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 UniqFM ( isNullUFM )
57 import UniqSet ( emptyUniqSet )
59 import Util ( isSingleton )
60 import ListSetOps ( removeDups )
61 import Maybes ( expectJust )
63 import SrcLoc ( Located(..), unLoc, getLoc, noLoc )
66 import List ( unzip4 )
73 thenM :: Monad a => a b -> (b -> a c) -> a c
76 thenM_ :: Monad a => a b -> a c -> a c
79 returnM :: Monad m => a -> m a
82 mappM :: (Monad m) => (a -> m b) -> [a] -> m [b]
85 mappM_ :: (Monad m) => (a -> m b) -> [a] -> m ()
88 checkM :: Monad m => Bool -> m () -> m ()
92 %************************************************************************
94 \subsubsection{Expressions}
96 %************************************************************************
99 rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars)
100 rnExprs ls = rnExprs' ls emptyUniqSet
102 rnExprs' [] acc = returnM ([], acc)
103 rnExprs' (expr:exprs) acc
104 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
106 -- Now we do a "seq" on the free vars because typically it's small
107 -- or empty, especially in very long lists of constants
109 acc' = acc `plusFV` fvExpr
111 (grubby_seqNameSet acc' rnExprs') exprs acc' `thenM` \ (exprs', fvExprs) ->
112 returnM (expr':exprs', fvExprs)
114 -- Grubby little function to do "seq" on namesets; replace by proper seq when GHC can do seq
115 grubby_seqNameSet ns result | isNullUFM ns = result
119 Variables. We look up the variable and return the resulting name.
122 rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars)
123 rnLExpr = wrapLocFstM rnExpr
125 rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
128 = do name <- lookupOccRn v
129 ignore_asserts <- doptM Opt_IgnoreAsserts
130 finish_var ignore_asserts name
132 finish_var ignore_asserts name
133 | ignore_asserts || not (name `hasKey` assertIdKey)
134 = return (HsVar name, unitFV name)
136 = do { (e, fvs) <- mkAssertErrorExpr
137 ; return (e, fvs `addOneFV` name) }
140 = newIPNameRn v `thenM` \ name ->
141 returnM (HsIPVar name, emptyFVs)
143 rnExpr (HsLit lit@(HsString s))
145 opt_OverloadedStrings <- doptM Opt_OverloadedStrings
146 ; if opt_OverloadedStrings then
147 rnExpr (HsOverLit (mkHsIsString s placeHolderType))
148 else -- Same as below
150 returnM (HsLit lit, emptyFVs)
155 returnM (HsLit lit, emptyFVs)
157 rnExpr (HsOverLit lit)
158 = rnOverLit lit `thenM` \ (lit', fvs) ->
159 returnM (HsOverLit lit', fvs)
161 rnExpr (HsApp fun arg)
162 = rnLExpr fun `thenM` \ (fun',fvFun) ->
163 rnLExpr arg `thenM` \ (arg',fvArg) ->
164 returnM (HsApp fun' arg', fvFun `plusFV` fvArg)
166 rnExpr (OpApp e1 op _ e2)
167 = rnLExpr e1 `thenM` \ (e1', fv_e1) ->
168 rnLExpr e2 `thenM` \ (e2', fv_e2) ->
169 rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) ->
172 -- When renaming code synthesised from "deriving" declarations
173 -- we used to avoid fixity stuff, but we can't easily tell any
174 -- more, so I've removed the test. Adding HsPars in TcGenDeriv
175 -- should prevent bad things happening.
176 lookupFixityRn op_name `thenM` \ fixity ->
177 mkOpAppRn e1' op' fixity e2' `thenM` \ final_e ->
180 fv_e1 `plusFV` fv_op `plusFV` fv_e2)
183 = rnLExpr e `thenM` \ (e', fv_e) ->
184 lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) ->
185 mkNegAppRn e' neg_name `thenM` \ final_e ->
186 returnM (final_e, fv_e `plusFV` fv_neg)
189 = rnLExpr e `thenM` \ (e', fvs_e) ->
190 returnM (HsPar e', fvs_e)
192 -- Template Haskell extensions
193 -- Don't ifdef-GHCI them because we want to fail gracefully
194 -- (not with an rnExpr crash) in a stage-1 compiler.
195 rnExpr e@(HsBracket br_body)
196 = checkTH e "bracket" `thenM_`
197 rnBracket br_body `thenM` \ (body', fvs_e) ->
198 returnM (HsBracket body', fvs_e)
200 rnExpr e@(HsSpliceE splice)
201 = rnSplice splice `thenM` \ (splice', fvs) ->
202 returnM (HsSpliceE splice', fvs)
205 rnExpr e@(HsQuasiQuoteE _) = pprPanic "Cant do quasiquotation without GHCi" (ppr e)
207 rnExpr e@(HsQuasiQuoteE qq)
208 = rnQuasiQuote qq `thenM` \ (qq', fvs_qq) ->
209 runQuasiQuoteExpr qq' `thenM` \ (L _ expr') ->
210 rnExpr expr' `thenM` \ (expr'', fvs_expr) ->
211 returnM (expr'', fvs_qq `plusFV` fvs_expr)
214 rnExpr section@(SectionL expr op)
215 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
216 rnLExpr op `thenM` \ (op', fvs_op) ->
217 checkSectionPrec InfixL section op' expr' `thenM_`
218 returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
220 rnExpr section@(SectionR op expr)
221 = rnLExpr op `thenM` \ (op', fvs_op) ->
222 rnLExpr expr `thenM` \ (expr', fvs_expr) ->
223 checkSectionPrec InfixR section op' expr' `thenM_`
224 returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
226 rnExpr (HsCoreAnn ann expr)
227 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
228 returnM (HsCoreAnn ann expr', fvs_expr)
230 rnExpr (HsSCC lbl expr)
231 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
232 returnM (HsSCC lbl expr', fvs_expr)
233 rnExpr (HsTickPragma info expr)
234 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
235 returnM (HsTickPragma info expr', fvs_expr)
237 rnExpr (HsLam matches)
238 = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) ->
239 returnM (HsLam matches', fvMatch)
241 rnExpr (HsCase expr matches)
242 = rnLExpr expr `thenM` \ (new_expr, e_fvs) ->
243 rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) ->
244 returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs)
246 rnExpr (HsLet binds expr)
247 = rnLocalBindsAndThen binds $ \ binds' ->
248 rnLExpr expr `thenM` \ (expr',fvExpr) ->
249 returnM (HsLet binds' expr', fvExpr)
251 rnExpr e@(HsDo do_or_lc stmts body _)
252 = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $
254 ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) }
256 rnExpr (ExplicitList _ exps)
257 = rnExprs exps `thenM` \ (exps', fvs) ->
258 returnM (ExplicitList placeHolderType exps', fvs)
260 rnExpr (ExplicitPArr _ exps)
261 = rnExprs exps `thenM` \ (exps', fvs) ->
262 returnM (ExplicitPArr placeHolderType exps', fvs)
264 rnExpr e@(ExplicitTuple exps boxity)
265 = checkTupSize (length exps) `thenM_`
266 rnExprs exps `thenM` \ (exps', fvs) ->
267 returnM (ExplicitTuple exps' boxity, fvs)
269 rnExpr (RecordCon con_id _ rbinds)
270 = do { conname <- lookupLocatedOccRn con_id
271 ; (rbinds', fvRbinds) <- rnHsRecFields_Con conname rnLExpr rbinds
272 ; return (RecordCon conname noPostTcExpr rbinds',
273 fvRbinds `addOneFV` unLoc conname) }
275 rnExpr (RecordUpd expr rbinds _ _ _)
276 = do { (expr', fvExpr) <- rnLExpr expr
277 ; (rbinds', fvRbinds) <- rnHsRecFields_Update rnLExpr rbinds
278 ; return (RecordUpd expr' rbinds' [] [] [],
279 fvExpr `plusFV` fvRbinds) }
281 rnExpr (ExprWithTySig expr pty)
282 = do { (pty', fvTy) <- rnHsTypeFVs doc pty
283 ; (expr', fvExpr) <- bindSigTyVarsFV (hsExplicitTvs pty') $
285 ; return (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy) }
287 doc = text "In an expression type signature"
289 rnExpr (HsIf p b1 b2)
290 = rnLExpr p `thenM` \ (p', fvP) ->
291 rnLExpr b1 `thenM` \ (b1', fvB1) ->
292 rnLExpr b2 `thenM` \ (b2', fvB2) ->
293 returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
296 = rnHsTypeFVs doc a `thenM` \ (t, fvT) ->
297 returnM (HsType t, fvT)
299 doc = text "In a type argument"
301 rnExpr (ArithSeq _ seq)
302 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
303 returnM (ArithSeq noPostTcExpr new_seq, fvs)
305 rnExpr (PArrSeq _ seq)
306 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
307 returnM (PArrSeq noPostTcExpr new_seq, fvs)
310 These three are pattern syntax appearing in expressions.
311 Since all the symbols are reservedops we can simply reject them.
312 We return a (bogus) EWildPat in each case.
315 rnExpr e@EWildPat = patSynErr e
316 rnExpr e@(EAsPat {}) = patSynErr e
317 rnExpr e@(EViewPat {}) = patSynErr e
318 rnExpr e@(ELazyPat {}) = patSynErr e
321 %************************************************************************
325 %************************************************************************
328 rnExpr (HsProc pat body)
330 rnPatsAndThen_LocalRightwards ProcExpr [pat] $ \ [pat'] ->
331 rnCmdTop body `thenM` \ (body',fvBody) ->
332 returnM (HsProc pat' body', fvBody)
334 rnExpr (HsArrApp arrow arg _ ho rtl)
335 = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) ->
336 rnLExpr arg `thenM` \ (arg',fvArg) ->
337 returnM (HsArrApp arrow' arg' placeHolderType ho rtl,
338 fvArrow `plusFV` fvArg)
340 select_arrow_scope tc = case ho of
341 HsHigherOrderApp -> tc
342 HsFirstOrderApp -> escapeArrowScope tc
345 rnExpr (HsArrForm op (Just _) [arg1, arg2])
346 = escapeArrowScope (rnLExpr op)
347 `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) ->
348 rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) ->
349 rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) ->
353 lookupFixityRn op_name `thenM` \ fixity ->
354 mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e ->
357 fv_arg1 `plusFV` fv_op `plusFV` fv_arg2)
359 rnExpr (HsArrForm op fixity cmds)
360 = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) ->
361 rnCmdArgs cmds `thenM` \ (cmds',fvCmds) ->
362 returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds)
364 rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
369 %************************************************************************
373 %************************************************************************
376 rnCmdArgs [] = returnM ([], emptyFVs)
378 = rnCmdTop arg `thenM` \ (arg',fvArg) ->
379 rnCmdArgs args `thenM` \ (args',fvArgs) ->
380 returnM (arg':args', fvArg `plusFV` fvArgs)
383 rnCmdTop = wrapLocFstM rnCmdTop'
385 rnCmdTop' (HsCmdTop cmd _ _ _)
386 = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) ->
388 cmd_names = [arrAName, composeAName, firstAName] ++
389 nameSetToList (methodNamesCmd (unLoc cmd'))
391 -- Generate the rebindable syntax for the monad
392 lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) ->
394 returnM (HsCmdTop cmd' [] placeHolderType cmd_names',
395 fvCmd `plusFV` cmd_fvs)
397 ---------------------------------------------------
398 -- convert OpApp's in a command context to HsArrForm's
400 convertOpFormsLCmd :: LHsCmd id -> LHsCmd id
401 convertOpFormsLCmd = fmap convertOpFormsCmd
403 convertOpFormsCmd :: HsCmd id -> HsCmd id
405 convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e
406 convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match)
407 convertOpFormsCmd (OpApp c1 op fixity c2)
409 arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType []
410 arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType []
412 HsArrForm op (Just fixity) [arg1, arg2]
414 convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c)
417 convertOpFormsCmd (HsCase exp matches)
418 = HsCase exp (convertOpFormsMatch matches)
420 convertOpFormsCmd (HsIf exp c1 c2)
421 = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2)
423 convertOpFormsCmd (HsLet binds cmd)
424 = HsLet binds (convertOpFormsLCmd cmd)
426 convertOpFormsCmd (HsDo ctxt stmts body ty)
427 = HsDo ctxt (map (fmap convertOpFormsStmt) stmts)
428 (convertOpFormsLCmd body) ty
430 -- Anything else is unchanged. This includes HsArrForm (already done),
431 -- things with no sub-commands, and illegal commands (which will be
432 -- caught by the type checker)
433 convertOpFormsCmd c = c
435 convertOpFormsStmt (BindStmt pat cmd _ _)
436 = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr
437 convertOpFormsStmt (ExprStmt cmd _ _)
438 = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType
439 convertOpFormsStmt (RecStmt stmts lvs rvs es binds)
440 = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds
441 convertOpFormsStmt stmt = stmt
443 convertOpFormsMatch (MatchGroup ms ty)
444 = MatchGroup (map (fmap convert) ms) ty
445 where convert (Match pat mty grhss)
446 = Match pat mty (convertOpFormsGRHSs grhss)
448 convertOpFormsGRHSs (GRHSs grhss binds)
449 = GRHSs (map convertOpFormsGRHS grhss) binds
451 convertOpFormsGRHS = fmap convert
453 convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd)
455 ---------------------------------------------------
456 type CmdNeeds = FreeVars -- Only inhabitants are
457 -- appAName, choiceAName, loopAName
459 -- find what methods the Cmd needs (loop, choice, apply)
460 methodNamesLCmd :: LHsCmd Name -> CmdNeeds
461 methodNamesLCmd = methodNamesCmd . unLoc
463 methodNamesCmd :: HsCmd Name -> CmdNeeds
465 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsFirstOrderApp _rtl)
467 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsHigherOrderApp _rtl)
469 methodNamesCmd cmd@(HsArrForm {}) = emptyFVs
471 methodNamesCmd (HsPar c) = methodNamesLCmd c
473 methodNamesCmd (HsIf p c1 c2)
474 = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName
476 methodNamesCmd (HsLet b c) = methodNamesLCmd c
478 methodNamesCmd (HsDo sc stmts body ty)
479 = methodNamesStmts stmts `plusFV` methodNamesLCmd body
481 methodNamesCmd (HsApp c e) = methodNamesLCmd c
483 methodNamesCmd (HsLam match) = methodNamesMatch match
485 methodNamesCmd (HsCase scrut matches)
486 = methodNamesMatch matches `addOneFV` choiceAName
488 methodNamesCmd other = emptyFVs
489 -- Other forms can't occur in commands, but it's not convenient
490 -- to error here so we just do what's convenient.
491 -- The type checker will complain later
493 ---------------------------------------------------
494 methodNamesMatch (MatchGroup ms _)
495 = plusFVs (map do_one ms)
497 do_one (L _ (Match pats sig_ty grhss)) = methodNamesGRHSs grhss
499 -------------------------------------------------
501 methodNamesGRHSs (GRHSs grhss binds) = plusFVs (map methodNamesGRHS grhss)
503 -------------------------------------------------
504 methodNamesGRHS (L _ (GRHS stmts rhs)) = methodNamesLCmd rhs
506 ---------------------------------------------------
507 methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts)
509 ---------------------------------------------------
510 methodNamesLStmt = methodNamesStmt . unLoc
512 methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd
513 methodNamesStmt (BindStmt pat cmd _ _) = methodNamesLCmd cmd
514 methodNamesStmt (RecStmt stmts _ _ _ _)
515 = methodNamesStmts stmts `addOneFV` loopAName
516 methodNamesStmt (LetStmt b) = emptyFVs
517 methodNamesStmt (ParStmt ss) = emptyFVs
518 methodNamesStmt (TransformStmt _ _ _) = emptyFVs
519 methodNamesStmt (GroupStmt _ _) = emptyFVs
520 -- ParStmt, TransformStmt and GroupStmt can't occur in commands, but it's not convenient to error
521 -- here so we just do what's convenient
525 %************************************************************************
529 %************************************************************************
532 rnArithSeq (From expr)
533 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
534 returnM (From expr', fvExpr)
536 rnArithSeq (FromThen expr1 expr2)
537 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
538 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
539 returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2)
541 rnArithSeq (FromTo expr1 expr2)
542 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
543 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
544 returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2)
546 rnArithSeq (FromThenTo expr1 expr2 expr3)
547 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
548 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
549 rnLExpr expr3 `thenM` \ (expr3', fvExpr3) ->
550 returnM (FromThenTo expr1' expr2' expr3',
551 plusFVs [fvExpr1, fvExpr2, fvExpr3])
554 %************************************************************************
556 Template Haskell brackets
558 %************************************************************************
561 rnBracket (VarBr n) = do { name <- lookupOccRn n
562 ; this_mod <- getModule
563 ; checkM (nameIsLocalOrFrom this_mod name) $ -- Reason: deprecation checking asumes the
564 do { loadInterfaceForName msg name -- home interface is loaded, and this is the
565 ; return () } -- only way that is going to happen
566 ; returnM (VarBr name, unitFV name) }
568 msg = ptext SLIT("Need interface for Template Haskell quoted Name")
570 rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e
571 ; return (ExpBr e', fvs) }
573 rnBracket (PatBr p) = do { addErr (ptext SLIT("Tempate Haskell pattern brackets are not supported yet"));
576 rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t
577 ; return (TypBr t', fvs) }
579 doc = ptext SLIT("In a Template-Haskell quoted type")
580 rnBracket (DecBr group)
581 = do { gbl_env <- getGblEnv
583 ; let new_gbl_env = gbl_env { -- Set the module to thFAKE. The top-level names from the bracketed
584 -- declarations will go into the name cache, and we don't want them to
585 -- confuse the Names for the current module.
586 -- By using a pretend module, thFAKE, we keep them safely out of the way.
589 -- The emptyDUs is so that we just collect uses for this group alone
590 -- in the call to rnSrcDecls below
592 ; setGblEnv new_gbl_env $ do {
594 -- In this situation we want to *shadow* top-level bindings.
596 -- bar = [d| foo = 1 |]
597 -- If we don't shadow, we'll get an ambiguity complaint when we do
598 -- a lookupTopBndrRn (which uses lookupGreLocalRn) on the binder of the 'foo'
600 -- Furthermore, arguably if the splice does define foo, that should hide
601 -- any foo's further out
603 -- The shadowing is acheived by calling rnSrcDecls with True as the shadowing flag
604 ; (tcg_env, group') <- rnSrcDecls True group
606 -- Discard the tcg_env; it contains only extra info about fixity
607 ; return (DecBr group', allUses (tcg_dus tcg_env)) } }
610 %************************************************************************
612 \subsubsection{@Stmt@s: in @do@ expressions}
614 %************************************************************************
617 rnStmts :: HsStmtContext Name -> [LStmt RdrName]
618 -> RnM (thing, FreeVars)
619 -> RnM (([LStmt Name], thing), FreeVars)
621 rnStmts (MDoExpr _) = rnMDoStmts
622 rnStmts ctxt = rnNormalStmts ctxt
624 rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName]
625 -> RnM (thing, FreeVars)
626 -> RnM (([LStmt Name], thing), FreeVars)
627 -- Used for cases *other* than recursive mdo
628 -- Implements nested scopes
630 rnNormalStmts ctxt [] thing_inside
631 = do { (thing, fvs) <- thing_inside
632 ; return (([],thing), fvs) }
634 rnNormalStmts ctxt (L loc stmt : stmts) thing_inside
635 = do { ((stmt', (stmts', thing)), fvs) <- rnStmt ctxt stmt $
636 rnNormalStmts ctxt stmts thing_inside
637 ; return (((L loc stmt' : stmts'), thing), fvs) }
640 rnStmt :: HsStmtContext Name -> Stmt RdrName
641 -> RnM (thing, FreeVars)
642 -> RnM ((Stmt Name, thing), FreeVars)
644 rnStmt ctxt (ExprStmt expr _ _) thing_inside
645 = do { (expr', fv_expr) <- rnLExpr expr
646 ; (then_op, fvs1) <- lookupSyntaxName thenMName
647 ; (thing, fvs2) <- thing_inside
648 ; return ((ExprStmt expr' then_op placeHolderType, thing),
649 fv_expr `plusFV` fvs1 `plusFV` fvs2) }
651 rnStmt ctxt (BindStmt pat expr _ _) thing_inside
652 = do { (expr', fv_expr) <- rnLExpr expr
653 -- The binders do not scope over the expression
654 ; (bind_op, fvs1) <- lookupSyntaxName bindMName
655 ; (fail_op, fvs2) <- lookupSyntaxName failMName
656 ; rnPatsAndThen_LocalRightwards (StmtCtxt ctxt) [pat] $ \ [pat'] -> do
657 { (thing, fvs3) <- thing_inside
658 ; return ((BindStmt pat' expr' bind_op fail_op, thing),
659 fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }}
660 -- fv_expr shouldn't really be filtered by the rnPatsAndThen
661 -- but it does not matter because the names are unique
663 rnStmt ctxt (LetStmt binds) thing_inside = do
664 checkErr (ok ctxt binds) (badIpBinds (ptext SLIT("a parallel list comprehension:")) binds)
665 rnLocalBindsAndThen binds $ \binds' -> do
666 (thing, fvs) <- thing_inside
667 return ((LetStmt binds', thing), fvs)
669 -- We do not allow implicit-parameter bindings in a parallel
670 -- list comprehension. I'm not sure what it might mean.
671 ok (ParStmtCtxt _) (HsIPBinds _) = False
674 rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside
676 rn_rec_stmts_and_then rec_stmts $ \ segs ->
677 thing_inside `thenM` \ (thing, fvs) ->
679 segs_w_fwd_refs = addFwdRefs segs
680 (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs
681 later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs)
682 fwd_vars = nameSetToList (plusFVs fs)
684 rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds
686 returnM ((rec_stmt, thing), uses `plusFV` fvs)
688 doc = text "In a recursive do statement"
690 rnStmt ctxt (TransformStmt (stmts, _) usingExpr maybeByExpr) thing_inside = do
691 checkIsTransformableListComp ctxt
693 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
694 ((stmts', binders, (maybeByExpr', thing)), fvs) <-
695 rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \unshadowed_bndrs -> do
696 (maybeByExpr', fv_maybeByExpr) <- rnMaybeLExpr maybeByExpr
697 (thing, fv_thing) <- thing_inside
699 return ((maybeByExpr', thing), fv_maybeByExpr `plusFV` fv_thing)
701 return ((TransformStmt (stmts', binders) usingExpr' maybeByExpr', thing), fv_usingExpr `plusFV` fvs)
703 rnMaybeLExpr Nothing = return (Nothing, emptyFVs)
704 rnMaybeLExpr (Just expr) = do
705 (expr', fv_expr) <- rnLExpr expr
706 return (Just expr', fv_expr)
708 rnStmt ctxt (GroupStmt (stmts, _) groupByClause) thing_inside = do
709 checkIsTransformableListComp ctxt
711 -- We must rename the using expression in the context before the transform is begun
712 groupByClauseAction <-
713 case groupByClause of
714 GroupByNothing usingExpr -> do
715 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
716 (return . return) (GroupByNothing usingExpr', fv_usingExpr)
717 GroupBySomething eitherUsingExpr byExpr -> do
718 (eitherUsingExpr', fv_eitherUsingExpr) <-
719 case eitherUsingExpr of
720 Right _ -> return (Right $ HsVar groupWithName, unitNameSet groupWithName)
722 (usingExpr', fv_usingExpr) <- rnLExpr usingExpr
723 return (Left usingExpr', fv_usingExpr)
726 (byExpr', fv_byExpr) <- rnLExpr byExpr
727 return (GroupBySomething eitherUsingExpr' byExpr', fv_eitherUsingExpr `plusFV` fv_byExpr)
729 -- We only use rnNormalStmtsAndFindUsedBinders to get unshadowed_bndrs, so
730 -- perhaps we could refactor this to use rnNormalStmts directly?
731 ((stmts', _, (groupByClause', usedBinderMap, thing)), fvs) <-
732 rnNormalStmtsAndFindUsedBinders (TransformStmtCtxt ctxt) stmts $ \unshadowed_bndrs -> do
733 (groupByClause', fv_groupByClause) <- groupByClauseAction
735 unshadowed_bndrs' <- mapM newLocalName unshadowed_bndrs
736 let binderMap = zip unshadowed_bndrs unshadowed_bndrs'
738 -- Bind the "thing" inside a context where we have REBOUND everything
739 -- bound by the statements before the group. This is necessary since after
740 -- the grouping the same identifiers actually have different meanings
741 -- i.e. they refer to lists not singletons!
742 (thing, fv_thing) <- bindLocalNames unshadowed_bndrs' thing_inside
744 -- We remove entries from the binder map that are not used in the thing_inside.
745 -- We can then use that usage information to ensure that the free variables do
746 -- not contain the things we just bound, but do contain the things we need to
747 -- make those bindings (i.e. the corresponding non-listy variables)
749 -- Note that we also retain those entries which have an old binder in our
750 -- own free variables (the using or by expression). This is because this map
751 -- is reused in the desugarer to create the type to bind from the statements
752 -- that occur before this one. If the binders we need are not in the map, they
753 -- will never get bound into our desugared expression and hence the simplifier
754 -- crashes as we refer to variables that don't exist!
755 let usedBinderMap = filter
756 (\(old_binder, new_binder) ->
757 (new_binder `elemNameSet` fv_thing) ||
758 (old_binder `elemNameSet` fv_groupByClause)) binderMap
759 (usedOldBinders, usedNewBinders) = unzip usedBinderMap
760 real_fv_thing = (delListFromNameSet fv_thing usedNewBinders) `plusFV` (mkNameSet usedOldBinders)
762 return ((groupByClause', usedBinderMap, thing), fv_groupByClause `plusFV` real_fv_thing)
764 traceRn (text "rnStmt: implicitly rebound these used binders:" <+> ppr usedBinderMap)
765 return ((GroupStmt (stmts', usedBinderMap) groupByClause', thing), fvs)
767 rnStmt ctxt (ParStmt segs) thing_inside
768 = do { parallel_list_comp <- doptM Opt_ParallelListComp
769 ; checkM parallel_list_comp parStmtErr
770 ; ((segs', thing), fvs) <- rnParallelStmts (ParStmtCtxt ctxt) segs thing_inside
771 ; return ((ParStmt segs', thing), fvs) }
774 rnNormalStmtsAndFindUsedBinders :: HsStmtContext Name
776 -> ([Name] -> RnM (thing, FreeVars))
777 -> RnM (([LStmt Name], [Name], thing), FreeVars)
778 rnNormalStmtsAndFindUsedBinders ctxt stmts thing_inside = do
779 ((stmts', (used_bndrs, inner_thing)), fvs) <- rnNormalStmts ctxt stmts $ do
780 -- Find the Names that are bound by stmts that
781 -- by assumption we have just renamed
782 local_env <- getLocalRdrEnv
784 stmts_binders = collectLStmtsBinders stmts
785 bndrs = map (expectJust "rnStmt"
786 . lookupLocalRdrEnv local_env
787 . unLoc) stmts_binders
789 -- If shadow, we'll look up (Unqual x) twice, getting
790 -- the second binding both times, which is the
792 unshadowed_bndrs = nub bndrs
794 -- Typecheck the thing inside, passing on all
795 -- the Names bound before it for its information
796 (thing, fvs) <- thing_inside unshadowed_bndrs
798 -- Figure out which of the bound names are used
799 -- after the statements we renamed
800 let used_bndrs = filter (`elemNameSet` fvs) bndrs
801 return ((used_bndrs, thing), fvs)
803 -- Flatten the tuple returned by the above call a bit!
804 return ((stmts', used_bndrs, inner_thing), fvs)
807 rnParallelStmts ctxt segs thing_inside = do
808 orig_lcl_env <- getLocalRdrEnv
809 go orig_lcl_env [] segs
811 go orig_lcl_env bndrs [] = do
812 let (bndrs', dups) = removeDups cmpByOcc bndrs
813 inner_env = extendLocalRdrEnv orig_lcl_env bndrs'
816 (thing, fvs) <- setLocalRdrEnv inner_env thing_inside
817 return (([], thing), fvs)
819 go orig_lcl_env bndrs_so_far ((stmts, _) : segs) = do
820 ((stmts', bndrs, (segs', thing)), fvs) <- rnNormalStmtsAndFindUsedBinders ctxt stmts $ \new_bndrs -> do
821 -- Typecheck the thing inside, passing on all
822 -- the Names bound, but separately; revert the envt
823 setLocalRdrEnv orig_lcl_env $ do
824 go orig_lcl_env (new_bndrs ++ bndrs_so_far) segs
826 let seg' = (stmts', bndrs)
827 return (((seg':segs'), thing), delListFromNameSet fvs bndrs)
829 cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2
830 dupErr vs = addErr (ptext SLIT("Duplicate binding in parallel list comprehension for:")
831 <+> quotes (ppr (head vs)))
834 checkIsTransformableListComp :: HsStmtContext Name -> RnM ()
835 checkIsTransformableListComp ctxt = do
836 -- Ensure we are really within a list comprehension because otherwise the
837 -- desugarer will break when we come to operate on a parallel array
838 checkM (notParallelArray ctxt) transformStmtOutsideListCompErr
840 -- Ensure the user has turned the correct flag on
841 transform_list_comp <- doptM Opt_TransformListComp
842 checkM transform_list_comp transformStmtErr
844 notParallelArray PArrComp = False
845 notParallelArray _ = True
850 %************************************************************************
852 \subsubsection{mdo expressions}
854 %************************************************************************
857 type FwdRefs = NameSet
858 type Segment stmts = (Defs,
859 Uses, -- May include defs
860 FwdRefs, -- A subset of uses that are
861 -- (a) used before they are bound in this segment, or
862 -- (b) used here, and bound in subsequent segments
863 stmts) -- Either Stmt or [Stmt]
866 ----------------------------------------------------
868 rnMDoStmts :: [LStmt RdrName]
869 -> RnM (thing, FreeVars)
870 -> RnM (([LStmt Name], thing), FreeVars)
871 rnMDoStmts stmts thing_inside
872 = -- Step1: Bring all the binders of the mdo into scope
873 -- (Remember that this also removes the binders from the
874 -- finally-returned free-vars.)
875 -- And rename each individual stmt, making a
876 -- singleton segment. At this stage the FwdRefs field
877 -- isn't finished: it's empty for all except a BindStmt
878 -- for which it's the fwd refs within the bind itself
879 -- (This set may not be empty, because we're in a recursive
881 rn_rec_stmts_and_then stmts $ \ segs -> do {
883 ; (thing, fvs_later) <- thing_inside
886 -- Step 2: Fill in the fwd refs.
887 -- The segments are all singletons, but their fwd-ref
888 -- field mentions all the things used by the segment
889 -- that are bound after their use
890 segs_w_fwd_refs = addFwdRefs segs
892 -- Step 3: Group together the segments to make bigger segments
893 -- Invariant: in the result, no segment uses a variable
894 -- bound in a later segment
895 grouped_segs = glomSegments segs_w_fwd_refs
897 -- Step 4: Turn the segments into Stmts
898 -- Use RecStmt when and only when there are fwd refs
899 -- Also gather up the uses from the end towards the
900 -- start, so we can tell the RecStmt which things are
901 -- used 'after' the RecStmt
902 (stmts', fvs) = segsToStmts grouped_segs fvs_later
904 ; return ((stmts', thing), fvs) }
906 doc = text "In a recursive mdo-expression"
908 ---------------------------------------------
910 -- wrapper that does both the left- and right-hand sides
911 rn_rec_stmts_and_then :: [LStmt RdrName]
912 -- assumes that the FreeVars returned includes
913 -- the FreeVars of the Segments
914 -> ([Segment (LStmt Name)] -> RnM (a, FreeVars))
916 rn_rec_stmts_and_then s cont = do
917 -- (A) make the mini fixity env for all of the stmts
918 fix_env <- makeMiniFixityEnv (collectRecStmtsFixities s)
921 new_lhs_and_fv <- rn_rec_stmts_lhs fix_env s
923 -- bring them and their fixities into scope
924 let bound_names = map unLoc $ collectLStmtsBinders (map fst new_lhs_and_fv)
925 bindLocalNamesFV_WithFixities bound_names fix_env $
926 warnUnusedLocalBinds bound_names $ do
928 -- (C) do the right-hand-sides and thing-inside
929 segs <- rn_rec_stmts bound_names new_lhs_and_fv
933 -- get all the fixity decls in any Let stmt
934 collectRecStmtsFixities l =
935 foldr (\ s -> \acc -> case s of
936 (L loc (LetStmt (HsValBinds (ValBindsIn _ sigs)))) ->
937 foldr (\ sig -> \ acc -> case sig of
938 (L loc (FixSig s)) -> (L loc s) : acc
944 rn_rec_stmt_lhs :: UniqFM (Located Fixity) -- mini fixity env for the names we're about to bind
945 -- these fixities need to be brought into scope with the names
947 -- rename LHS, and return its FVs
948 -- Warning: we will only need the FreeVars below in the case of a BindStmt,
949 -- so we don't bother to compute it accurately in the other cases
950 -> RnM [(LStmtLR Name RdrName, FreeVars)]
952 rn_rec_stmt_lhs fix_env (L loc (ExprStmt expr a b)) = return [(L loc (ExprStmt expr a b),
953 -- this is actually correct
956 rn_rec_stmt_lhs fix_env (L loc (BindStmt pat expr a b))
958 -- should the ctxt be MDo instead?
959 (pat', fv_pat) <- rnBindPat (localRecNameMaker fix_env) pat
960 return [(L loc (BindStmt pat' expr a b),
963 rn_rec_stmt_lhs fix_env (L loc (LetStmt binds@(HsIPBinds _)))
964 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
967 rn_rec_stmt_lhs fix_env (L loc (LetStmt (HsValBinds binds)))
968 = do binds' <- rnValBindsLHS fix_env binds
969 return [(L loc (LetStmt (HsValBinds binds')),
970 -- Warning: this is bogus; see function invariant
974 rn_rec_stmt_lhs fix_env (L loc (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec
975 = rn_rec_stmts_lhs fix_env stmts
977 rn_rec_stmt_lhs _ stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo
978 = pprPanic "rn_rec_stmt" (ppr stmt)
980 rn_rec_stmt_lhs _ stmt@(L _ (TransformStmt _ _ _)) -- Syntactically illegal in mdo
981 = pprPanic "rn_rec_stmt" (ppr stmt)
983 rn_rec_stmt_lhs _ stmt@(L _ (GroupStmt _ _)) -- Syntactically illegal in mdo
984 = pprPanic "rn_rec_stmt" (ppr stmt)
986 rn_rec_stmts_lhs :: UniqFM (Located Fixity) -- mini fixity env for the names we're about to bind
987 -- these fixities need to be brought into scope with the names
989 -> RnM [(LStmtLR Name RdrName, FreeVars)]
990 rn_rec_stmts_lhs fix_env stmts =
991 let boundNames = collectLStmtsBinders stmts
992 doc = text "In a recursive mdo-expression"
994 -- First do error checking: we need to check for dups here because we
995 -- don't bind all of the variables from the Stmt at once
996 -- with bindLocatedLocals.
997 checkDupRdrNames doc boundNames
998 mappM (rn_rec_stmt_lhs fix_env) stmts `thenM` \ ls -> returnM (concat ls)
1003 rn_rec_stmt :: [Name] -> LStmtLR Name RdrName -> FreeVars -> RnM [Segment (LStmt Name)]
1004 -- Rename a Stmt that is inside a RecStmt (or mdo)
1005 -- Assumes all binders are already in scope
1006 -- Turns each stmt into a singleton Stmt
1007 rn_rec_stmt all_bndrs (L loc (ExprStmt expr _ _)) _
1008 = rnLExpr expr `thenM` \ (expr', fvs) ->
1009 lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) ->
1010 returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet,
1011 L loc (ExprStmt expr' then_op placeHolderType))]
1013 rn_rec_stmt all_bndrs (L loc (BindStmt pat' expr _ _)) fv_pat
1014 = rnLExpr expr `thenM` \ (expr', fv_expr) ->
1015 lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) ->
1016 lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) ->
1018 bndrs = mkNameSet (collectPatBinders pat')
1019 fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2
1021 returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs,
1022 L loc (BindStmt pat' expr' bind_op fail_op))]
1024 rn_rec_stmt all_bndrs (L loc (LetStmt binds@(HsIPBinds _))) _
1025 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
1028 rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds'))) _ = do
1029 (binds', du_binds) <-
1030 -- fixities and unused are handled above in rn_rec_stmts_and_then
1031 rnValBindsRHS all_bndrs binds'
1032 returnM [(duDefs du_binds, duUses du_binds,
1033 emptyNameSet, L loc (LetStmt (HsValBinds binds')))]
1035 -- no RecStmt case becuase they get flattened above when doing the LHSes
1036 rn_rec_stmt all_bndrs stmt@(L loc (RecStmt stmts _ _ _ _)) _
1037 = pprPanic "rn_rec_stmt: RecStmt" (ppr stmt)
1039 rn_rec_stmt all_bndrs stmt@(L _ (ParStmt _)) _ -- Syntactically illegal in mdo
1040 = pprPanic "rn_rec_stmt: ParStmt" (ppr stmt)
1042 rn_rec_stmt all_bndrs stmt@(L _ (TransformStmt _ _ _)) _ -- Syntactically illegal in mdo
1043 = pprPanic "rn_rec_stmt: TransformStmt" (ppr stmt)
1045 rn_rec_stmt all_bndrs stmt@(L _ (GroupStmt _ _)) _ -- Syntactically illegal in mdo
1046 = pprPanic "rn_rec_stmt: GroupStmt" (ppr stmt)
1048 rn_rec_stmts :: [Name] -> [(LStmtLR Name RdrName, FreeVars)] -> RnM [Segment (LStmt Name)]
1049 rn_rec_stmts bndrs stmts = mappM (uncurry (rn_rec_stmt bndrs)) stmts `thenM` \ segs_s ->
1050 returnM (concat segs_s)
1052 ---------------------------------------------
1053 addFwdRefs :: [Segment a] -> [Segment a]
1054 -- So far the segments only have forward refs *within* the Stmt
1055 -- (which happens for bind: x <- ...x...)
1056 -- This function adds the cross-seg fwd ref info
1059 = fst (foldr mk_seg ([], emptyNameSet) pairs)
1061 mk_seg (defs, uses, fwds, stmts) (segs, later_defs)
1062 = (new_seg : segs, all_defs)
1064 new_seg = (defs, uses, new_fwds, stmts)
1065 all_defs = later_defs `unionNameSets` defs
1066 new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs)
1067 -- Add the downstream fwd refs here
1069 ----------------------------------------------------
1070 -- Glomming the singleton segments of an mdo into
1071 -- minimal recursive groups.
1073 -- At first I thought this was just strongly connected components, but
1074 -- there's an important constraint: the order of the stmts must not change.
1077 -- mdo { x <- ...y...
1084 -- Here, the first stmt mention 'y', which is bound in the third.
1085 -- But that means that the innocent second stmt (p <- z) gets caught
1086 -- up in the recursion. And that in turn means that the binding for
1087 -- 'z' has to be included... and so on.
1089 -- Start at the tail { r <- x }
1090 -- Now add the next one { z <- y ; r <- x }
1091 -- Now add one more { q <- x ; z <- y ; r <- x }
1092 -- Now one more... but this time we have to group a bunch into rec
1093 -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x }
1094 -- Now one more, which we can add on without a rec
1096 -- rec { y <- ...x... ; q <- x ; z <- y } ;
1098 -- Finally we add the last one; since it mentions y we have to
1099 -- glom it togeher with the first two groups
1100 -- { rec { x <- ...y...; p <- z ; y <- ...x... ;
1101 -- q <- x ; z <- y } ;
1104 glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]]
1106 glomSegments [] = []
1107 glomSegments ((defs,uses,fwds,stmt) : segs)
1108 -- Actually stmts will always be a singleton
1109 = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others
1111 segs' = glomSegments segs
1112 (extras, others) = grab uses segs'
1113 (ds, us, fs, ss) = unzip4 extras
1115 seg_defs = plusFVs ds `plusFV` defs
1116 seg_uses = plusFVs us `plusFV` uses
1117 seg_fwds = plusFVs fs `plusFV` fwds
1118 seg_stmts = stmt : concat ss
1120 grab :: NameSet -- The client
1122 -> ([Segment a], -- Needed by the 'client'
1123 [Segment a]) -- Not needed by the client
1124 -- The result is simply a split of the input
1126 = (reverse yeses, reverse noes)
1128 (noes, yeses) = span not_needed (reverse dus)
1129 not_needed (defs,_,_,_) = not (intersectsNameSet defs uses)
1132 ----------------------------------------------------
1133 segsToStmts :: [Segment [LStmt Name]]
1134 -> FreeVars -- Free vars used 'later'
1135 -> ([LStmt Name], FreeVars)
1137 segsToStmts [] fvs_later = ([], fvs_later)
1138 segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later
1139 = ASSERT( not (null ss) )
1140 (new_stmt : later_stmts, later_uses `plusFV` uses)
1142 (later_stmts, later_uses) = segsToStmts segs fvs_later
1143 new_stmt | non_rec = head ss
1144 | otherwise = L (getLoc (head ss)) $
1145 RecStmt ss (nameSetToList used_later) (nameSetToList fwds)
1148 non_rec = isSingleton ss && isEmptyNameSet fwds
1149 used_later = defs `intersectNameSet` later_uses
1150 -- The ones needed after the RecStmt
1153 %************************************************************************
1155 \subsubsection{Assertion utils}
1157 %************************************************************************
1160 srcSpanPrimLit :: SrcSpan -> HsExpr Name
1161 srcSpanPrimLit span = HsLit (HsStringPrim (mkFastString (showSDoc (ppr span))))
1163 mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars)
1164 -- Return an expression for (assertError "Foo.hs:27")
1166 = getSrcSpanM `thenM` \ sloc ->
1168 expr = HsApp (L sloc (HsVar assertErrorName))
1169 (L sloc (srcSpanPrimLit sloc))
1171 returnM (expr, emptyFVs)
1174 %************************************************************************
1176 \subsubsection{Errors}
1178 %************************************************************************
1181 patSynErr e = do { addErr (sep [ptext SLIT("Pattern syntax in expression context:"),
1183 ; return (EWildPat, emptyFVs) }
1186 parStmtErr = addErr (ptext SLIT("Illegal parallel list comprehension: use -XParallelListComp"))
1188 transformStmtErr = addErr (ptext SLIT("Illegal transform or grouping list comprehension: use -XTransformListComp"))
1189 transformStmtOutsideListCompErr = addErr (ptext SLIT("Currently you may only use transform or grouping comprehensions within list comprehensions, not parallel array comprehensions"))
1191 badIpBinds what binds
1192 = hang (ptext SLIT("Implicit-parameter bindings illegal in") <+> what)