2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Tidying up Core}
8 tidyCorePgm, tidyExpr, tidyCoreExpr,
12 #include "HsVersions.h"
14 import CmdLineOpts ( DynFlags, DynFlag(..), opt_OmitInterfacePragmas )
16 import CoreUnfold ( noUnfolding, mkTopUnfolding, okToUnfoldInHiFile )
17 import CoreFVs ( ruleSomeFreeVars, exprSomeFreeVars )
18 import PprCore ( pprIdCoreRule )
19 import CoreLint ( showPass, endPass )
22 import Var ( Id, Var )
23 import Id ( idType, idInfo, idName, isExportedId,
24 idSpecialisation, idUnique,
25 mkVanillaGlobal, isLocalId,
26 isImplicitId, mkUserLocal, setIdInfo
28 import IdInfo {- loads of stuff -}
29 import NewDemand ( isBottomingSig, topSig )
30 import BasicTypes ( isNeverActive )
31 import Name ( getOccName, nameOccName, mkLocalName, mkGlobalName,
32 localiseName, isGlobalName, nameSrcLoc
34 import NameEnv ( filterNameEnv )
35 import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
36 import Type ( tidyTopType, tidyType, tidyTyVarBndr )
37 import Module ( Module, moduleName )
38 import HscTypes ( PersistentCompilerState( pcs_PRS ),
39 PersistentRenamerState( prsOrig ),
40 NameSupply( nsNames, nsUniqs ),
41 TypeEnv, extendTypeEnvList, typeEnvIds,
42 ModDetails(..), TyThing(..)
44 import FiniteMap ( lookupFM, addToFM )
45 import Maybes ( orElse )
46 import ErrUtils ( showPass, dumpIfSet_core )
47 import SrcLoc ( noSrcLoc )
48 import UniqFM ( mapUFM )
49 import UniqSupply ( splitUniqSupply, uniqFromSupply )
50 import List ( partition )
51 import Util ( mapAccumL )
52 import Maybe ( isJust )
58 %************************************************************************
60 \subsection{What goes on}
62 %************************************************************************
68 Step 1: Figure out external Ids
69 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
70 First we figure out which Ids are "external" Ids. An
71 "external" Id is one that is visible from outside the compilation
73 a) the user exported ones
74 b) ones mentioned in the unfoldings, workers,
75 or rules of externally-visible ones
76 This exercise takes a sweep of the bindings bottom to top. Actually,
77 in Step 2 we're also going to need to know which Ids should be
78 exported with their unfoldings, so we produce not an IdSet but an
82 Step 2: Tidy the program
83 ~~~~~~~~~~~~~~~~~~~~~~~~
84 Next we traverse the bindings top to bottom. For each *top-level*
87 1. Make it into a GlobalId
89 2. Give it a system-wide Unique.
90 [Even non-exported things need system-wide Uniques because the
91 byte-code generator builds a single Name->BCO symbol table.]
93 We use the NameSupply kept in the PersistentRenamerState as the
94 source of such system-wide uniques.
96 For external Ids, use the original-name cache in the NameSupply
97 to ensure that the unique assigned is the same as the Id had
98 in any previous compilation run.
100 3. If it's an external Id, make it have a global Name, otherwise
101 make it have a local Name.
102 This is used by the code generator to decide whether
103 to make the label externally visible
105 4. Give external Ids a "tidy" occurrence name. This means
106 we can print them in interface files without confusing
107 "x" (unique 5) with "x" (unique 10).
109 5. Give it its UTTERLY FINAL IdInfo; in ptic,
110 * Its IdDetails becomes VanillaGlobal, reflecting the fact that
111 from now on we regard it as a global, not local, Id
113 * its unfolding, if it should have one
115 * its arity, computed from the number of visible lambdas
117 * its CAF info, computed from what is free in its RHS
120 Finally, substitute these new top-level binders consistently
121 throughout, including in unfoldings. We also tidy binders in
122 RHSs, so that they print nicely in interfaces.
125 tidyCorePgm :: DynFlags -> Module
126 -> PersistentCompilerState
127 -> CgInfoEnv -- Information from the back end,
128 -- to be splatted into the IdInfo
130 -> IO (PersistentCompilerState, ModDetails)
132 tidyCorePgm dflags mod pcs cg_info_env
133 (ModDetails { md_types = env_tc, md_insts = insts_tc,
134 md_binds = binds_in, md_rules = orphans_in })
135 = do { showPass dflags "Tidy Core"
137 ; let ext_ids = findExternalSet binds_in orphans_in
138 ; let ext_rules = findExternalRules binds_in orphans_in ext_ids
140 -- We also make sure to avoid any exported binders. Consider
141 -- f{-u1-} = 1 -- Local decl
143 -- f{-u2-} = 2 -- Exported decl
145 -- The second exported decl must 'get' the name 'f', so we
146 -- have to put 'f' in the avoids list before we get to the first
147 -- decl. tidyTopId then does a no-op on exported binders.
148 ; let prs = pcs_PRS pcs
149 orig_ns = prsOrig prs
151 init_tidy_env = (orig_ns, initTidyOccEnv avoids, emptyVarEnv)
152 avoids = [getOccName name | bndr <- typeEnvIds env_tc,
153 let name = idName bndr,
155 -- In computing our "avoids" list, we must include
157 -- all things with global names (assigned once and for
158 -- all by the renamer)
159 -- since their names are "taken".
160 -- The type environment is a convenient source of such things.
162 ; let ((orig_ns', occ_env, subst_env), tidy_binds)
163 = mapAccumL (tidyTopBind mod ext_ids cg_info_env)
164 init_tidy_env binds_in
166 ; let tidy_rules = tidyIdRules (occ_env,subst_env) ext_rules
168 ; let prs' = prs { prsOrig = orig_ns' }
169 pcs' = pcs { pcs_PRS = prs' }
171 ; let final_ids = [ id
173 , id <- bindersOf bind
174 , isGlobalName (idName id)]
176 -- Dfuns are local Ids that might have
177 -- changed their unique during tidying
178 ; let lookup_dfun_id id = lookupVarEnv subst_env id `orElse`
179 pprPanic "lookup_dfun_id" (ppr id)
182 ; let tidy_type_env = mkFinalTypeEnv env_tc final_ids
183 tidy_dfun_ids = map lookup_dfun_id insts_tc
185 ; let tidy_details = ModDetails { md_types = tidy_type_env,
186 md_rules = tidy_rules,
187 md_insts = tidy_dfun_ids,
188 md_binds = tidy_binds }
190 ; endPass dflags "Tidy Core" Opt_D_dump_simpl tidy_binds
191 ; dumpIfSet_core dflags Opt_D_dump_simpl
193 (vcat (map pprIdCoreRule tidy_rules))
195 ; return (pcs', tidy_details)
198 tidyCoreExpr :: CoreExpr -> IO CoreExpr
199 tidyCoreExpr expr = return (tidyExpr emptyTidyEnv expr)
203 %************************************************************************
205 \subsection{Write a new interface file}
207 %************************************************************************
210 mkFinalTypeEnv :: TypeEnv -- From typechecker
214 mkFinalTypeEnv type_env final_ids
215 = extendTypeEnvList (filterNameEnv keep_it type_env)
218 -- The competed type environment is gotten from
219 -- a) keeping the types and classes
220 -- b) removing all Ids,
221 -- c) adding Ids with correct IdInfo, including unfoldings,
222 -- gotten from the bindings
223 -- From (c) we keep only those Ids with Global names;
224 -- the CoreTidy pass makes sure these are all and only
225 -- the externally-accessible ones
226 -- This truncates the type environment to include only the
227 -- exported Ids and things needed from them, which saves space
229 -- However, we do keep things like constructors, which should not appear
230 -- in interface files, because they are needed by importing modules when
231 -- using the compilation manager
233 -- We keep implicit Ids, because they won't appear
234 -- in the bindings from which final_ids are derived!
235 keep_it (AnId id) = isImplicitId id -- Remove all Ids except implicit ones
236 keep_it other = True -- Keep all TyCons and Classes
240 findExternalRules :: [CoreBind]
241 -> [IdCoreRule] -- Orphan rules
242 -> IdEnv a -- Ids that are exported, so we need their rules
244 -- The complete rules are gotten by combining
245 -- a) the orphan rules
246 -- b) rules embedded in the top-level Ids
247 findExternalRules binds orphan_rules ext_ids
248 | opt_OmitInterfacePragmas = []
250 = orphan_rules ++ local_rules
252 local_rules = [ (id, rule)
253 | id <- bindersOfBinds binds,
254 id `elemVarEnv` ext_ids,
255 rule <- rulesRules (idSpecialisation id),
256 not (isBuiltinRule rule)
257 -- We can't print builtin rules in interface files
258 -- Since they are built in, an importing module
259 -- will have access to them anyway
263 %************************************************************************
265 \subsection{Step 1: finding externals}
267 %************************************************************************
270 findExternalSet :: [CoreBind] -> [IdCoreRule]
271 -> IdEnv Bool -- In domain => external
272 -- Range = True <=> show unfolding
273 -- Step 1 from the notes above
274 findExternalSet binds orphan_rules
275 = foldr find init_needed binds
277 orphan_rule_ids :: IdSet
278 orphan_rule_ids = unionVarSets [ ruleSomeFreeVars isLocalId rule
279 | (_, rule) <- orphan_rules]
280 init_needed :: IdEnv Bool
281 init_needed = mapUFM (\_ -> False) orphan_rule_ids
282 -- The mapUFM is a bit cheesy. It is a cheap way
283 -- to turn the set of orphan_rule_ids, which we use to initialise
284 -- the sweep, into a mapping saying 'don't expose unfolding'
285 -- (When we come to the binding site we may change our mind, of course.)
287 find (NonRec id rhs) needed
288 | need_id needed id = addExternal (id,rhs) needed
290 find (Rec prs) needed = find_prs prs needed
292 -- For a recursive group we have to look for a fixed point
294 | null needed_prs = needed
295 | otherwise = find_prs other_prs new_needed
297 (needed_prs, other_prs) = partition (need_pr needed) prs
298 new_needed = foldr addExternal needed needed_prs
300 -- The 'needed' set contains the Ids that are needed by earlier
301 -- interface file emissions. If the Id isn't in this set, and isn't
302 -- exported, there's no need to emit anything
303 need_id needed_set id = id `elemVarEnv` needed_set || isExportedId id
304 need_pr needed_set (id,rhs) = need_id needed_set id
306 addExternal :: (Id,CoreExpr) -> IdEnv Bool -> IdEnv Bool
307 -- The Id is needed; extend the needed set
308 -- with it and its dependents (free vars etc)
309 addExternal (id,rhs) needed
310 = extendVarEnv (foldVarSet add_occ needed new_needed_ids)
313 add_occ id needed = extendVarEnv needed id False
314 -- "False" because we don't know we need the Id's unfolding
315 -- We'll override it later when we find the binding site
317 new_needed_ids | opt_OmitInterfacePragmas = emptyVarSet
318 | otherwise = worker_ids `unionVarSet`
319 unfold_ids `unionVarSet`
323 dont_inline = isNeverActive (inlinePragInfo idinfo)
324 loop_breaker = isLoopBreaker (occInfo idinfo)
325 bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
326 spec_ids = rulesRhsFreeVars (specInfo idinfo)
327 worker_info = workerInfo idinfo
329 -- Stuff to do with the Id's unfolding
330 -- The simplifier has put an up-to-date unfolding
331 -- in the IdInfo, but the RHS will do just as well
332 unfolding = unfoldingInfo idinfo
333 rhs_is_small = not (neverUnfold unfolding)
335 -- We leave the unfolding there even if there is a worker
336 -- In GHCI the unfolding is used by importers
337 -- When writing an interface file, we omit the unfolding
338 -- if there is a worker
339 show_unfold = not bottoming_fn && -- Not necessary
342 rhs_is_small && -- Small enough
343 okToUnfoldInHiFile rhs -- No casms etc
345 unfold_ids | show_unfold = exprSomeFreeVars isLocalId rhs
346 | otherwise = emptyVarSet
348 worker_ids = case worker_info of
349 HasWorker work_id _ -> unitVarSet work_id
350 otherwise -> emptyVarSet
354 %************************************************************************
356 \subsection{Step 2: top-level tidying}
358 %************************************************************************
362 type TopTidyEnv = (NameSupply, TidyOccEnv, VarEnv Var)
364 -- TopTidyEnv: when tidying we need to know
365 -- * ns: The NameSupply, containing a unique supply and any pre-ordained Names.
366 -- These may have arisen because the
367 -- renamer read in an interface file mentioning M.$wf, say,
368 -- and assigned it unique r77. If, on this compilation, we've
369 -- invented an Id whose name is $wf (but with a different unique)
370 -- we want to rename it to have unique r77, so that we can do easy
371 -- comparisons with stuff from the interface file
373 -- * occ_env: The TidyOccEnv, which tells us which local occurrences
376 -- * subst_env: A Var->Var mapping that substitutes the new Var for the old
381 tidyTopBind :: Module
382 -> IdEnv Bool -- Domain = Ids that should be external
383 -- True <=> their unfolding is external too
385 -> TopTidyEnv -> CoreBind
386 -> (TopTidyEnv, CoreBind)
388 tidyTopBind mod ext_ids cg_info_env top_tidy_env (NonRec bndr rhs)
389 = ((orig,occ,subst) , NonRec bndr' rhs')
391 ((orig,occ,subst), bndr')
392 = tidyTopBinder mod ext_ids cg_info_env
393 rec_tidy_env rhs' top_tidy_env bndr
394 rec_tidy_env = (occ,subst)
395 rhs' = tidyExpr rec_tidy_env rhs
397 tidyTopBind mod ext_ids cg_info_env top_tidy_env (Rec prs)
398 = (final_env, Rec prs')
400 (final_env@(_,occ,subst), prs') = mapAccumL do_one top_tidy_env prs
401 rec_tidy_env = (occ,subst)
403 do_one top_tidy_env (bndr,rhs)
404 = ((orig,occ,subst), (bndr',rhs'))
406 ((orig,occ,subst), bndr')
407 = tidyTopBinder mod ext_ids cg_info_env
408 rec_tidy_env rhs' top_tidy_env bndr
410 rhs' = tidyExpr rec_tidy_env rhs
412 tidyTopBinder :: Module -> IdEnv Bool -> CgInfoEnv
413 -> TidyEnv -> CoreExpr
414 -- The TidyEnv is used to tidy the IdInfo
415 -- The expr is the already-tided RHS
416 -- Both are knot-tied: don't look at them!
417 -> TopTidyEnv -> Id -> (TopTidyEnv, Id)
418 -- NB: tidyTopBinder doesn't affect the unique supply
420 tidyTopBinder mod ext_ids cg_info_env rec_tidy_env rhs
421 env@(ns2, occ_env2, subst_env2) id
422 -- This function is the heart of Step 2
423 -- The rec_tidy_env is the one to use for the IdInfo
424 -- It's necessary because when we are dealing with a recursive
425 -- group, a variable late in the group might be mentioned
426 -- in the IdInfo of one early in the group
428 -- The rhs is already tidied
430 = ((orig_env', occ_env', subst_env'), id')
432 (orig_env', occ_env', name') = tidyTopName mod ns2 occ_env2
435 ty' = tidyTopType (idType id)
436 idinfo = tidyTopIdInfo rec_tidy_env is_external
437 (idInfo id) unfold_info
438 (lookupCgInfo cg_info_env name')
440 id' = mkVanillaGlobal name' ty' idinfo
442 subst_env' = extendVarEnv subst_env2 id id'
444 maybe_external = lookupVarEnv ext_ids id
445 is_external = isJust maybe_external
447 -- Expose an unfolding if ext_ids tells us to
448 show_unfold = maybe_external `orElse` False
449 unfold_info | show_unfold = mkTopUnfolding rhs
450 | otherwise = noUnfolding
453 -- tidyTopIdInfo creates the final IdInfo for top-level
454 -- binders. There are two delicate pieces:
456 -- * Arity. We assume that the simplifier has just run, so
457 -- that there is a reasonable arity on each binder.
458 -- After CoreTidy, this arity must not change any more.
459 -- Indeed, CorePrep must eta expand where necessary to make
460 -- the manifest arity equal to the claimed arity.
462 -- * CAF info, which comes from the CoreToStg pass via a knot.
463 -- The CAF info will not be looked at by the downstream stuff:
464 -- it *generates* it, and knot-ties it back. It will only be
465 -- looked at by (a) MkIface when generating an interface file
466 -- (b) In GHCi, importing modules
467 -- Nevertheless, we add the info here so that it propagates to all
468 -- occurrences of the binders in RHSs, and hence to occurrences in
469 -- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
471 -- An alterative would be to do a second pass over the unfoldings
472 -- of Ids, and rules, right at the top, but that would be a pain.
474 tidyTopIdInfo tidy_env is_external idinfo unfold_info cg_info
475 | opt_OmitInterfacePragmas || not is_external
476 -- Only basic info if the Id isn't external, or if we don't have -O
479 | otherwise -- Add extra optimisation info
481 `setInlinePragInfo` inlinePragInfo idinfo
482 `setUnfoldingInfo` unfold_info
483 `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
484 -- NB: we throw away the Rules
485 -- They have already been extracted by findExternalRules
488 -- baasic_info is attached to every top-level binder
489 basic_info = vanillaIdInfo
491 `setArityInfo` arityInfo idinfo
492 `setNewStrictnessInfo` newStrictnessInfo idinfo
494 -- This is where we set names to local/global based on whether they really are
495 -- externally visible (see comment at the top of this module). If the name
496 -- was previously local, we have to give it a unique occurrence name if
497 -- we intend to globalise it.
498 tidyTopName mod ns occ_env external name
499 | global && internal = (ns, occ_env, localiseName name)
501 | global && external = (ns, occ_env, name)
502 -- Global names are assumed to have been allocated by the renamer,
503 -- so they already have the "right" unique
504 -- And it's a system-wide unique too
506 | local && internal = (ns_w_local, occ_env', new_local_name)
507 -- Even local, internal names must get a unique occurrence, because
508 -- if we do -split-objs we globalise the name later, in the code generator
510 -- Similarly, we must make sure it has a system-wide Unique, because
511 -- the byte-code generator builds a system-wide Name->BCO symbol table
513 | local && external = case lookupFM ns_names key of
514 Just orig -> (ns, occ_env', orig)
515 Nothing -> (ns_w_global, occ_env', new_global_name)
516 -- If we want to globalise a currently-local name, check
517 -- whether we have already assigned a unique for it.
518 -- If so, use it; if not, extend the table (ns_w_global).
519 -- This is needed when *re*-compiling a module in GHCi; we want to
520 -- use the same name for externally-visible things as we did before.
523 global = isGlobalName name
525 internal = not external
527 (occ_env', occ') = tidyOccName occ_env (nameOccName name)
528 key = (moduleName mod, occ')
529 ns_names = nsNames ns
530 ns_uniqs = nsUniqs ns
531 (us1, us2) = splitUniqSupply ns_uniqs
532 uniq = uniqFromSupply us1
533 loc = nameSrcLoc name
535 new_local_name = mkLocalName uniq occ' loc
536 new_global_name = mkGlobalName uniq mod occ' loc
538 ns_w_local = ns { nsUniqs = us2 }
539 ns_w_global = ns { nsUniqs = us2, nsNames = addToFM ns_names key new_global_name }
542 ------------ Worker --------------
543 tidyWorker tidy_env (HasWorker work_id wrap_arity)
544 = HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
545 tidyWorker tidy_env other
548 ------------ Rules --------------
549 tidyIdRules :: TidyEnv -> [IdCoreRule] -> [IdCoreRule]
550 tidyIdRules env [] = []
551 tidyIdRules env ((fn,rule) : rules)
552 = tidyRule env rule =: \ rule ->
553 tidyIdRules env rules =: \ rules ->
554 ((tidyVarOcc env fn, rule) : rules)
556 tidyRule :: TidyEnv -> CoreRule -> CoreRule
557 tidyRule env rule@(BuiltinRule _ _) = rule
558 tidyRule env (Rule name act vars tpl_args rhs)
559 = tidyBndrs env vars =: \ (env', vars) ->
560 map (tidyExpr env') tpl_args =: \ tpl_args ->
561 (Rule name act vars tpl_args (tidyExpr env' rhs))
564 %************************************************************************
566 \subsection{Step 2: inner tidying
568 %************************************************************************
573 -> (TidyEnv, CoreBind)
575 tidyBind env (NonRec bndr rhs)
576 = tidyLetBndr env (bndr,rhs) =: \ (env', bndr') ->
577 (env', NonRec bndr' (tidyExpr env' rhs))
579 tidyBind env (Rec prs)
580 = mapAccumL tidyLetBndr env prs =: \ (env', bndrs') ->
581 map (tidyExpr env') (map snd prs) =: \ rhss' ->
582 (env', Rec (zip bndrs' rhss'))
585 tidyExpr env (Var v) = Var (tidyVarOcc env v)
586 tidyExpr env (Type ty) = Type (tidyType env ty)
587 tidyExpr env (Lit lit) = Lit lit
588 tidyExpr env (App f a) = App (tidyExpr env f) (tidyExpr env a)
589 tidyExpr env (Note n e) = Note (tidyNote env n) (tidyExpr env e)
591 tidyExpr env (Let b e)
592 = tidyBind env b =: \ (env', b') ->
593 Let b' (tidyExpr env' e)
595 tidyExpr env (Case e b alts)
596 = tidyBndr env b =: \ (env', b) ->
597 Case (tidyExpr env e) b (map (tidyAlt env') alts)
599 tidyExpr env (Lam b e)
600 = tidyBndr env b =: \ (env', b) ->
601 Lam b (tidyExpr env' e)
604 tidyAlt env (con, vs, rhs)
605 = tidyBndrs env vs =: \ (env', vs) ->
606 (con, vs, tidyExpr env' rhs)
608 tidyNote env (Coerce t1 t2) = Coerce (tidyType env t1) (tidyType env t2)
609 tidyNote env note = note
613 %************************************************************************
615 \subsection{Tidying up non-top-level binders}
617 %************************************************************************
620 tidyVarOcc (_, var_env) v = case lookupVarEnv var_env v of
624 -- tidyBndr is used for lambda and case binders
625 tidyBndr :: TidyEnv -> Var -> (TidyEnv, Var)
627 | isTyVar var = tidyTyVarBndr env var
628 | otherwise = tidyIdBndr env var
630 tidyBndrs :: TidyEnv -> [Var] -> (TidyEnv, [Var])
631 tidyBndrs env vars = mapAccumL tidyBndr env vars
633 tidyLetBndr :: TidyEnv -> (Id, CoreExpr) -> (TidyEnv, Var)
634 -- Used for local (non-top-level) let(rec)s
635 tidyLetBndr env (id,rhs)
636 = ((tidy_env,new_var_env), final_id)
638 ((tidy_env,var_env), new_id) = tidyIdBndr env id
640 -- We need to keep around any interesting strictness and demand info
641 -- because later on we may need to use it when converting to A-normal form.
643 -- f (g x), where f is strict in its argument, will be converted
644 -- into case (g x) of z -> f z by CorePrep, but only if f still
645 -- has its strictness info.
647 -- Similarly for the demand info - on a let binder, this tells
648 -- CorePrep to turn the let into a case.
650 -- Similarly arity info for eta expansion in CorePrep
651 final_id = new_id `setIdInfo` new_info
653 new_info = vanillaIdInfo
654 `setArityInfo` arityInfo idinfo
655 `setNewStrictnessInfo` newStrictnessInfo idinfo
656 `setNewDemandInfo` newDemandInfo idinfo
658 -- Override the env we get back from tidyId with the new IdInfo
659 -- so it gets propagated to the usage sites.
660 new_var_env = extendVarEnv var_env id final_id
662 tidyIdBndr :: TidyEnv -> Id -> (TidyEnv, Id)
663 tidyIdBndr env@(tidy_env, var_env) id
664 = -- Non-top-level variables
666 -- Give the Id a fresh print-name, *and* rename its type
667 -- The SrcLoc isn't important now,
668 -- though we could extract it from the Id
670 -- All nested Ids now have the same IdInfo, namely none,
671 -- which should save some space.
672 (tidy_env', occ') = tidyOccName tidy_env (getOccName id)
673 ty' = tidyType env (idType id)
674 id' = mkUserLocal occ' (idUnique id) ty' noSrcLoc
675 var_env' = extendVarEnv var_env id id'
677 ((tidy_env', var_env'), id')