%
-% (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( tcMonoExpr )
-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(..), HsDoContext(..),
+ pprMatch, getMatchLoc, pprMatchContext, isDoExpr,
+ mkMonoBind, nullMonoBinds, collectSigTysFromPats
+ )
+import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedMatchContext )
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat )
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 Pretty
-import RnHsSyn ( RnName{-instance Outputable-} )
-import Type ( isTyVarTy, mkFunTy, getFunTy_maybe )
-import Util
+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 VarSet
+import Var ( Id )
+import Bag
+import Util ( isSingleton, lengthExceeds, notNull )
+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 :: RnName
- -> 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 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 -> [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 [] 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}
-data FunOrCase = MCase | MFun RnName -- 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)]
+ -> 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
- :: TcType s -- This gives the expected
- -- result-type of the Match. Early unification
- -- with this guy gives better error messages
+tcMatch :: [(Name,Id)]
+ -> RenamedMatchContext
-> 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
+ -> 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)
+
+ 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}
+
+
+%************************************************************************
+%* *
+\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
- 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)
+ 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
)
-tcMatch (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- returnTc (GRHSMatch grhss_and_binds', lie, grhss_ty)
+
+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) $
+
+ -- 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) ->
+
+ -- 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 ("existential context of a data constructor")
+ tv_list = bagToList ex_tvs
+ not_overloaded id = not (isOverloadedTy (idType id))
\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
-noOfArgs ms = map args_in_match ms
+ [ (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}
+tcStmts do_or_lc m_ty stmts
+ = ASSERT( notNull 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}
-@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{Errors and contexts}
+%* *
+%************************************************************************
+
+@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same
+number of args are used in each equation.
\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
+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}
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
\begin{code}
-matchCtxt MCase match sty
- = ppHang (ppStr "In a \"case\" branch:")
- 4 (pprMatch sty True{-is_case-} match)
+varyingArgsErr name matches
+ = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
-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])
-\end{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)
+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
-\begin{code}
-varyingArgsErr name matches sty
- = ppSep [ppStr "Varying number of arguments for function", ppr sty name]
+ ppr_id id ty = ppr id <+> dcolon <+> ppr ty
+ -- Don't zonk the types so we get the separate, un-unified versions
\end{code}