\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where
+module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
+ matchCtxt, TcMatchCtxt(..),
+ tcStmts, tcDoStmts,
+ tcDoStmt, tcMDoStmt, tcGuardStmt
+ ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcExpr( tcExpr )
-
-import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
- MonoBinds(..), StmtCtxt(..), Stmt(..),
- pprMatch, getMatchLoc, consLetStmt,
- mkMonoBind, collectSigTysFromPats
- )
-import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt )
-import TcHsSyn ( TcMatch, TcGRHSs, TcStmt )
-
-import TcMonad
-import TcMonoType ( kcHsSigType, tcTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt )
-import Inst ( LIE, plusLIE, emptyLIE, plusLIEs )
-import TcEnv ( tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars )
-import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig )
-import TcType ( TcType, newTyVarTy )
-import TcBinds ( tcBindsAndThen )
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcUnify ( unifyFunTy, unifyTauTy )
+import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr )
+
+import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..),
+ Match(..), LMatch, GRHSs(..), GRHS(..),
+ Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
+ pprMatch, isIrrefutableHsPat, mkHsCoerce,
+ pprMatchContext, pprStmtContext,
+ noSyntaxExpr, matchGroupArity, pprMatches,
+ ExprCoFn )
+
+import TcRnMonad
+import TcHsType ( tcPatSig, UserTypeCtxt(..) )
+import Inst ( newMethodFromName )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv,
+ tcExtendTyVarEnv2 )
+import TcPat ( PatCtxt(..), tcPats, tcPat )
+import TcMType ( newFlexiTyVarTy, newFlexiTyVarTys )
+import TcType ( TcType, TcRhoType,
+ BoxySigmaType, BoxyRhoType,
+ mkFunTys, mkFunTy, mkAppTy, mkTyConApp,
+ liftedTypeKind )
+import TcBinds ( tcLocalBinds )
+import TcUnify ( boxySplitAppTy, boxySplitTyConApp, boxySplitListTy,
+ subFunTys, tcSubExp, withBox )
+import TcSimplify ( bindInstsOfLocalFuns )
import Name ( Name )
-import TysWiredIn ( boolTy )
-
-import BasicTypes ( RecFlag(..) )
-import Type ( tyVarsOfType, isTauTy, mkFunTy, boxedTypeKind, openTypeKind )
-import VarSet
-import Var ( Id )
-import Bag
+import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy )
+import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName )
+import Id ( idType, mkLocalId )
+import TyCon ( TyCon )
+import Util ( isSingleton )
import Outputable
+import SrcLoc ( Located(..), getLoc )
+import ErrUtils ( Message )
+
import List ( nub )
\end{code}
same number of arguments before using @tcMatches@ to do the work.
\begin{code}
-tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group
- -> Name
- -> TcType -- Expected type
- -> [RenamedMatch]
- -> TcM s ([TcMatch], LIE)
-
-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) (
- checkTc (sameNoOfArgs matches)
- (varyingArgsErr fun_name matches)
- ) `thenTc_`
+tcMatchesFun :: Name
+ -> MatchGroup Name
+ -> BoxyRhoType -- Expected type of function
+ -> TcM (ExprCoFn, MatchGroup TcId) -- Returns type of body
+
+tcMatchesFun fun_name matches exp_ty
+ = do { -- Check that they all have the same no of arguments
+ -- Location is in the monad, set the caller 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...
+ checkArgs fun_name matches
-- 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
- -- No need to zonk expected_ty, because unifyFunTy does that on the fly
- tcMatches xve matches expected_ty (FunRhs fun_name)
+ -- This is one of two places places we call subFunTys
+ -- The point is that if expected_y is a "hole", we want
+ -- to make pat_tys and rhs_ty as "holes" too.
+ ; subFunTys doc n_pats exp_ty $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty matches
+ }
+ where
+ doc = ptext SLIT("The equation(s) for") <+> quotes (ppr fun_name)
+ <+> ptext SLIT("have") <+> speakNOf n_pats (ptext SLIT("argument"))
+ n_pats = matchGroupArity matches
+ match_ctxt = MC { mc_what = FunRhs fun_name, mc_body = tcPolyExpr }
\end{code}
@tcMatchesCase@ doesn't do the argument-count check because the
parser guarantees that each equation has exactly one argument.
\begin{code}
-tcMatchesCase :: [RenamedMatch] -- The case alternatives
- -> TcType -- Type of whole case expressions
- -> TcM s (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 s (TcMatch, LIE)
-tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaBody
+tcMatchesCase :: TcMatchCtxt -- Case context
+ -> TcRhoType -- Type of scrutinee
+ -> MatchGroup Name -- The case alternatives
+ -> BoxyRhoType -- Type of whole case expressions
+ -> TcM (MatchGroup TcId) -- Translated alternatives
+
+tcMatchesCase ctxt scrut_ty matches res_ty
+ = tcMatches ctxt [scrut_ty] res_ty matches
+
+tcMatchLambda :: MatchGroup Name -> BoxyRhoType -> TcM (ExprCoFn, MatchGroup TcId)
+tcMatchLambda match res_ty
+ = subFunTys doc n_pats res_ty $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty match
+ where
+ n_pats = matchGroupArity match
+ doc = sep [ ptext SLIT("The lambda expression")
+ <+> quotes (pprSetDepth 1 $ pprMatches LambdaExpr match),
+ -- The pprSetDepth makes the abstraction print briefly
+ ptext SLIT("has") <+> speakNOf n_pats (ptext SLIT("arguments"))]
+ match_ctxt = MC { mc_what = LambdaExpr,
+ mc_body = tcPolyExpr }
\end{code}
+@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
\begin{code}
-tcMatches :: [(Name,Id)]
- -> [RenamedMatch]
- -> TcType
- -> StmtCtxt
- -> TcM s ([TcMatch], LIE)
-
-tcMatches xve matches expected_ty fun_or_case
- = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) ->
- returnTc (matches, plusLIEs lies)
+tcGRHSsPat :: GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId)
+tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty
where
- tc_match match = tcMatch xve match expected_ty fun_or_case
+ match_ctxt = MC { mc_what = PatBindRhs,
+ mc_body = tcPolyExpr }
\end{code}
%************************************************************************
\begin{code}
-tcMatch :: [(Name,Id)]
- -> RenamedMatch
- -> TcType -- Expected result-type of the Match.
- -- Early unification with this guy gives better error messages
- -> StmtCtxt
- -> TcM s (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
-
+tcMatches :: TcMatchCtxt
+ -> [BoxySigmaType] -- Expected pattern types
+ -> BoxyRhoType -- Expected result-type of the Match.
+ -> MatchGroup Name
+ -> TcM (MatchGroup TcId)
+
+data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module
+ = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is
+ mc_body :: LHsExpr Name -- Type checker for a body of an alternative
+ -> BoxyRhoType
+ -> TcM (LHsExpr TcId) }
+
+tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _)
+ = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
+ ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) }
+
+-------------
+tcMatch :: TcMatchCtxt
+ -> [BoxySigmaType] -- Expected pattern types
+ -> BoxyRhoType -- Expected result-type of the Match.
+ -> LMatch Name
+ -> TcM (LMatch TcId)
+
+tcMatch ctxt pat_tys rhs_ty match
+ = wrapLocM (tc_match ctxt pat_tys rhs_ty) match
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_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 s (TcGRHSs, LIE)
-
-tcGRHSs (GRHSs grhss binds _) expected_ty ctxt
- = tcBindsAndThen glue_on binds (tc_grhss grhss)
+ tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
+ = addErrCtxt (matchCtxt (mc_what ctxt) match) $
+ do { (pats', grhss') <- tcPats LamPat pats pat_tys rhs_ty $
+ tc_grhss ctxt maybe_rhs_sig grhss
+ ; returnM (Match pats' Nothing grhss') }
+
+ tc_grhss ctxt Nothing grhss rhs_ty
+ = tcGRHSs ctxt grhss rhs_ty -- No result signature
+
+ tc_grhss ctxt (Just res_sig) grhss rhs_ty
+ = do { (inner_ty, sig_tvs) <- tcPatSig ResSigCtxt res_sig rhs_ty
+ ; tcExtendTyVarEnv2 sig_tvs $
+ tcGRHSs ctxt grhss inner_ty }
+
+-------------
+tcGRHSs :: TcMatchCtxt -> GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId)
+
+-- Notice that we pass in the full res_ty, so that we get
+-- good inference from simple things like
+-- f = \(x::forall a.a->a) -> <stuff>
+-- We used to force it to be a monotype when there was more than one guard
+-- but we don't need to do that any more
+
+tcGRHSs ctxt (GRHSs grhss binds) res_ty
+ = do { (binds', grhss') <- tcLocalBinds binds $
+ mappM (wrapLocM (tcGRHS ctxt res_ty)) grhss
+
+ ; returnM (GRHSs grhss' binds') }
+
+-------------
+tcGRHS :: TcMatchCtxt -> BoxyRhoType -> GRHS Name -> TcM (GRHS TcId)
+
+tcGRHS ctxt res_ty (GRHS guards rhs)
+ = do { (guards', rhs') <- tcStmts stmt_ctxt tcGuardStmt guards res_ty $
+ mc_body ctxt rhs
+ ; return (GRHS guards' rhs') }
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) guarded expected_ty `thenTc` \ (guarded', lie) ->
- returnTc (GRHS guarded' locn, lie)
+ stmt_ctxt = PatGuard (mc_what ctxt)
\end{code}
%************************************************************************
%* *
-\subsection{tcMatchPats}
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
%* *
%************************************************************************
\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
- )
+tcDoStmts :: HsStmtContext Name
+ -> [LStmt Name]
+ -> LHsExpr Name
+ -> BoxyRhoType
+ -> TcM (HsExpr TcId) -- Returns a HsDo
+tcDoStmts ListComp stmts body res_ty
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty $
+ tcBody (doBodyCtxt ListComp body) body
+ ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) }
+
+tcDoStmts PArrComp stmts body res_ty
+ = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty $
+ tcBody (doBodyCtxt PArrComp body) body
+ ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) }
+
+tcDoStmts DoExpr stmts body res_ty
+ = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty
+ ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty
+ ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty) stmts res_ty' $
+ tcBody (doBodyCtxt DoExpr body) body
+ ; return (HsDo DoExpr stmts' body' res_ty') }
+
+tcDoStmts ctxt@(MDoExpr _) stmts body res_ty
+ = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty
+ ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty
+ tc_rhs rhs = withBox liftedTypeKind $ \ pat_ty ->
+ tcMonoExpr rhs (mkAppTy m_ty pat_ty)
+
+ ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty' $
+ tcBody (doBodyCtxt ctxt body) body
+
+ ; let names = [mfixName, bindMName, thenMName, returnMName, failMName]
+ ; insts <- mapM (newMethodFromName DoOrigin m_ty) names
+ ; return (HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty') }
+
+tcDoStmts ctxt stmts body res_ty = pprPanic "tcDoStmts" (pprStmtContext ctxt)
+
+tcBody :: Message -> LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr TcId)
+tcBody ctxt body res_ty
+ = -- addErrCtxt ctxt $ -- This context adds little that is useful
+ tcPolyExpr body res_ty
\end{code}
%* *
%************************************************************************
-
\begin{code}
-tcStmts :: StmtCtxt
- -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs
- -> [RenamedStmt]
- -> TcType -- elt_ty, where type of the comprehension is (m elt_ty)
- -> TcM s ([TcStmt], LIE)
-
-tcStmts do_or_lc m (stmt@(ReturnStmt exp) : stmts) elt_ty
- = 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 [stmt@(ExprStmt exp src_loc)] elt_ty
- = 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 (stmt@(ExprStmt exp src_loc) : stmts) elt_ty
- = 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 stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
- returnTc (ExprStmt exp' src_loc : stmts',
- exp_lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m (stmt@(GuardStmt exp src_loc) : stmts) elt_ty
- = 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 stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
- returnTc (GuardStmt exp' src_loc : stmts',
- exp_lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m (stmt@(BindStmt pat exp src_loc) : stmts) elt_ty
- = 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
- new_val_env = bagToList pat_bndrs
- pat_ids = map snd new_val_env
- pat_tv_list = bagToList pat_tvs
- in
-
- -- 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 stmts elt_ty
- ) `thenTc` \ (stmts', 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) ->
-
- returnTc (BindStmt pat' exp' src_loc :
- consLetStmt (mkMonoBind dict_binds [] Recursive) stmts',
- lie_req `plusLIE` final_lie)
-
-tcStmts do_or_lc m (LetStmt binds : stmts) elt_ty
- = 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 stmts elt_ty)
- where
- combine is_rec binds' stmts' = consLetStmt (mkMonoBind binds' [] is_rec) stmts'
-
-
-isDoStmt DoStmt = True
-isDoStmt other = False
+type TcStmtChecker
+ = forall thing. HsStmtContext Name
+ -> Stmt Name
+ -> BoxyRhoType -- Result type for comprehension
+ -> (BoxyRhoType -> TcM thing) -- Checker for what follows the stmt
+ -> TcM (Stmt TcId, thing)
+
+ -- The incoming BoxyRhoType may be refined by type refinements
+ -- before being passed to the thing_inside
+
+tcStmts :: HsStmtContext Name
+ -> TcStmtChecker -- NB: higher-rank type
+ -> [LStmt Name]
+ -> BoxyRhoType
+ -> (BoxyRhoType -> TcM thing)
+ -> TcM ([LStmt TcId], thing)
+
+-- Note the higher-rank type. stmt_chk is applied at different
+-- types in the equations for tcStmts
+
+tcStmts ctxt stmt_chk [] res_ty thing_inside
+ = do { thing <- thing_inside res_ty
+ ; return ([], thing) }
+
+-- LetStmts are handled uniformly, regardless of context
+tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside
+ = do { (binds', (stmts',thing)) <- tcLocalBinds binds $
+ tcStmts ctxt stmt_chk stmts res_ty thing_inside
+ ; return (L loc (LetStmt binds') : stmts', thing) }
+
+-- For the vanilla case, handle the location-setting part
+tcStmts ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside
+ = do { (stmt', (stmts', thing)) <-
+ setSrcSpan loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ stmt_chk ctxt stmt res_ty $ \ res_ty' ->
+ popErrCtxt $
+ tcStmts ctxt stmt_chk stmts res_ty' $
+ thing_inside
+ ; return (L loc stmt' : stmts', thing) }
+
+--------------------------------
+-- Pattern guards
+tcGuardStmt :: TcStmtChecker
+tcGuardStmt ctxt (ExprStmt guard _ _) res_ty thing_inside
+ = do { guard' <- tcMonoExpr guard boolTy
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) }
+
+tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside
+ = do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; (pat', thing) <- tcPat LamPat pat rhs_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcGuardStmt ctxt stmt res_ty thing_inside
+ = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt)
+
+
+--------------------------------
+-- List comprehensions and PArrays
+
+tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray)
+ -> TcStmtChecker
+
+-- A generator, pat <- rhs
+tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) res_ty thing_inside
+ = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ ty ->
+ tcMonoExpr rhs (mkTyConApp m_tc [ty])
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+-- A boolean guard
+tcLcStmt m_tc ctxt (ExprStmt rhs _ _) res_ty thing_inside
+ = do { rhs' <- tcMonoExpr rhs boolTy
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' noSyntaxExpr boolTy, thing) }
+
+-- A parallel set of 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.
+
+tcLcStmt m_tc ctxt (ParStmt bndr_stmts_s) elt_ty thing_inside
+ = do { (pairs', thing) <- loop bndr_stmts_s
+ ; return (ParStmt pairs', thing) }
+ where
+ -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing)
+ loop [] = do { thing <- thing_inside elt_ty -- No refinement from pattern
+ ; return ([], thing) } -- matching in the branches
+
+ loop ((stmts, names) : pairs)
+ = do { (stmts', (ids, pairs', thing))
+ <- tcStmts ctxt (tcLcStmt m_tc) stmts elt_ty $ \ elt_ty' ->
+ do { ids <- tcLookupLocalIds names
+ ; (pairs', thing) <- loop pairs
+ ; return (ids, pairs', thing) }
+ ; return ( (stmts', ids) : pairs', thing ) }
+
+tcLcStmt m_tc ctxt stmt elt_ty thing_inside
+ = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Do-notation
+-- The main excitement here is dealing with rebindable syntax
+
+tcDoStmt :: TcType -- Monad type, m
+ -> TcStmtChecker
+
+tcDoStmt m_ty ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
+ = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ pat_ty ->
+ tcMonoExpr rhs (mkAppTy m_ty pat_ty)
+ -- We should use type *inference* for the RHS computations, becuase of GADTs.
+ -- do { pat <- rhs; <rest> }
+ -- is rather like
+ -- case rhs of { pat -> <rest> }
+ -- We do inference on rhs, so that information about its type can be refined
+ -- when type-checking the pattern.
+
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+
+ -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b
+ ; let bind_ty = mkFunTys [mkAppTy m_ty pat_ty,
+ mkFunTy pat_ty res_ty] res_ty
+ ; bind_op' <- tcSyntaxOp DoOrigin bind_op bind_ty
+ -- If (but only if) the pattern can fail,
+ -- typecheck the 'fail' operator
+ ; fail_op' <- if isIrrefutableHsPat pat'
+ then return noSyntaxExpr
+ else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy res_ty)
+ ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
+
+
+tcDoStmt m_ty ctxt (ExprStmt rhs then_op _) res_ty thing_inside
+ = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b
+ a_ty <- newFlexiTyVarTy liftedTypeKind
+ ; let rhs_ty = mkAppTy m_ty a_ty
+ then_ty = mkFunTys [rhs_ty, res_ty] res_ty
+ ; then_op' <- tcSyntaxOp DoOrigin then_op then_ty
+ ; rhs' <- tcPolyExpr rhs rhs_ty
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' then_op' rhs_ty, thing) }
+
+tcDoStmt m_ty ctxt stmt res_ty thing_inside
+ = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Mdo-notation
+-- The distinctive features here are
+-- (a) RecStmts, and
+-- (b) no rebindable syntax
+
+tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference
+ -> TcStmtChecker
+tcMDoStmt tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
+ = do { (rhs', pat_ty) <- tc_rhs rhs
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcMDoStmt tc_rhs ctxt (ExprStmt rhs then_op _) res_ty thing_inside
+ = do { (rhs', elt_ty) <- tc_rhs rhs
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) }
+
+tcMDoStmt tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) res_ty thing_inside
+ = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind
+ ; let rec_ids = zipWith mkLocalId recNames rec_tys
+ ; tcExtendIdEnv rec_ids $ do
+ { (stmts', (later_ids, rec_rets))
+ <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ res_ty' ->
+ -- ToDo: res_ty not really right
+ do { rec_rets <- zipWithM tc_ret recNames rec_tys
+ ; later_ids <- tcLookupLocalIds laterNames
+ ; return (later_ids, rec_rets) }
+
+ ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE (thing_inside res_ty))
+ -- NB: The rec_ids for the recursive things
+ -- already scope over this part. This binding may shadow
+ -- some of them with polymorphic things with the same Name
+ -- (see note [RecStmt] in HsExpr)
+ ; lie_binds <- bindInstsOfLocalFuns lie later_ids
+
+ ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, thing)
+ }}
+ where
+ -- Unify the types of the "final" Ids with those of "knot-tied" Ids
+ tc_ret rec_name mono_ty
+ = do { poly_id <- tcLookupId rec_name
+ -- poly_id may have a polymorphic type
+ -- but mono_ty is just a monomorphic type variable
+ ; co_fn <- tcSubExp (idType poly_id) mono_ty
+ ; return (mkHsCoerce co_fn (HsVar poly_id)) }
+
+tcMDoStmt tc_rhs ctxt stmt res_ty thing_inside
+ = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt)
+
\end{code}
number of args are used in each equation.
\begin{code}
-sameNoOfArgs :: [RenamedMatch] -> Bool
-sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1
+checkArgs :: Name -> MatchGroup Name -> TcM ()
+checkArgs fun (MatchGroup (match1:matches) _)
+ | null bad_matches = return ()
+ | otherwise
+ = failWithTc (vcat [ptext SLIT("Equations for") <+> quotes (ppr fun) <+>
+ ptext SLIT("have different numbers of arguments"),
+ nest 2 (ppr (getLoc match1)),
+ nest 2 (ppr (getLoc (head bad_matches)))])
where
- args_in_match :: RenamedMatch -> Int
- args_in_match (Match _ pats _ _) = length pats
+ n_args1 = args_in_match match1
+ bad_matches = [m | m <- matches, args_in_match m /= n_args1]
+
+ args_in_match :: LMatch Name -> Int
+ args_in_match (L _ (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 ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
+ 4 (pprMatch ctxt match)
-matchCtxt LambdaBody match
- = hang (ptext SLIT("In the lambda expression"))
- 4 (pprMatch (True, empty) match)
+doBodyCtxt :: HsStmtContext Name -> LHsExpr Name -> SDoc
+doBodyCtxt ctxt body = hang (ptext SLIT("In the result of") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr body)
-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")
+stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr stmt)
\end{code}
projects / ghc-hetmet.git / blobdiff