2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[RnExpr]{Renaming of expressions}
6 Basically dependency analysis.
8 Handles @Match@, @GRHSs@, @HsExpr@, and @Qualifier@ datatypes. In
9 general, all of these functions return a renamed thing, and a set of
14 rnLExpr, rnExpr, rnStmts
17 #include "HsVersions.h"
20 import {-# SOURCE #-} TcSplice( runQuasiQuoteExpr )
23 import RnSource ( rnSrcDecls, rnSplice, checkTH )
24 import RnBinds ( rnLocalBindsAndThen, rnValBindsLHS, rnValBindsRHS,
25 rnMatchGroup, makeMiniFixityEnv)
29 import RnTypes ( rnHsTypeFVs,
30 mkOpFormRn, mkOpAppRn, mkNegAppRn, checkSectionPrec)
32 import DynFlags ( DynFlag(..) )
33 import BasicTypes ( FixityDirection(..) )
34 import PrelNames ( thFAKE, hasKey, assertIdKey, assertErrorName,
35 loopAName, choiceAName, appAName, arrAName, composeAName, firstAName,
36 negateName, thenMName, bindMName, failMName, groupWithName )
41 import LoadIface ( loadInterfaceForName )
44 import Util ( isSingleton )
45 import ListSetOps ( removeDups )
46 import Maybes ( expectJust )
51 import List ( unzip4 )
58 thenM :: Monad a => a b -> (b -> a c) -> a c
61 thenM_ :: Monad a => a b -> a c -> a c
64 returnM :: Monad m => a -> m a
67 mappM :: (Monad m) => (a -> m b) -> [a] -> m [b]
70 checkM :: Monad m => Bool -> m () -> m ()
74 %************************************************************************
76 \subsubsection{Expressions}
78 %************************************************************************
81 rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars)
82 rnExprs ls = rnExprs' ls emptyUniqSet
84 rnExprs' [] acc = returnM ([], acc)
85 rnExprs' (expr:exprs) acc
86 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
88 -- Now we do a "seq" on the free vars because typically it's small
89 -- or empty, especially in very long lists of constants
91 acc' = acc `plusFV` fvExpr
93 acc' `seq` rnExprs' exprs acc' `thenM` \ (exprs', fvExprs) ->
94 returnM (expr':exprs', fvExprs)
97 Variables. We look up the variable and return the resulting name.
100 rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars)
101 rnLExpr = wrapLocFstM rnExpr
103 rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
106 = do name <- lookupOccRn v
107 ignore_asserts <- doptM Opt_IgnoreAsserts
108 finish_var ignore_asserts name
110 finish_var ignore_asserts name
111 | ignore_asserts || not (name `hasKey` assertIdKey)
112 = return (HsVar name, unitFV name)
114 = do { (e, fvs) <- mkAssertErrorExpr
115 ; return (e, fvs `addOneFV` name) }
118 = newIPNameRn v `thenM` \ name ->
119 returnM (HsIPVar name, emptyFVs)
121 rnExpr (HsLit lit@(HsString s))
123 opt_OverloadedStrings <- doptM Opt_OverloadedStrings
124 ; if opt_OverloadedStrings then
125 rnExpr (HsOverLit (mkHsIsString s placeHolderType))
126 else -- Same as below
128 returnM (HsLit lit, emptyFVs)
133 returnM (HsLit lit, emptyFVs)
135 rnExpr (HsOverLit lit)
136 = rnOverLit lit `thenM` \ (lit', fvs) ->
137 returnM (HsOverLit lit', fvs)
139 rnExpr (HsApp fun arg)
140 = rnLExpr fun `thenM` \ (fun',fvFun) ->
141 rnLExpr arg `thenM` \ (arg',fvArg) ->
142 returnM (HsApp fun' arg', fvFun `plusFV` fvArg)
144 rnExpr (OpApp e1 op _ e2)
145 = rnLExpr e1 `thenM` \ (e1', fv_e1) ->
146 rnLExpr e2 `thenM` \ (e2', fv_e2) ->
147 rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) ->
150 -- When renaming code synthesised from "deriving" declarations
151 -- we used to avoid fixity stuff, but we can't easily tell any
152 -- more, so I've removed the test. Adding HsPars in TcGenDeriv
153 -- should prevent bad things happening.
154 lookupFixityRn op_name `thenM` \ fixity ->
155 mkOpAppRn e1' op' fixity e2' `thenM` \ final_e ->
158 fv_e1 `plusFV` fv_op `plusFV` fv_e2)
161 = rnLExpr e `thenM` \ (e', fv_e) ->
162 lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) ->
163 mkNegAppRn e' neg_name `thenM` \ final_e ->
164 returnM (final_e, fv_e `plusFV` fv_neg)
167 = rnLExpr e `thenM` \ (e', fvs_e) ->
168 returnM (HsPar e', fvs_e)
170 -- Template Haskell extensions
171 -- Don't ifdef-GHCI them because we want to fail gracefully
172 -- (not with an rnExpr crash) in a stage-1 compiler.
173 rnExpr e@(HsBracket br_body)
174 = checkTH e "bracket" `thenM_`
175 rnBracket br_body `thenM` \ (body', fvs_e) ->
176 returnM (HsBracket body', fvs_e)
178 rnExpr (HsSpliceE splice)
179 = rnSplice splice `thenM` \ (splice', fvs) ->
180 returnM (HsSpliceE splice', fvs)
183 rnExpr e@(HsQuasiQuoteE _) = pprPanic "Cant do quasiquotation without GHCi" (ppr e)
185 rnExpr (HsQuasiQuoteE qq)
186 = rnQuasiQuote qq `thenM` \ (qq', fvs_qq) ->
187 runQuasiQuoteExpr qq' `thenM` \ (L _ expr') ->
188 rnExpr expr' `thenM` \ (expr'', fvs_expr) ->
189 returnM (expr'', fvs_qq `plusFV` fvs_expr)
192 rnExpr section@(SectionL expr op)
193 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
194 rnLExpr op `thenM` \ (op', fvs_op) ->
195 checkSectionPrec InfixL section op' expr' `thenM_`
196 returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
198 rnExpr section@(SectionR op expr)
199 = rnLExpr op `thenM` \ (op', fvs_op) ->
200 rnLExpr expr `thenM` \ (expr', fvs_expr) ->
201 checkSectionPrec InfixR section op' expr' `thenM_`
202 returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
204 rnExpr (HsCoreAnn ann expr)
205 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
206 returnM (HsCoreAnn ann expr', fvs_expr)
208 rnExpr (HsSCC lbl expr)
209 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
210 returnM (HsSCC lbl expr', fvs_expr)
211 rnExpr (HsTickPragma info expr)
212 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
213 returnM (HsTickPragma info expr', fvs_expr)
215 rnExpr (HsLam matches)
216 = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) ->
217 returnM (HsLam matches', fvMatch)
219 rnExpr (HsCase expr matches)
220 = rnLExpr expr `thenM` \ (new_expr, e_fvs) ->
221 rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) ->
222 returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs)
224 rnExpr (HsLet binds expr)
225 = rnLocalBindsAndThen binds $ \ binds' ->
226 rnLExpr expr `thenM` \ (expr',fvExpr) ->
227 returnM (HsLet binds' expr', fvExpr)
229 rnExpr (HsDo do_or_lc stmts body _)
230 = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $
232 ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) }
234 rnExpr (ExplicitList _ exps)
235 = rnExprs exps `thenM` \ (exps', fvs) ->
236 returnM (ExplicitList placeHolderType exps', fvs)
238 rnExpr (ExplicitPArr _ exps)
239 = rnExprs exps `thenM` \ (exps', fvs) ->
240 returnM (ExplicitPArr placeHolderType exps', fvs)
242 rnExpr (ExplicitTuple exps boxity)
243 = checkTupSize (length exps) `thenM_`
244 rnExprs exps `thenM` \ (exps', fvs) ->
245 returnM (ExplicitTuple exps' boxity, fvs)
247 rnExpr (RecordCon con_id _ rbinds)
248 = do { conname <- lookupLocatedOccRn con_id
249 ; (rbinds', fvRbinds) <- rnHsRecFields_Con conname rnLExpr rbinds
250 ; return (RecordCon conname noPostTcExpr rbinds',
251 fvRbinds `addOneFV` unLoc conname) }
253 rnExpr (RecordUpd expr rbinds _ _ _)
254 = do { (expr', fvExpr) <- rnLExpr expr
255 ; (rbinds', fvRbinds) <- rnHsRecFields_Update rnLExpr rbinds
256 ; return (RecordUpd expr' rbinds' [] [] [],
257 fvExpr `plusFV` fvRbinds) }
259 rnExpr (ExprWithTySig expr pty)
260 = do { (pty', fvTy) <- rnHsTypeFVs doc pty
261 ; (expr', fvExpr) <- bindSigTyVarsFV (hsExplicitTvs pty') $
263 ; return (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy) }
265 doc = text "In an expression type signature"
267 rnExpr (HsIf p b1 b2)
268 = rnLExpr p `thenM` \ (p', fvP) ->
269 rnLExpr b1 `thenM` \ (b1', fvB1) ->
270 rnLExpr b2 `thenM` \ (b2', fvB2) ->
271 returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
274 = rnHsTypeFVs doc a `thenM` \ (t, fvT) ->
275 returnM (HsType t, fvT)
277 doc = text "In a type argument"
279 rnExpr (ArithSeq _ seq)
280 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
281 returnM (ArithSeq noPostTcExpr new_seq, fvs)
283 rnExpr (PArrSeq _ seq)
284 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
285 returnM (PArrSeq noPostTcExpr new_seq, fvs)
288 These three are pattern syntax appearing in expressions.
289 Since all the symbols are reservedops we can simply reject them.
290 We return a (bogus) EWildPat in each case.
293 rnExpr e@EWildPat = patSynErr e
294 rnExpr e@(EAsPat {}) = patSynErr e
295 rnExpr e@(EViewPat {}) = patSynErr e
296 rnExpr e@(ELazyPat {}) = patSynErr e
299 %************************************************************************
303 %************************************************************************
306 rnExpr (HsProc pat body)
308 rnPatsAndThen_LocalRightwards ProcExpr [pat] $ \ [pat'] ->
309 rnCmdTop body `thenM` \ (body',fvBody) ->
310 returnM (HsProc pat' body', fvBody)
312 rnExpr (HsArrApp arrow arg _ ho rtl)
313 = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) ->
314 rnLExpr arg `thenM` \ (arg',fvArg) ->
315 returnM (HsArrApp arrow' arg' placeHolderType ho rtl,
316 fvArrow `plusFV` fvArg)
318 select_arrow_scope tc = case ho of
319 HsHigherOrderApp -> tc
320 HsFirstOrderApp -> escapeArrowScope tc
323 rnExpr (HsArrForm op (Just _) [arg1, arg2])
324 = escapeArrowScope (rnLExpr op)
325 `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) ->
326 rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) ->
327 rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) ->
331 lookupFixityRn op_name `thenM` \ fixity ->
332 mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e ->
335 fv_arg1 `plusFV` fv_op `plusFV` fv_arg2)
337 rnExpr (HsArrForm op fixity cmds)
338 = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) ->
339 rnCmdArgs cmds `thenM` \ (cmds',fvCmds) ->
340 returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds)
342 rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
347 %************************************************************************
351 %************************************************************************
354 rnCmdArgs :: [LHsCmdTop RdrName] -> RnM ([LHsCmdTop Name], FreeVars)
355 rnCmdArgs [] = returnM ([], emptyFVs)
357 = rnCmdTop arg `thenM` \ (arg',fvArg) ->
358 rnCmdArgs args `thenM` \ (args',fvArgs) ->
359 returnM (arg':args', fvArg `plusFV` fvArgs)
361 rnCmdTop :: LHsCmdTop RdrName -> RnM (LHsCmdTop Name, FreeVars)
362 rnCmdTop = wrapLocFstM rnCmdTop'
364 rnCmdTop' (HsCmdTop cmd _ _ _)
365 = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) ->
367 cmd_names = [arrAName, composeAName, firstAName] ++
368 nameSetToList (methodNamesCmd (unLoc cmd'))
370 -- Generate the rebindable syntax for the monad
371 lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) ->
373 returnM (HsCmdTop cmd' [] placeHolderType cmd_names',
374 fvCmd `plusFV` cmd_fvs)
376 ---------------------------------------------------
377 -- convert OpApp's in a command context to HsArrForm's
379 convertOpFormsLCmd :: LHsCmd id -> LHsCmd id
380 convertOpFormsLCmd = fmap convertOpFormsCmd
382 convertOpFormsCmd :: HsCmd id -> HsCmd id
384 convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e
385 convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match)
386 convertOpFormsCmd (OpApp c1 op fixity c2)
388 arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType []
389 arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType []
391 HsArrForm op (Just fixity) [arg1, arg2]
393 convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c)
395 convertOpFormsCmd (HsCase exp matches)
396 = HsCase exp (convertOpFormsMatch matches)
398 convertOpFormsCmd (HsIf exp c1 c2)
399 = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2)
401 convertOpFormsCmd (HsLet binds cmd)
402 = HsLet binds (convertOpFormsLCmd cmd)
404 convertOpFormsCmd (HsDo ctxt stmts body ty)
405 = HsDo ctxt (map (fmap convertOpFormsStmt) stmts)
406 (convertOpFormsLCmd body) ty
408 -- Anything else is unchanged. This includes HsArrForm (already done),
409 -- things with no sub-commands, and illegal commands (which will be
410 -- caught by the type checker)
411 convertOpFormsCmd c = c
413 convertOpFormsStmt :: StmtLR id id -> StmtLR id id
414 convertOpFormsStmt (BindStmt pat cmd _ _)
415 = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr
416 convertOpFormsStmt (ExprStmt cmd _ _)
417 = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType
418 convertOpFormsStmt (RecStmt stmts lvs rvs es binds)
419 = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds
420 convertOpFormsStmt stmt = stmt
422 convertOpFormsMatch :: MatchGroup id -> MatchGroup id
423 convertOpFormsMatch (MatchGroup ms ty)
424 = MatchGroup (map (fmap convert) ms) ty
425 where convert (Match pat mty grhss)
426 = Match pat mty (convertOpFormsGRHSs grhss)
428 convertOpFormsGRHSs :: GRHSs id -> GRHSs id
429 convertOpFormsGRHSs (GRHSs grhss binds)
430 = GRHSs (map convertOpFormsGRHS grhss) binds
432 convertOpFormsGRHS :: Located (GRHS id) -> Located (GRHS id)
433 convertOpFormsGRHS = fmap convert
435 convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd)
437 ---------------------------------------------------
438 type CmdNeeds = FreeVars -- Only inhabitants are
439 -- appAName, choiceAName, loopAName
441 -- find what methods the Cmd needs (loop, choice, apply)
442 methodNamesLCmd :: LHsCmd Name -> CmdNeeds
443 methodNamesLCmd = methodNamesCmd . unLoc
445 methodNamesCmd :: HsCmd Name -> CmdNeeds
447 methodNamesCmd (HsArrApp _arrow _arg _ HsFirstOrderApp _rtl)
449 methodNamesCmd (HsArrApp _arrow _arg _ HsHigherOrderApp _rtl)
451 methodNamesCmd (HsArrForm {}) = emptyFVs
453 methodNamesCmd (HsPar c) = methodNamesLCmd c
455 methodNamesCmd (HsIf _ c1 c2)
456 = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName
458 methodNamesCmd (HsLet _ c) = methodNamesLCmd c
460 methodNamesCmd (HsDo _ stmts body _)
461 = methodNamesStmts stmts `plusFV` methodNamesLCmd body
463 methodNamesCmd (HsApp c _) = methodNamesLCmd c
465 methodNamesCmd (HsLam match) = methodNamesMatch match
467 methodNamesCmd (HsCase _ matches)
468 = methodNamesMatch matches `addOneFV` choiceAName
470 methodNamesCmd _ = emptyFVs
471 -- Other forms can't occur in commands, but it's not convenient
472 -- to error here so we just do what's convenient.
473 -- The type checker will complain later
475 ---------------------------------------------------
476 methodNamesMatch :: MatchGroup Name -> FreeVars
477 methodNamesMatch (MatchGroup ms _)
478 = plusFVs (map do_one ms)
480 do_one (L _ (Match _ _ grhss)) = methodNamesGRHSs grhss
482 -------------------------------------------------
484 methodNamesGRHSs :: GRHSs Name -> FreeVars
485 methodNamesGRHSs (GRHSs grhss _) = plusFVs (map methodNamesGRHS grhss)
487 -------------------------------------------------
489 methodNamesGRHS :: Located (GRHS Name) -> CmdNeeds
490 methodNamesGRHS (L _ (GRHS _ rhs)) = methodNamesLCmd rhs
492 ---------------------------------------------------
493 methodNamesStmts :: [Located (StmtLR Name Name)] -> FreeVars
494 methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts)
496 ---------------------------------------------------
497 methodNamesLStmt :: Located (StmtLR Name Name) -> FreeVars
498 methodNamesLStmt = methodNamesStmt . unLoc
500 methodNamesStmt :: StmtLR Name Name -> FreeVars
501 methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd
502 methodNamesStmt (BindStmt _ cmd _ _) = methodNamesLCmd cmd
503 methodNamesStmt (RecStmt stmts _ _ _ _)
504 = methodNamesStmts stmts `addOneFV` loopAName
505 methodNamesStmt (LetStmt _) = emptyFVs
506 methodNamesStmt (ParStmt _) = emptyFVs
507 methodNamesStmt (TransformStmt _ _ _) = emptyFVs
508 methodNamesStmt (GroupStmt _ _) = emptyFVs
509 -- ParStmt, TransformStmt and GroupStmt can't occur in commands, but it's not convenient to error
510 -- here so we just do what's convenient
514 %************************************************************************
518 %************************************************************************
521 rnArithSeq :: ArithSeqInfo RdrName -> RnM (ArithSeqInfo Name, FreeVars)
522 rnArithSeq (From expr)
523 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
524 returnM (From expr', fvExpr)
526 rnArithSeq (FromThen expr1 expr2)
527 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
528 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
529 returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2)
531 rnArithSeq (FromTo expr1 expr2)
532 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
533 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
534 returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2)
536 rnArithSeq (FromThenTo expr1 expr2 expr3)
537 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
538 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
539 rnLExpr expr3 `thenM` \ (expr3', fvExpr3) ->
540 returnM (FromThenTo expr1' expr2' expr3',
541 plusFVs [fvExpr1, fvExpr2, fvExpr3])
544 %************************************************************************
546 Template Haskell brackets
548 %************************************************************************
551 rnBracket :: HsBracket RdrName -> RnM (HsBracket Name, FreeVars)
552 rnBracket (VarBr n) = do { name <- lookupOccRn n
553 ; this_mod <- getModule
554 ; checkM (nameIsLocalOrFrom this_mod name) $ -- Reason: deprecation checking asumes the
555 do { loadInterfaceForName msg name -- home interface is loaded, and this is the
556 ; return () } -- only way that is going to happen
557 ; returnM (VarBr name, unitFV name) }
559 msg = ptext (sLit "Need interface for Template Haskell quoted Name")
561 rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e
562 ; return (ExpBr e', fvs) }
564 rnBracket (PatBr _) = do { addErr (ptext (sLit "Tempate Haskell pattern brackets are not supported yet"));
567 rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t
568 ; return (TypBr t', fvs) }
570 doc = ptext (sLit "In a Template-Haskell quoted type")
571 rnBracket (DecBr group)
572 = do { gbl_env <- getGblEnv
574 ; let new_gbl_env = gbl_env { -- Set the module to thFAKE. The top-level names from the bracketed
575 -- declarations will go into the name cache, and we don't want them to
576 -- confuse the Names for the current module.
577 -- By using a pretend module, thFAKE, we keep them safely out of the way.
580 -- The emptyDUs is so that we just collect uses for this group alone
581 -- in the call to rnSrcDecls below
583 ; setGblEnv new_gbl_env $ do {
585 -- In this situation we want to *shadow* top-level bindings.
587 -- bar = [d| foo = 1 |]
588 -- If we don't shadow, we'll get an ambiguity complaint when we do
589 -- a lookupTopBndrRn (which uses lookupGreLocalRn) on the binder of the 'foo'
591 -- Furthermore, arguably if the splice does define foo, that should hide
592 -- any foo's further out
594 -- The shadowing is acheived by calling rnSrcDecls with True as the shadowing flag
595 ; (tcg_env, group') <- rnSrcDecls True group
597 -- Discard the tcg_env; it contains only extra info about fixity
598 ; return (DecBr group', allUses (tcg_dus tcg_env)) } }
601 %************************************************************************
603 \subsubsection{@Stmt@s: in @do@ expressions}
605 %************************************************************************
608 rnStmts :: HsStmtContext Name -> [LStmt RdrName]
609 -> RnM (thing, FreeVars)
610 -> RnM (([LStmt Name], thing), FreeVars)
612 rnStmts (MDoExpr _) = rnMDoStmts
613 rnStmts ctxt = rnNormalStmts ctxt
615 rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName]
616 -> RnM (thing, FreeVars)
617 -> RnM (([LStmt Name], thing), FreeVars)
618 -- Used for cases *other* than recursive mdo
619 -- Implements nested scopes
621 rnNormalStmts _ [] thing_inside
622 = do { (thing, fvs) <- thing_inside
623 ; return (([],thing), fvs) }
625 rnNormalStmts ctxt (L loc stmt : stmts) thing_inside
626 = do { ((stmt', (stmts', thing)), fvs) <- rnStmt ctxt stmt $
627 rnNormalStmts ctxt stmts thing_inside
628 ; return (((L loc stmt' : stmts'), thing), fvs) }
631 rnStmt :: HsStmtContext Name -> Stmt RdrName
632 -> RnM (thing, FreeVars)
633 -> RnM ((Stmt Name, thing), FreeVars)
635 rnStmt _ (ExprStmt expr _ _) thing_inside
636 = do { (expr', fv_expr) <- rnLExpr expr
637 ; (then_op, fvs1) <- lookupSyntaxName thenMName
638 ; (thing, fvs2) <- thing_inside
639 ; return ((ExprStmt expr' then_op placeHolderType, thing),
640 fv_expr `plusFV` fvs1 `plusFV` fvs2) }
642 rnStmt ctxt (BindStmt pat expr _ _) thing_inside
643 = do { (expr', fv_expr) <- rnLExpr expr
644 -- The binders do not scope over the expression
645 ; (bind_op, fvs1) <- lookupSyntaxName bindMName
646 ; (fail_op, fvs2) <- lookupSyntaxName failMName
647 ; rnPatsAndThen_LocalRightwards (StmtCtxt ctxt) [pat] $ \ [pat'] -> do
648 { (thing, fvs3) <- thing_inside
649 ; return ((BindStmt pat' expr' bind_op fail_op, thing),
650 fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }}
651 -- fv_expr shouldn't really be filtered by the rnPatsAndThen
652 -- but it does not matter because the names are unique
654 rnStmt ctxt (LetStmt binds) thing_inside
655 = do { checkLetStmt ctxt binds
656 ; rnLocalBindsAndThen binds $ \binds' -> do
657 { (thing, fvs) <- thing_inside
658 ; return ((LetStmt binds', thing), fvs) } }
660 rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside
661 = do { checkRecStmt ctxt
662 ; rn_rec_stmts_and_then rec_stmts $ \ segs -> do
663 { (thing, fvs) <- thing_inside
665 segs_w_fwd_refs = addFwdRefs segs
666 (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs
667 later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs)
668 fwd_vars = nameSetToList (plusFVs fs)
670 rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds
671 ; return ((rec_stmt, thing), uses `plusFV` fvs) } }
673 rnStmt ctxt (ParStmt segs) thing_inside
674 = do { checkParStmt ctxt
675 ; ((segs', thing), fvs) <- rnParallelStmts (ParStmtCtxt ctxt) segs thing_inside
676 ; return ((ParStmt segs', thing), fvs) }
678 rnStmt ctxt (TransformStmt (stmts, _) usingExpr maybeByExpr) thing_inside = do
679 checkTransformStmt ctxt
681 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
682 ((stmts', binders, (maybeByExpr', thing)), fvs) <-
683 rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \_unshadowed_bndrs -> do
684 (maybeByExpr', fv_maybeByExpr) <- rnMaybeLExpr maybeByExpr
685 (thing, fv_thing) <- thing_inside
687 return ((maybeByExpr', thing), fv_maybeByExpr `plusFV` fv_thing)
689 return ((TransformStmt (stmts', binders) usingExpr' maybeByExpr', thing), fv_usingExpr `plusFV` fvs)
691 rnMaybeLExpr Nothing = return (Nothing, emptyFVs)
692 rnMaybeLExpr (Just expr) = do
693 (expr', fv_expr) <- rnLExpr expr
694 return (Just expr', fv_expr)
696 rnStmt ctxt (GroupStmt (stmts, _) groupByClause) thing_inside = do
697 checkTransformStmt ctxt
699 -- We must rename the using expression in the context before the transform is begun
700 groupByClauseAction <-
701 case groupByClause of
702 GroupByNothing usingExpr -> do
703 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
704 (return . return) (GroupByNothing usingExpr', fv_usingExpr)
705 GroupBySomething eitherUsingExpr byExpr -> do
706 (eitherUsingExpr', fv_eitherUsingExpr) <-
707 case eitherUsingExpr of
708 Right _ -> return (Right $ HsVar groupWithName, unitNameSet groupWithName)
710 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
711 return (Left usingExpr', fv_usingExpr)
714 (byExpr', fv_byExpr) <- rnLExpr byExpr
715 return (GroupBySomething eitherUsingExpr' byExpr', fv_eitherUsingExpr `plusFV` fv_byExpr)
717 -- We only use rnNormalStmtsAndFindUsedBinders to get unshadowed_bndrs, so
718 -- perhaps we could refactor this to use rnNormalStmts directly?
719 ((stmts', _, (groupByClause', usedBinderMap, thing)), fvs) <-
720 rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \unshadowed_bndrs -> do
721 (groupByClause', fv_groupByClause) <- groupByClauseAction
723 unshadowed_bndrs' <- mapM newLocalName unshadowed_bndrs
724 let binderMap = zip unshadowed_bndrs unshadowed_bndrs'
726 -- Bind the "thing" inside a context where we have REBOUND everything
727 -- bound by the statements before the group. This is necessary since after
728 -- the grouping the same identifiers actually have different meanings
729 -- i.e. they refer to lists not singletons!
730 (thing, fv_thing) <- bindLocalNames unshadowed_bndrs' thing_inside
732 -- We remove entries from the binder map that are not used in the thing_inside.
733 -- We can then use that usage information to ensure that the free variables do
734 -- not contain the things we just bound, but do contain the things we need to
735 -- make those bindings (i.e. the corresponding non-listy variables)
737 -- Note that we also retain those entries which have an old binder in our
738 -- own free variables (the using or by expression). This is because this map
739 -- is reused in the desugarer to create the type to bind from the statements
740 -- that occur before this one. If the binders we need are not in the map, they
741 -- will never get bound into our desugared expression and hence the simplifier
742 -- crashes as we refer to variables that don't exist!
743 let usedBinderMap = filter
744 (\(old_binder, new_binder) ->
745 (new_binder `elemNameSet` fv_thing) ||
746 (old_binder `elemNameSet` fv_groupByClause)) binderMap
747 (usedOldBinders, usedNewBinders) = unzip usedBinderMap
748 real_fv_thing = (delListFromNameSet fv_thing usedNewBinders) `plusFV` (mkNameSet usedOldBinders)
750 return ((groupByClause', usedBinderMap, thing), fv_groupByClause `plusFV` real_fv_thing)
752 traceRn (text "rnStmt: implicitly rebound these used binders:" <+> ppr usedBinderMap)
753 return ((GroupStmt (stmts', usedBinderMap) groupByClause', thing), fvs)
755 rnNormalStmtsAndFindUsedBinders :: HsStmtContext Name
757 -> ([Name] -> RnM (thing, FreeVars))
758 -> RnM (([LStmt Name], [Name], thing), FreeVars)
759 rnNormalStmtsAndFindUsedBinders ctxt stmts thing_inside = do
760 ((stmts', (used_bndrs, inner_thing)), fvs) <- rnNormalStmts ctxt stmts $ do
761 -- Find the Names that are bound by stmts that
762 -- by assumption we have just renamed
763 local_env <- getLocalRdrEnv
765 stmts_binders = collectLStmtsBinders stmts
766 bndrs = map (expectJust "rnStmt"
767 . lookupLocalRdrEnv local_env
768 . unLoc) stmts_binders
770 -- If shadow, we'll look up (Unqual x) twice, getting
771 -- the second binding both times, which is the
773 unshadowed_bndrs = nub bndrs
775 -- Typecheck the thing inside, passing on all
776 -- the Names bound before it for its information
777 (thing, fvs) <- thing_inside unshadowed_bndrs
779 -- Figure out which of the bound names are used
780 -- after the statements we renamed
781 let used_bndrs = filter (`elemNameSet` fvs) bndrs
782 return ((used_bndrs, thing), fvs)
784 -- Flatten the tuple returned by the above call a bit!
785 return ((stmts', used_bndrs, inner_thing), fvs)
787 rnParallelStmts :: HsStmtContext Name -> [([LStmt RdrName], [RdrName])]
788 -> RnM (thing, FreeVars)
789 -> RnM (([([LStmt Name], [Name])], thing), FreeVars)
790 rnParallelStmts ctxt segs thing_inside = do
791 orig_lcl_env <- getLocalRdrEnv
792 go orig_lcl_env [] segs
794 go orig_lcl_env bndrs [] = do
795 let (bndrs', dups) = removeDups cmpByOcc bndrs
796 inner_env = extendLocalRdrEnv orig_lcl_env bndrs'
799 (thing, fvs) <- setLocalRdrEnv inner_env thing_inside
800 return (([], thing), fvs)
802 go orig_lcl_env bndrs_so_far ((stmts, _) : segs) = do
803 ((stmts', bndrs, (segs', thing)), fvs) <- rnNormalStmtsAndFindUsedBinders ctxt stmts $ \new_bndrs -> do
804 -- Typecheck the thing inside, passing on all
805 -- the Names bound, but separately; revert the envt
806 setLocalRdrEnv orig_lcl_env $ do
807 go orig_lcl_env (new_bndrs ++ bndrs_so_far) segs
809 let seg' = (stmts', bndrs)
810 return (((seg':segs'), thing), delListFromNameSet fvs bndrs)
812 cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2
813 dupErr vs = addErr (ptext (sLit "Duplicate binding in parallel list comprehension for:")
814 <+> quotes (ppr (head vs)))
818 %************************************************************************
820 \subsubsection{mdo expressions}
822 %************************************************************************
825 type FwdRefs = NameSet
826 type Segment stmts = (Defs,
827 Uses, -- May include defs
828 FwdRefs, -- A subset of uses that are
829 -- (a) used before they are bound in this segment, or
830 -- (b) used here, and bound in subsequent segments
831 stmts) -- Either Stmt or [Stmt]
834 ----------------------------------------------------
836 rnMDoStmts :: [LStmt RdrName]
837 -> RnM (thing, FreeVars)
838 -> RnM (([LStmt Name], thing), FreeVars)
839 rnMDoStmts stmts thing_inside
840 = -- Step1: Bring all the binders of the mdo into scope
841 -- (Remember that this also removes the binders from the
842 -- finally-returned free-vars.)
843 -- And rename each individual stmt, making a
844 -- singleton segment. At this stage the FwdRefs field
845 -- isn't finished: it's empty for all except a BindStmt
846 -- for which it's the fwd refs within the bind itself
847 -- (This set may not be empty, because we're in a recursive
849 rn_rec_stmts_and_then stmts $ \ segs -> do {
851 ; (thing, fvs_later) <- thing_inside
854 -- Step 2: Fill in the fwd refs.
855 -- The segments are all singletons, but their fwd-ref
856 -- field mentions all the things used by the segment
857 -- that are bound after their use
858 segs_w_fwd_refs = addFwdRefs segs
860 -- Step 3: Group together the segments to make bigger segments
861 -- Invariant: in the result, no segment uses a variable
862 -- bound in a later segment
863 grouped_segs = glomSegments segs_w_fwd_refs
865 -- Step 4: Turn the segments into Stmts
866 -- Use RecStmt when and only when there are fwd refs
867 -- Also gather up the uses from the end towards the
868 -- start, so we can tell the RecStmt which things are
869 -- used 'after' the RecStmt
870 (stmts', fvs) = segsToStmts grouped_segs fvs_later
872 ; return ((stmts', thing), fvs) }
874 ---------------------------------------------
876 -- wrapper that does both the left- and right-hand sides
877 rn_rec_stmts_and_then :: [LStmt RdrName]
878 -- assumes that the FreeVars returned includes
879 -- the FreeVars of the Segments
880 -> ([Segment (LStmt Name)] -> RnM (a, FreeVars))
882 rn_rec_stmts_and_then s cont
883 = do { -- (A) Make the mini fixity env for all of the stmts
884 fix_env <- makeMiniFixityEnv (collectRecStmtsFixities s)
887 ; new_lhs_and_fv <- rn_rec_stmts_lhs fix_env s
889 -- ...bring them and their fixities into scope
890 ; let bound_names = map unLoc $ collectLStmtsBinders (map fst new_lhs_and_fv)
891 ; bindLocalNamesFV_WithFixities bound_names fix_env $ do
893 -- (C) do the right-hand-sides and thing-inside
894 { segs <- rn_rec_stmts bound_names new_lhs_and_fv
895 ; (res, fvs) <- cont segs
896 ; warnUnusedLocalBinds bound_names fvs
897 ; return (res, fvs) }}
899 -- get all the fixity decls in any Let stmt
900 collectRecStmtsFixities :: [LStmtLR RdrName RdrName] -> [LFixitySig RdrName]
901 collectRecStmtsFixities l =
902 foldr (\ s -> \acc -> case s of
903 (L _ (LetStmt (HsValBinds (ValBindsIn _ sigs)))) ->
904 foldr (\ sig -> \ acc -> case sig of
905 (L loc (FixSig s)) -> (L loc s) : acc
911 rn_rec_stmt_lhs :: MiniFixityEnv
913 -- rename LHS, and return its FVs
914 -- Warning: we will only need the FreeVars below in the case of a BindStmt,
915 -- so we don't bother to compute it accurately in the other cases
916 -> RnM [(LStmtLR Name RdrName, FreeVars)]
918 rn_rec_stmt_lhs _ (L loc (ExprStmt expr a b)) = return [(L loc (ExprStmt expr a b),
919 -- this is actually correct
922 rn_rec_stmt_lhs fix_env (L loc (BindStmt pat expr a b))
924 -- should the ctxt be MDo instead?
925 (pat', fv_pat) <- rnBindPat (localRecNameMaker fix_env) pat
926 return [(L loc (BindStmt pat' expr a b),
929 rn_rec_stmt_lhs _ (L _ (LetStmt binds@(HsIPBinds _)))
930 = do { addErr (badIpBinds (ptext (sLit "an mdo expression")) binds)
933 rn_rec_stmt_lhs fix_env (L loc (LetStmt (HsValBinds binds)))
934 = do binds' <- rnValBindsLHS fix_env binds
935 return [(L loc (LetStmt (HsValBinds binds')),
936 -- Warning: this is bogus; see function invariant
940 rn_rec_stmt_lhs fix_env (L _ (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec
941 = rn_rec_stmts_lhs fix_env stmts
943 rn_rec_stmt_lhs _ stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo
944 = pprPanic "rn_rec_stmt" (ppr stmt)
946 rn_rec_stmt_lhs _ stmt@(L _ (TransformStmt _ _ _)) -- Syntactically illegal in mdo
947 = pprPanic "rn_rec_stmt" (ppr stmt)
949 rn_rec_stmt_lhs _ stmt@(L _ (GroupStmt _ _)) -- Syntactically illegal in mdo
950 = pprPanic "rn_rec_stmt" (ppr stmt)
952 rn_rec_stmt_lhs _ (L _ (LetStmt EmptyLocalBinds))
953 = panic "rn_rec_stmt LetStmt EmptyLocalBinds"
955 rn_rec_stmts_lhs :: MiniFixityEnv
957 -> RnM [(LStmtLR Name RdrName, FreeVars)]
958 rn_rec_stmts_lhs fix_env stmts =
959 let boundNames = collectLStmtsBinders stmts
960 doc = text "In a recursive mdo-expression"
962 -- First do error checking: we need to check for dups here because we
963 -- don't bind all of the variables from the Stmt at once
964 -- with bindLocatedLocals.
965 checkDupRdrNames doc boundNames
966 mappM (rn_rec_stmt_lhs fix_env) stmts `thenM` \ ls -> returnM (concat ls)
971 rn_rec_stmt :: [Name] -> LStmtLR Name RdrName -> FreeVars -> RnM [Segment (LStmt Name)]
972 -- Rename a Stmt that is inside a RecStmt (or mdo)
973 -- Assumes all binders are already in scope
974 -- Turns each stmt into a singleton Stmt
975 rn_rec_stmt _ (L loc (ExprStmt expr _ _)) _
976 = rnLExpr expr `thenM` \ (expr', fvs) ->
977 lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) ->
978 returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet,
979 L loc (ExprStmt expr' then_op placeHolderType))]
981 rn_rec_stmt _ (L loc (BindStmt pat' expr _ _)) fv_pat
982 = rnLExpr expr `thenM` \ (expr', fv_expr) ->
983 lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) ->
984 lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) ->
986 bndrs = mkNameSet (collectPatBinders pat')
987 fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2
989 returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs,
990 L loc (BindStmt pat' expr' bind_op fail_op))]
992 rn_rec_stmt _ (L _ (LetStmt binds@(HsIPBinds _))) _
993 = do { addErr (badIpBinds (ptext (sLit "an mdo expression")) binds)
996 rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds'))) _ = do
997 (binds', du_binds) <-
998 -- fixities and unused are handled above in rn_rec_stmts_and_then
999 rnValBindsRHS all_bndrs binds'
1000 returnM [(duDefs du_binds, duUses du_binds,
1001 emptyNameSet, L loc (LetStmt (HsValBinds binds')))]
1003 -- no RecStmt case becuase they get flattened above when doing the LHSes
1004 rn_rec_stmt _ stmt@(L _ (RecStmt _ _ _ _ _)) _
1005 = pprPanic "rn_rec_stmt: RecStmt" (ppr stmt)
1007 rn_rec_stmt _ stmt@(L _ (ParStmt _)) _ -- Syntactically illegal in mdo
1008 = pprPanic "rn_rec_stmt: ParStmt" (ppr stmt)
1010 rn_rec_stmt _ stmt@(L _ (TransformStmt _ _ _)) _ -- Syntactically illegal in mdo
1011 = pprPanic "rn_rec_stmt: TransformStmt" (ppr stmt)
1013 rn_rec_stmt _ stmt@(L _ (GroupStmt _ _)) _ -- Syntactically illegal in mdo
1014 = pprPanic "rn_rec_stmt: GroupStmt" (ppr stmt)
1016 rn_rec_stmt _ (L _ (LetStmt EmptyLocalBinds)) _
1017 = panic "rn_rec_stmt: LetStmt EmptyLocalBinds"
1019 rn_rec_stmts :: [Name] -> [(LStmtLR Name RdrName, FreeVars)] -> RnM [Segment (LStmt Name)]
1020 rn_rec_stmts bndrs stmts = mappM (uncurry (rn_rec_stmt bndrs)) stmts `thenM` \ segs_s ->
1021 returnM (concat segs_s)
1023 ---------------------------------------------
1024 addFwdRefs :: [Segment a] -> [Segment a]
1025 -- So far the segments only have forward refs *within* the Stmt
1026 -- (which happens for bind: x <- ...x...)
1027 -- This function adds the cross-seg fwd ref info
1030 = fst (foldr mk_seg ([], emptyNameSet) pairs)
1032 mk_seg (defs, uses, fwds, stmts) (segs, later_defs)
1033 = (new_seg : segs, all_defs)
1035 new_seg = (defs, uses, new_fwds, stmts)
1036 all_defs = later_defs `unionNameSets` defs
1037 new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs)
1038 -- Add the downstream fwd refs here
1040 ----------------------------------------------------
1041 -- Glomming the singleton segments of an mdo into
1042 -- minimal recursive groups.
1044 -- At first I thought this was just strongly connected components, but
1045 -- there's an important constraint: the order of the stmts must not change.
1048 -- mdo { x <- ...y...
1055 -- Here, the first stmt mention 'y', which is bound in the third.
1056 -- But that means that the innocent second stmt (p <- z) gets caught
1057 -- up in the recursion. And that in turn means that the binding for
1058 -- 'z' has to be included... and so on.
1060 -- Start at the tail { r <- x }
1061 -- Now add the next one { z <- y ; r <- x }
1062 -- Now add one more { q <- x ; z <- y ; r <- x }
1063 -- Now one more... but this time we have to group a bunch into rec
1064 -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x }
1065 -- Now one more, which we can add on without a rec
1067 -- rec { y <- ...x... ; q <- x ; z <- y } ;
1069 -- Finally we add the last one; since it mentions y we have to
1070 -- glom it togeher with the first two groups
1071 -- { rec { x <- ...y...; p <- z ; y <- ...x... ;
1072 -- q <- x ; z <- y } ;
1075 glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]]
1077 glomSegments [] = []
1078 glomSegments ((defs,uses,fwds,stmt) : segs)
1079 -- Actually stmts will always be a singleton
1080 = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others
1082 segs' = glomSegments segs
1083 (extras, others) = grab uses segs'
1084 (ds, us, fs, ss) = unzip4 extras
1086 seg_defs = plusFVs ds `plusFV` defs
1087 seg_uses = plusFVs us `plusFV` uses
1088 seg_fwds = plusFVs fs `plusFV` fwds
1089 seg_stmts = stmt : concat ss
1091 grab :: NameSet -- The client
1093 -> ([Segment a], -- Needed by the 'client'
1094 [Segment a]) -- Not needed by the client
1095 -- The result is simply a split of the input
1097 = (reverse yeses, reverse noes)
1099 (noes, yeses) = span not_needed (reverse dus)
1100 not_needed (defs,_,_,_) = not (intersectsNameSet defs uses)
1103 ----------------------------------------------------
1104 segsToStmts :: [Segment [LStmt Name]]
1105 -> FreeVars -- Free vars used 'later'
1106 -> ([LStmt Name], FreeVars)
1108 segsToStmts [] fvs_later = ([], fvs_later)
1109 segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later
1110 = ASSERT( not (null ss) )
1111 (new_stmt : later_stmts, later_uses `plusFV` uses)
1113 (later_stmts, later_uses) = segsToStmts segs fvs_later
1114 new_stmt | non_rec = head ss
1115 | otherwise = L (getLoc (head ss)) $
1116 RecStmt ss (nameSetToList used_later) (nameSetToList fwds)
1119 non_rec = isSingleton ss && isEmptyNameSet fwds
1120 used_later = defs `intersectNameSet` later_uses
1121 -- The ones needed after the RecStmt
1124 %************************************************************************
1126 \subsubsection{Assertion utils}
1128 %************************************************************************
1131 srcSpanPrimLit :: SrcSpan -> HsExpr Name
1132 srcSpanPrimLit span = HsLit (HsStringPrim (mkFastString (showSDoc (ppr span))))
1134 mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars)
1135 -- Return an expression for (assertError "Foo.hs:27")
1137 = getSrcSpanM `thenM` \ sloc ->
1139 expr = HsApp (L sloc (HsVar assertErrorName))
1140 (L sloc (srcSpanPrimLit sloc))
1142 returnM (expr, emptyFVs)
1145 %************************************************************************
1147 \subsubsection{Errors}
1149 %************************************************************************
1153 ----------------------
1154 -- Checking when a particular Stmt is ok
1155 checkLetStmt :: HsStmtContext Name -> HsLocalBinds RdrName -> RnM ()
1156 checkLetStmt (ParStmtCtxt _) (HsIPBinds binds) = addErr (badIpBinds (ptext (sLit "a parallel list comprehension:")) binds)
1157 checkLetStmt _ctxt _binds = return ()
1158 -- We do not allow implicit-parameter bindings in a parallel
1159 -- list comprehension. I'm not sure what it might mean.
1162 checkRecStmt :: HsStmtContext Name -> RnM ()
1163 checkRecStmt (MDoExpr {}) = return () -- Recursive stmt ok in 'mdo'
1164 checkRecStmt (DoExpr {}) = return () -- ..and in 'do' but only because of arrows:
1165 -- proc x -> do { ...rec... }
1166 -- We don't have enough context to distinguish this situation here
1167 -- so we leave it to the type checker
1168 checkRecStmt ctxt = addErr msg
1170 msg = ptext (sLit "Illegal 'rec' stmt in") <+> pprStmtContext ctxt
1173 checkParStmt :: HsStmtContext Name -> RnM ()
1175 = do { parallel_list_comp <- doptM Opt_ParallelListComp
1176 ; checkErr parallel_list_comp msg }
1178 msg = ptext (sLit "Illegal parallel list comprehension: use -XParallelListComp")
1181 checkTransformStmt :: HsStmtContext Name -> RnM ()
1182 checkTransformStmt ListComp -- Ensure we are really within a list comprehension because otherwise the
1183 -- desugarer will break when we come to operate on a parallel array
1184 = do { transform_list_comp <- doptM Opt_TransformListComp
1185 ; checkErr transform_list_comp msg }
1187 msg = ptext (sLit "Illegal transform or grouping list comprehension: use -XTransformListComp")
1188 checkTransformStmt (ParStmtCtxt ctxt) = checkTransformStmt ctxt -- Ok to nest inside a parallel comprehension
1189 checkTransformStmt (TransformStmtCtxt ctxt) = checkTransformStmt ctxt -- Ok to nest inside a parallel comprehension
1190 checkTransformStmt ctxt = addErr msg
1192 msg = ptext (sLit "Illegal transform or grouping in") <+> pprStmtContext ctxt
1195 patSynErr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
1196 patSynErr e = do { addErr (sep [ptext (sLit "Pattern syntax in expression context:"),
1198 ; return (EWildPat, emptyFVs) }
1200 badIpBinds :: Outputable a => SDoc -> a -> SDoc
1201 badIpBinds what binds
1202 = hang (ptext (sLit "Implicit-parameter bindings illegal in") <+> what)