X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMatches.lhs;h=f8f2f4b0e9b4e667fa43e01ff54aae0e9d6bcb8c;hb=fd7d044fe32e5685b35f16833b81794a61a98bc7;hp=6be207626fcb4df302c8000dd652144088af1a0e;hpb=438596897ebbe25a07e1c82085cfbc5bdb00f09e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs index 6be2076..f8f2f4b 100644 --- a/ghc/compiler/typecheck/TcMatches.lhs +++ b/ghc/compiler/typecheck/TcMatches.lhs @@ -4,214 +4,478 @@ \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( tcMonoExpr ) -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, RenamedMatchContext ) +import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat ) import TcMonad -import TcMonoType ( checkSigTyVars, noSigs, existentialPatCtxt ) -import Inst ( Inst, LIE, plusLIE, emptyLIE ) -import TcEnv ( tcExtendEnvWithPat, tcExtendGlobalTyVars ) -import TcPat ( tcPat ) -import TcType ( TcType, newTyVarTy ) -import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns ) -import TcUnify ( unifyFunTy ) +import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) ) +import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList ) +import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv2 ) +import TcPat ( tcPat, tcMonoPatBndr ) +import TcMType ( newTyVarTy, zonkTcType, zapToType ) +import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType, + mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind ) +import TcBinds ( tcBindsAndThen ) +import TcUnify ( subFunTy, checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) ) +import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns ) import Name ( Name ) - +import TysWiredIn ( boolTy ) +import Id ( idType ) +import CoreFVs ( idFreeTyVars ) import BasicTypes ( RecFlag(..) ) -import Type ( Kind, tyVarsOfType, isTauTy, mkFunTy, openTypeKind ) import VarSet -import Util +import Var ( Id ) import Bag +import Util ( isSingleton, lengthExceeds ) 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 + -- No need to zonk expected_ty, because subFunTy does that on the fly + 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 ctxt matches expected_ty + = -- If there is more than one branch, and expected_ty is a 'hole', + -- all branches must be types, not type schemes, otherwise the + -- in which we check them would affect the result. + (if lengthExceeds matches 1 then + zapToType expected_ty + else + returnNF_Tc expected_ty) `thenNF_Tc` \ expected_ty' -> + + mapAndUnzipTc (tc_match expected_ty') matches `thenTc` \ (matches, lies) -> + returnTc (matches, plusLIEs lies) + where + tc_match expected_ty match = tcMatch xve ctxt match expected_ty \end{code} + +%************************************************************************ +%* * +\subsection{tcMatch} +%* * +%************************************************************************ + \begin{code} -tcMatchExpected - :: RenamedMatch - -> TcType s -- Expected result-type of the Match. - -- Early unification with this guy gives better error messages - -> StmtCtxt - -> TcM s (TcMatch s,LIE s) +tcMatch :: [(Name,Id)] + -> RenamedMatchContext + -> RenamedMatch + -> TcType -- 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 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) -tcMatchExpected match expected_ty ctxt - = tcMatchExpected_help emptyBag emptyBag emptyLIE match expected_ty ctxt + where + tc_grhss rhs_ty + = tcExtendLocalValEnv2 xve1 $ + + -- Deal with the result signature + case maybe_rhs_sig of + Nothing -> tcGRHSs ctxt grhss rhs_ty + + Just sig -> tcAddScopedTyVars [sig] $ + -- Bring into scope the type variables in the signature + tcHsSigType ResSigCtxt sig `thenTc` \ sig_ty -> + tcGRHSs ctxt grhss sig_ty `thenTc` \ (grhss', lie1) -> + tcSubExp rhs_ty sig_ty `thenTc` \ (co_fn, lie2) -> + returnTc (lift_grhss co_fn rhs_ty grhss', + lie1 `plusLIE` lie2) + +-- lift_grhss pushes the coercion down to the right hand sides, +-- because there is no convenient place to hang it otherwise. +lift_grhss co_fn rhs_ty grhss + | isIdCoercion co_fn = grhss +lift_grhss co_fn rhs_ty (GRHSs grhss binds ty) + = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we + where + 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 + +-- 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) + 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) +\end{code} -tcMatchExpected_help bound_tvs bound_ids bound_lie - the_match@(PatMatch pat match) expected_ty ctxt - = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) -> +%************************************************************************ +%* * +\subsection{tcMatchPats} +%* * +%************************************************************************ + +\begin{code} +tcMatchPats + :: [RenamedPat] -> TcType + -> (TcType -> TcM (a, LIE)) + -> TcM ([TypecheckedPat], 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 + -- then do the thing inside + tc_match_pats pats expected_ty thing_inside + + ) `thenTc` \ (pats', lie_req, ex_tvs, ex_ids, ex_lie, result) -> + + -- STEP 4: Check for existentially bound type variables + -- Do this *outside* the scope of the tcAddScopedTyVars, else checkSigTyVars + -- complains that 'a' is captured by the inscope 'a'! (Test (d) in checkSigTyVars.) + -- + -- I'm a bit concerned that lie_req1 from an 'inner' pattern in the list + -- might need (via lie_req2) something made available from an 'outer' + -- pattern. But it's inconvenient to deal with, and I can't find an example + tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req expected_ty `thenTc` \ (lie_req', ex_binds) -> + -- NB: we *must* pass "expected_ty" not "result_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 (pats', result, lie_req', ex_binds) + +tc_match_pats [] expected_ty thing_inside + = thing_inside expected_ty `thenTc` \ (answer, lie) -> + returnTc ([], lie, emptyBag, [], emptyLIE, answer) + +tc_match_pats (pat:pats) expected_ty thing_inside + = subFunTy expected_ty $ \ arg_ty rest_ty -> + -- This is the unique place we call subFunTy + -- The point is that if expected_y is a "hole", we want + -- to make arg_ty and rest_ty as "holes" too. + tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, ex_tvs, pat_bndrs, ex_lie) -> + let + xve = bagToList pat_bndrs + ex_ids = [id | (_, id) <- xve] + -- ex_ids is all the pattern-bound Ids, a superset + -- of the existential Ids used in checkExistentialPat + in + tcExtendLocalValEnv2 xve $ + tc_match_pats pats rest_ty thing_inside `thenTc` \ (pats', lie_reqs, exs_tvs, exs_ids, exs_lie, answer) -> + returnTc ( pat':pats', + lie_req `plusLIE` lie_reqs, + ex_tvs `unionBags` exs_tvs, + ex_ids ++ exs_ids, + ex_lie `plusLIE` exs_lie, + answer + ) + - tcPat noSigs pat arg_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail_lie) -> +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 + -> 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 ex_tvs ex_ids ex_lie lie_req match_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 ex_lie ) + returnTc (lie_req, EmptyMonoBinds) + + | otherwise + = tcAddErrCtxtM (sigPatCtxt tv_list ex_ids match_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) -> + -- 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 ex_ids `thenTc` \ (lie1, inst_binds) -> - returnTc (PatMatch pat' match', pat_lie `plusLIE` lie_match) + -- Deal with overloaded functions bound by the pattern + tcSimplifyCheck doc tv_list (lieToList ex_lie) lie1 `thenTc` \ (lie2, dict_binds) -> + checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `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 = not (isOverloadedTy (idType id)) +\end{code} -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_` - tcExtendEnvWithPat bound_ids ( - tcGRHSsAndBinds grhss_and_binds expected_ty ctxt - ) `thenTc` \ (GRHSsAndBindsOut grhss binds ty, lie) -> +%************************************************************************ +%* * +\subsection{tcStmts} +%* * +%************************************************************************ +Typechecking statements is rendered a bit tricky by parallel list comprehensions: - -- 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) -> + [ (g x, h x) | ... ; let g v = ... + | ... ; let h v = ... ] - -- 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) -> +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: - 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) + data T = forall a. Show a => C a - -- glue_on just avoids stupid dross - glue_on EmptyMonoBinds binds = binds -- The common case - glue_on mbinds binds = MonoBind mbinds [] Recursive `ThenBinds` binds -\end{code} + [ (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. -@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. +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} -noOfArgs :: [RenamedMatch] -> [Int] - -noOfArgs ms = map args_in_match ms +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 -> + tcMonoExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) -> + tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ _ -> + tcPopErrCtxt thing_inside + ) `thenTc` \ ([pat'], thing, lie, dict_binds) -> + returnTc (combine (BindStmt pat' exp' src_loc) + (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 -> + tcMonoExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) -> + returnTc (ExprStmt exp' any_ty locn, lie) + else + tcMonoExpr exp boolTy `thenNF_Tc` \ (exp', lie) -> + returnTc (ExprStmt exp' boolTy locn, lie) + ) `thenTc` \ (stmt', stmt_lie) -> + + thing_inside `thenTc` \ (thing, stmts_lie) -> + + returnTc (combine stmt' 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 + tcMonoExpr exp (m res_elt_ty) + else + tcMonoExpr 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 = isSingleton (nub (map args_in_match matches)) + where + args_in_match :: RenamedMatch -> Int + args_in_match (Match pats _ _) = length pats +\end{code} \begin{code} 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 (pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match) +stmtCtxt do_or_lc stmt = hang (pprMatchContext do_or_lc <> colon) 4 (ppr stmt) + +sigPatCtxt bound_tvs bound_ids match_ty tidy_env + = zonkTcType match_ty `thenNF_Tc` \ match_ty' -> + let + (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) + (env2, tidy_mty) = tidyOpenType env1 match_ty' + in + returnNF_Tc (env1, + sep [ptext SLIT("When checking an existential match that binds"), + nest 4 (vcat (zipWith ppr_id show_ids tidy_tys)), + ptext SLIT("and whose type is") <+> ppr tidy_mty]) + 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}