%
-% (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}
+module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
+ tcStmts, tcStmtsAndThen, tcGRHSs
+ ) where
+
#include "HsVersions.h"
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where
-
-import TcMonad -- typechecking monad machinery
-import TcMonadFns ( mkIdsWithOpenTyVarTys )
-import AbsSyn -- the stuff being typechecked
-
-import AbsPrel ( mkFunTy )
-import AbsUniType ( isTyVarTy, maybeUnpackFunTy )
-import E ( E, growE_LVE, LVE(..), GVE(..) )
-#if USE_ATTACK_PRAGMAS
-import CE
-import TCE
-#endif
-import Errors ( varyingArgsErr, Error(..), UnifyErrContext(..) )
-import LIE ( LIE, plusLIE )
-import Maybes ( Maybe(..) )
-import TcGRHSs ( tcGRHSsAndBinds )
-import TcPat ( tcPat )
-import Unify ( unifyTauTy, unifyTauTyList )
-import Util
+import {-# SOURCE #-} TcExpr( tcExpr )
+
+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 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 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 :: E -> Name
- -> UniType -- Expected type
+tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group
+ -> Name
+ -> TcType -- Expected type
-> [RenamedMatch]
- -> TcM ([TypecheckedMatch], LIE)
+ -> TcM ([TcMatch], LIE)
-tcMatchesFun e 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...
-
- addSrcLocTc (get_Match_loc first_match) (
-
- -- Check that they all have the same no of arguments
- checkTc (not (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
- applyTcSubstToTy expected_ty `thenNF_Tc` \ expected_ty' ->
- tcMatchesExpected e expected_ty' (\ m -> FunMonoBindsCtxt fun_name [m]) 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 :: E -> [RenamedMatch]
- -> TcM ([TypecheckedMatch], LIE, UniType)
+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}
+
-tcMatchesCase e matches
- =
+\begin{code}
+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}
- -- Typecheck them
- tcMatches e matches `thenTc` \ (matches', lie, tys@(first_ty:_)) ->
- -- Set the location to that of the first equation, so that
- -- any inter-equation error messages get some vaguely sensible location
- addSrcLocTc (get_Match_loc (head matches)) (
- unifyTauTyList tys (CaseBranchesCtxt matches)
- ) `thenTc_`
+%************************************************************************
+%* *
+\subsection{tcMatch}
+%* *
+%************************************************************************
- returnTc (matches', lie, first_ty)
+\begin{code}
+tcMatch :: [(Name,Id)]
+ -> RenamedMatch
+ -> TcType -- Expected result-type of the Match.
+ -- Early unification with this guy gives better error messages
+ -> HsMatchContext
+ -> TcM (TcMatch, LIE)
+
+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
+
+ 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 ->
+
+ -- 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
+
+ where
+ 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}
+%************************************************************************
+%* *
+\subsection{tcMatchPats}
+%* *
+%************************************************************************
+
\begin{code}
-tcMatchesExpected :: E
- -> UniType
- -> (RenamedMatch -> UnifyErrContext)
- -> [RenamedMatch]
- -> TcM ([TypecheckedMatch], LIE)
-
-tcMatchesExpected e expected_ty err_ctxt_fn [match]
- = addSrcLocTc (get_Match_loc match) (
- tcMatchExpected e expected_ty (err_ctxt_fn match) match
- ) `thenTc` \ (match', lie) ->
- returnTc ([match'], lie)
-
-tcMatchesExpected e expected_ty err_ctxt_fn ms@(match1 : matches)
- = addSrcLocTc (get_Match_loc match1) (
- tcMatchExpected e expected_ty (err_ctxt_fn match1) match1
- ) `thenTc` \ (match1', lie1) ->
- tcMatchesExpected e expected_ty err_ctxt_fn matches `thenTc` \ (matches', lie2) ->
- returnTc (match1' : matches', plusLIE lie1 lie2)
-
-tcMatches :: E -> [RenamedMatch] -> TcM ([TypecheckedMatch], LIE, [UniType])
-
-tcMatches e [match]
- = tcMatch e match `thenTc` \ (match', lie, ty) ->
- returnTc ([match'], lie, [ty])
-
-tcMatches e ms@(match1 : matches)
- = addSrcLocTc (get_Match_loc match1) (
- tcMatch e match1
- ) `thenTc` \ (match1', lie1, match1_ty) ->
- tcMatches e matches `thenTc` \ (matches', lie2, matches_ty) ->
- returnTc (match1' : matches', plusLIE lie1 lie2, match1_ty : matches_ty)
+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}
+
+%************************************************************************
+%* *
+\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}
-tcMatchExpected
- :: E
- -> UniType -- This gives the expected
- -- result-type of the Match. Early unification
- -- with this guy gives better error messages
- -> UnifyErrContext
- -> RenamedMatch
- -> TcM (TypecheckedMatch,LIE)
- -- NB No type returned, because it was passed
- -- in instead!
-
-tcMatchExpected e expected_ty err_ctxt the_match@(PatMatch pat match)
- = case maybeUnpackFunTy expected_ty of
-
- Nothing -> -- Not a function type (eg type variable)
- -- So use tcMatch instead
- tcMatch e the_match `thenTc` \ (match', lie_match, match_ty) ->
- unifyTauTy match_ty expected_ty err_ctxt `thenTc_`
- returnTc (match', lie_match)
-
- Just (arg_ty,rest_ty) -> -- It's a function type!
- let binders = collectPatBinders pat
- in
- mkIdsWithOpenTyVarTys binders `thenNF_Tc` \ lve ->
- let e' = growE_LVE e lve
- in
- tcPat e' pat `thenTc` \ (pat', lie_pat, pat_ty) ->
-
- unifyTauTy arg_ty pat_ty err_ctxt `thenTc_`
- tcMatchExpected e' rest_ty err_ctxt match `thenTc` \ (match', lie_match) ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match)
-
-tcMatchExpected e expected_ty err_ctxt (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds e grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- unifyTauTy grhss_ty expected_ty err_ctxt `thenTc_`
- returnTc (GRHSMatch grhss_and_binds', lie)
-
-tcMatch :: E
- -> RenamedMatch
- -> TcM (TypecheckedMatch,LIE,UniType)
-
-tcMatch e (PatMatch pat match)
- = let binders = collectPatBinders pat
- in
- mkIdsWithOpenTyVarTys binders `thenNF_Tc` \ lve ->
- let e' = growE_LVE e lve
+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
- tcPat e' pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- tcMatch e' match `thenTc` \ (match', lie_match, match_ty) ->
--- We don't do this any more, do we?
--- applyTcSubstToTy pat_ty `thenNF_Tc`\ pat_ty' ->
+ -- 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) ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match,
- mkFunTy pat_ty match_ty)
+ tcStmtsAndThen combine do_or_lc m_ty stmts do_next `thenTc` \ (thing, stmts_lie) ->
-tcMatch e (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds e grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- returnTc (GRHSMatch grhss_and_binds', lie, grhss_ty)
+ returnTc (combine (ExprStmt exp' locn) thing,
+ stmt_lie `plusLIE` stmts_lie)
+
+
+------------------------------
+ -- 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}
-@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{Errors and contexts}
+%* *
+%************************************************************************
-\begin{code}
-noOfArgs :: [RenamedMatch] -> [Int]
+@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same
+number of args are used in each equation.
-noOfArgs ms = map args_in_match ms
+\begin{code}
+sameNoOfArgs :: [RenamedMatch] -> Bool
+sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1
where
args_in_match :: RenamedMatch -> Int
- args_in_match (GRHSMatch _) = 0
- args_in_match (PatMatch _ match) = 1 + args_in_match match
+ args_in_match (Match _ pats _ _) = length pats
\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.
-
\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
+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}