X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=32fd91e821374a7e84d822759b98e8ffc6da2290;hb=ebf2c80221ccf11aeb7a0a2be27bfc72529855a5;hp=d5bae6830c95cdc889643a5f191d6b371c8fe40f;hpb=7d61cb61daa5e433a0cb85b34b7f0c58b2f961ff;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index d5bae68..32fd91e 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -1,220 +1,471 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[TcMatches]{Typecheck some @Matches@} \begin{code} -#include "HsVersions.h" +module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, + tcStmts, tcStmtsAndThen, tcGRHSs + ) where -module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where +#include "HsVersions.h" -import Ubiq +import {-# SOURCE #-} TcExpr( tcExpr ) -import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat, - HsExpr, HsBinds, OutPat, Fake, - collectPatBinders, pprMatch ) -import RnHsSyn ( RenamedMatch(..) ) -import TcHsSyn ( TcIdOcc(..), TcMatch(..) ) +import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..), + MonoBinds(..), Stmt(..), HsMatchContext(..), + pprMatch, getMatchLoc, pprMatchContext, isDoExpr, + mkMonoBind, nullMonoBinds, collectSigTysFromPats + ) +import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds ) import TcMonad -import Inst ( Inst, LIE(..), plusLIE ) -import TcEnv ( newMonoIds ) -import TcLoop ( tcGRHSsAndBinds ) -import TcPat ( tcPat ) -import TcType ( TcType(..), TcMaybe, zonkTcType ) -import Unify ( unifyTauTy, unifyTauTyList ) - -import Kind ( Kind, mkTypeKind ) +import TcMonoType ( kcHsSigType, tcTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt ) +import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) +import TcEnv ( TcId, tcLookupLocalIds, tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars ) +import TcPat ( tcPat, tcMonoPatBndr, polyPatSig ) +import TcType ( TcType, newTyVarTy ) +import TcBinds ( tcBindsAndThen ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) +import TcUnify ( unifyFunTy, unifyTauTy ) import Name ( Name ) -import Pretty -import Type ( isTyVarTy, mkFunTy, getFunTy_maybe ) -import Util +import TysWiredIn ( boolTy, mkListTy ) +import Id ( idType ) +import BasicTypes ( RecFlag(..) ) +import Type ( tyVarsOfType, isTauTy, mkFunTy, + liftedTypeKind, openTypeKind, splitSigmaTy ) +import VarSet +import Var ( Id ) +import Bag +import Outputable +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 (get_Match_loc first_match) ( - - -- Check that they all have the same no of arguments - checkTc (all_same (noOfArgs matches)) - (varyingArgsErr fun_name matches) `thenTc_` + tcAddSrcLoc (getMatchLoc first_match) ( + 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 - -- We need to substitute so that we can see as much about the type as possible - zonkTcType expected_ty `thenNF_Tc` \ expected_ty' -> - tcMatchesExpected expected_ty' (MFun fun_name) matches - - ) - where - all_same :: [Int] -> Bool - all_same [] = True -- Should never happen (ToDo: panic?) - all_same [x] = True - all_same (x:xs) = all ((==) x) xs + -- No need to zonk expected_ty, because unifyFunTy does that on the fly + tcMatches xve matches expected_ty (FunRhs fun_name) \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 -> [RenamedMatch] -> TcM s ([TcMatch s], LIE s) -tcMatchesCase expected_ty matches = tcMatchesExpected expected_ty MCase matches +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 [] matches (mkFunTy scrut_ty expr_ty) CaseAlt `thenTc` \ (matches', lie) -> + returnTc (scrut_ty, matches', lie) + +tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE) +tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaExpr \end{code} \begin{code} -data FunOrCase = MCase | MFun Name -- Records whether doing fun or case rhss; - -- used to produced better error messages - -tcMatchesExpected :: TcType s - -> FunOrCase - -> [RenamedMatch] - -> TcM s ([TcMatch s], LIE s) - -tcMatchesExpected expected_ty fun_or_case [match] - = tcAddSrcLoc (get_Match_loc match) $ - tcAddErrCtxt (matchCtxt fun_or_case match) $ - tcMatchExpected expected_ty match `thenTc` \ (match', lie) -> - returnTc ([match'], lie) - -tcMatchesExpected expected_ty fun_or_case (match1 : matches) - = tcAddSrcLoc (get_Match_loc match1) ( - tcAddErrCtxt (matchCtxt fun_or_case match1) $ - tcMatchExpected expected_ty match1 - ) `thenTc` \ (match1', lie1) -> - tcMatchesExpected expected_ty fun_or_case matches `thenTc` \ (matches', lie2) -> - returnTc (match1' : matches', plusLIE lie1 lie2) - -tcMatches :: [RenamedMatch] -> TcM s ([TcMatch s], LIE s, [TcType s]) - -tcMatches [match] - = tcAddSrcLoc (get_Match_loc match) $ - tcMatch match `thenTc` \ (match', lie, ty) -> - returnTc ([match'], lie, [ty]) - -tcMatches (match1 : matches) - = tcAddSrcLoc (get_Match_loc match1) ( - tcMatch match1 - ) `thenTc` \ (match1', lie1, match1_ty) -> - tcMatches matches `thenTc` \ (matches', lie2, matches_ty) -> - returnTc (match1' : matches', plusLIE lie1 lie2, match1_ty : matches_ty) +tcMatches :: [(Name,Id)] + -> [RenamedMatch] + -> TcType + -> HsMatchContext + -> TcM ([TcMatch], LIE) + +tcMatches xve matches expected_ty fun_or_case + = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) -> + returnTc (matches, plusLIEs lies) + where + tc_match match = tcMatch xve match expected_ty fun_or_case \end{code} + +%************************************************************************ +%* * +\subsection{tcMatch} +%* * +%************************************************************************ + \begin{code} -tcMatchExpected - :: TcType s -- This gives the expected - -- result-type of the Match. Early unification - -- with this guy gives better error messages +tcMatch :: [(Name,Id)] -> RenamedMatch - -> TcM s (TcMatch s,LIE s) -- NB No type returned, because it was passed - -- in instead! - -tcMatchExpected expected_ty the_match@(PatMatch pat match) - = case getFunTy_maybe expected_ty of - - Nothing -> -- Not a function type (eg type variable) - -- So use tcMatch instead - tcMatch the_match `thenTc` \ (match', lie_match, match_ty) -> - unifyTauTy match_ty expected_ty `thenTc_` - returnTc (match', lie_match) - - Just (arg_ty,rest_ty) -> -- It's a function type! - let binders = collectPatBinders pat - in - newMonoIds binders mkTypeKind (\ _ -> - tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) -> - unifyTauTy arg_ty pat_ty `thenTc_` - tcMatchExpected rest_ty match `thenTc` \ (match', lie_match) -> - returnTc (PatMatch pat' match', - plusLIE lie_pat lie_match) - ) - -tcMatchExpected expected_ty (GRHSMatch grhss_and_binds) - = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) -> - unifyTauTy grhss_ty expected_ty `thenTc_` - returnTc (GRHSMatch grhss_and_binds', lie) - -tcMatch :: RenamedMatch -> TcM s (TcMatch s, LIE s, TcType s) - -tcMatch (PatMatch pat match) - = let binders = collectPatBinders pat - in - newMonoIds binders mkTypeKind (\ _ -> - tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) -> - tcMatch match `thenTc` \ (match', lie_match, match_ty) -> - returnTc (PatMatch pat' match', - plusLIE lie_pat lie_match, - mkFunTy pat_ty match_ty) - ) + -> TcType -- Expected result-type of the Match. + -- Early unification with this guy gives better error messages + -> HsMatchContext + -> TcM (TcMatch, LIE) -tcMatch (GRHSMatch grhss_and_binds) - = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) -> - returnTc (GRHSMatch grhss_and_binds', lie, grhss_ty) -\end{code} +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 -@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. + 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 openTypeKind `thenNF_Tc` \ tyvar_ty -> -\begin{code} -noOfArgs :: [RenamedMatch] -> [Int] + -- Extend the tyvar env and check the match itself + tcTyVars sig_tvs (mapTc_ kcHsSigType sig_tys) `thenTc` \ 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 -noOfArgs ms = map args_in_match ms where - args_in_match :: RenamedMatch -> Int - args_in_match (GRHSMatch _) = 0 - args_in_match (PatMatch _ match) = 1 + args_in_match match + sig_tys = case maybe_rhs_sig of { Just t -> [t]; Nothing -> [] } + ++ collectSigTysFromPats pats + + 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 + 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 + tcCheckExistentialPat pat_ids ex_tvs lie_avail + (lie_req1 `plusLIE` lie_req2) + rhs_ty `thenTc` \ (lie_req', ex_binds) -> + + -- Phew! All done. + let + match' = Match [] pats' Nothing (glue_on Recursive ex_binds grhss') + in + returnTc (pat_ids, (match', 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 -> HsMatchContext + -> TcM (TcGRHSs, LIE) + +tcGRHSs (GRHSs grhss binds _) expected_ty ctxt + = 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) + + +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 lie_req ids `thenTc` \ (lie1, inst_binds) -> + + -- Deal with overloaded functions bound by the pattern + tcSimplifyCheck doc tv_list + (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) -> + checkSigTyVars tv_list emptyVarSet `thenTc_` + + returnTc (lie2, dict_binds `AndMonoBinds` inst_binds) + where + doc = text ("the existential context of a data constructor") + tv_list = bagToList ex_tvs + not_overloaded id = case splitSigmaTy (idType id) of + (_, theta, _) -> null theta \end{code} -@get_Match_loc@ takes a @RenamedMatch@ and returns the -source-location gotten from the GRHS inside. -THis is something of a nuisance, but no more. + +%************************************************************************ +%* * +\subsection{tcMatchPats} +%* * +%************************************************************************ \begin{code} -get_Match_loc :: RenamedMatch -> SrcLoc - -get_Match_loc (PatMatch _ m) = get_Match_loc m -get_Match_loc (GRHSMatch (GRHSsAndBindsIn (g:_) _)) - = get_GRHS_loc g - where - get_GRHS_loc (OtherwiseGRHS _ locn) = locn - get_GRHS_loc (GRHS _ _ locn) = locn +tcMatchPats [] expected_ty + = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE) + +tcMatchPats (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) -> + 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 + ) \end{code} -Errors and contexts -~~~~~~~~~~~~~~~~~~~ + +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ + +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} -matchCtxt MCase match sty - = ppHang (ppStr "In a \"case\" branch:") - 4 (pprMatch sty True{-is_case-} match) +tcStmts do_or_lc m_ty stmts + = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE)) + +tcStmtsAndThen + :: (TcStmt -> thing -> thing) -- Combiner + -> HsMatchContext + -> (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 + + -- LetStmt +tcStmtsAndThen combine do_or_lc m_ty (LetStmt binds : stmts) do_next + = tcBindsAndThen -- No error context, but a binding group is + (glue_binds combine) -- rather a large thing for an error context anyway + binds + (tcStmtsAndThen combine do_or_lc m_ty stmts do_next) + + -- BindStmt +tcStmtsAndThen combine do_or_lc m_ty@(m,elt_ty) (stmt@(BindStmt pat exp src_loc) : stmts) do_next + = tcAddSrcLoc src_loc ( + tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty -> + tcPat tcMonoPatBndr 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) -> + let + new_val_env = bagToList pat_bndrs + pat_ids = map snd new_val_env + in + + -- 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 ( + tcStmtsAndThen combine do_or_lc m_ty stmts do_next + ) `thenTc` \ (thing, stmts_lie) -> + + -- Reinstate context for existential checks + tcSetErrCtxt (stmtCtxt do_or_lc stmt) $ + tcCheckExistentialPat pat_ids pat_tvs lie_avail + stmts_lie (m elt_ty) `thenTc` \ (final_lie, dict_binds) -> + + returnTc (combine (BindStmt pat' exp' src_loc) + (glue_binds combine Recursive dict_binds thing), + lie_req `plusLIE` final_lie) + + + -- ParStmt +tcStmtsAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s : stmts) do_next + = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) -> + returnTc (combine (ParStmtOut pairs') thing, lie) + where + loop [] + = tcStmtsAndThen combine do_or_lc m_ty stmts do_next `thenTc` \ (thing, stmts_lie) -> + returnTc (([], thing), stmts_lie) + + loop ((bndrs,stmts) : pairs) + = tcStmtsAndThen + combine_par ListComp (mkListTy, not_required) stmts + (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) + not_required = panic "tcStmtsAndThen: elt_ty" + + -- The simple-statment case +tcStmtsAndThen combine do_or_lc m_ty (stmt@(ExprStmt exp locn):stmts) do_next + = tcSetErrCtxt (stmtCtxt do_or_lc stmt) ( + tcExprStmt do_or_lc m_ty exp (null stmts) + ) `thenTc` \ (exp', stmt_lie) -> + + tcStmtsAndThen combine do_or_lc m_ty stmts do_next `thenTc` \ (thing, stmts_lie) -> + + returnTc (combine (ExprStmt exp' locn) thing, + stmt_lie `plusLIE` stmts_lie) -matchCtxt (MFun fun) match sty - = ppHang (ppBesides [ppStr "In an equation for function ", ppr sty fun, ppChar ':']) - 4 (ppBesides [ppr sty fun, ppSP, pprMatch sty False{-not case-} match]) + +------------------------------ + -- ExprStmt; see comments with HsExpr.HsStmt + -- for meaning of ExprStmt +tcExprStmt do_or_lc (m, res_elt_ty) exp is_last_stmt + = compute_expr_ty `thenNF_Tc` \ expr_ty -> + tcExpr exp expr_ty + where + compute_expr_ty + | is_last_stmt = if isDoExpr do_or_lc then + returnNF_Tc (m res_elt_ty) + else + returnNF_Tc res_elt_ty + + | otherwise = if isDoExpr do_or_lc then + newTyVarTy openTypeKind `thenNF_Tc` \ any_ty -> + returnNF_Tc (m any_ty) + else + returnNF_Tc boolTy + +------------------------------ +glue_binds combine is_rec binds thing + | nullMonoBinds binds = thing + | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing \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} -varyingArgsErr name matches sty - = ppSep [ppStr "Varying number of arguments for function", ppr sty name] +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 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 LambdaExpr 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 (pprMatchContext do_or_lc <> colon) 4 (ppr stmt) \end{code}