import CmdLineOpts ( DynFlags, DynFlag(..), opt_OmitInterfacePragmas )
import CoreSyn
import CoreUnfold ( noUnfolding, mkTopUnfolding, okToUnfoldInHiFile )
-import CoreFVs ( ruleSomeFreeVars, exprSomeFreeVars,
- ruleSomeLhsFreeVars )
+import CoreFVs ( ruleLhsFreeIds, ruleRhsFreeVars, exprSomeFreeVars )
+import PprCore ( pprIdCoreRule )
import CoreLint ( showPass, endPass )
+import CoreUtils ( exprArity )
import VarEnv
import VarSet
-import Var ( Id, Var, varName )
+import Var ( Id, Var )
import Id ( idType, idInfo, idName, isExportedId,
idSpecialisation, idUnique,
- mkVanillaGlobal, isLocalId, isImplicitId,
- hasNoBinding, mkUserLocal
+ mkVanillaGlobal, isLocalId,
+ isImplicitId, mkUserLocal, setIdInfo
)
import IdInfo {- loads of stuff -}
-import Name ( getOccName, nameOccName, globaliseName, setNameOcc,
- localiseName, isGlobalName, isLocalName
+import NewDemand ( isBottomingSig, topSig )
+import BasicTypes ( isNeverActive )
+import Name ( getOccName, nameOccName, mkInternalName, mkExternalName,
+ localiseName, isExternalName, nameSrcLoc
)
import NameEnv ( filterNameEnv )
import OccName ( TidyOccEnv, initTidyOccEnv, tidyOccName )
-import Type ( tidyTopType, tidyType, tidyTyVar )
+import Type ( tidyTopType, tidyType, tidyTyVarBndr )
import Module ( Module, moduleName )
import HscTypes ( PersistentCompilerState( pcs_PRS ),
PersistentRenamerState( prsOrig ),
- NameSupply( nsNames ), OrigNameCache,
- TypeEnv, extendTypeEnvList,
+ NameSupply( nsNames, nsUniqs ),
+ TypeEnv, extendTypeEnvList, typeEnvIds,
ModDetails(..), TyThing(..)
)
import FiniteMap ( lookupFM, addToFM )
-import Maybes ( maybeToBool, orElse )
-import ErrUtils ( showPass )
+import Maybes ( orElse )
+import ErrUtils ( showPass, dumpIfSet_core )
import SrcLoc ( noSrcLoc )
import UniqFM ( mapUFM )
+import UniqSupply ( splitUniqSupply, uniqFromSupply )
import List ( partition )
import Util ( mapAccumL )
+import Maybe ( isJust )
import Outputable
\end{code}
Step 2: Tidy the program
~~~~~~~~~~~~~~~~~~~~~~~~
-Next we traverse the bindings top to bottom. For each top-level
+Next we traverse the bindings top to bottom. For each *top-level*
binder
- - Make all external Ids have Global names and vice versa
+ 1. Make it into a GlobalId
+
+ 2. Give it a system-wide Unique.
+ [Even non-exported things need system-wide Uniques because the
+ byte-code generator builds a single Name->BCO symbol table.]
+
+ We use the NameSupply kept in the PersistentRenamerState as the
+ source of such system-wide uniques.
+
+ For external Ids, use the original-name cache in the NameSupply
+ to ensure that the unique assigned is the same as the Id had
+ in any previous compilation run.
+
+ 3. If it's an external Id, make it have a global Name, otherwise
+ make it have a local Name.
This is used by the code generator to decide whether
to make the label externally visible
- - Give external ids a "tidy" occurrence name. This means
+ 4. Give external Ids a "tidy" occurrence name. This means
we can print them in interface files without confusing
"x" (unique 5) with "x" (unique 10).
- - Give external Ids the same Unique as they had before
- if the name is in the renamer's name cache
-
- - Give the Id its UTTERLY FINAL IdInfo; in ptic,
+ 5. Give it its UTTERLY FINAL IdInfo; in ptic,
* Its IdDetails becomes VanillaGlobal, reflecting the fact that
from now on we regard it as a global, not local, Id
; let ext_ids = findExternalSet binds_in orphans_in
; let ext_rules = findExternalRules binds_in orphans_in ext_ids
+ -- findExternalRules filters ext_rules to avoid binders that
+ -- aren't externally visible; but the externally-visible binders
+ -- are computed (by findExternalSet) assuming that all orphan
+ -- rules are exported. So in fact we may export more than we
+ -- need. (It's a sort of mutual recursion.)
- ; let ((orig_env', occ_env, subst_env), tidy_binds)
+ -- We also make sure to avoid any exported binders. Consider
+ -- f{-u1-} = 1 -- Local decl
+ -- ...
+ -- f{-u2-} = 2 -- Exported decl
+ --
+ -- The second exported decl must 'get' the name 'f', so we
+ -- have to put 'f' in the avoids list before we get to the first
+ -- decl. tidyTopId then does a no-op on exported binders.
+ ; let prs = pcs_PRS pcs
+ orig_ns = prsOrig prs
+
+ init_tidy_env = (orig_ns, initTidyOccEnv avoids, emptyVarEnv)
+ avoids = [getOccName name | bndr <- typeEnvIds env_tc,
+ let name = idName bndr,
+ isExternalName name]
+ -- In computing our "avoids" list, we must include
+ -- all implicit Ids
+ -- all things with global names (assigned once and for
+ -- all by the renamer)
+ -- since their names are "taken".
+ -- The type environment is a convenient source of such things.
+
+ ; let ((orig_ns', occ_env, subst_env), tidy_binds)
= mapAccumL (tidyTopBind mod ext_ids cg_info_env)
init_tidy_env binds_in
; let tidy_rules = tidyIdRules (occ_env,subst_env) ext_rules
- ; let prs' = prs { prsOrig = orig { nsNames = orig_env' } }
+ ; let prs' = prs { prsOrig = orig_ns' }
pcs' = pcs { pcs_PRS = prs' }
- ; let final_ids = [ id | bind <- tidy_binds
+ ; let final_ids = [ id
+ | bind <- tidy_binds
, id <- bindersOf bind
- , isGlobalName (idName id)]
+ , isExternalName (idName id)]
-- Dfuns are local Ids that might have
-- changed their unique during tidying
md_binds = tidy_binds }
; endPass dflags "Tidy Core" Opt_D_dump_simpl tidy_binds
+ ; dumpIfSet_core dflags Opt_D_dump_simpl
+ "Tidy Core Rules"
+ (vcat (map pprIdCoreRule tidy_rules))
; return (pcs', tidy_details)
}
- where
- -- We also make sure to avoid any exported binders. Consider
- -- f{-u1-} = 1 -- Local decl
- -- ...
- -- f{-u2-} = 2 -- Exported decl
- --
- -- The second exported decl must 'get' the name 'f', so we
- -- have to put 'f' in the avoids list before we get to the first
- -- decl. tidyTopId then does a no-op on exported binders.
- prs = pcs_PRS pcs
- orig = prsOrig prs
- orig_env = nsNames orig
-
- init_tidy_env = (orig_env, initTidyOccEnv avoids, emptyVarEnv)
- avoids = [getOccName bndr | bndr <- bindersOfBinds binds_in,
- isGlobalName (idName bndr)]
tidyCoreExpr :: CoreExpr -> IO CoreExpr
tidyCoreExpr expr = return (tidyExpr emptyTidyEnv expr)
-- in interface files, because they are needed by importing modules when
-- using the compilation manager
- -- We keep constructor workers, because they won't appear
+ -- We keep implicit Ids, because they won't appear
-- in the bindings from which final_ids are derived!
- keep_it (AnId id) = hasNoBinding id -- Remove all Ids except constructor workers
+ keep_it (AnId id) = isImplicitId id -- Remove all Ids except implicit ones
keep_it other = True -- Keep all TyCons and Classes
\end{code}
findExternalRules binds orphan_rules ext_ids
| opt_OmitInterfacePragmas = []
| otherwise
- = orphan_rules ++ local_rules
+ = filter needed_rule (orphan_rules ++ local_rules)
where
local_rules = [ (id, rule)
| id <- bindersOfBinds binds,
id `elemVarEnv` ext_ids,
- rule <- rulesRules (idSpecialisation id),
- not (isBuiltinRule rule),
- -- We can't print builtin rules in interface files
- -- Since they are built in, an importing module
- -- will have access to them anyway
-
- -- Sept 00: I've disabled this test. It doesn't stop
- -- many, if any, rules from coming out, and to make it
- -- work properly we need to add ????
- -- (put it back in for now)
- isEmptyVarSet (ruleSomeLhsFreeVars (isLocalName . varName) rule)
-
- -- Spit out a rule only if none of its LHS free
- -- vars are LocalName things i.e. things that
- -- aren't visible to importing modules This is a
- -- good reason not to do it when we emit the Id
- -- itself
+ rule <- rulesRules (idSpecialisation id)
]
+ needed_rule (id, rule)
+ = not (isBuiltinRule rule)
+ -- We can't print builtin rules in interface files
+ -- Since they are built in, an importing module
+ -- will have access to them anyway
+
+ && not (any internal_id (varSetElems (ruleLhsFreeIds rule)))
+ -- Don't export a rule whose LHS mentions an Id that
+ -- is completely internal (i.e. not visible to an
+ -- importing module)
+
+ internal_id id = isLocalId id && not (id `elemVarEnv` ext_ids)
\end{code}
%************************************************************************
= foldr find init_needed binds
where
orphan_rule_ids :: IdSet
- orphan_rule_ids = unionVarSets [ ruleSomeFreeVars isLocalId rule
+ orphan_rule_ids = unionVarSets [ ruleRhsFreeVars rule
| (_, rule) <- orphan_rules]
init_needed :: IdEnv Bool
init_needed = mapUFM (\_ -> False) orphan_rule_ids
spec_ids
idinfo = idInfo id
- dont_inline = isNeverInlinePrag (inlinePragInfo idinfo)
+ dont_inline = isNeverActive (inlinePragInfo idinfo)
loop_breaker = isLoopBreaker (occInfo idinfo)
- bottoming_fn = isBottomingStrictness (strictnessInfo idinfo)
+ bottoming_fn = isBottomingSig (newStrictnessInfo idinfo `orElse` topSig)
spec_ids = rulesRhsFreeVars (specInfo idinfo)
worker_info = workerInfo idinfo
\begin{code}
-type TopTidyEnv = (OrigNameCache, TidyOccEnv, VarEnv Var)
+type TopTidyEnv = (NameSupply, TidyOccEnv, VarEnv Var)
-- TopTidyEnv: when tidying we need to know
--- * orig_env: Any pre-ordained Names. These may have arisen because the
+-- * ns: The NameSupply, containing a unique supply and any pre-ordained Names.
+-- These may have arisen because the
-- renamer read in an interface file mentioning M.$wf, say,
-- and assigned it unique r77. If, on this compilation, we've
-- invented an Id whose name is $wf (but with a different unique)
= ((orig,occ,subst) , NonRec bndr' rhs')
where
((orig,occ,subst), bndr')
- = tidyTopBinder mod ext_ids cg_info_env rec_tidy_env rhs' top_tidy_env bndr
+ = tidyTopBinder mod ext_ids cg_info_env
+ rec_tidy_env rhs rhs' top_tidy_env bndr
rec_tidy_env = (occ,subst)
rhs' = tidyExpr rec_tidy_env rhs
= ((orig,occ,subst), (bndr',rhs'))
where
((orig,occ,subst), bndr')
- = tidyTopBinder mod ext_ids cg_info_env
- rec_tidy_env rhs' top_tidy_env bndr
+ = tidyTopBinder mod ext_ids cg_info_env
+ rec_tidy_env rhs rhs' top_tidy_env bndr
rhs' = tidyExpr rec_tidy_env rhs
- -- the CafInfo for a recursive group says whether *any* rhs in
- -- the group may refer indirectly to a CAF (because then, they all do).
- (bndrs, rhss) = unzip prs'
- pred v = v `notElem` bndrs
-
-
-tidyTopBinder :: Module -> IdEnv Bool
- -> CgInfoEnv
- -> TidyEnv -> CoreExpr
- -- The TidyEnv is used to tidy the IdInfo
- -- The expr is the already-tided RHS
- -- Both are knot-tied: don't look at them!
+tidyTopBinder :: Module -> IdEnv Bool -> CgInfoEnv
+ -> TidyEnv -- The TidyEnv is used to tidy the IdInfo
+ -> CoreExpr -- RHS *before* tidying
+ -> CoreExpr -- RHS *after* tidying
+ -- The TidyEnv and the after-tidying RHS are
+ -- both are knot-tied: don't look at them!
-> TopTidyEnv -> Id -> (TopTidyEnv, Id)
-- NB: tidyTopBinder doesn't affect the unique supply
-tidyTopBinder mod ext_ids cg_info_env tidy_env rhs
- env@(orig_env2, occ_env2, subst_env2) id
-
- | isImplicitId id -- Don't mess with constructors,
- = (env, id) -- record selectors, and the like
-
- | otherwise
+tidyTopBinder mod ext_ids cg_info_env rec_tidy_env rhs tidy_rhs
+ env@(ns2, occ_env2, subst_env2) id
-- This function is the heart of Step 2
- -- The second env is the one to use for the IdInfo
+ -- The rec_tidy_env is the one to use for the IdInfo
-- It's necessary because when we are dealing with a recursive
-- group, a variable late in the group might be mentioned
-- in the IdInfo of one early in the group
= ((orig_env', occ_env', subst_env'), id')
where
- (orig_env', occ_env', name') = tidyTopName mod orig_env2 occ_env2
+ (orig_env', occ_env', name') = tidyTopName mod ns2 occ_env2
is_external
(idName id)
- ty' = tidyTopType (idType id)
- cg_info = lookupCgInfo cg_info_env name'
- idinfo' = tidyIdInfo tidy_env is_external unfold_info cg_info id
+ ty' = tidyTopType (idType id)
+ idinfo = tidyTopIdInfo rec_tidy_env is_external
+ (idInfo id) unfold_info arity
+ (lookupCgInfo cg_info_env name')
+
+ id' = mkVanillaGlobal name' ty' idinfo
- id' = mkVanillaGlobal name' ty' idinfo'
subst_env' = extendVarEnv subst_env2 id id'
maybe_external = lookupVarEnv ext_ids id
- is_external = maybeToBool maybe_external
+ is_external = isJust maybe_external
-- Expose an unfolding if ext_ids tells us to
+ -- Remember that ext_ids maps an Id to a Bool:
+ -- True to show the unfolding, False to hide it
show_unfold = maybe_external `orElse` False
- unfold_info | show_unfold = mkTopUnfolding rhs
+ unfold_info | show_unfold = mkTopUnfolding tidy_rhs
| otherwise = noUnfolding
+ -- Usually the Id will have an accurate arity on it, because
+ -- the simplifier has just run, but not always.
+ -- One case I found was when the last thing the simplifier
+ -- did was to let-bind a non-atomic argument and then float
+ -- it to the top level. So it seems more robust just to
+ -- fix it here.
+ arity = exprArity rhs
-tidyIdInfo tidy_env is_external unfold_info cg_info id
- | opt_OmitInterfacePragmas || not is_external
- -- No IdInfo if the Id isn't external, or if we don't have -O
- = vanillaIdInfo
- `setCgInfo` cg_info
- `setStrictnessInfo` strictnessInfo core_idinfo
- -- Keep strictness; it's used by CorePrep
- | otherwise
- = vanillaIdInfo
- `setCgInfo` cg_info
- `setCprInfo` cprInfo core_idinfo
- `setStrictnessInfo` strictnessInfo core_idinfo
- `setInlinePragInfo` inlinePragInfo core_idinfo
- `setUnfoldingInfo` unfold_info
- `setWorkerInfo` tidyWorker tidy_env (workerInfo core_idinfo)
- -- NB: we throw away the Rules
- -- They have already been extracted by findExternalRules
- where
- core_idinfo = idInfo id
+-- tidyTopIdInfo creates the final IdInfo for top-level
+-- binders. There are two delicate pieces:
+--
+-- * Arity. After CoreTidy, this arity must not change any more.
+-- Indeed, CorePrep must eta expand where necessary to make
+-- the manifest arity equal to the claimed arity.
+--
+-- * CAF info, which comes from the CoreToStg pass via a knot.
+-- The CAF info will not be looked at by the downstream stuff:
+-- it *generates* it, and knot-ties it back. It will only be
+-- looked at by (a) MkIface when generating an interface file
+-- (b) In GHCi, importing modules
+-- Nevertheless, we add the info here so that it propagates to all
+-- occurrences of the binders in RHSs, and hence to occurrences in
+-- unfoldings, which are inside Ids imported by GHCi. Ditto RULES.
+--
+-- An alterative would be to do a second pass over the unfoldings
+-- of Ids, and rules, right at the top, but that would be a pain.
+
+tidyTopIdInfo tidy_env is_external idinfo unfold_info arity cg_info
+ | opt_OmitInterfacePragmas || not is_external
+ -- Only basic info if the Id isn't external, or if we don't have -O
+ = basic_info
+
+ | otherwise -- Add extra optimisation info
+ = basic_info
+ `setInlinePragInfo` inlinePragInfo idinfo
+ `setUnfoldingInfo` unfold_info
+ `setWorkerInfo` tidyWorker tidy_env (workerInfo idinfo)
+ -- NB: we throw away the Rules
+ -- They have already been extracted by findExternalRules
+
+ where
+ -- baasic_info is attached to every top-level binder
+ basic_info = vanillaIdInfo
+ `setCgInfo` cg_info
+ `setArityInfo` arity
+ `setAllStrictnessInfo` newStrictnessInfo idinfo
-- This is where we set names to local/global based on whether they really are
-- externally visible (see comment at the top of this module). If the name
-- was previously local, we have to give it a unique occurrence name if
--- we intend to globalise it.
-tidyTopName mod orig_env occ_env external name
- | global && internal = (orig_env, occ_env, localiseName name)
+-- we intend to externalise it.
+tidyTopName mod ns occ_env external name
+ | global && internal = (ns, occ_env, localiseName name)
- | local && internal = (orig_env, occ_env', setNameOcc name occ')
- -- Even local, internal names must get a unique occurrence, because
- -- if we do -split-objs we globalise the name later, n the code generator
-
- | global && external = (orig_env, occ_env, name)
+ | global && external = (ns, occ_env, name)
-- Global names are assumed to have been allocated by the renamer,
-- so they already have the "right" unique
+ -- And it's a system-wide unique too
- | local && external = case lookupFM orig_env key of
- Just orig -> (orig_env, occ_env', orig)
- Nothing -> (addToFM orig_env key global_name, occ_env', global_name)
- -- If we want to globalise a currently-local name, check
+ | local && internal = (ns_w_local, occ_env', new_local_name)
+ -- Even local, internal names must get a unique occurrence, because
+ -- if we do -split-objs we externalise the name later, in the code generator
+ --
+ -- Similarly, we must make sure it has a system-wide Unique, because
+ -- the byte-code generator builds a system-wide Name->BCO symbol table
+
+ | local && external = case lookupFM ns_names key of
+ Just orig -> (ns, occ_env', orig)
+ Nothing -> (ns_w_global, occ_env', new_external_name)
+ -- If we want to externalise a currently-local name, check
-- whether we have already assigned a unique for it.
- -- If so, use it; if not, extend the table
+ -- If so, use it; if not, extend the table (ns_w_global).
+ -- This is needed when *re*-compiling a module in GHCi; we want to
+ -- use the same name for externally-visible things as we did before.
where
- (occ_env', occ') = tidyOccName occ_env (nameOccName name)
- key = (moduleName mod, occ')
- global_name = globaliseName (setNameOcc name occ') mod
- global = isGlobalName name
+ global = isExternalName name
local = not global
internal = not external
+ (occ_env', occ') = tidyOccName occ_env (nameOccName name)
+ key = (moduleName mod, occ')
+ ns_names = nsNames ns
+ ns_uniqs = nsUniqs ns
+ (us1, us2) = splitUniqSupply ns_uniqs
+ uniq = uniqFromSupply us1
+ loc = nameSrcLoc name
+
+ new_local_name = mkInternalName uniq occ' loc
+ new_external_name = mkExternalName uniq mod occ' loc
+
+ ns_w_local = ns { nsUniqs = us2 }
+ ns_w_global = ns { nsUniqs = us2, nsNames = addToFM ns_names key new_external_name }
+
+
------------ Worker --------------
tidyWorker tidy_env (HasWorker work_id wrap_arity)
= HasWorker (tidyVarOcc tidy_env work_id) wrap_arity
((tidyVarOcc env fn, rule) : rules)
tidyRule :: TidyEnv -> CoreRule -> CoreRule
-tidyRule env rule@(BuiltinRule _) = rule
-tidyRule env (Rule name vars tpl_args rhs)
+tidyRule env rule@(BuiltinRule _ _) = rule
+tidyRule env (Rule name act vars tpl_args rhs)
= tidyBndrs env vars =: \ (env', vars) ->
map (tidyExpr env') tpl_args =: \ tpl_args ->
- (Rule name vars tpl_args (tidyExpr env' rhs))
+ (Rule name act vars tpl_args (tidyExpr env' rhs))
\end{code}
%************************************************************************
-> (TidyEnv, CoreBind)
tidyBind env (NonRec bndr rhs)
- = tidyBndrWithRhs env (bndr,rhs) =: \ (env', bndr') ->
+ = tidyLetBndr env (bndr,rhs) =: \ (env', bndr') ->
(env', NonRec bndr' (tidyExpr env' rhs))
tidyBind env (Rec prs)
- = mapAccumL tidyBndrWithRhs env prs =: \ (env', bndrs') ->
+ = mapAccumL tidyLetBndr env prs =: \ (env', bndrs') ->
map (tidyExpr env') (map snd prs) =: \ rhss' ->
(env', Rec (zip bndrs' rhss'))
-- tidyBndr is used for lambda and case binders
tidyBndr :: TidyEnv -> Var -> (TidyEnv, Var)
tidyBndr env var
- | isTyVar var = tidyTyVar env var
- | otherwise = tidyId env var
+ | isTyVar var = tidyTyVarBndr env var
+ | otherwise = tidyIdBndr env var
tidyBndrs :: TidyEnv -> [Var] -> (TidyEnv, [Var])
tidyBndrs env vars = mapAccumL tidyBndr env vars
--- tidyBndrWithRhs is used for let binders
-tidyBndrWithRhs :: TidyEnv -> (Id, CoreExpr) -> (TidyEnv, Var)
-tidyBndrWithRhs env (id,rhs) = tidyId env id
-
-tidyId :: TidyEnv -> Id -> (TidyEnv, Id)
-tidyId env@(tidy_env, var_env) id
- = -- Non-top-level variables
+tidyLetBndr :: TidyEnv -> (Id, CoreExpr) -> (TidyEnv, Var)
+-- Used for local (non-top-level) let(rec)s
+tidyLetBndr env (id,rhs)
+ = ((tidy_env,new_var_env), final_id)
+ where
+ ((tidy_env,var_env), new_id) = tidyIdBndr env id
+
+ -- We need to keep around any interesting strictness and demand info
+ -- because later on we may need to use it when converting to A-normal form.
+ -- eg.
+ -- f (g x), where f is strict in its argument, will be converted
+ -- into case (g x) of z -> f z by CorePrep, but only if f still
+ -- has its strictness info.
+ --
+ -- Similarly for the demand info - on a let binder, this tells
+ -- CorePrep to turn the let into a case.
+ --
+ -- Similarly arity info for eta expansion in CorePrep
+ final_id = new_id `setIdInfo` new_info
+ idinfo = idInfo id
+ new_info = vanillaIdInfo
+ `setArityInfo` exprArity rhs
+ `setAllStrictnessInfo` newStrictnessInfo idinfo
+ `setNewDemandInfo` newDemandInfo idinfo
+
+ -- Override the env we get back from tidyId with the new IdInfo
+ -- so it gets propagated to the usage sites.
+ new_var_env = extendVarEnv var_env id final_id
+
+-- Non-top-level variables
+tidyIdBndr :: TidyEnv -> Id -> (TidyEnv, Id)
+tidyIdBndr env@(tidy_env, var_env) id
+ = -- do this pattern match strictly, otherwise we end up holding on to
+ -- stuff in the OccName.
+ case tidyOccName tidy_env (getOccName id) of { (tidy_env', occ') ->
let
-- Give the Id a fresh print-name, *and* rename its type
-- The SrcLoc isn't important now,
-- though we could extract it from the Id
--
- -- All local Ids now have the same IdInfo, which should save some
- -- space.
- (tidy_env', occ') = tidyOccName tidy_env (getOccName id)
- ty' = tidyType (tidy_env,var_env) (idType id)
+ -- All nested Ids now have the same IdInfo, namely none,
+ -- which should save some space.
+ ty' = tidyType env (idType id)
id' = mkUserLocal occ' (idUnique id) ty' noSrcLoc
var_env' = extendVarEnv var_env id id'
in
((tidy_env', var_env'), id')
+ }
\end{code}
\begin{code}