%
-% (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, tcGRHSs ) where
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where
+#include "HsVersions.h"
-IMP_Ubiq()
+import {-# SOURCE #-} TcExpr( tcExpr )
-import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat,
- HsExpr, HsBinds, OutPat, Fake,
- collectPatBinders, pprMatch )
-import RnHsSyn ( SYN_IE(RenamedMatch) )
-import TcHsSyn ( TcIdOcc(..), SYN_IE(TcMatch) )
+import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
+ MonoBinds(..), StmtCtxt(..), Stmt(..),
+ pprMatch, getMatchLoc,
+ mkMonoBind, nullMonoBinds, collectSigTysFromPats
+ )
+import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt )
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds )
import TcMonad
-import Inst ( Inst, SYN_IE(LIE), plusLIE )
-import TcEnv ( newMonoIds )
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-import TcPat ( tcPat )
-import TcType ( SYN_IE(TcType), TcMaybe, zonkTcType )
-import Unify ( unifyTauTy, unifyTauTyList )
-import Name ( Name {- instance Outputable -} )
-
-import Kind ( Kind, mkTypeKind )
-import Pretty
-import Type ( isTyVarTy, mkFunTy, getFunTy_maybe )
-import Util
+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 :: 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 LambdaBody
\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
+ -> StmtCtxt
+ -> 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 expected_ty match_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 pat_ty arg_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 expected_ty grhss_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 (\ _ ->
- -- NB TypeKind; lambda-bound variables are allowed
- -- to unify with unboxed types.
-
- 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
+ -> StmtCtxt
+ -> 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 -> StmtCtxt
+ -> 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 (ppPStr SLIT("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
+ -> StmtCtxt
+ -> (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
-matchCtxt (MFun fun) match sty
- = ppHang (ppBesides [ppPStr SLIT("In an equation for function "), ppr sty fun, ppChar ':'])
- 4 (ppBesides [ppr sty fun, ppSP, pprMatch sty False{-not case-} match])
+ -- 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:stmts) do_next
+ = tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
+ tcSimpleStmt do_or_lc m_ty stmt (null stmts)
+ ) `thenTc` \ (stmt', stmt_lie) ->
+
+ tcStmtsAndThen combine do_or_lc m_ty stmts do_next `thenTc` \ (thing, stmts_lie) ->
+
+ returnTc (combine stmt' thing,
+ stmt_lie `plusLIE` stmts_lie)
+
+
+------------------------------
+ -- ReturnStmt
+tcSimpleStmt do_or_lc (_,elt_ty) (ReturnStmt exp) is_last_stmt
+ = ASSERT( is_last_stmt )
+ tcExpr exp elt_ty `thenTc` \ (exp', exp_lie) ->
+ returnTc (ReturnStmt exp', exp_lie)
+
+ -- ExprStmt
+tcSimpleStmt do_or_lc (m, elt_ty) (ExprStmt exp src_loc) is_last_stmt
+ = tcAddSrcLoc src_loc $
+ (if is_last_stmt then -- do { ... ; wuggle } wuggle : m elt_ty
+ returnNF_Tc elt_ty
+ else -- do { ... ; wuggle ; .... } wuggle : m any_ty
+ ASSERT( isDoStmt do_or_lc )
+ newTyVarTy openTypeKind
+ ) `thenNF_Tc` \ arg_ty ->
+ tcExpr exp (m arg_ty) `thenTc` \ (exp', exp_lie) ->
+ returnTc (ExprStmt exp' src_loc, exp_lie)
+
+ -- GuardStmt
+tcSimpleStmt do_or_lc m_ty (GuardStmt exp src_loc) is_last_stmt
+ = ASSERT( not (isDoStmt do_or_lc) )
+ tcAddSrcLoc src_loc $
+ tcExpr exp boolTy `thenTc` \ (exp', exp_lie) ->
+ returnTc (GuardStmt exp' src_loc, exp_lie)
+
+------------------------------
+glue_binds combine is_rec binds thing
+ | nullMonoBinds binds = thing
+ | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing
+
+isDoStmt DoStmt = True
+isDoStmt other = False
\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 [ppPStr SLIT("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 LambdaBody 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 (ptext SLIT("In") <+> what <> colon)
+ 4 (ppr stmt)
+ where
+ what = case do_or_lc of
+ ListComp -> ptext SLIT("a list-comprehension qualifier")
+ DoStmt -> ptext SLIT("a do statement")
+ PatBindRhs -> thing <+> ptext SLIT("a pattern binding")
+ FunRhs f -> thing <+> ptext SLIT("an equation for") <+> quotes (ppr f)
+ CaseAlt -> thing <+> ptext SLIT("a case alternative")
+ LambdaBody -> thing <+> ptext SLIT("a lambda abstraction")
+ thing = case stmt of
+ BindStmt _ _ _ -> ptext SLIT("a pattern guard for")
+ GuardStmt _ _ -> ptext SLIT("a guard for")
+ ExprStmt _ _ -> ptext SLIT("the right-hand side of")
\end{code}
projects / ghc-hetmet.git / blobdiff