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"
19 import RnSource ( rnSrcDecls, rnSplice, checkTH )
20 import RnBinds ( rnLocalBindsAndThen, rnValBinds,
21 rnMatchGroup, trimWith )
25 import HscTypes ( availNames )
26 import RnNames ( getLocalDeclBinders, extendRdrEnvRn )
27 import RnTypes ( rnHsTypeFVs, rnLPat, rnOverLit, rnPatsAndThen, rnLit,
28 mkOpFormRn, mkOpAppRn, mkNegAppRn, checkSectionPrec,
29 dupFieldErr, checkTupSize )
30 import DynFlags ( DynFlag(..) )
31 import BasicTypes ( FixityDirection(..) )
32 import SrcLoc ( SrcSpan )
33 import PrelNames ( thFAKE, hasKey, assertIdKey, assertErrorName,
34 loopAName, choiceAName, appAName, arrAName, composeAName, firstAName,
35 negateName, thenMName, bindMName, failMName )
37 import Name ( Name, nameOccName, nameIsLocalOrFrom )
39 import RdrName ( RdrName, extendLocalRdrEnv, lookupLocalRdrEnv, hideSomeUnquals )
40 import LoadIface ( loadInterfaceForName )
41 import UniqFM ( isNullUFM )
42 import UniqSet ( emptyUniqSet )
44 import Util ( isSingleton )
45 import ListSetOps ( removeDups )
46 import Maybes ( expectJust )
48 import SrcLoc ( Located(..), unLoc, getLoc, cmpLocated )
51 import List ( unzip4 )
55 %************************************************************************
57 \subsubsection{Expressions}
59 %************************************************************************
62 rnExprs :: [LHsExpr RdrName] -> RnM ([LHsExpr Name], FreeVars)
63 rnExprs ls = rnExprs' ls emptyUniqSet
65 rnExprs' [] acc = returnM ([], acc)
66 rnExprs' (expr:exprs) acc
67 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
69 -- Now we do a "seq" on the free vars because typically it's small
70 -- or empty, especially in very long lists of constants
72 acc' = acc `plusFV` fvExpr
74 (grubby_seqNameSet acc' rnExprs') exprs acc' `thenM` \ (exprs', fvExprs) ->
75 returnM (expr':exprs', fvExprs)
77 -- Grubby little function to do "seq" on namesets; replace by proper seq when GHC can do seq
78 grubby_seqNameSet ns result | isNullUFM ns = result
82 Variables. We look up the variable and return the resulting name.
85 rnLExpr :: LHsExpr RdrName -> RnM (LHsExpr Name, FreeVars)
86 rnLExpr = wrapLocFstM rnExpr
88 rnExpr :: HsExpr RdrName -> RnM (HsExpr Name, FreeVars)
91 = do name <- lookupOccRn v
92 ignore_asserts <- doptM Opt_IgnoreAsserts
93 finish_var ignore_asserts name
95 finish_var ignore_asserts name
96 | ignore_asserts || not (name `hasKey` assertIdKey)
97 = return (HsVar name, unitFV name)
99 = do { (e, fvs) <- mkAssertErrorExpr
100 ; return (e, fvs `addOneFV` name) }
103 = newIPNameRn v `thenM` \ name ->
104 returnM (HsIPVar name, emptyFVs)
106 rnExpr (HsLit lit@(HsString s))
108 opt_OverloadedStrings <- doptM Opt_OverloadedStrings
109 ; if opt_OverloadedStrings then
110 rnExpr (HsOverLit (mkHsIsString s))
111 else -- Same as below
113 returnM (HsLit lit, emptyFVs)
118 returnM (HsLit lit, emptyFVs)
120 rnExpr (HsOverLit lit)
121 = rnOverLit lit `thenM` \ (lit', fvs) ->
122 returnM (HsOverLit lit', fvs)
124 rnExpr (HsApp fun arg)
125 = rnLExpr fun `thenM` \ (fun',fvFun) ->
126 rnLExpr arg `thenM` \ (arg',fvArg) ->
127 returnM (HsApp fun' arg', fvFun `plusFV` fvArg)
129 rnExpr (OpApp e1 op _ e2)
130 = rnLExpr e1 `thenM` \ (e1', fv_e1) ->
131 rnLExpr e2 `thenM` \ (e2', fv_e2) ->
132 rnLExpr op `thenM` \ (op'@(L _ (HsVar op_name)), fv_op) ->
135 -- When renaming code synthesised from "deriving" declarations
136 -- we used to avoid fixity stuff, but we can't easily tell any
137 -- more, so I've removed the test. Adding HsPars in TcGenDeriv
138 -- should prevent bad things happening.
139 lookupFixityRn op_name `thenM` \ fixity ->
140 mkOpAppRn e1' op' fixity e2' `thenM` \ final_e ->
143 fv_e1 `plusFV` fv_op `plusFV` fv_e2)
146 = rnLExpr e `thenM` \ (e', fv_e) ->
147 lookupSyntaxName negateName `thenM` \ (neg_name, fv_neg) ->
148 mkNegAppRn e' neg_name `thenM` \ final_e ->
149 returnM (final_e, fv_e `plusFV` fv_neg)
152 = rnLExpr e `thenM` \ (e', fvs_e) ->
153 returnM (HsPar e', fvs_e)
155 -- Template Haskell extensions
156 -- Don't ifdef-GHCI them because we want to fail gracefully
157 -- (not with an rnExpr crash) in a stage-1 compiler.
158 rnExpr e@(HsBracket br_body)
159 = checkTH e "bracket" `thenM_`
160 rnBracket br_body `thenM` \ (body', fvs_e) ->
161 returnM (HsBracket body', fvs_e)
163 rnExpr e@(HsSpliceE splice)
164 = rnSplice splice `thenM` \ (splice', fvs) ->
165 returnM (HsSpliceE splice', fvs)
167 rnExpr section@(SectionL expr op)
168 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
169 rnLExpr op `thenM` \ (op', fvs_op) ->
170 checkSectionPrec InfixL section op' expr' `thenM_`
171 returnM (SectionL expr' op', fvs_op `plusFV` fvs_expr)
173 rnExpr section@(SectionR op expr)
174 = rnLExpr op `thenM` \ (op', fvs_op) ->
175 rnLExpr expr `thenM` \ (expr', fvs_expr) ->
176 checkSectionPrec InfixR section op' expr' `thenM_`
177 returnM (SectionR op' expr', fvs_op `plusFV` fvs_expr)
179 rnExpr (HsCoreAnn ann expr)
180 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
181 returnM (HsCoreAnn ann expr', fvs_expr)
183 rnExpr (HsSCC lbl expr)
184 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
185 returnM (HsSCC lbl expr', fvs_expr)
186 rnExpr (HsTickPragma info expr)
187 = rnLExpr expr `thenM` \ (expr', fvs_expr) ->
188 returnM (HsTickPragma info expr', fvs_expr)
190 rnExpr (HsLam matches)
191 = rnMatchGroup LambdaExpr matches `thenM` \ (matches', fvMatch) ->
192 returnM (HsLam matches', fvMatch)
194 rnExpr (HsCase expr matches)
195 = rnLExpr expr `thenM` \ (new_expr, e_fvs) ->
196 rnMatchGroup CaseAlt matches `thenM` \ (new_matches, ms_fvs) ->
197 returnM (HsCase new_expr new_matches, e_fvs `plusFV` ms_fvs)
199 rnExpr (HsLet binds expr)
200 = rnLocalBindsAndThen binds $ \ binds' ->
201 rnLExpr expr `thenM` \ (expr',fvExpr) ->
202 returnM (HsLet binds' expr', fvExpr)
204 rnExpr e@(HsDo do_or_lc stmts body _)
205 = do { ((stmts', body'), fvs) <- rnStmts do_or_lc stmts $
207 ; return (HsDo do_or_lc stmts' body' placeHolderType, fvs) }
209 rnExpr (ExplicitList _ exps)
210 = rnExprs exps `thenM` \ (exps', fvs) ->
211 returnM (ExplicitList placeHolderType exps', fvs)
213 rnExpr (ExplicitPArr _ exps)
214 = rnExprs exps `thenM` \ (exps', fvs) ->
215 returnM (ExplicitPArr placeHolderType exps', fvs)
217 rnExpr e@(ExplicitTuple exps boxity)
218 = checkTupSize (length exps) `thenM_`
219 rnExprs exps `thenM` \ (exps', fvs) ->
220 returnM (ExplicitTuple exps' boxity, fvs)
222 rnExpr (RecordCon con_id _ (HsRecordBinds rbinds))
223 = lookupLocatedOccRn con_id `thenM` \ conname ->
224 rnRbinds "construction" rbinds `thenM` \ (rbinds', fvRbinds) ->
225 returnM (RecordCon conname noPostTcExpr (HsRecordBinds rbinds'),
226 fvRbinds `addOneFV` unLoc conname)
228 rnExpr (RecordUpd expr (HsRecordBinds rbinds) _ _ _)
229 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
230 rnRbinds "update" rbinds `thenM` \ (rbinds', fvRbinds) ->
231 returnM (RecordUpd expr' (HsRecordBinds rbinds') [] [] [],
232 fvExpr `plusFV` fvRbinds)
234 rnExpr (ExprWithTySig expr pty)
235 = do { (pty', fvTy) <- rnHsTypeFVs doc pty
236 ; (expr', fvExpr) <- bindSigTyVarsFV (hsExplicitTvs pty') $
238 ; return (ExprWithTySig expr' pty', fvExpr `plusFV` fvTy) }
240 doc = text "In an expression type signature"
242 rnExpr (HsIf p b1 b2)
243 = rnLExpr p `thenM` \ (p', fvP) ->
244 rnLExpr b1 `thenM` \ (b1', fvB1) ->
245 rnLExpr b2 `thenM` \ (b2', fvB2) ->
246 returnM (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
249 = rnHsTypeFVs doc a `thenM` \ (t, fvT) ->
250 returnM (HsType t, fvT)
252 doc = text "In a type argument"
254 rnExpr (ArithSeq _ seq)
255 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
256 returnM (ArithSeq noPostTcExpr new_seq, fvs)
258 rnExpr (PArrSeq _ seq)
259 = rnArithSeq seq `thenM` \ (new_seq, fvs) ->
260 returnM (PArrSeq noPostTcExpr new_seq, fvs)
263 These three are pattern syntax appearing in expressions.
264 Since all the symbols are reservedops we can simply reject them.
265 We return a (bogus) EWildPat in each case.
268 rnExpr e@EWildPat = patSynErr e
269 rnExpr e@(EAsPat {}) = patSynErr e
270 rnExpr e@(ELazyPat {}) = patSynErr e
273 %************************************************************************
277 %************************************************************************
280 rnExpr (HsProc pat body)
282 rnPatsAndThen ProcExpr [pat] $ \ [pat'] ->
283 rnCmdTop body `thenM` \ (body',fvBody) ->
284 returnM (HsProc pat' body', fvBody)
286 rnExpr (HsArrApp arrow arg _ ho rtl)
287 = select_arrow_scope (rnLExpr arrow) `thenM` \ (arrow',fvArrow) ->
288 rnLExpr arg `thenM` \ (arg',fvArg) ->
289 returnM (HsArrApp arrow' arg' placeHolderType ho rtl,
290 fvArrow `plusFV` fvArg)
292 select_arrow_scope tc = case ho of
293 HsHigherOrderApp -> tc
294 HsFirstOrderApp -> escapeArrowScope tc
297 rnExpr (HsArrForm op (Just _) [arg1, arg2])
298 = escapeArrowScope (rnLExpr op)
299 `thenM` \ (op'@(L _ (HsVar op_name)),fv_op) ->
300 rnCmdTop arg1 `thenM` \ (arg1',fv_arg1) ->
301 rnCmdTop arg2 `thenM` \ (arg2',fv_arg2) ->
305 lookupFixityRn op_name `thenM` \ fixity ->
306 mkOpFormRn arg1' op' fixity arg2' `thenM` \ final_e ->
309 fv_arg1 `plusFV` fv_op `plusFV` fv_arg2)
311 rnExpr (HsArrForm op fixity cmds)
312 = escapeArrowScope (rnLExpr op) `thenM` \ (op',fvOp) ->
313 rnCmdArgs cmds `thenM` \ (cmds',fvCmds) ->
314 returnM (HsArrForm op' fixity cmds', fvOp `plusFV` fvCmds)
316 rnExpr other = pprPanic "rnExpr: unexpected expression" (ppr other)
321 %************************************************************************
325 %************************************************************************
328 rnCmdArgs [] = returnM ([], emptyFVs)
330 = rnCmdTop arg `thenM` \ (arg',fvArg) ->
331 rnCmdArgs args `thenM` \ (args',fvArgs) ->
332 returnM (arg':args', fvArg `plusFV` fvArgs)
335 rnCmdTop = wrapLocFstM rnCmdTop'
337 rnCmdTop' (HsCmdTop cmd _ _ _)
338 = rnLExpr (convertOpFormsLCmd cmd) `thenM` \ (cmd', fvCmd) ->
340 cmd_names = [arrAName, composeAName, firstAName] ++
341 nameSetToList (methodNamesCmd (unLoc cmd'))
343 -- Generate the rebindable syntax for the monad
344 lookupSyntaxTable cmd_names `thenM` \ (cmd_names', cmd_fvs) ->
346 returnM (HsCmdTop cmd' [] placeHolderType cmd_names',
347 fvCmd `plusFV` cmd_fvs)
349 ---------------------------------------------------
350 -- convert OpApp's in a command context to HsArrForm's
352 convertOpFormsLCmd :: LHsCmd id -> LHsCmd id
353 convertOpFormsLCmd = fmap convertOpFormsCmd
355 convertOpFormsCmd :: HsCmd id -> HsCmd id
357 convertOpFormsCmd (HsApp c e) = HsApp (convertOpFormsLCmd c) e
358 convertOpFormsCmd (HsLam match) = HsLam (convertOpFormsMatch match)
359 convertOpFormsCmd (OpApp c1 op fixity c2)
361 arg1 = L (getLoc c1) $ HsCmdTop (convertOpFormsLCmd c1) [] placeHolderType []
362 arg2 = L (getLoc c2) $ HsCmdTop (convertOpFormsLCmd c2) [] placeHolderType []
364 HsArrForm op (Just fixity) [arg1, arg2]
366 convertOpFormsCmd (HsPar c) = HsPar (convertOpFormsLCmd c)
369 convertOpFormsCmd (HsCase exp matches)
370 = HsCase exp (convertOpFormsMatch matches)
372 convertOpFormsCmd (HsIf exp c1 c2)
373 = HsIf exp (convertOpFormsLCmd c1) (convertOpFormsLCmd c2)
375 convertOpFormsCmd (HsLet binds cmd)
376 = HsLet binds (convertOpFormsLCmd cmd)
378 convertOpFormsCmd (HsDo ctxt stmts body ty)
379 = HsDo ctxt (map (fmap convertOpFormsStmt) stmts)
380 (convertOpFormsLCmd body) ty
382 -- Anything else is unchanged. This includes HsArrForm (already done),
383 -- things with no sub-commands, and illegal commands (which will be
384 -- caught by the type checker)
385 convertOpFormsCmd c = c
387 convertOpFormsStmt (BindStmt pat cmd _ _)
388 = BindStmt pat (convertOpFormsLCmd cmd) noSyntaxExpr noSyntaxExpr
389 convertOpFormsStmt (ExprStmt cmd _ _)
390 = ExprStmt (convertOpFormsLCmd cmd) noSyntaxExpr placeHolderType
391 convertOpFormsStmt (RecStmt stmts lvs rvs es binds)
392 = RecStmt (map (fmap convertOpFormsStmt) stmts) lvs rvs es binds
393 convertOpFormsStmt stmt = stmt
395 convertOpFormsMatch (MatchGroup ms ty)
396 = MatchGroup (map (fmap convert) ms) ty
397 where convert (Match pat mty grhss)
398 = Match pat mty (convertOpFormsGRHSs grhss)
400 convertOpFormsGRHSs (GRHSs grhss binds)
401 = GRHSs (map convertOpFormsGRHS grhss) binds
403 convertOpFormsGRHS = fmap convert
405 convert (GRHS stmts cmd) = GRHS stmts (convertOpFormsLCmd cmd)
407 ---------------------------------------------------
408 type CmdNeeds = FreeVars -- Only inhabitants are
409 -- appAName, choiceAName, loopAName
411 -- find what methods the Cmd needs (loop, choice, apply)
412 methodNamesLCmd :: LHsCmd Name -> CmdNeeds
413 methodNamesLCmd = methodNamesCmd . unLoc
415 methodNamesCmd :: HsCmd Name -> CmdNeeds
417 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsFirstOrderApp _rtl)
419 methodNamesCmd cmd@(HsArrApp _arrow _arg _ HsHigherOrderApp _rtl)
421 methodNamesCmd cmd@(HsArrForm {}) = emptyFVs
423 methodNamesCmd (HsPar c) = methodNamesLCmd c
425 methodNamesCmd (HsIf p c1 c2)
426 = methodNamesLCmd c1 `plusFV` methodNamesLCmd c2 `addOneFV` choiceAName
428 methodNamesCmd (HsLet b c) = methodNamesLCmd c
430 methodNamesCmd (HsDo sc stmts body ty)
431 = methodNamesStmts stmts `plusFV` methodNamesLCmd body
433 methodNamesCmd (HsApp c e) = methodNamesLCmd c
435 methodNamesCmd (HsLam match) = methodNamesMatch match
437 methodNamesCmd (HsCase scrut matches)
438 = methodNamesMatch matches `addOneFV` choiceAName
440 methodNamesCmd other = emptyFVs
441 -- Other forms can't occur in commands, but it's not convenient
442 -- to error here so we just do what's convenient.
443 -- The type checker will complain later
445 ---------------------------------------------------
446 methodNamesMatch (MatchGroup ms _)
447 = plusFVs (map do_one ms)
449 do_one (L _ (Match pats sig_ty grhss)) = methodNamesGRHSs grhss
451 -------------------------------------------------
453 methodNamesGRHSs (GRHSs grhss binds) = plusFVs (map methodNamesGRHS grhss)
455 -------------------------------------------------
456 methodNamesGRHS (L _ (GRHS stmts rhs)) = methodNamesLCmd rhs
458 ---------------------------------------------------
459 methodNamesStmts stmts = plusFVs (map methodNamesLStmt stmts)
461 ---------------------------------------------------
462 methodNamesLStmt = methodNamesStmt . unLoc
464 methodNamesStmt (ExprStmt cmd _ _) = methodNamesLCmd cmd
465 methodNamesStmt (BindStmt pat cmd _ _) = methodNamesLCmd cmd
466 methodNamesStmt (RecStmt stmts _ _ _ _)
467 = methodNamesStmts stmts `addOneFV` loopAName
468 methodNamesStmt (LetStmt b) = emptyFVs
469 methodNamesStmt (ParStmt ss) = emptyFVs
470 -- ParStmt can't occur in commands, but it's not convenient to error
471 -- here so we just do what's convenient
475 %************************************************************************
479 %************************************************************************
482 rnArithSeq (From expr)
483 = rnLExpr expr `thenM` \ (expr', fvExpr) ->
484 returnM (From expr', fvExpr)
486 rnArithSeq (FromThen expr1 expr2)
487 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
488 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
489 returnM (FromThen expr1' expr2', fvExpr1 `plusFV` fvExpr2)
491 rnArithSeq (FromTo expr1 expr2)
492 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
493 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
494 returnM (FromTo expr1' expr2', fvExpr1 `plusFV` fvExpr2)
496 rnArithSeq (FromThenTo expr1 expr2 expr3)
497 = rnLExpr expr1 `thenM` \ (expr1', fvExpr1) ->
498 rnLExpr expr2 `thenM` \ (expr2', fvExpr2) ->
499 rnLExpr expr3 `thenM` \ (expr3', fvExpr3) ->
500 returnM (FromThenTo expr1' expr2' expr3',
501 plusFVs [fvExpr1, fvExpr2, fvExpr3])
505 %************************************************************************
507 \subsubsection{@Rbinds@s and @Rpats@s: in record expressions}
509 %************************************************************************
513 = mappM_ field_dup_err dup_fields `thenM_`
514 mapFvRn rn_rbind rbinds `thenM` \ (rbinds', fvRbind) ->
515 returnM (rbinds', fvRbind)
517 (_, dup_fields) = removeDups cmpLocated [ f | (f,_) <- rbinds ]
519 field_dup_err dups = mappM_ (\f -> addLocErr f (dupFieldErr str)) dups
521 rn_rbind (field, expr)
522 = lookupLocatedGlobalOccRn field `thenM` \ fieldname ->
523 rnLExpr expr `thenM` \ (expr', fvExpr) ->
524 returnM ((fieldname, expr'), fvExpr `addOneFV` unLoc fieldname)
527 %************************************************************************
529 Template Haskell brackets
531 %************************************************************************
534 rnBracket (VarBr n) = do { name <- lookupOccRn n
535 ; this_mod <- getModule
536 ; checkM (nameIsLocalOrFrom this_mod name) $ -- Reason: deprecation checking asumes the
537 do { loadInterfaceForName msg name -- home interface is loaded, and this is the
538 ; return () } -- only way that is going to happen
539 ; returnM (VarBr name, unitFV name) }
541 msg = ptext SLIT("Need interface for Template Haskell quoted Name")
543 rnBracket (ExpBr e) = do { (e', fvs) <- rnLExpr e
544 ; return (ExpBr e', fvs) }
545 rnBracket (PatBr p) = do { (p', fvs) <- rnLPat p
546 ; return (PatBr p', fvs) }
547 rnBracket (TypBr t) = do { (t', fvs) <- rnHsTypeFVs doc t
548 ; return (TypBr t', fvs) }
550 doc = ptext SLIT("In a Template-Haskell quoted type")
551 rnBracket (DecBr group)
552 = do { gbl_env <- getGblEnv
554 ; let gbl_env1 = gbl_env { tcg_mod = thFAKE }
555 -- Note the thFAKE. The top-level names from the bracketed
556 -- declarations will go into the name cache, and we don't want them to
557 -- confuse the Names for the current module.
558 -- By using a pretend module, thFAKE, we keep them safely out of the way.
560 ; avails <- getLocalDeclBinders gbl_env1 group
561 ; let names = concatMap availNames avails
563 ; let new_occs = map nameOccName names
564 trimmed_rdr_env = hideSomeUnquals (tcg_rdr_env gbl_env) new_occs
566 ; rdr_env' <- extendRdrEnvRn trimmed_rdr_env avails
567 -- In this situation we want to *shadow* top-level bindings.
569 -- bar = [d| foo = 1|]
570 -- If we don't shadow, we'll get an ambiguity complaint when we do
571 -- a lookupTopBndrRn (which uses lookupGreLocalRn) on the binder of the 'foo'
573 -- Furthermore, arguably if the splice does define foo, that should hide
574 -- any foo's further out
576 -- The shadowing is acheived by the call to hideSomeUnquals, which removes
577 -- the unqualified bindings of things defined by the bracket
579 ; setGblEnv (gbl_env { tcg_rdr_env = rdr_env',
580 tcg_dus = emptyDUs }) $ do
581 -- The emptyDUs is so that we just collect uses for this group alone
583 { (tcg_env, group') <- rnSrcDecls group
584 -- Discard the tcg_env; it contains only extra info about fixity
585 ; return (DecBr group', allUses (tcg_dus tcg_env)) } }
588 %************************************************************************
590 \subsubsection{@Stmt@s: in @do@ expressions}
592 %************************************************************************
595 rnStmts :: HsStmtContext Name -> [LStmt RdrName]
596 -> RnM (thing, FreeVars)
597 -> RnM (([LStmt Name], thing), FreeVars)
599 rnStmts (MDoExpr _) = rnMDoStmts
600 rnStmts ctxt = rnNormalStmts ctxt
602 rnNormalStmts :: HsStmtContext Name -> [LStmt RdrName]
603 -> RnM (thing, FreeVars)
604 -> RnM (([LStmt Name], thing), FreeVars)
605 -- Used for cases *other* than recursive mdo
606 -- Implements nested scopes
608 rnNormalStmts ctxt [] thing_inside
609 = do { (thing, fvs) <- thing_inside
610 ; return (([],thing), fvs) }
612 rnNormalStmts ctxt (L loc stmt : stmts) thing_inside
613 = do { ((stmt', (stmts', thing)), fvs)
614 <- rnStmt ctxt stmt $
615 rnNormalStmts ctxt stmts thing_inside
616 ; return (((L loc stmt' : stmts'), thing), fvs) }
618 rnStmt :: HsStmtContext Name -> Stmt RdrName
619 -> RnM (thing, FreeVars)
620 -> RnM ((Stmt Name, thing), FreeVars)
622 rnStmt ctxt (ExprStmt expr _ _) thing_inside
623 = do { (expr', fv_expr) <- rnLExpr expr
624 ; (then_op, fvs1) <- lookupSyntaxName thenMName
625 ; (thing, fvs2) <- thing_inside
626 ; return ((ExprStmt expr' then_op placeHolderType, thing),
627 fv_expr `plusFV` fvs1 `plusFV` fvs2) }
629 rnStmt ctxt (BindStmt pat expr _ _) thing_inside
630 = do { (expr', fv_expr) <- rnLExpr expr
631 -- The binders do not scope over the expression
632 ; (bind_op, fvs1) <- lookupSyntaxName bindMName
633 ; (fail_op, fvs2) <- lookupSyntaxName failMName
634 ; rnPatsAndThen (StmtCtxt ctxt) [pat] $ \ [pat'] -> do
635 { (thing, fvs3) <- thing_inside
636 ; return ((BindStmt pat' expr' bind_op fail_op, thing),
637 fv_expr `plusFV` fvs1 `plusFV` fvs2 `plusFV` fvs3) }}
638 -- fv_expr shouldn't really be filtered by the rnPatsAndThen
639 -- but it does not matter because the names are unique
641 rnStmt ctxt (LetStmt binds) thing_inside
642 = do { checkErr (ok ctxt binds)
643 (badIpBinds (ptext SLIT("a parallel list comprehension:")) binds)
644 ; rnLocalBindsAndThen binds $ \ binds' -> do
645 { (thing, fvs) <- thing_inside
646 ; return ((LetStmt binds', thing), fvs) }}
648 -- We do not allow implicit-parameter bindings in a parallel
649 -- list comprehension. I'm not sure what it might mean.
650 ok (ParStmtCtxt _) (HsIPBinds _) = False
653 rnStmt ctxt (RecStmt rec_stmts _ _ _ _) thing_inside
654 = bindLocatedLocalsRn doc (collectLStmtsBinders rec_stmts) $ \ bndrs ->
655 rn_rec_stmts bndrs rec_stmts `thenM` \ segs ->
656 thing_inside `thenM` \ (thing, fvs) ->
658 segs_w_fwd_refs = addFwdRefs segs
659 (ds, us, fs, rec_stmts') = unzip4 segs_w_fwd_refs
660 later_vars = nameSetToList (plusFVs ds `intersectNameSet` fvs)
661 fwd_vars = nameSetToList (plusFVs fs)
663 rec_stmt = RecStmt rec_stmts' later_vars fwd_vars [] emptyLHsBinds
665 returnM ((rec_stmt, thing), uses `plusFV` fvs)
667 doc = text "In a recursive do statement"
669 rnStmt ctxt (ParStmt segs) thing_inside
670 = do { opt_GlasgowExts <- doptM Opt_GlasgowExts
671 ; checkM opt_GlasgowExts parStmtErr
672 ; orig_lcl_env <- getLocalRdrEnv
673 ; ((segs',thing), fvs) <- go orig_lcl_env [] segs
674 ; return ((ParStmt segs', thing), fvs) }
676 -- type ParSeg id = [([LStmt id], [id])]
677 -- go :: NameSet -> [ParSeg RdrName]
678 -- -> RnM (([ParSeg Name], thing), FreeVars)
680 go orig_lcl_env bndrs []
681 = do { let { (bndrs', dups) = removeDups cmpByOcc bndrs
682 ; inner_env = extendLocalRdrEnv orig_lcl_env bndrs' }
684 ; (thing, fvs) <- setLocalRdrEnv inner_env thing_inside
685 ; return (([], thing), fvs) }
687 go orig_lcl_env bndrs_so_far ((stmts, _) : segs)
688 = do { ((stmts', (bndrs, segs', thing)), fvs)
689 <- rnNormalStmts par_ctxt stmts $ do
690 { -- Find the Names that are bound by stmts
691 lcl_env <- getLocalRdrEnv
692 ; let { rdr_bndrs = collectLStmtsBinders stmts
693 ; bndrs = map ( expectJust "rnStmt"
694 . lookupLocalRdrEnv lcl_env
696 ; new_bndrs = nub bndrs ++ bndrs_so_far
697 -- The nub is because there might be shadowing
699 -- So we'll look up (Unqual x) twice, getting
700 -- the second binding both times, which is the
703 -- Typecheck the thing inside, passing on all
704 -- the Names bound, but separately; revert the envt
705 ; ((segs', thing), fvs) <- setLocalRdrEnv orig_lcl_env $
706 go orig_lcl_env new_bndrs segs
708 -- Figure out which of the bound names are used
709 ; let used_bndrs = filter (`elemNameSet` fvs) bndrs
710 ; return ((used_bndrs, segs', thing), fvs) }
712 ; let seg' = (stmts', bndrs)
713 ; return (((seg':segs'), thing),
714 delListFromNameSet fvs bndrs) }
716 par_ctxt = ParStmtCtxt ctxt
718 cmpByOcc n1 n2 = nameOccName n1 `compare` nameOccName n2
719 dupErr vs = addErr (ptext SLIT("Duplicate binding in parallel list comprehension for:")
720 <+> quotes (ppr (head vs)))
724 %************************************************************************
726 \subsubsection{mdo expressions}
728 %************************************************************************
731 type FwdRefs = NameSet
732 type Segment stmts = (Defs,
733 Uses, -- May include defs
734 FwdRefs, -- A subset of uses that are
735 -- (a) used before they are bound in this segment, or
736 -- (b) used here, and bound in subsequent segments
737 stmts) -- Either Stmt or [Stmt]
740 ----------------------------------------------------
741 rnMDoStmts :: [LStmt RdrName]
742 -> RnM (thing, FreeVars)
743 -> RnM (([LStmt Name], thing), FreeVars)
744 rnMDoStmts stmts thing_inside
745 = -- Step1: bring all the binders of the mdo into scope
746 -- Remember that this also removes the binders from the
747 -- finally-returned free-vars
748 bindLocatedLocalsRn doc (collectLStmtsBinders stmts) $ \ bndrs ->
750 -- Step 2: Rename each individual stmt, making a
751 -- singleton segment. At this stage the FwdRefs field
752 -- isn't finished: it's empty for all except a BindStmt
753 -- for which it's the fwd refs within the bind itself
754 -- (This set may not be empty, because we're in a recursive
756 segs <- rn_rec_stmts bndrs stmts
758 ; (thing, fvs_later) <- thing_inside
761 -- Step 3: Fill in the fwd refs.
762 -- The segments are all singletons, but their fwd-ref
763 -- field mentions all the things used by the segment
764 -- that are bound after their use
765 segs_w_fwd_refs = addFwdRefs segs
767 -- Step 4: Group together the segments to make bigger segments
768 -- Invariant: in the result, no segment uses a variable
769 -- bound in a later segment
770 grouped_segs = glomSegments segs_w_fwd_refs
772 -- Step 5: Turn the segments into Stmts
773 -- Use RecStmt when and only when there are fwd refs
774 -- Also gather up the uses from the end towards the
775 -- start, so we can tell the RecStmt which things are
776 -- used 'after' the RecStmt
777 (stmts', fvs) = segsToStmts grouped_segs fvs_later
779 ; return ((stmts', thing), fvs) }
781 doc = text "In a recursive mdo-expression"
783 ---------------------------------------------
784 rn_rec_stmts :: [Name] -> [LStmt RdrName] -> RnM [Segment (LStmt Name)]
785 rn_rec_stmts bndrs stmts = mappM (rn_rec_stmt bndrs) stmts `thenM` \ segs_s ->
786 returnM (concat segs_s)
788 ----------------------------------------------------
789 rn_rec_stmt :: [Name] -> LStmt RdrName -> RnM [Segment (LStmt Name)]
790 -- Rename a Stmt that is inside a RecStmt (or mdo)
791 -- Assumes all binders are already in scope
792 -- Turns each stmt into a singleton Stmt
794 rn_rec_stmt all_bndrs (L loc (ExprStmt expr _ _))
795 = rnLExpr expr `thenM` \ (expr', fvs) ->
796 lookupSyntaxName thenMName `thenM` \ (then_op, fvs1) ->
797 returnM [(emptyNameSet, fvs `plusFV` fvs1, emptyNameSet,
798 L loc (ExprStmt expr' then_op placeHolderType))]
800 rn_rec_stmt all_bndrs (L loc (BindStmt pat expr _ _))
801 = rnLExpr expr `thenM` \ (expr', fv_expr) ->
802 rnLPat pat `thenM` \ (pat', fv_pat) ->
803 lookupSyntaxName bindMName `thenM` \ (bind_op, fvs1) ->
804 lookupSyntaxName failMName `thenM` \ (fail_op, fvs2) ->
806 bndrs = mkNameSet (collectPatBinders pat')
807 fvs = fv_expr `plusFV` fv_pat `plusFV` fvs1 `plusFV` fvs2
809 returnM [(bndrs, fvs, bndrs `intersectNameSet` fvs,
810 L loc (BindStmt pat' expr' bind_op fail_op))]
812 rn_rec_stmt all_bndrs (L loc (LetStmt binds@(HsIPBinds _)))
813 = do { addErr (badIpBinds (ptext SLIT("an mdo expression")) binds)
816 rn_rec_stmt all_bndrs (L loc (LetStmt (HsValBinds binds)))
817 = rnValBinds (trimWith all_bndrs) binds `thenM` \ (binds', du_binds) ->
818 returnM [(duDefs du_binds, duUses du_binds,
819 emptyNameSet, L loc (LetStmt (HsValBinds binds')))]
821 rn_rec_stmt all_bndrs (L loc (RecStmt stmts _ _ _ _)) -- Flatten Rec inside Rec
822 = rn_rec_stmts all_bndrs stmts
824 rn_rec_stmt all_bndrs stmt@(L _ (ParStmt _)) -- Syntactically illegal in mdo
825 = pprPanic "rn_rec_stmt" (ppr stmt)
827 ---------------------------------------------
828 addFwdRefs :: [Segment a] -> [Segment a]
829 -- So far the segments only have forward refs *within* the Stmt
830 -- (which happens for bind: x <- ...x...)
831 -- This function adds the cross-seg fwd ref info
834 = fst (foldr mk_seg ([], emptyNameSet) pairs)
836 mk_seg (defs, uses, fwds, stmts) (segs, later_defs)
837 = (new_seg : segs, all_defs)
839 new_seg = (defs, uses, new_fwds, stmts)
840 all_defs = later_defs `unionNameSets` defs
841 new_fwds = fwds `unionNameSets` (uses `intersectNameSet` later_defs)
842 -- Add the downstream fwd refs here
844 ----------------------------------------------------
845 -- Glomming the singleton segments of an mdo into
846 -- minimal recursive groups.
848 -- At first I thought this was just strongly connected components, but
849 -- there's an important constraint: the order of the stmts must not change.
852 -- mdo { x <- ...y...
859 -- Here, the first stmt mention 'y', which is bound in the third.
860 -- But that means that the innocent second stmt (p <- z) gets caught
861 -- up in the recursion. And that in turn means that the binding for
862 -- 'z' has to be included... and so on.
864 -- Start at the tail { r <- x }
865 -- Now add the next one { z <- y ; r <- x }
866 -- Now add one more { q <- x ; z <- y ; r <- x }
867 -- Now one more... but this time we have to group a bunch into rec
868 -- { rec { y <- ...x... ; q <- x ; z <- y } ; r <- x }
869 -- Now one more, which we can add on without a rec
871 -- rec { y <- ...x... ; q <- x ; z <- y } ;
873 -- Finally we add the last one; since it mentions y we have to
874 -- glom it togeher with the first two groups
875 -- { rec { x <- ...y...; p <- z ; y <- ...x... ;
876 -- q <- x ; z <- y } ;
879 glomSegments :: [Segment (LStmt Name)] -> [Segment [LStmt Name]]
882 glomSegments ((defs,uses,fwds,stmt) : segs)
883 -- Actually stmts will always be a singleton
884 = (seg_defs, seg_uses, seg_fwds, seg_stmts) : others
886 segs' = glomSegments segs
887 (extras, others) = grab uses segs'
888 (ds, us, fs, ss) = unzip4 extras
890 seg_defs = plusFVs ds `plusFV` defs
891 seg_uses = plusFVs us `plusFV` uses
892 seg_fwds = plusFVs fs `plusFV` fwds
893 seg_stmts = stmt : concat ss
895 grab :: NameSet -- The client
897 -> ([Segment a], -- Needed by the 'client'
898 [Segment a]) -- Not needed by the client
899 -- The result is simply a split of the input
901 = (reverse yeses, reverse noes)
903 (noes, yeses) = span not_needed (reverse dus)
904 not_needed (defs,_,_,_) = not (intersectsNameSet defs uses)
907 ----------------------------------------------------
908 segsToStmts :: [Segment [LStmt Name]]
909 -> FreeVars -- Free vars used 'later'
910 -> ([LStmt Name], FreeVars)
912 segsToStmts [] fvs_later = ([], fvs_later)
913 segsToStmts ((defs, uses, fwds, ss) : segs) fvs_later
914 = ASSERT( not (null ss) )
915 (new_stmt : later_stmts, later_uses `plusFV` uses)
917 (later_stmts, later_uses) = segsToStmts segs fvs_later
918 new_stmt | non_rec = head ss
919 | otherwise = L (getLoc (head ss)) $
920 RecStmt ss (nameSetToList used_later) (nameSetToList fwds)
923 non_rec = isSingleton ss && isEmptyNameSet fwds
924 used_later = defs `intersectNameSet` later_uses
925 -- The ones needed after the RecStmt
928 %************************************************************************
930 \subsubsection{Assertion utils}
932 %************************************************************************
935 srcSpanPrimLit :: SrcSpan -> HsExpr Name
936 srcSpanPrimLit span = HsLit (HsStringPrim (mkFastString (showSDoc (ppr span))))
938 mkAssertErrorExpr :: RnM (HsExpr Name, FreeVars)
939 -- Return an expression for (assertError "Foo.hs:27")
941 = getSrcSpanM `thenM` \ sloc ->
943 expr = HsApp (L sloc (HsVar assertErrorName))
944 (L sloc (srcSpanPrimLit sloc))
946 returnM (expr, emptyFVs)
949 %************************************************************************
951 \subsubsection{Errors}
953 %************************************************************************
956 patSynErr e = do { addErr (sep [ptext SLIT("Pattern syntax in expression context:"),
958 ; return (EWildPat, emptyFVs) }
960 parStmtErr = addErr (ptext SLIT("Illegal parallel list comprehension: use -fglasgow-exts"))
962 badIpBinds what binds
963 = hang (ptext SLIT("Implicit-parameter bindings illegal in") <+> what)