\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
- tcDoStmts, tcStmtsAndThen, tcGRHSs, tcThingWithSig
+module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, matchCtxt,
+ tcDoStmts, tcStmtsAndThen, tcStmts, tcGRHSs, tcThingWithSig,
+ tcMatchPats,
+ TcStmtCtxt(..)
) where
#include "HsVersions.h"
import HsSyn ( HsExpr(..), HsBinds(..), Match(..), GRHSs(..), GRHS(..),
MonoBinds(..), Stmt(..), HsMatchContext(..), HsStmtContext(..),
+ ReboundNames,
pprMatch, getMatchLoc, isDoExpr,
pprMatchContext, pprStmtContext, pprStmtResultContext,
- mkMonoBind, collectSigTysFromPats, andMonoBindList
+ mkMonoBind, collectSigTysFromPats, andMonoBindList, glueBindsOnGRHSs
)
-import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt,
+import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedHsExpr,
RenamedPat, RenamedMatchContext )
-import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds,
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds, TcExpr,
TcMonoBinds, TcPat, TcStmt, ExprCoFn,
isIdCoercion, (<$>), (<.>) )
import TcPat ( tcPat, tcMonoPatBndr )
import TcMType ( newTyVarTy, newTyVarTys, zonkTcType )
import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType,
- tyVarsOfType, tidyOpenTypes, tidyOpenType, isSigmaTy,
+ tyVarsOfTypes, tidyOpenTypes, tidyOpenType, isSigmaTy,
mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind,
mkArrowKind, mkAppTy )
import TcBinds ( tcBindsAndThen )
import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedBranches, readExpectedType,
- unifyTauTy, subFunTy, unifyPArrTy, unifyListTy, unifyFunTy,
+ unifyTauTy, subFunTys, unifyPArrTy, unifyListTy, unifyFunTy,
checkSigTyVarsWrt, tcSubExp, tcGen )
import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
import Name ( Name )
-- because inconsistency between branches
-- may show up as something wrong with the (non-existent) type signature
- -- No need to zonk expected_ty, because subFunTy does that on the fly
+ -- No need to zonk expected_ty, because subFunTys does that on the fly
tcMatches (FunRhs fun_name) matches expected_ty
\end{code}
tcMatch ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty
= addSrcLoc (getMatchLoc match) $ -- At one stage I removed this;
addErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back
- tcMatchPats pats expected_ty tc_grhss `thenM` \ (pats', grhss', ex_binds) ->
- returnM (Match pats' Nothing (glue_on ex_binds grhss'))
+ 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 rhs_ty
- = -- Deal with the result signature
- case maybe_rhs_sig of
- Nothing -> tcGRHSs ctxt 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
lift_stmt (ResultStmt e l) = ResultStmt (co_fn <$> e) l
lift_stmt stmt = stmt
--- glue_on just avoids stupid dross
-glue_on EmptyBinds grhss = grhss -- The common case
-glue_on binds1 (GRHSs grhss binds2 ty)
- = GRHSs grhss (binds1 `ThenBinds` binds2) ty
-
-
tcGRHSs :: RenamedMatchContext -> RenamedGRHSs
-> Expected TcRhoType
-> TcM TcGRHSs
-- 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 glue_on binds $
- tcMonoExpr rhs exp_ty `thenM` \ rhs' ->
- readExpectedType exp_ty `thenM` \ exp_ty' ->
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ tcMonoExpr 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 glue_on binds $
- zapExpectedType exp_ty `thenM` \ 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 ctxt,
+ sc_rhs = tcCheckRho,
+ sc_body = \ body -> tcCheckRho body exp_ty',
+ sc_ty = exp_ty' }
+
tc_grhs (GRHS guarded locn)
- = addSrcLoc locn $
- tcStmts (PatGuard ctxt) m_ty guarded `thenM` \ guarded' ->
+ = addSrcLoc locn $
+ tcStmts stmt_ctxt guarded `thenM` \ guarded' ->
returnM (GRHS guarded' locn)
-
- m_ty = (\ty -> ty, exp_ty')
in
mappM tc_grhs grhss `thenM` \ grhss' ->
returnM (GRHSs grhss' EmptyBinds exp_ty')
\begin{code}
tcMatchPats
- :: [RenamedPat] -> Expected TcRhoType
- -> (Expected TcRhoType -> TcM a)
+ :: [(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
-- then do the thing inside
- getLIE (tc_match_pats pats expected_ty thing_inside)
+ getLIE (tc_match_pats pats_w_tys thing_inside)
) `thenM` \ ((pats', ex_tvs, ex_ids, ex_lie, result), lie_req) ->
-- 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
- readExpectedType expected_ty `thenM` \ exp_ty ->
- tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req exp_ty `thenM` \ ex_binds ->
- -- NB: we *must* pass "exp_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).
+ -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int).
returnM (pats', result, mkMonoBind Recursive ex_binds)
-tc_match_pats [] expected_ty thing_inside
- = thing_inside expected_ty `thenM` \ answer ->
+tc_match_pats [] thing_inside
+ = thing_inside `thenM` \ answer ->
returnM ([], emptyBag, [], [], 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 `thenM` \ (pat', ex_tvs, pat_bndrs, ex_lie) ->
+tc_match_pats ((pat,pat_ty):pats) thing_inside
+ = tcPat tcMonoPatBndr pat pat_ty `thenM` \ (pat', ex_tvs, pat_bndrs, ex_lie) ->
let
xve = bagToList pat_bndrs
ex_ids = [id | (_, id) <- xve]
-- of the existential Ids used in checkExistentialPat
in
tcExtendLocalValEnv2 xve $
- tc_match_pats pats rest_ty thing_inside `thenM` \ (pats', exs_tvs, exs_ids, exs_lie, answer) ->
+ 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,
-- (b) to generate helpful error messages
-> [Inst] -- and context
-> [Inst] -- Required context
- -> TcType -- and type of the Match; vars in here must not escape
+ -> [(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 match_ty
+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
returnM EmptyMonoBinds
| otherwise
- = addErrCtxtM (sigPatCtxt tv_list ex_ids match_ty) $
+ = -- 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
-- Deal with overloaded functions bound by the pattern
tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds ->
- checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `thenM_`
+
+ -- Check for type variable escape
+ checkSigTyVarsWrt (tyVarsOfTypes tys) tv_list `thenM_`
returnM (dict_binds `AndMonoBinds` inst_binds)
where
%************************************************************************
\begin{code}
-tcDoStmts :: HsStmtContext Name -> [RenamedStmt] -> [Name]
+tcDoStmts :: HsStmtContext Name
+ -> [RenamedStmt] -> ReboundNames Name
-> TcRhoType -- To keep it simple, we don't have an "expected" type here
- -> TcM (TcMonoBinds, [TcStmt], [Id])
+ -> TcM ([TcStmt], ReboundNames TcId)
tcDoStmts PArrComp stmts method_names res_ty
- = unifyPArrTy res_ty `thenM` \elt_ty ->
- tcStmts PArrComp (mkPArrTy, elt_ty) stmts `thenM` \ stmts' ->
- returnM (EmptyMonoBinds, stmts', [{- unused -}])
+ = 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 ->
- tcStmts ListComp (mkListTy, elt_ty) stmts `thenM` \ stmts' ->
- returnM (EmptyMonoBinds, stmts', [{- unused -}])
+ = unifyListTy res_ty ` thenM` \ elt_ty ->
+ tcComprehension ListComp mkListTy elt_ty stmts `thenM` \ stmts' ->
+ returnM (stmts', [{- unused -}])
-tcDoStmts do_or_mdo_expr stmts method_names res_ty
+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_`
-
- tcStmts do_or_mdo_expr (mkAppTy m_ty, elt_ty) stmts `thenM` \ stmts' ->
+ 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,
-- then = case d of (t,r) -> t
-- then = then
-- where the second "then" sees that it already exists in the "available" stuff.
- --
- mapAndUnzipM (tc_syn_name m_ty)
- (zipEqual "tcDoStmts" currentMonadNames method_names) `thenM` \ (binds, ids) ->
- returnM (andMonoBindList binds, stmts', ids)
+ 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
- currentMonadNames = case do_or_mdo_expr of
- DoExpr -> monadNames
- MDoExpr -> monadNames ++ [mfixName]
- tc_syn_name :: TcType -> (Name,Name) -> TcM (TcMonoBinds, Id)
- tc_syn_name m_ty (std_nm, usr_nm)
- = tcSyntaxName DoOrigin m_ty std_nm usr_nm `thenM` \ (expr, expr_ty) ->
- case expr of
- HsVar v -> returnM (EmptyMonoBinds, v)
- other -> newUnique `thenM` \ uniq ->
- let
- id = mkSysLocal FSLIT("syn") uniq expr_ty
- in
- returnM (VarMonoBind id expr, id)
+ 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}
group. But that's fine; there's no shadowing to worry about.
\begin{code}
-tcStmts do_or_lc m_ty stmts
+tcStmts ctxt stmts
= ASSERT( notNull stmts )
- tcStmtsAndThen (:) do_or_lc m_ty stmts (returnM [])
-
+ 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
- -> HsStmtContext Name
- -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs
- -- res_ty, the type of the entire comprehension
- -- used at the end for the type of (return x)
- -- or the final expression in do-notation
+ -> TcStmtCtxt
-> [RenamedStmt]
-> 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
- = addSrcLoc src_loc $
- addErrCtxt (stmtCtxt do_or_lc stmt) $
- newTyVarTy liftedTypeKind `thenM` \ pat_ty ->
- tcCheckRho exp (m pat_ty) `thenM` \ exp' ->
- tcMatchPats [pat] (Check (mkFunTy pat_ty (m elt_ty))) (\ _ ->
+ -- 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
+tcStmtAndThen combine ctxt (ParStmt bndr_stmts_s) thing_inside
= loop bndr_stmts_s `thenM` \ (pairs', thing) ->
- returnM (combine (ParStmtOut pairs') thing)
+ returnM (combine (ParStmt pairs') thing)
where
- loop []
- = thing_inside `thenM` \ thing ->
- returnM ([], thing)
-
- loop ((bndrs,stmts) : pairs)
- = tcStmtsAndThen
- combine_par 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 `thenM` \ bndrs' ->
- loop pairs `thenM` \ (pairs', thing) ->
- returnM ([], (bndrs', pairs', thing))) `thenM` \ (stmts', (bndrs', pairs', thing)) ->
+ loop [] = thing_inside `thenM` \ thing ->
+ returnM ([], thing)
- returnM ((bndrs',stmts') : pairs', thing)
+ loop ((stmts, bndrs) : pairs)
+ = tcStmtsAndThen combine_par ctxt stmts $
+ -- Notice we pass on ctxt; the result type is used only
+ -- to get escaping type variables for checkExistentialPat
+ tcLookupLocalIds bndrs `thenM` \ bndrs' ->
+ loop pairs `thenM` \ (pairs', thing) ->
+ returnM (([], bndrs') : pairs', thing)
- combine_par stmt (stmts, thing) = (stmt:stmts, thing)
+ combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing)
-- RecStmt
-tcStmtAndThen combine do_or_lc m_ty (RecStmt recNames stmts _) thing_inside
+tcStmtAndThen combine ctxt (RecStmt stmts laterNames recNames _) thing_inside
= newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys ->
let
- mono_ids = zipWith mkLocalId recNames recTys
+ rec_ids = zipWith mkLocalId recNames recTys
in
- tcExtendLocalValEnv mono_ids $
- tcStmtsAndThen combine_rec do_or_lc m_ty stmts (
- mappM tc_ret (recNames `zip` recTys) `thenM` \ rets ->
- returnM ([], rets)
- ) `thenM` \ (stmts', rets) ->
-
- -- NB: it's the mono_ids that scope over this part
+ 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 mono_ids stmts' rets) thing)
+ returnM (combine (RecStmt stmts' later_ids rec_ids rec_rets) thing)
where
combine_rec stmt (stmts, thing) = (stmt:stmts, thing)
tcSubExp (Check mono_ty) (idType poly_id) `thenM` \ co_fn ->
returnM (co_fn <$> HsVar poly_id)
- -- ExprStmt
-tcStmtAndThen combine do_or_lc m_ty@(m, _) stmt@(ExprStmt exp _ locn) thing_inside
- = addErrCtxt (stmtCtxt do_or_lc stmt) (
- if isDoExpr do_or_lc then
- newTyVarTy openTypeKind `thenM` \ any_ty ->
- tcCheckRho exp (m any_ty) `thenM` \ exp' ->
- returnM (ExprStmt exp' any_ty locn)
- else
- tcCheckRho exp boolTy `thenM` \ exp' ->
- returnM (ExprStmt exp' boolTy locn)
- ) `thenM` \ stmt' ->
-
- thing_inside `thenM` \ thing ->
- returnM (combine stmt' thing)
-
-
-- Result statements
-tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside
- = addErrCtxt (resCtxt do_or_lc stmt) (
- if isDoExpr do_or_lc then
- tcCheckRho exp (m res_elt_ty)
- else
- tcCheckRho exp res_elt_ty
- ) `thenM` \ exp' ->
-
- thing_inside `thenM` \ thing ->
-
+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)
varyingArgsErr name matches
= sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
-matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match)
-stmtCtxt do_or_lc stmt = hang (ptext SLIT("In") <+> pprStmtContext do_or_lc <> colon) 4 (ppr stmt)
-resCtxt do_or_lc stmt = hang (ptext SLIT("In") <+> pprStmtResultContext do_or_lc <> colon) 4 (ppr stmt)
-
-sigPatCtxt bound_tvs bound_ids match_ty tidy_env
- = zonkTcType match_ty `thenM` \ match_ty' ->
+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_mty) = tidyOpenType env1 match_ty'
+ (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("and whose type is") <+> ppr tidy_mty])
+ 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
+ ppr_id id ty = ppr id <+> dcolon <+> ppr ty
-- Don't zonk the types so we get the separate, un-unified versions
\end{code}
projects / ghc-hetmet.git / blobdiff