside = -- STEP 1: Bring pattern-signature type variables into scope - tcAddScopedTyVars (collectSigTysFromPats pats) ( + tcAddScopedTyVars (collectSigTysFromPats (map fst pats_w_tys)) ( -- 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) -> + -- then do the thing inside + getLIE (tc_match_pats pats_w_tys thing_inside) - 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) -> + ) `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 @@ -235,85 +316,134 @@ tcMatchPats pats expected_ty thing_inside -- 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 + 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 (a -> Int). - - returnTc (result, lie_req1 `plusLIE` lie_req2', ex_binds) - -tcAddScopedTyVars :: [RenamedHsType] -> TcM a -> TcM a --- Find the not-already-in-scope signature type variables, --- kind-check them, and bring them into scope --- --- We no longer specify that these type variables must be univerally --- quantified (lots of email on the subject). If you want to put that --- back in, you need to --- a) Do a checkSigTyVars after thing_inside --- b) More insidiously, don't pass in expected_ty, else --- we unify with it too early and checkSigTyVars barfs --- Instead you have to pass in a fresh ty var, and unify --- it with expected_ty afterwards -tcAddScopedTyVars sig_tys thing_inside - = tcGetEnv `thenNF_Tc` \ env -> + -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int). + + returnM (pats', result, mkMonoBind Recursive ex_binds) + +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 - all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys - sig_tvs = filter not_in_scope (nameSetToList all_sig_tvs) - not_in_scope tv = not (tcInLocalScope env tv) - in - tcScopedTyVars sig_tvs (kcHsSigTypes sig_tys) thing_inside - -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 + 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 $ + 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( isEmptyLIE lie_avail ) - returnTc (lie_req, EmptyMonoBinds) + = ASSERT( null ex_lie ) + extendLIEs lie_req `thenM_` + returnM EmptyMonoBinds | otherwise - = tcExtendGlobalTyVars (tyVarsOfType match_ty) $ - tcAddErrCtxtM (sigPatCtxt tv_list ids) $ + = -- 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 - bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) -> + getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, lie) -> -- 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_` + tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds -> + + -- Check for type variable escape + checkSigTyVarsWrt (tyVarsOfTypes tys) tv_list `thenM_` - returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) + returnM (dict_binds `AndMonoBinds` inst_binds) where - doc = text ("the existential context of a data constructor") + doc = text ("existential context of a data constructor") tv_list = bagToList ex_tvs not_overloaded id = not (isOverloadedTy (idType id)) +\end{code} -tc_match_pats [] expected_ty - = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) - -tc_match_pats (pat:pats) expected_ty - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> - 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 - ) + +%************************************************************************ +%* * +\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} +%* * +%************************************************************************ + +\begin{code} +tcDoStmts :: HsStmtContext Name + -> [RenamedStmt] -> ReboundNames Name + -> TcRhoType -- To keep it simple, we don't have an "expected" type here + -> TcM ([TcStmt], 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 } \end{code} @@ -346,105 +476,127 @@ 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)) - +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 :: RenamedHsExpr -> TcType -> TcM TcExpr, -- Type checker for RHS computations + sc_body :: RenamedHsExpr -> TcM TcExpr, -- Type checker for return computation + sc_ty :: TcType } -- Return type; used *only* to check + -- for escape in existential patterns 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) + -> TcStmtCtxt -> [RenamedStmt] - -> TcM (thing, LIE) - -> TcM (thing, LIE) + -> TcM thing + -> TcM thing -- Base case -tcStmtsAndThen combine do_or_lc m_ty [] do_next - = do_next +tcStmtsAndThen combine ctxt [] thing_inside + = thing_inside -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) +tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside + = tcStmtAndThen combine ctxt stmt $ + tcStmtsAndThen combine ctxt stmts $ + thing_inside -- LetStmt -tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside +tcStmtAndThen combine ctxt (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) + -- BindStmt +tcStmtAndThen combine ctxt stmt@(BindStmt pat exp src_loc) thing_inside + = addSrcLoc 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 (BindStmt pat' exp' src_loc) + (glue_binds combine dict_binds thing)) + + -- ExprStmt +tcStmtAndThen combine ctxt stmt@(ExprStmt exp _ src_loc) thing_inside + = addSrcLoc src_loc ( + addErrCtxt (stmtCtxt ctxt stmt) $ + if isDoExpr (sc_what ctxt) + then -- do or mdo; the expression is a computation + newTyVarTy openTypeKind `thenM` \ any_ty -> + sc_rhs ctxt exp any_ty `thenM` \ exp' -> + returnM (ExprStmt exp' any_ty src_loc) + else -- List comprehensions, pattern guards; expression is a boolean + tcCheckRho exp boolTy `thenM` \ exp' -> + returnM (ExprStmt exp' boolTy src_loc) + ) `thenM` \ stmt' -> + + thing_inside `thenM` \ thing -> + returnM (combine stmt' thing) -- 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) +tcStmtAndThen combine ctxt (ParStmt bndr_stmts_s) thing_inside + = loop bndr_stmts_s `thenM` \ (pairs', thing) -> + returnM (combine (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) + loop [] = thing_inside `thenM` \ thing -> + returnM ([], thing) - 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) -> + 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) - returnTc (combine stmt' thing, stmt_lie `plusLIE` stmts_lie) + combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing) + -- RecStmt +tcStmtAndThen combine ctxt (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 -> + + returnM (combine (RecStmt stmts' later_ids rec_ids rec_rets) 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 (co_fn <$> HsVar poly_id) -- 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) +tcStmtAndThen combine ctxt stmt@(ResultStmt exp locn) thing_inside + = addErrCtxt (stmtCtxt ctxt stmt) (sc_body ctxt exp) `thenM` \ exp' -> + thing_inside `thenM` \ thing -> + returnM (combine (ResultStmt exp' locn) thing) ------------------------------ -glue_binds combine is_rec binds thing - | nullMonoBinds binds = thing - | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing +glue_binds combine EmptyBinds thing = thing +glue_binds combine other_binds thing = combine (LetStmt other_binds) thing \end{code} @@ -462,16 +614,39 @@ sameNoOfArgs :: [RenamedMatch] -> Bool sameNoOfArgs matches = isSingleton (nub (map args_in_match matches)) where args_in_match :: RenamedMatch -> Int - args_in_match (Match _ pats _ _) = length pats + args_in_match (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) - 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") +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 + + ppr_id id ty = ppr id <+> dcolon <+> ppr ty + -- Don't zonk the types so we get the separate, un-unified versions \end{code}