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 -- The above warning supression flag is a temporary kludge.
15 -- While working on this module you are encouraged to remove it and fix
16 -- any warnings in the module. See
17 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
21 rnLExpr, rnExpr, rnStmts
24 #include "HsVersions.h"
27 import {-# SOURCE #-} TcSplice( runQuasiQuoteExpr )
30 import RnSource ( rnSrcDecls, rnSplice, checkTH )
31 import RnBinds ( rnLocalBindsAndThen, rnValBindsLHS, rnValBindsRHS,
32 rnMatchGroup, makeMiniFixityEnv)
36 import HscTypes ( availNames )
37 import RnNames ( getLocalDeclBinders, extendRdrEnvRn )
38 import RnTypes ( rnHsTypeFVs,
39 mkOpFormRn, mkOpAppRn, mkNegAppRn, checkSectionPrec)
40 import RnPat (rnQuasiQuote, rnOverLit, rnPatsAndThen_LocalRightwards, rnBindPat,
41 localRecNameMaker, rnLit,
42 rnHsRecFields_Con, rnHsRecFields_Update, checkTupSize)
43 import RdrName ( mkRdrUnqual )
44 import DynFlags ( DynFlag(..) )
45 import BasicTypes ( FixityDirection(..) )
46 import SrcLoc ( SrcSpan )
47 import PrelNames ( thFAKE, hasKey, assertIdKey, assertErrorName,
48 loopAName, choiceAName, appAName, arrAName, composeAName, firstAName,
49 negateName, thenMName, bindMName, failMName, groupWithName )
51 import Name ( Name, nameOccName, nameModule, nameIsLocalOrFrom )
54 import RdrName ( RdrName, extendLocalRdrEnv, lookupLocalRdrEnv, hideSomeUnquals )
55 import LoadIface ( loadInterfaceForName )
56 import UniqSet ( isEmptyUniqSet, emptyUniqSet )
58 import Util ( isSingleton )
59 import ListSetOps ( removeDups )
60 import Maybes ( expectJust )
62 import SrcLoc ( Located(..), unLoc, getLoc, noLoc )
65 import List ( unzip4 )
72 thenM :: Monad a => a b -> (b -> a c) -> a c
75 thenM_ :: Monad a => a b -> a c -> a c
78 returnM :: Monad m => a -> m a
81 mappM :: (Monad m) => (a -> m b) -> [a] -> m [b]
84 mappM_ :: (Monad m) => (a -> m b) -> [a] -> m ()
87 checkM :: Monad m => Bool -> m () -> m ()
91 %************************************************************************
93 \subsubsection{Expressions}
95 %************************************************************************
98 rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars)
99 rnExprs ls = rnExprs' ls emptyUniqSet
101 rnExprs' [] acc = returnM ([], acc)
102 rnExprs' (expr:exprs) acc
103 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
105 -- Now we do a "seq" on the free vars because typically it's small
106 -- or empty, especially in very long lists of constants
108 acc' = acc `plusFV` fvExpr
110 (grubby_seqNameSet acc' rnExprs') exprs acc' `thenM` \ (exprs', fvExprs) ->
111 returnM (expr':exprs', fvExprs)
113 -- Grubby little function to do "seq" on namesets; replace by proper seq when GHC can do seq
114 grubby_seqNameSet ns result | isEmptyUniqSet ns = result
118 Variables. We look up the variable and return the resulting name.
121 rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars)
122 rnLExpr = wrapLocFstM rnExpr
124 rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
127 = do name <- lookupOccRn v
128 ignore_asserts <- doptM Opt_IgnoreAsserts
129 finish_var ignore_asserts name
131 finish_var ignore_asserts name
132 | ignore_asserts || not (name `hasKey` assertIdKey)
133 = return (HsVar name, unitFV name)
135 = do { (e, fvs) <- mkAssertErrorExpr
136 ; return (e, fvs `addOneFV` name) }
139 = newIPNameRn v `thenM` \ name ->
140 returnM (HsIPVar name, emptyFVs)
142 rnExpr (HsLit lit@(HsString s))
144 opt_OverloadedStrings <- doptM Opt_OverloadedStrings
145 ; if opt_OverloadedStrings then
146 rnExpr (HsOverLit (mkHsIsString s placeHolderType))
147 else -- Same as below
149 returnM (HsLit lit, emptyFVs)
154 returnM (HsLit lit, emptyFVs)
156 rnExpr (HsOverLit lit)
157 = rnOverLit lit `thenM` \ (lit', fvs) ->
158 returnM (HsOverLit lit', fvs)
160 rnExpr (HsApp fun arg)
161 = rnLExpr fun `thenM` \ (fun',fvFun) ->
162 rnLExpr arg `thenM` \ (arg',fvArg) ->
163 returnM (HsApp fun' arg', fvFun `plusFV` fvArg)
165 rnExpr (OpApp e1 op _ e2)
166 = rnLExpr e1 `thenM` \ (e1', fv_e1) ->
167 rnLExpr e2 `thenM` \ (e2', fv_e2) ->
168 rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) ->
171 -- When renaming code synthesised from "deriving" declarations
172 -- we used to avoid fixity stuff, but we can't easily tell any
173 -- more, so I've removed the test. Adding HsPars in TcGenDeriv
174 -- should prevent bad things happening.
175 lookupFixityRn op_name `thenM` \ fixity ->
176 mkOpAppRn e1' op' fixity e2' `thenM` \ final_e ->
179 fv_e1 `plusFV` fv_op `plusFV` fv_e2)
182 = rnLExpr e `thenM` \ (e', fv_e) ->
183 lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) ->
184 mkNegAppRn e' neg_name `thenM` \ final_e ->
185 returnM (final_e, fv_e `plusFV` fv_neg)
188 = rnLExpr e `thenM` \ (e', fvs_e) ->
189 returnM (HsPar e', fvs_e)
191 -- Template Haskell extensions
192 -- Don't ifdef-GHCI them because we want to fail gracefully
193 -- (not with an rnExpr crash) in a stage-1 compiler.
194 rnExpr e@(HsBracket br_body)
195 = checkTH e "bracket" `thenM_`
196 rnBracket br_body `thenM` \ (body', fvs_e) ->
197 returnM (HsBracket body', fvs_e)
199 rnExpr e@(HsSpliceE splice)
200 = rnSplice splice `thenM` \ (splice', fvs) ->
201 returnM (HsSpliceE splice', fvs)
204 rnExpr e@(HsQuasiQuoteE _) = pprPanic "Cant do quasiquotation without GHCi" (ppr e)
206 rnExpr e@(HsQuasiQuoteE qq)
207 = rnQuasiQuote qq `thenM` \ (qq', fvs_qq) ->
208 runQuasiQuoteExpr qq' `thenM` \ (L _ expr') ->
209 rnExpr expr' `thenM` \ (expr'', fvs_expr) ->
210 returnM (expr'', fvs_qq `plusFV` fvs_expr)
213 rnExpr section@(SectionL expr op)
214 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
215 rnLExpr op `thenM` \ (op', fvs_op) ->
216 checkSectionPrec InfixL section op' expr' `thenM_`
217 returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
219 rnExpr section@(SectionR op expr)
220 = rnLExpr op `thenM` \ (op', fvs_op) ->
221 rnLExpr expr `thenM` \ (expr', fvs_expr) ->
222 checkSectionPrec InfixR section op' expr' `thenM_`
223 returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
225 rnExpr (HsCoreAnn ann expr)
226 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
227 returnM (HsCoreAnn ann expr', fvs_expr)
229 rnExpr (HsSCC lbl expr)
230 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
231 returnM (HsSCC lbl expr', fvs_expr)
232 rnExpr (HsTickPragma info expr)
233 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
234 returnM (HsTickPragma info expr', fvs_expr)
236 rnExpr (HsLam matches)
237 = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) ->
238 returnM (HsLam matches', fvMatch)
240 rnExpr (HsCase expr matches)
241 = rnLExpr expr `thenM` \ (new_expr, e_fvs) ->
242 rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) ->
243 returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs)
245 rnExpr (HsLet binds expr)
246 = rnLocalBindsAndThen binds $ \ binds' ->
247 rnLExpr expr `thenM` \ (expr',fvExpr) ->
248 returnM (HsLet binds' expr', fvExpr)
250 rnExpr e@(HsDo do_or_lc stmts body _)
251 = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $
253 ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) }
255 rnExpr (ExplicitList _ exps)
256 = rnExprs exps `thenM` \ (exps', fvs) ->
257 returnM (ExplicitList placeHolderType exps', fvs)
259 rnExpr (ExplicitPArr _ exps)
260 = rnExprs exps `thenM` \ (exps', fvs) ->
261 returnM (ExplicitPArr placeHolderType exps', fvs)
263 rnExpr e@(ExplicitTuple exps boxity)
264 = checkTupSize (length exps) `thenM_`
265 rnExprs exps `thenM` \ (exps', fvs) ->
266 returnM (ExplicitTuple exps' boxity, fvs)
268 rnExpr (RecordCon con_id _ rbinds)
269 = do { conname <- lookupLocatedOccRn con_id
270 ; (rbinds', fvRbinds) <- rnHsRecFields_Con conname rnLExpr rbinds
271 ; return (RecordCon conname noPostTcExpr rbinds',
272 fvRbinds `addOneFV` unLoc conname) }
274 rnExpr (RecordUpd expr rbinds _ _ _)
275 = do { (expr', fvExpr) <- rnLExpr expr
276 ; (rbinds', fvRbinds) <- rnHsRecFields_Update rnLExpr rbinds
277 ; return (RecordUpd expr' rbinds' [] [] [],
278 fvExpr `plusFV` fvRbinds) }
280 rnExpr (ExprWithTySig expr pty)
281 = do { (pty', fvTy) <- rnHsTypeFVs doc pty
282 ; (expr', fvExpr) <- bindSigTyVarsFV (hsExplicitTvs pty') $
284 ; return (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy) }
286 doc = text "In an expression type signature"
288 rnExpr (HsIf p b1 b2)
289 = rnLExpr p `thenM` \ (p', fvP) ->
290 rnLExpr b1 `thenM` \ (b1', fvB1) ->
291 rnLExpr b2 `thenM` \ (b2', fvB2) ->
292 returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
295 = rnHsTypeFVs doc a `thenM` \ (t, fvT) ->
296 returnM (HsType t, fvT)
298 doc = text "In a type argument"
300 rnExpr (ArithSeq _ seq)
301 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
302 returnM (ArithSeq noPostTcExpr new_seq, fvs)
304 rnExpr (PArrSeq _ seq)
305 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
306 returnM (PArrSeq noPostTcExpr new_seq, fvs)
309 These three are pattern syntax appearing in expressions.
310 Since all the symbols are reservedops we can simply reject them.
311 We return a (bogus) EWildPat in each case.
314 rnExpr e@EWildPat = patSynErr e
315 rnExpr e@(EAsPat {}) = patSynErr e
316 rnExpr e@(EViewPat {}) = patSynErr e
317 rnExpr e@(ELazyPat {}) = patSynErr e
320 %************************************************************************
324 %************************************************************************
327 rnExpr (HsProc pat body)
329 rnPatsAndThen_LocalRightwards ProcExpr [pat] $ \ [pat'] ->
330 rnCmdTop body `thenM` \ (body',fvBody) ->
331 returnM (HsProc pat' body', fvBody)
333 rnExpr (HsArrApp arrow arg _ ho rtl)
334 = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) ->
335 rnLExpr arg `thenM` \ (arg',fvArg) ->
336 returnM (HsArrApp arrow' arg' placeHolderType ho rtl,
337 fvArrow `plusFV` fvArg)
339 select_arrow_scope tc = case ho of
340 HsHigherOrderApp -> tc
341 HsFirstOrderApp -> escapeArrowScope tc
344 rnExpr (HsArrForm op (Just _) [arg1, arg2])
345 = escapeArrowScope (rnLExpr op)
346 `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) ->
347 rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) ->
348 rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) ->
352 lookupFixityRn op_name `thenM` \ fixity ->
353 mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e ->
356 fv_arg1 `plusFV` fv_op `plusFV` fv_arg2)
358 rnExpr (HsArrForm op fixity cmds)
359 = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) ->
360 rnCmdArgs cmds `thenM` \ (cmds',fvCmds) ->
361 returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds)
363 rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
368 %************************************************************************
372 %************************************************************************
375 rnCmdArgs [] = returnM ([], emptyFVs)
377 = rnCmdTop arg `thenM` \ (arg',fvArg) ->
378 rnCmdArgs args `thenM` \ (args',fvArgs) ->
379 returnM (arg':args', fvArg `plusFV` fvArgs)
382 rnCmdTop = wrapLocFstM rnCmdTop'
384 rnCmdTop' (HsCmdTop cmd _ _ _)
385 = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) ->
387 cmd_names = [arrAName, composeAName, firstAName] ++
388 nameSetToList (methodNamesCmd (unLoc cmd'))
390 -- Generate the rebindable syntax for the monad
391 lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) ->
393 returnM (HsCmdTop cmd' [] placeHolderType cmd_names',
394 fvCmd `plusFV` cmd_fvs)
396 ---------------------------------------------------
397 -- convert OpApp's in a command context to HsArrForm's
399 convertOpFormsLCmd :: LHsCmd id -> LHsCmd id
400 convertOpFormsLCmd = fmap convertOpFormsCmd
402 convertOpFormsCmd :: HsCmd id -> HsCmd id
404 convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e
405 convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match)
406 convertOpFormsCmd (OpApp c1 op fixity c2)
408 arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType []
409 arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType []
411 HsArrForm op (Just fixity) [arg1, arg2]
413 convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c)
415 convertOpFormsCmd (HsCase exp matches)
416 = HsCase exp (convertOpFormsMatch matches)
418 convertOpFormsCmd (HsIf exp c1 c2)
419 = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2)
421 convertOpFormsCmd (HsLet binds cmd)
422 = HsLet binds (convertOpFormsLCmd cmd)
424 convertOpFormsCmd (HsDo ctxt stmts body ty)
425 = HsDo ctxt (map (fmap convertOpFormsStmt) stmts)
426 (convertOpFormsLCmd body) ty
428 -- Anything else is unchanged. This includes HsArrForm (already done),
429 -- things with no sub-commands, and illegal commands (which will be
430 -- caught by the type checker)
431 convertOpFormsCmd c = c
433 convertOpFormsStmt (BindStmt pat cmd _ _)
434 = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr
435 convertOpFormsStmt (ExprStmt cmd _ _)
436 = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType
437 convertOpFormsStmt (RecStmt stmts lvs rvs es binds)
438 = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds
439 convertOpFormsStmt stmt = stmt
441 convertOpFormsMatch (MatchGroup ms ty)
442 = MatchGroup (map (fmap convert) ms) ty
443 where convert (Match pat mty grhss)
444 = Match pat mty (convertOpFormsGRHSs grhss)
446 convertOpFormsGRHSs (GRHSs grhss binds)
447 = GRHSs (map convertOpFormsGRHS grhss) binds
449 convertOpFormsGRHS = fmap convert
451 convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd)
453 ---------------------------------------------------
454 type CmdNeeds = FreeVars -- Only inhabitants are
455 -- appAName, choiceAName, loopAName
457 -- find what methods the Cmd needs (loop, choice, apply)
458 methodNamesLCmd :: LHsCmd Name -> CmdNeeds
459 methodNamesLCmd = methodNamesCmd . unLoc
461 methodNamesCmd :: HsCmd Name -> CmdNeeds
463 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsFirstOrderApp _rtl)
465 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsHigherOrderApp _rtl)
467 methodNamesCmd cmd@(HsArrForm {}) = emptyFVs
469 methodNamesCmd (HsPar c) = methodNamesLCmd c
471 methodNamesCmd (HsIf p c1 c2)
472 = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName
474 methodNamesCmd (HsLet b c) = methodNamesLCmd c
476 methodNamesCmd (HsDo sc stmts body ty)
477 = methodNamesStmts stmts `plusFV` methodNamesLCmd body
479 methodNamesCmd (HsApp c e) = methodNamesLCmd c
481 methodNamesCmd (HsLam match) = methodNamesMatch match
483 methodNamesCmd (HsCase scrut matches)
484 = methodNamesMatch matches `addOneFV` choiceAName
486 methodNamesCmd other = emptyFVs
487 -- Other forms can't occur in commands, but it's not convenient
488 -- to error here so we just do what's convenient.
489 -- The type checker will complain later
491 ---------------------------------------------------
492 methodNamesMatch (MatchGroup ms _)
493 = plusFVs (map do_one ms)
495 do_one (L _ (Match pats sig_ty grhss)) = methodNamesGRHSs grhss
497 -------------------------------------------------
499 methodNamesGRHSs (GRHSs grhss binds) = plusFVs (map methodNamesGRHS grhss)
501 -------------------------------------------------
502 methodNamesGRHS (L _ (GRHS stmts rhs)) = methodNamesLCmd rhs
504 ---------------------------------------------------
505 methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts)
507 ---------------------------------------------------
508 methodNamesLStmt = methodNamesStmt . unLoc
510 methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd
511 methodNamesStmt (BindStmt pat cmd _ _) = methodNamesLCmd cmd
512 methodNamesStmt (RecStmt stmts _ _ _ _)
513 = methodNamesStmts stmts `addOneFV` loopAName
514 methodNamesStmt (LetStmt b) = emptyFVs
515 methodNamesStmt (ParStmt ss) = emptyFVs
516 methodNamesStmt (TransformStmt _ _ _) = emptyFVs
517 methodNamesStmt (GroupStmt _ _) = emptyFVs
518 -- ParStmt, TransformStmt and GroupStmt can't occur in commands, but it's not convenient to error
519 -- here so we just do what's convenient
523 %************************************************************************
527 %************************************************************************
530 rnArithSeq (From expr)
531 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
532 returnM (From expr', fvExpr)
534 rnArithSeq (FromThen expr1 expr2)
535 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
536 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
537 returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2)
539 rnArithSeq (FromTo expr1 expr2)
540 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
541 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
542 returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2)
544 rnArithSeq (FromThenTo expr1 expr2 expr3)
545 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
546 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
547 rnLExpr expr3 `thenM` \ (expr3', fvExpr3) ->
548 returnM (FromThenTo expr1' expr2' expr3',
549 plusFVs [fvExpr1, fvExpr2, fvExpr3])
552 %************************************************************************
554 Template Haskell brackets
556 %************************************************************************
559 rnBracket (VarBr n) = do { name <- lookupOccRn n
560 ; this_mod <- getModule
561 ; checkM (nameIsLocalOrFrom this_mod name) $ -- Reason: deprecation checking asumes the
562 do { loadInterfaceForName msg name -- home interface is loaded, and this is the
563 ; return () } -- only way that is going to happen
564 ; returnM (VarBr name, unitFV name) }
566 msg = ptext SLIT("Need interface for Template Haskell quoted Name")
568 rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e
569 ; return (ExpBr e', fvs) }
571 rnBracket (PatBr p) = do { addErr (ptext SLIT("Tempate Haskell pattern brackets are not supported yet"));
574 rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t
575 ; return (TypBr t', fvs) }
577 doc = ptext SLIT("In a Template-Haskell quoted type")
578 rnBracket (DecBr group)
579 = do { gbl_env <- getGblEnv
581 ; let new_gbl_env = gbl_env { -- Set the module to thFAKE. The top-level names from the bracketed
582 -- declarations will go into the name cache, and we don't want them to
583 -- confuse the Names for the current module.
584 -- By using a pretend module, thFAKE, we keep them safely out of the way.
587 -- The emptyDUs is so that we just collect uses for this group alone
588 -- in the call to rnSrcDecls below
590 ; setGblEnv new_gbl_env $ do {
592 -- In this situation we want to *shadow* top-level bindings.
594 -- bar = [d| foo = 1 |]
595 -- If we don't shadow, we'll get an ambiguity complaint when we do
596 -- a lookupTopBndrRn (which uses lookupGreLocalRn) on the binder of the 'foo'
598 -- Furthermore, arguably if the splice does define foo, that should hide
599 -- any foo's further out
601 -- The shadowing is acheived by calling rnSrcDecls with True as the shadowing flag
602 ; (tcg_env, group') <- rnSrcDecls True group
604 -- Discard the tcg_env; it contains only extra info about fixity
605 ; return (DecBr group', allUses (tcg_dus tcg_env)) } }
608 %************************************************************************
610 \subsubsection{@Stmt@s: in @do@ expressions}
612 %************************************************************************
615 rnStmts :: HsStmtContext Name -> [LStmt RdrName]
616 -> RnM (thing, FreeVars)
617 -> RnM (([LStmt Name], thing), FreeVars)
619 rnStmts (MDoExpr _) = rnMDoStmts
620 rnStmts ctxt = rnNormalStmts ctxt
622 rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName]
623 -> RnM (thing, FreeVars)
624 -> RnM (([LStmt Name], thing), FreeVars)
625 -- Used for cases *other* than recursive mdo
626 -- Implements nested scopes
628 rnNormalStmts ctxt [] thing_inside
629 = do { (thing, fvs) <- thing_inside
630 ; return (([],thing), fvs) }
632 rnNormalStmts ctxt (L loc stmt : stmts) thing_inside
633 = do { ((stmt', (stmts', thing)), fvs) <- rnStmt ctxt stmt $
634 rnNormalStmts ctxt stmts thing_inside
635 ; return (((L loc stmt' : stmts'), thing), fvs) }
638 rnStmt :: HsStmtContext Name -> Stmt RdrName
639 -> RnM (thing, FreeVars)
640 -> RnM ((Stmt Name, thing), FreeVars)
642 rnStmt ctxt (ExprStmt expr _ _) thing_inside
643 = do { (expr', fv_expr) <- rnLExpr expr
644 ; (then_op, fvs1) <- lookupSyntaxName thenMName
645 ; (thing, fvs2) <- thing_inside
646 ; return ((ExprStmt expr' then_op placeHolderType, thing),
647 fv_expr `plusFV` fvs1 `plusFV` fvs2) }
649 rnStmt ctxt (BindStmt pat expr _ _) thing_inside
650 = do { (expr', fv_expr) <- rnLExpr expr
651 -- The binders do not scope over the expression
652 ; (bind_op, fvs1) <- lookupSyntaxName bindMName
653 ; (fail_op, fvs2) <- lookupSyntaxName failMName
654 ; rnPatsAndThen_LocalRightwards (StmtCtxt ctxt) [pat] $ \ [pat'] -> do
655 { (thing, fvs3) <- thing_inside
656 ; return ((BindStmt pat' expr' bind_op fail_op, thing),
657 fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }}
658 -- fv_expr shouldn't really be filtered by the rnPatsAndThen
659 -- but it does not matter because the names are unique
661 rnStmt ctxt (LetStmt binds) thing_inside
662 = do { checkLetStmt ctxt binds
663 ; rnLocalBindsAndThen binds $ \binds' -> do
664 { (thing, fvs) <- thing_inside
665 ; return ((LetStmt binds', thing), fvs) } }
667 rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside
668 = do { checkRecStmt ctxt
669 ; rn_rec_stmts_and_then rec_stmts $ \ segs -> do
670 { (thing, fvs) <- thing_inside
672 segs_w_fwd_refs = addFwdRefs segs
673 (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs
674 later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs)
675 fwd_vars = nameSetToList (plusFVs fs)
677 rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds
678 ; return ((rec_stmt, thing), uses `plusFV` fvs) } }
680 rnStmt ctxt (ParStmt segs) thing_inside
681 = do { checkParStmt ctxt
682 ; ((segs', thing), fvs) <- rnParallelStmts (ParStmtCtxt ctxt) segs thing_inside
683 ; return ((ParStmt segs', thing), fvs) }
685 rnStmt ctxt (TransformStmt (stmts, _) usingExpr maybeByExpr) thing_inside = do
686 checkTransformStmt ctxt
688 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
689 ((stmts', binders, (maybeByExpr', thing)), fvs) <-
690 rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \unshadowed_bndrs -> do
691 (maybeByExpr', fv_maybeByExpr) <- rnMaybeLExpr maybeByExpr
692 (thing, fv_thing) <- thing_inside
694 return ((maybeByExpr', thing), fv_maybeByExpr `plusFV` fv_thing)
696 return ((TransformStmt (stmts', binders) usingExpr' maybeByExpr', thing), fv_usingExpr `plusFV` fvs)
698 rnMaybeLExpr Nothing = return (Nothing, emptyFVs)
699 rnMaybeLExpr (Just expr) = do
700 (expr', fv_expr) <- rnLExpr expr
701 return (Just expr', fv_expr)
703 rnStmt ctxt (GroupStmt (stmts, _) groupByClause) thing_inside = do
704 checkTransformStmt ctxt
706 -- We must rename the using expression in the context before the transform is begun
707 groupByClauseAction <-
708 case groupByClause of
709 GroupByNothing usingExpr -> do
710 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
711 (return . return) (GroupByNothing usingExpr', fv_usingExpr)
712 GroupBySomething eitherUsingExpr byExpr -> do
713 (eitherUsingExpr', fv_eitherUsingExpr) <-
714 case eitherUsingExpr of
715 Right _ -> return (Right $ HsVar groupWithName, unitNameSet groupWithName)
717 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
718 return (Left usingExpr', fv_usingExpr)
721 (byExpr', fv_byExpr) <- rnLExpr byExpr
722 return (GroupBySomething eitherUsingExpr' byExpr', fv_eitherUsingExpr `plusFV` fv_byExpr)
724 -- We only use rnNormalStmtsAndFindUsedBinders to get unshadowed_bndrs, so
725 -- perhaps we could refactor this to use rnNormalStmts directly?
726 ((stmts', _, (groupByClause', usedBinderMap, thing)), fvs) <-
727 rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \unshadowed_bndrs -> do
728 (groupByClause', fv_groupByClause) <- groupByClauseAction
730 unshadowed_bndrs' <- mapM newLocalName unshadowed_bndrs
731 let binderMap = zip unshadowed_bndrs unshadowed_bndrs'
733 -- Bind the "thing" inside a context where we have REBOUND everything
734 -- bound by the statements before the group. This is necessary since after
735 -- the grouping the same identifiers actually have different meanings
736 -- i.e. they refer to lists not singletons!
737 (thing, fv_thing) <- bindLocalNames unshadowed_bndrs' thing_inside
739 -- We remove entries from the binder map that are not used in the thing_inside.
740 -- We can then use that usage information to ensure that the free variables do
741 -- not contain the things we just bound, but do contain the things we need to
742 -- make those bindings (i.e. the corresponding non-listy variables)
744 -- Note that we also retain those entries which have an old binder in our
745 -- own free variables (the using or by expression). This is because this map
746 -- is reused in the desugarer to create the type to bind from the statements
747 -- that occur before this one. If the binders we need are not in the map, they
748 -- will never get bound into our desugared expression and hence the simplifier
749 -- crashes as we refer to variables that don't exist!
750 let usedBinderMap = filter
751 (\(old_binder, new_binder) ->
752 (new_binder `elemNameSet` fv_thing) ||
753 (old_binder `elemNameSet` fv_groupByClause)) binderMap
754 (usedOldBinders, usedNewBinders) = unzip usedBinderMap
755 real_fv_thing = (delListFromNameSet fv_thing usedNewBinders) `plusFV` (mkNameSet usedOldBinders)
757 return ((groupByClause', usedBinderMap, thing), fv_groupByClause `plusFV` real_fv_thing)
759 traceRn (text "rnStmt: implicitly rebound these used binders:" <+> ppr usedBinderMap)
760 return ((GroupStmt (stmts', usedBinderMap) groupByClause', thing), fvs)
762 rnNormalStmtsAndFindUsedBinders :: HsStmtContext Name
764 -> ([Name] -> RnM (thing, FreeVars))
765 -> RnM (([LStmt Name], [Name], thing), FreeVars)
766 rnNormalStmtsAndFindUsedBinders ctxt stmts thing_inside = do
767 ((stmts', (used_bndrs, inner_thing)), fvs) <- rnNormalStmts ctxt stmts $ do
768 -- Find the Names that are bound by stmts that
769 -- by assumption we have just renamed
770 local_env <- getLocalRdrEnv
772 stmts_binders = collectLStmtsBinders stmts
773 bndrs = map (expectJust "rnStmt"
774 . lookupLocalRdrEnv local_env
775 . unLoc) stmts_binders
777 -- If shadow, we'll look up (Unqual x) twice, getting
778 -- the second binding both times, which is the
780 unshadowed_bndrs = nub bndrs
782 -- Typecheck the thing inside, passing on all
783 -- the Names bound before it for its information
784 (thing, fvs) <- thing_inside unshadowed_bndrs
786 -- Figure out which of the bound names are used
787 -- after the statements we renamed
788 let used_bndrs = filter (`elemNameSet` fvs) bndrs
789 return ((used_bndrs, thing), fvs)
791 -- Flatten the tuple returned by the above call a bit!
792 return ((stmts', used_bndrs, inner_thing), fvs)
795 rnParallelStmts ctxt segs thing_inside = do
796 orig_lcl_env <- getLocalRdrEnv
797 go orig_lcl_env [] segs
799 go orig_lcl_env bndrs [] = do
800 let (bndrs', dups) = removeDups cmpByOcc bndrs
801 inner_env = extendLocalRdrEnv orig_lcl_env bndrs'
804 (thing, fvs) <- setLocalRdrEnv inner_env thing_inside
805 return (([], thing), fvs)
807 go orig_lcl_env bndrs_so_far ((stmts, _) : segs) = do
808 ((stmts', bndrs, (segs', thing)), fvs) <- rnNormalStmtsAndFindUsedBinders ctxt stmts $ \new_bndrs -> do
809 -- Typecheck the thing inside, passing on all
810 -- the Names bound, but separately; revert the envt
811 setLocalRdrEnv orig_lcl_env $ do
812 go orig_lcl_env (new_bndrs ++ bndrs_so_far) segs
814 let seg' = (stmts', bndrs)
815 return (((seg':segs'), thing), delListFromNameSet fvs bndrs)
817 cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2
818 dupErr vs = addErr (ptext SLIT("Duplicate binding in parallel list comprehension for:")
819 <+> quotes (ppr (head vs)))
823 %************************************************************************
825 \subsubsection{mdo expressions}
827 %************************************************************************
830 type FwdRefs = NameSet
831 type Segment stmts = (Defs,
832 Uses, -- May include defs
833 FwdRefs, -- A subset of uses that are
834 -- (a) used before they are bound in this segment, or
835 -- (b) used here, and bound in subsequent segments
836 stmts) -- Either Stmt or [Stmt]
839 ----------------------------------------------------
841 rnMDoStmts :: [LStmt RdrName]
842 -> RnM (thing, FreeVars)
843 -> RnM (([LStmt Name], thing), FreeVars)
844 rnMDoStmts stmts thing_inside
845 = -- Step1: Bring all the binders of the mdo into scope
846 -- (Remember that this also removes the binders from the
847 -- finally-returned free-vars.)
848 -- And rename each individual stmt, making a
849 -- singleton segment. At this stage the FwdRefs field
850 -- isn't finished: it's empty for all except a BindStmt
851 -- for which it's the fwd refs within the bind itself
852 -- (This set may not be empty, because we're in a recursive
854 rn_rec_stmts_and_then stmts $ \ segs -> do {
856 ; (thing, fvs_later) <- thing_inside
859 -- Step 2: Fill in the fwd refs.
860 -- The segments are all singletons, but their fwd-ref
861 -- field mentions all the things used by the segment
862 -- that are bound after their use
863 segs_w_fwd_refs = addFwdRefs segs
865 -- Step 3: Group together the segments to make bigger segments
866 -- Invariant: in the result, no segment uses a variable
867 -- bound in a later segment
868 grouped_segs = glomSegments segs_w_fwd_refs
870 -- Step 4: Turn the segments into Stmts
871 -- Use RecStmt when and only when there are fwd refs
872 -- Also gather up the uses from the end towards the
873 -- start, so we can tell the RecStmt which things are
874 -- used 'after' the RecStmt
875 (stmts', fvs) = segsToStmts grouped_segs fvs_later
877 ; return ((stmts', thing), fvs) }
879 doc = text "In a recursive mdo-expression"
881 ---------------------------------------------
883 -- wrapper that does both the left- and right-hand sides
884 rn_rec_stmts_and_then :: [LStmt RdrName]
885 -- assumes that the FreeVars returned includes
886 -- the FreeVars of the Segments
887 -> ([Segment (LStmt Name)] -> RnM (a, FreeVars))
889 rn_rec_stmts_and_then s cont
890 = do { -- (A) Make the mini fixity env for all of the stmts
891 fix_env <- makeMiniFixityEnv (collectRecStmtsFixities s)
894 ; new_lhs_and_fv <- rn_rec_stmts_lhs fix_env s
896 -- ...bring them and their fixities into scope
897 ; let bound_names = map unLoc $ collectLStmtsBinders (map fst new_lhs_and_fv)
898 ; bindLocalNamesFV_WithFixities bound_names fix_env $ do
900 -- (C) do the right-hand-sides and thing-inside
901 { segs <- rn_rec_stmts bound_names new_lhs_and_fv
902 ; (res, fvs) <- cont segs
903 ; warnUnusedLocalBinds bound_names fvs
904 ; return (res, fvs) }}
906 -- get all the fixity decls in any Let stmt
907 collectRecStmtsFixities l =
908 foldr (\ s -> \acc -> case s of
909 (L loc (LetStmt (HsValBinds (ValBindsIn _ sigs)))) ->
910 foldr (\ sig -> \ acc -> case sig of
911 (L loc (FixSig s)) -> (L loc s) : acc
917 rn_rec_stmt_lhs :: UniqFM (Located Fixity) -- mini fixity env for the names we're about to bind
918 -- these fixities need to be brought into scope with the names
920 -- rename LHS, and return its FVs
921 -- Warning: we will only need the FreeVars below in the case of a BindStmt,
922 -- so we don't bother to compute it accurately in the other cases
923 -> RnM [(LStmtLR Name RdrName, FreeVars)]
925 rn_rec_stmt_lhs fix_env (L loc (ExprStmt expr a b)) = return [(L loc (ExprStmt expr a b),
926 -- this is actually correct
929 rn_rec_stmt_lhs fix_env (L loc (BindStmt pat expr a b))
931 -- should the ctxt be MDo instead?
932 (pat', fv_pat) <- rnBindPat (localRecNameMaker fix_env) pat
933 return [(L loc (BindStmt pat' expr a b),
936 rn_rec_stmt_lhs fix_env (L loc (LetStmt binds@(HsIPBinds _)))
937 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
940 rn_rec_stmt_lhs fix_env (L loc (LetStmt (HsValBinds binds)))
941 = do binds' <- rnValBindsLHS fix_env binds
942 return [(L loc (LetStmt (HsValBinds binds')),
943 -- Warning: this is bogus; see function invariant
947 rn_rec_stmt_lhs fix_env (L loc (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec
948 = rn_rec_stmts_lhs fix_env stmts
950 rn_rec_stmt_lhs _ stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo
951 = pprPanic "rn_rec_stmt" (ppr stmt)
953 rn_rec_stmt_lhs _ stmt@(L _ (TransformStmt _ _ _)) -- Syntactically illegal in mdo
954 = pprPanic "rn_rec_stmt" (ppr stmt)
956 rn_rec_stmt_lhs _ stmt@(L _ (GroupStmt _ _)) -- Syntactically illegal in mdo
957 = pprPanic "rn_rec_stmt" (ppr stmt)
959 rn_rec_stmts_lhs :: UniqFM (Located Fixity) -- mini fixity env for the names we're about to bind
960 -- these fixities need to be brought into scope with the names
962 -> RnM [(LStmtLR Name RdrName, FreeVars)]
963 rn_rec_stmts_lhs fix_env stmts =
964 let boundNames = collectLStmtsBinders stmts
965 doc = text "In a recursive mdo-expression"
967 -- First do error checking: we need to check for dups here because we
968 -- don't bind all of the variables from the Stmt at once
969 -- with bindLocatedLocals.
970 checkDupRdrNames doc boundNames
971 mappM (rn_rec_stmt_lhs fix_env) stmts `thenM` \ ls -> returnM (concat ls)
976 rn_rec_stmt :: [Name] -> LStmtLR Name RdrName -> FreeVars -> RnM [Segment (LStmt Name)]
977 -- Rename a Stmt that is inside a RecStmt (or mdo)
978 -- Assumes all binders are already in scope
979 -- Turns each stmt into a singleton Stmt
980 rn_rec_stmt all_bndrs (L loc (ExprStmt expr _ _)) _
981 = rnLExpr expr `thenM` \ (expr', fvs) ->
982 lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) ->
983 returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet,
984 L loc (ExprStmt expr' then_op placeHolderType))]
986 rn_rec_stmt all_bndrs (L loc (BindStmt pat' expr _ _)) fv_pat
987 = rnLExpr expr `thenM` \ (expr', fv_expr) ->
988 lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) ->
989 lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) ->
991 bndrs = mkNameSet (collectPatBinders pat')
992 fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2
994 returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs,
995 L loc (BindStmt pat' expr' bind_op fail_op))]
997 rn_rec_stmt all_bndrs (L loc (LetStmt binds@(HsIPBinds _))) _
998 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
1001 rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds'))) _ = do
1002 (binds', du_binds) <-
1003 -- fixities and unused are handled above in rn_rec_stmts_and_then
1004 rnValBindsRHS all_bndrs binds'
1005 returnM [(duDefs du_binds, duUses du_binds,
1006 emptyNameSet, L loc (LetStmt (HsValBinds binds')))]
1008 -- no RecStmt case becuase they get flattened above when doing the LHSes
1009 rn_rec_stmt all_bndrs stmt@(L loc (RecStmt stmts _ _ _ _)) _
1010 = pprPanic "rn_rec_stmt: RecStmt" (ppr stmt)
1012 rn_rec_stmt all_bndrs stmt@(L _ (ParStmt _)) _ -- Syntactically illegal in mdo
1013 = pprPanic "rn_rec_stmt: ParStmt" (ppr stmt)
1015 rn_rec_stmt all_bndrs stmt@(L _ (TransformStmt _ _ _)) _ -- Syntactically illegal in mdo
1016 = pprPanic "rn_rec_stmt: TransformStmt" (ppr stmt)
1018 rn_rec_stmt all_bndrs stmt@(L _ (GroupStmt _ _)) _ -- Syntactically illegal in mdo
1019 = pprPanic "rn_rec_stmt: GroupStmt" (ppr stmt)
1021 rn_rec_stmts :: [Name] -> [(LStmtLR Name RdrName, FreeVars)] -> RnM [Segment (LStmt Name)]
1022 rn_rec_stmts bndrs stmts = mappM (uncurry (rn_rec_stmt bndrs)) stmts `thenM` \ segs_s ->
1023 returnM (concat segs_s)
1025 ---------------------------------------------
1026 addFwdRefs :: [Segment a] -> [Segment a]
1027 -- So far the segments only have forward refs *within* the Stmt
1028 -- (which happens for bind: x <- ...x...)
1029 -- This function adds the cross-seg fwd ref info
1032 = fst (foldr mk_seg ([], emptyNameSet) pairs)
1034 mk_seg (defs, uses, fwds, stmts) (segs, later_defs)
1035 = (new_seg : segs, all_defs)
1037 new_seg = (defs, uses, new_fwds, stmts)
1038 all_defs = later_defs `unionNameSets` defs
1039 new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs)
1040 -- Add the downstream fwd refs here
1042 ----------------------------------------------------
1043 -- Glomming the singleton segments of an mdo into
1044 -- minimal recursive groups.
1046 -- At first I thought this was just strongly connected components, but
1047 -- there's an important constraint: the order of the stmts must not change.
1050 -- mdo { x <- ...y...
1057 -- Here, the first stmt mention 'y', which is bound in the third.
1058 -- But that means that the innocent second stmt (p <- z) gets caught
1059 -- up in the recursion. And that in turn means that the binding for
1060 -- 'z' has to be included... and so on.
1062 -- Start at the tail { r <- x }
1063 -- Now add the next one { z <- y ; r <- x }
1064 -- Now add one more { q <- x ; z <- y ; r <- x }
1065 -- Now one more... but this time we have to group a bunch into rec
1066 -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x }
1067 -- Now one more, which we can add on without a rec
1069 -- rec { y <- ...x... ; q <- x ; z <- y } ;
1071 -- Finally we add the last one; since it mentions y we have to
1072 -- glom it togeher with the first two groups
1073 -- { rec { x <- ...y...; p <- z ; y <- ...x... ;
1074 -- q <- x ; z <- y } ;
1077 glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]]
1079 glomSegments [] = []
1080 glomSegments ((defs,uses,fwds,stmt) : segs)
1081 -- Actually stmts will always be a singleton
1082 = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others
1084 segs' = glomSegments segs
1085 (extras, others) = grab uses segs'
1086 (ds, us, fs, ss) = unzip4 extras
1088 seg_defs = plusFVs ds `plusFV` defs
1089 seg_uses = plusFVs us `plusFV` uses
1090 seg_fwds = plusFVs fs `plusFV` fwds
1091 seg_stmts = stmt : concat ss
1093 grab :: NameSet -- The client
1095 -> ([Segment a], -- Needed by the 'client'
1096 [Segment a]) -- Not needed by the client
1097 -- The result is simply a split of the input
1099 = (reverse yeses, reverse noes)
1101 (noes, yeses) = span not_needed (reverse dus)
1102 not_needed (defs,_,_,_) = not (intersectsNameSet defs uses)
1105 ----------------------------------------------------
1106 segsToStmts :: [Segment [LStmt Name]]
1107 -> FreeVars -- Free vars used 'later'
1108 -> ([LStmt Name], FreeVars)
1110 segsToStmts [] fvs_later = ([], fvs_later)
1111 segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later
1112 = ASSERT( not (null ss) )
1113 (new_stmt : later_stmts, later_uses `plusFV` uses)
1115 (later_stmts, later_uses) = segsToStmts segs fvs_later
1116 new_stmt | non_rec = head ss
1117 | otherwise = L (getLoc (head ss)) $
1118 RecStmt ss (nameSetToList used_later) (nameSetToList fwds)
1121 non_rec = isSingleton ss && isEmptyNameSet fwds
1122 used_later = defs `intersectNameSet` later_uses
1123 -- The ones needed after the RecStmt
1126 %************************************************************************
1128 \subsubsection{Assertion utils}
1130 %************************************************************************
1133 srcSpanPrimLit :: SrcSpan -> HsExpr Name
1134 srcSpanPrimLit span = HsLit (HsStringPrim (mkFastString (showSDoc (ppr span))))
1136 mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars)
1137 -- Return an expression for (assertError "Foo.hs:27")
1139 = getSrcSpanM `thenM` \ sloc ->
1141 expr = HsApp (L sloc (HsVar assertErrorName))
1142 (L sloc (srcSpanPrimLit sloc))
1144 returnM (expr, emptyFVs)
1147 %************************************************************************
1149 \subsubsection{Errors}
1151 %************************************************************************
1155 ----------------------
1156 -- Checking when a particular Stmt is ok
1157 checkLetStmt :: HsStmtContext Name -> HsLocalBinds RdrName -> RnM ()
1158 checkLetStmt (ParStmtCtxt _) (HsIPBinds binds) = addErr (badIpBinds (ptext SLIT("a parallel list comprehension:")) binds)
1159 checkLetStmt _ctxt _binds = return ()
1160 -- We do not allow implicit-parameter bindings in a parallel
1161 -- list comprehension. I'm not sure what it might mean.
1164 checkRecStmt :: HsStmtContext Name -> RnM ()
1165 checkRecStmt (MDoExpr {}) = return () -- Recursive stmt ok in 'mdo'
1166 checkRecStmt (DoExpr {}) = return () -- ..and in 'do' but only because of arrows:
1167 -- proc x -> do { ...rec... }
1168 -- We don't have enough context to distinguish this situation here
1169 -- so we leave it to the type checker
1170 checkRecStmt ctxt = addErr msg
1172 msg = ptext SLIT("Illegal 'rec' stmt in") <+> pprStmtContext ctxt
1175 checkParStmt :: HsStmtContext Name -> RnM ()
1177 = do { parallel_list_comp <- doptM Opt_ParallelListComp
1178 ; checkErr parallel_list_comp msg }
1180 msg = ptext SLIT("Illegal parallel list comprehension: use -XParallelListComp")
1183 checkTransformStmt :: HsStmtContext Name -> RnM ()
1184 checkTransformStmt ListComp -- Ensure we are really within a list comprehension because otherwise the
1185 -- desugarer will break when we come to operate on a parallel array
1186 = do { transform_list_comp <- doptM Opt_TransformListComp
1187 ; checkErr transform_list_comp msg }
1189 msg = ptext SLIT("Illegal transform or grouping list comprehension: use -XTransformListComp")
1190 checkTransformStmt (ParStmtCtxt ctxt) = checkTransformStmt ctxt -- Ok to nest inside a parallel comprehension
1191 checkTransformStmt (TransformStmtCtxt ctxt) = checkTransformStmt ctxt -- Ok to nest inside a parallel comprehension
1192 checkTransformStmt ctxt = addErr msg
1194 msg = ptext SLIT("Illegal transform or grouping in") <+> pprStmtContext ctxt
1197 patSynErr e = do { addErr (sep [ptext SLIT("Pattern syntax in expression context:"),
1199 ; return (EWildPat, emptyFVs) }
1201 badIpBinds what binds
1202 = hang (ptext SLIT("Implicit-parameter bindings illegal in") <+> what)