X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=20c2a44a49e4c18d61a79282a68b64ba90bf41c0;hb=2c6d73e2ca9a545c4295c6f532cd3612e7fd3d8d;hp=6be207626fcb4df302c8000dd652144088af1a0e;hpb=438596897ebbe25a07e1c82085cfbc5bdb00f09e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 6be2076..20c2a44 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,211 +4,456 @@ \section[TcMatches]{Typecheck some @Matches@} \begin{code} -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchExpected ) where +module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, + tcStmts, tcStmtsAndThen, tcGRHSs + ) where #include "HsVersions.h" -import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds ) +import {-# SOURCE #-} TcExpr( tcExpr ) -import HsSyn ( HsBinds(..), Match(..), GRHSsAndBinds(..), - MonoBinds(..), StmtCtxt(..), - pprMatch, getMatchLoc +import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), + MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..), + pprMatch, getMatchLoc, pprMatchContext, isDoExpr, + mkMonoBind, nullMonoBinds, collectSigTysFromPats ) -import RnHsSyn ( RenamedMatch ) -import TcHsSyn ( TcMatch ) +import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedHsType, + RenamedMatchContext, extractHsTyVars ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat, TypecheckedMatchContext ) import TcMonad -import TcMonoType ( checkSigTyVars, noSigs, existentialPatCtxt ) -import Inst ( Inst, LIE, plusLIE, emptyLIE ) -import TcEnv ( tcExtendEnvWithPat, tcExtendGlobalTyVars ) -import TcPat ( tcPat ) +import TcMonoType ( kcHsSigTypes, tcScopedTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt ) +import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) +import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars, + tcInLocalScope ) +import TcPat ( tcPat, tcMonoPatBndr, polyPatSig ) import TcType ( TcType, newTyVarTy ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcUnify ( unifyFunTy ) +import TcBinds ( tcBindsAndThen ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcUnify ( unifyFunTy, unifyTauTy ) import Name ( Name ) - +import TysWiredIn ( boolTy ) +import Id ( idType ) import BasicTypes ( RecFlag(..) ) -import Type ( Kind, tyVarsOfType, isTauTy, mkFunTy, openTypeKind ) +import Type ( tyVarsOfType, isTauTy, mkFunTy, + liftedTypeKind, openTypeKind, splitSigmaTy ) +import NameSet import VarSet -import Util +import Var ( Id ) import Bag import Outputable -import SrcLoc (SrcLoc) +import List ( nub ) \end{code} +%************************************************************************ +%* * +\subsection{tcMatchesFun, tcMatchesCase} +%* * +%************************************************************************ + @tcMatchesFun@ typechecks a @[Match]@ list which occurs in a @FunMonoBind@. The second argument is the name of the function, which 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 - -> TcType s -- Expected type +tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group + -> Name + -> TcType -- Expected type -> [RenamedMatch] - -> TcM s ([TcMatch s], LIE s) + -> TcM ([TcMatch], LIE) -tcMatchesFun fun_name expected_ty matches@(first_match:_) - = -- Set the location to that of the first equation, so that +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) ( - - -- Check that they all have the same no of arguments - checkTc (all_same (noOfArgs matches)) - (varyingArgsErr fun_name matches) `thenTc_` + checkTc (sameNoOfArgs matches) + (varyingArgsErr fun_name matches) + ) `thenTc_` -- 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 - tcMatchesExpected matches expected_ty (FunRhs fun_name) - - ) - where - all_same :: [Int] -> Bool - all_same [] = True -- Should never happen (ToDo: panic?) - all_same [x] = True - all_same (x:xs) = all ((==) x) xs + tcMatches xve (FunRhs fun_name) matches expected_ty \end{code} @tcMatchesCase@ doesn't do the argument-count check because the parser guarantees that each equation has exactly one argument. \begin{code} -tcMatchesCase :: TcType s -- Type of whole case expressions - -> [RenamedMatch] -- The case alternatives - -> TcM s (TcType s, -- Inferred type of the scrutinee - [TcMatch s], -- Translated alternatives - LIE s) +tcMatchesCase :: [RenamedMatch] -- The case alternatives + -> TcType -- Type of whole case expressions + -> TcM (TcType, -- Inferred type of the scrutinee + [TcMatch], -- Translated alternatives + LIE) -tcMatchesCase expr_ty matches +tcMatchesCase matches expr_ty = newTyVarTy openTypeKind `thenNF_Tc` \ scrut_ty -> - tcMatchesExpected matches (mkFunTy scrut_ty expr_ty) CaseAlt `thenTc` \ (matches', lie) -> + 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 \end{code} \begin{code} -tcMatchesExpected :: [RenamedMatch] - -> TcType s - -> StmtCtxt - -> TcM s ([TcMatch s], LIE s) - -tcMatchesExpected [match] expected_ty fun_or_case - = tcAddSrcLoc (getMatchLoc match) $ - tcAddErrCtxt (matchCtxt fun_or_case match) $ - tcMatchExpected match expected_ty fun_or_case `thenTc` \ (match', lie) -> - returnTc ([match'], lie) - -tcMatchesExpected (match1 : matches) expected_ty fun_or_case - = tcAddSrcLoc (getMatchLoc match1) ( - tcAddErrCtxt (matchCtxt fun_or_case match1) $ - tcMatchExpected match1 expected_ty fun_or_case - ) `thenTc` \ (match1', lie1) -> - tcMatchesExpected matches expected_ty fun_or_case `thenTc` \ (matches', lie2) -> - returnTc (match1' : matches', plusLIE lie1 lie2) +tcMatches :: [(Name,Id)] + -> RenamedMatchContext + -> [RenamedMatch] + -> TcType + -> TcM ([TcMatch], LIE) + +tcMatches xve fun_or_case matches expected_ty + = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> + returnTc (matches, plusLIEs lies) + where + tc_match match = tcMatch xve fun_or_case match expected_ty \end{code} + +%************************************************************************ +%* * +\subsection{tcMatch} +%* * +%************************************************************************ + \begin{code} -tcMatchExpected - :: RenamedMatch - -> TcType s -- Expected result-type of the Match. +tcMatch :: [(Name,Id)] + -> RenamedMatchContext + -> RenamedMatch + -> TcType -- Expected result-type of the Match. -- Early unification with this guy gives better error messages - -> StmtCtxt - -> TcM s (TcMatch s,LIE s) + -> TcM (TcMatch, LIE) -tcMatchExpected match expected_ty ctxt - = tcMatchExpected_help emptyBag emptyBag emptyLIE match expected_ty ctxt +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) + 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 + tc_result_sig maybe_rhs_sig ( -tcMatchExpected_help bound_tvs bound_ids bound_lie - the_match@(PatMatch pat match) expected_ty ctxt - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> + -- Typecheck the body + tcExtendLocalValEnv xve1 $ + tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) -> + returnTc ((pats', grhss'), lie) + ) - tcPat noSigs pat arg_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail_lie) -> + tc_result_sig Nothing thing_inside + = thing_inside + tc_result_sig (Just sig) thing_inside + = tcAddScopedTyVars [sig] $ + tcHsSigType sig `thenTc` \ sig_ty -> - tcMatchExpected_help - (bound_tvs `unionBags` pat_tvs) - (bound_ids `unionBags` pat_ids) - (bound_lie `plusLIE` avail_lie) - match rest_ty ctxt `thenTc` \ (match', lie_match) -> + -- 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 expected_ty sig_ty `thenTc_` + thing_inside - returnTc (PatMatch pat' match', pat_lie `plusLIE` lie_match) + -- 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 -tcMatchExpected_help bound_tvs bound_ids bound_lie - (GRHSMatch grhss_and_binds) expected_ty ctxt - = -- 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 expected_ty) - lurkingRank2SigErr `thenTc_` +tcGRHSs :: RenamedMatchContext -> RenamedGRHSs + -> TcType + -> TcM (TcGRHSs, LIE) - tcExtendEnvWithPat bound_ids ( - tcGRHSsAndBinds grhss_and_binds expected_ty ctxt - ) `thenTc` \ (GRHSsAndBindsOut grhss binds ty, lie) -> +tcGRHSs ctxt (GRHSs grhss binds _) expected_ty + = tcBindsAndThen glue_on binds (tc_grhss grhss) + 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, expected_ty) guarded `thenTc` \ (guarded', lie) -> + returnTc (GRHS guarded' locn, lie) +\end{code} - -- Check for existentially bound type variables - tcExtendGlobalTyVars (tyVarsOfType expected_ty) ( - tcAddErrCtxtM (existentialPatCtxt bound_tvs bound_ids) $ - checkSigTyVars (bagToList bound_tvs) `thenTc` \ zonked_pat_tvs -> - tcSimplifyAndCheck - (text ("the existential context of a data constructor")) - (mkVarSet zonked_pat_tvs) - bound_lie lie - ) `thenTc` \ (ex_lie, ex_binds) -> +%************************************************************************ +%* * +\subsection{tcMatchPats} +%* * +%************************************************************************ + +\begin{code} +tcMatchPats + :: [RenamedPat] -> TcType + -> ([TypecheckedPat] -> TcType -> TcM (a, LIE)) + -> TcM (a, LIE, TcDictBinds) +-- Typecheck the patterns, extend the environment to bind the variables, +-- do the thing inside, use any existentially-bound dictionaries to +-- discharge parts of the returning LIE, and deal with pattern type +-- signatures + +tcMatchPats pats expected_ty thing_inside + = -- STEP 1: Bring pattern-signature type variables into scope + tcAddScopedTyVars (collectSigTysFromPats pats) $ + + -- STEP 2: Typecheck the patterns themselves, gathering all the stuff + tc_match_pats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) -> + + -- STEP 3: Extend the environment, and do the thing inside + let + xve = bagToList pat_bndrs + pat_ids = map snd xve + in + tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) -> + + -- STEP 4: Check for existentially bound type variables + -- 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 rhs_ty `thenTc` \ (lie_req2', ex_binds) -> + + 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 -> + 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 result type; vars in here must not escape + -> TcM (LIE, TcDictBinds) -- LIE to float out and dict bindings +tcCheckExistentialPat ids ex_tvs lie_avail lie_req result_ty + | isEmptyBag ex_tvs && all not_overloaded ids + -- Short cut for case when there are no existentials + -- and no polymorphic overloaded variables + -- e.g. f :: (forall a. Ord a => a -> a) -> Int -> Int + -- f op x = .... + -- Here we must discharge op Methods + = ASSERT( isEmptyLIE lie_avail ) + returnTc (lie_req, EmptyMonoBinds) + + | otherwise + = tcExtendGlobalTyVars (tyVarsOfType result_ty) $ + tcAddErrCtxtM (sigPatCtxt tv_list ids) $ -- In case there are any polymorpic, overloaded binders in the pattern -- (which can happen in the case of rank-2 type signatures, or data constructors -- with polymorphic arguments), we must do a bindInstsOfLocalFns here - bindInstsOfLocalFuns ex_lie bound_id_list `thenTc` \ (inst_lie, inst_binds) -> + bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) -> - let - binds' = ex_binds `glue_on` (inst_binds `glue_on` binds) - in - returnTc (GRHSMatch (GRHSsAndBindsOut grhss binds' ty), inst_lie) - where - bound_id_list = map snd (bagToList bound_ids) + -- 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_` - -- glue_on just avoids stupid dross - glue_on EmptyMonoBinds binds = binds -- The common case - glue_on mbinds binds = MonoBind mbinds [] Recursive `ThenBinds` binds + returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) + where + doc = text ("the existential context of a data constructor") + tv_list = bagToList ex_tvs + not_overloaded id = case splitSigmaTy (idType id) of + (_, theta, _) -> null theta + +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 + ) \end{code} -@noOfArgs@ takes a @[RenamedMatch]@ and returns a list telling how -many arguments were used in each of the equations. This is used to -report a sensible error message when different equations have -different numbers of arguments. +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ -\begin{code} -noOfArgs :: [RenamedMatch] -> [Int] +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. -noOfArgs ms = map args_in_match ms +\begin{code} +tcStmts do_or_lc m_ty stmts + = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE)) + +tcStmtsAndThen + :: (TcStmt -> thing -> thing) -- Combiner + -> RenamedMatchContext + -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs + -- elt_ty, where type of the comprehension is (m elt_ty) + -> [RenamedStmt] + -> TcM (thing, LIE) + -> TcM (thing, LIE) + + -- Base case +tcStmtsAndThen combine do_or_lc m_ty [] do_next + = do_next + +tcStmtsAndThen combine do_or_lc m_ty (stmt:stmts) do_next + = tcStmtAndThen combine do_or_lc m_ty stmt + (tcStmtsAndThen combine do_or_lc m_ty stmts do_next) + + -- LetStmt +tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside + = tcBindsAndThen -- No error context, but a binding group is + (glue_binds combine) -- rather a large thing for an error context anyway + binds + thing_inside + +tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) thing_inside + = tcAddSrcLoc src_loc $ + tcAddErrCtxt (stmtCtxt do_or_lc stmt) $ + newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> + tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> + tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ [pat'] _ -> + tcPopErrCtxt $ + thing_inside `thenTc` \ (thing, lie) -> + returnTc ((BindStmt pat' exp' src_loc, thing), lie) + ) `thenTc` \ ((stmt', thing), lie, dict_binds) -> + returnTc (combine stmt' (glue_binds combine Recursive dict_binds thing), + lie `plusLIE` exp_lie) + + + -- ParStmt +tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside + = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) -> + returnTc (combine (ParStmtOut pairs') thing, lie) where - args_in_match :: RenamedMatch -> Int - args_in_match (GRHSMatch _) = 0 - args_in_match (PatMatch _ match) = 1 + args_in_match match + loop [] + = thing_inside `thenTc` \ (thing, stmts_lie) -> + returnTc (([], thing), stmts_lie) + + loop ((bndrs,stmts) : pairs) + = tcStmtsAndThen + combine_par (DoCtxt ListComp) m_ty stmts + -- Notice we pass on m_ty; the result type is used only + -- to get escaping type variables for checkExistentialPat + (tcLookupLocalIds bndrs `thenNF_Tc` \ bndrs' -> + loop pairs `thenTc` \ ((pairs', thing), lie) -> + returnTc (([], (bndrs', pairs', thing)), lie)) `thenTc` \ ((stmts', (bndrs', pairs', thing)), lie) -> + + returnTc ( ((bndrs',stmts') : pairs', thing), lie) + + combine_par stmt (stmts, thing) = (stmt:stmts, thing) + + -- ExprStmt +tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp locn) thing_inside + = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( + if isDoExpr do_or_lc then + newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> + tcExpr exp (m any_ty) + else + tcExpr exp boolTy + ) `thenTc` \ (exp', stmt_lie) -> + + thing_inside `thenTc` \ (thing, stmts_lie) -> + + returnTc (combine (ExprStmt exp' locn) thing, + stmt_lie `plusLIE` stmts_lie) + + + -- Result statements +tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside + = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( + if isDoExpr do_or_lc then + tcExpr exp (m res_elt_ty) + else + tcExpr exp res_elt_ty + ) `thenTc` \ (exp', stmt_lie) -> + + thing_inside `thenTc` \ (thing, stmts_lie) -> + + returnTc (combine (ResultStmt exp' locn) thing, + stmt_lie `plusLIE` stmts_lie) + + +------------------------------ +glue_binds combine is_rec binds thing + | nullMonoBinds binds = thing + | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing \end{code} -Errors and contexts -~~~~~~~~~~~~~~~~~~~ -\begin{code} -matchCtxt CaseAlt match - = hang (ptext SLIT("In a \"case\" branch:")) - 4 (pprMatch True{-is_case-} match) -matchCtxt (FunRhs fun) match - = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr fun), char ':']) - 4 (hcat [ppr fun, space, pprMatch False{-not case-} match]) -\end{code} +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same +number of args are used in each equation. +\begin{code} +sameNoOfArgs :: [RenamedMatch] -> Bool +sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1 + where + args_in_match :: RenamedMatch -> Int + 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)]