%
-% (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, tcMatchExpected ) where
+module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
+import {-# SOURCE #-} TcExpr( tcExpr )
-import HsSyn ( HsBinds(..), Match(..), GRHSsAndBinds(..), GRHS(..),
- HsExpr(..), MonoBinds(..),
- collectPatBinders, pprMatch, getMatchLoc
+import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
+ MonoBinds(..), StmtCtxt(..), Stmt(..),
+ pprMatch, getMatchLoc, consLetStmt,
+ mkMonoBind, collectSigTysFromPats
)
-import RnHsSyn ( RenamedMatch )
-import TcHsSyn ( TcIdBndr, TcMatch )
+import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt )
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt )
import TcMonad
-import Inst ( Inst, LIE, plusLIE )
-import TcEnv ( TcIdOcc(..), newMonoIds )
-import TcPat ( tcPat )
-import TcType ( TcType, TcMaybe, zonkTcType, newTyVarTy )
-import TcSimplify ( bindInstsOfLocalFuns )
-import Unify ( unifyTauTy, unifyTauTyList, unifyFunTy )
-import Name ( Name {- instance Outputable -} )
-
-import Kind ( Kind, mkTypeKind )
+import TcMonoType ( kcHsSigType, tcTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt )
+import Inst ( LIE, plusLIE, emptyLIE, plusLIEs )
+import TcEnv ( TcId, tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars )
+import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig )
+import TcType ( TcType, newTyVarTy )
+import TcBinds ( tcBindsAndThen )
+import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
+import TcUnify ( unifyFunTy, unifyTauTy, unifyListTy )
+import Name ( Name )
+import TysWiredIn ( boolTy )
+
import BasicTypes ( RecFlag(..) )
-import Type ( isTyVarTy, isTauTy, mkFunTy, splitFunTy_maybe )
-import Util
+import Type ( tyVarsOfType, isTauTy, mkArrowKind, mkAppTy, mkFunTy,
+ boxedTypeKind, openTypeKind )
+import SrcLoc ( SrcLoc )
+import VarSet
+import Var ( Id )
+import Bag
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
- -- 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 -- 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 expr_ty matches
- = newTyVarTy mkTypeKind `thenNF_Tc` \ scrut_ty ->
- tcMatchesExpected (mkFunTy scrut_ty expr_ty) MCase matches `thenTc` \ (matches', lie) ->
+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
+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}
-tcMatchesExpected :: TcType s
- -> FunOrCase
- -> [RenamedMatch]
- -> TcM s ([TcMatch s], LIE s)
-tcMatchesExpected expected_ty fun_or_case [match]
- = tcAddSrcLoc (getMatchLoc 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 (getMatchLoc 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)
-\end{code}
+%************************************************************************
+%* *
+\subsection{tcMatch}
+%* *
+%************************************************************************
\begin{code}
-tcMatchExpected
- :: [TcIdBndr s] -- Ids bound by enclosing matches
- -> 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!
+ -> TcType -- Expected result-type of the Match.
+ -- Early unification with this guy gives better error messages
+ -> StmtCtxt
+ -> TcM (TcMatch, LIE)
-tcMatchExpected matched_ids expected_ty the_match@(PatMatch pat match)
- = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) ->
+tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt
+ = tcAddSrcLoc (getMatchLoc match) $
+ tcAddErrCtxt (matchCtxt ctxt match) $
- let binders = collectPatBinders pat
- in
- newMonoIds binders mkTypeKind (\ mono_ids ->
- tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- unifyTauTy pat_ty arg_ty `thenTc_`
+ if null sig_tvs then -- The common case
+ tc_match expected_ty `thenTc` \ (_, match_and_lie) ->
+ returnTc match_and_lie
- tcMatchExpected (mono_ids ++ matched_ids)
- rest_ty match `thenTc` \ (match', lie_match) ->
+ 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 ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match)
- )
+ -- 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) ->
-tcMatchExpected matched_ids expected_ty (GRHSMatch grhss_and_binds)
- = -- 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_`
+ -- Check that the scoped type variables from the patterns
+ -- have not been constrained
+ tcAddErrCtxtM (sigPatCtxt sig_tyvars pat_ids) (
+ checkSigTyVars sig_tyvars emptyVarSet
+ ) `thenTc_`
- tcGRHSsAndBinds expected_ty grhss_and_binds `thenTc` \ (GRHSsAndBindsOut grhss binds ty, lie) ->
+ -- *Now* we're free to unify with expected_ty
+ unifyTauTy expected_ty tyvar_ty `thenTc_`
- -- In case there are any polymorpic, overloaded binders in the pattern
+ 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
+ ex_tv_list = bagToList ex_tvs
+ 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
+ tcExtendGlobalTyVars (tyVarsOfType rhs_ty) (
+ tcAddErrCtxtM (sigPatCtxt ex_tv_list pat_ids) $
+ checkSigTyVars ex_tv_list emptyVarSet `thenTc` \ zonked_ex_tvs ->
+ tcSimplifyAndCheck
+ (text ("the existential context of a data constructor"))
+ (mkVarSet zonked_ex_tvs)
+ lie_avail (lie_req1 `plusLIE` lie_req2)
+ ) `thenTc` \ (lie_req', ex_binds) ->
+
+ -- STEP 6 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 matched_ids `thenTc` \ (lie', inst_mbinds) ->
+ bindInstsOfLocalFuns lie_req' pat_ids `thenTc` \ (lie_req'', inst_binds) ->
+
+ -- Phew! All done.
+ let
+ grhss'' = glue_on Recursive ex_binds $
+ glue_on Recursive inst_binds grhss'
+ in
+ returnTc (pat_ids, (Match [] pats' Nothing grhss'', 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 locn guarded
+ `thenTc` \ ((guarded', _), lie) ->
+ returnTc (GRHS guarded' locn, lie)
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{tcMatchPats}
+%* *
+%************************************************************************
+
+\begin{code}
+tcMatchPats [] expected_ty
+ = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE)
+
+tcMatchPats (pat:pats) expected_ty
+ = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) ->
+ tcPat tcPatBndr_NoSigs 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}
+%* *
+%************************************************************************
+
+
+\begin{code}
+tcParStep src_loc stmts
+ = newTyVarTy (mkArrowKind boxedTypeKind boxedTypeKind) `thenTc` \ m ->
+ newTyVarTy boxedTypeKind `thenTc` \ elt_ty ->
+ unifyListTy (mkAppTy m elt_ty) `thenTc_`
+
+ tcStmts ListComp (mkAppTy m) elt_ty src_loc stmts `thenTc` \ ((stmts', val_env), stmts_lie) ->
+ returnTc (stmts', val_env, stmts_lie)
+
+tcStmts :: StmtCtxt
+ -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs
+ -> TcType -- elt_ty, where type of the comprehension is (m elt_ty)
+ -> SrcLoc
+ -> [RenamedStmt]
+ -> TcM (([TcStmt], [(Name, TcId)]), LIE)
+
+tcStmts do_or_lc m elt_ty loc (ParStmtOut bndrstmtss : stmts)
+ = let (bndrss, stmtss) = unzip bndrstmtss in
+ mapAndUnzip3Tc (tcParStep loc) stmtss `thenTc` \ (stmtss', val_envs, lies) ->
+ let outstmts = zip (map (map snd) val_envs) stmtss'
+ lie = plusLIEs lies
+ new_val_env = concat val_envs
+ in
+ tcExtendLocalValEnv new_val_env (
+ tcStmts do_or_lc m elt_ty loc stmts) `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
+ returnTc ((ParStmtOut outstmts : stmts', rest_val_env ++ new_val_env), lie `plusLIE` stmts_lie)
+
+tcStmts do_or_lc m elt_ty loc (stmt@(ReturnStmt exp) : stmts)
+ = ASSERT( null stmts )
+ tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
+ tcExpr exp elt_ty `thenTc` \ (exp', exp_lie) ->
+ returnTc (([ReturnStmt exp'], []), exp_lie)
+
+ -- ExprStmt at the end
+tcStmts do_or_lc m elt_ty loc [stmt@(ExprStmt exp src_loc)]
+ = tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
+ tcExpr exp (m elt_ty) `thenTc` \ (exp', exp_lie) ->
+ returnTc (([ExprStmt exp' src_loc], []), exp_lie)
+
+ -- ExprStmt not at the end
+tcStmts do_or_lc m elt_ty loc (stmt@(ExprStmt exp src_loc) : stmts)
+ = ASSERT( isDoStmt do_or_lc )
+ tcAddSrcLoc src_loc (
+ tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
+ -- exp has type (m tau) for some tau (doesn't matter what)
+ newTyVarTy openTypeKind `thenNF_Tc` \ any_ty ->
+ tcExpr exp (m any_ty)
+ ) `thenTc` \ (exp', exp_lie) ->
+ tcStmts do_or_lc m elt_ty loc stmts `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
+ returnTc ((ExprStmt exp' src_loc : stmts', rest_val_env),
+ exp_lie `plusLIE` stmts_lie)
+
+tcStmts do_or_lc m elt_ty loc (stmt@(GuardStmt exp src_loc) : stmts)
+ = ASSERT( not (isDoStmt do_or_lc) )
+ tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
+ tcAddSrcLoc src_loc $
+ tcExpr exp boolTy
+ ) `thenTc` \ (exp', exp_lie) ->
+ tcStmts do_or_lc m elt_ty loc stmts `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
+ -- ZZ is this right?
+ returnTc ((GuardStmt exp' src_loc : stmts', rest_val_env),
+ exp_lie `plusLIE` stmts_lie)
+
+tcStmts do_or_lc m elt_ty loc (stmt@(BindStmt pat exp src_loc) : stmts)
+ = tcAddSrcLoc src_loc (
+ tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
+ newTyVarTy boxedTypeKind `thenNF_Tc` \ pat_ty ->
+ tcPat tcPatBndr_NoSigs 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
- binds' = case inst_mbinds of
- EmptyMonoBinds -> binds -- The common case
- other -> MonoBind inst_mbinds [] Recursive `ThenBinds` binds
+ new_val_env = bagToList pat_bndrs
+ pat_ids = map snd new_val_env
+ pat_tv_list = bagToList pat_tvs
in
- returnTc (GRHSMatch (GRHSsAndBindsOut grhss binds' ty), lie')
+
+ -- 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 (
+ tcStmts do_or_lc m elt_ty loc stmts
+ ) `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
+
+
+ -- Reinstate context for existential checks
+ tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
+ tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $
+ tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $
+
+ checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs ->
+
+ tcSimplifyAndCheck
+ (text ("the existential context of a data constructor"))
+ (mkVarSet zonked_pat_tvs)
+ lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) ->
+
+ -- ZZ we have to be sure that concating the val_env lists preserves
+ -- shadowing properly...
+ returnTc ((BindStmt pat' exp' src_loc :
+ consLetStmt (mkMonoBind dict_binds [] Recursive) stmts',
+ rest_val_env ++ new_val_env),
+ lie_req `plusLIE` final_lie)
+
+tcStmts do_or_lc m elt_ty loc (LetStmt binds : stmts)
+ = tcBindsAndThen -- No error context, but a binding group is
+ combine -- rather a large thing for an error context anyway
+ binds
+ (tcStmts do_or_lc m elt_ty loc stmts) `thenTc` \ ((stmts', rest_val_env), lie) ->
+ -- ZZ fix val_env
+ returnTc ((stmts', rest_val_env), lie)
+ where
+ combine is_rec binds' (stmts', val_env) = (consLetStmt (mkMonoBind binds' [] is_rec) stmts', undefined)
+
+tcStmts do_or_lc m elt_ty loc [] = returnTc (([], []), emptyLIE)
+
+isDoStmt DoStmt = True
+isDoStmt other = False
\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}
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
\begin{code}
-matchCtxt MCase match
- = hang (ptext SLIT("In a \"case\" branch:"))
- 4 (pprMatch True{-is_case-} match)
+matchCtxt CaseAlt match
+ = hang (ptext SLIT("In a case alternative:"))
+ 4 (pprMatch (True,empty) {-is_case-} match)
-matchCtxt (MFun 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}
+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)
-\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")
+
+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