X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FcoreSyn%2FCoreSubst.lhs;h=7ca5a6787be15b3c95169877a0673f886cc57847;hp=8ca99fa18a5f789e27e15f357e1ce920a748f481;hb=a51fe79ebcdcb8285573a18f12cade2101533419;hpb=064812423073e89805c16311728cfded5d50e306 diff --git a/compiler/coreSyn/CoreSubst.lhs b/compiler/coreSyn/CoreSubst.lhs index 8ca99fa..7ca5a67 100644 --- a/compiler/coreSyn/CoreSubst.lhs +++ b/compiler/coreSyn/CoreSubst.lhs @@ -12,7 +12,8 @@ module CoreSubst ( -- ** Substituting into expressions and related types deShadowBinds, substSpec, substRulesForImportedIds, - substTy, substExpr, substBind, substUnfolding, + substTy, substExpr, substExprSC, substBind, substBindSC, + substUnfolding, substUnfoldingSC, substUnfoldingSource, lookupIdSubst, lookupTvSubst, substIdOcc, -- ** Operations on substitutions @@ -27,7 +28,7 @@ module CoreSubst ( cloneIdBndr, cloneIdBndrs, cloneRecIdBndrs, -- ** Simple expression optimiser - simpleOptExpr + simpleOptPgm, simpleOptExpr ) where #include "HsVersions.h" @@ -35,11 +36,13 @@ module CoreSubst ( import CoreSyn import CoreFVs import CoreUtils -import OccurAnal( occurAnalyseExpr ) +import PprCore +import OccurAnal( occurAnalyseExpr, occurAnalysePgm ) import qualified Type import Type ( Type, TvSubst(..), TvSubstEnv ) -import Coercion ( optCoercion ) +import Coercion ( isIdentityCoercion ) +import OptCoercion ( optCoercion ) import VarSet import VarEnv import Id @@ -49,6 +52,8 @@ import IdInfo import Unique import UniqSupply import Maybes +import ErrUtils +import DynFlags ( DynFlags, DynFlag(..) ) import BasicTypes ( isAlwaysActive ) import Outputable import PprCore () -- Instances @@ -202,7 +207,7 @@ extendTvSubstList (Subst in_scope ids tvs) prs = Subst in_scope ids (extendVarEn -- 'extendIdSubst' and 'extendTvSubst' extendSubst :: Subst -> Var -> CoreArg -> Subst extendSubst (Subst in_scope ids tvs) tv (Type ty) - = ASSERT( isTyVar tv ) Subst in_scope ids (extendVarEnv tvs tv ty) + = ASSERT( isTyCoVar tv ) Subst in_scope ids (extendVarEnv tvs tv ty) extendSubst (Subst in_scope ids tvs) id expr = ASSERT( isId id ) Subst in_scope (extendVarEnv ids id expr) tvs @@ -212,13 +217,13 @@ extendSubstList subst [] = subst extendSubstList subst ((var,rhs):prs) = extendSubstList (extendSubst subst var rhs) prs -- | Find the substitution for an 'Id' in the 'Subst' -lookupIdSubst :: Subst -> Id -> CoreExpr -lookupIdSubst (Subst in_scope ids _) v +lookupIdSubst :: SDoc -> Subst -> Id -> CoreExpr +lookupIdSubst doc (Subst in_scope ids _) v | not (isLocalId v) = Var v | Just e <- lookupVarEnv ids v = e | Just v' <- lookupInScope in_scope v = Var v' -- Vital! See Note [Extending the Subst] - | otherwise = WARN( True, ptext (sLit "CoreSubst.lookupIdSubst") <+> ppr v $$ ppr in_scope ) + | otherwise = WARN( True, ptext (sLit "CoreSubst.lookupIdSubst") <+> ppr v $$ ppr in_scope $$ doc) Var v -- | Find the substitution for a 'TyVar' in the 'Subst' @@ -282,24 +287,37 @@ instance Outputable Subst where -- -- Do *not* attempt to short-cut in the case of an empty substitution! -- See Note [Extending the Subst] -substExpr :: Subst -> CoreExpr -> CoreExpr -substExpr subst expr +substExprSC :: SDoc -> Subst -> CoreExpr -> CoreExpr +substExprSC _doc subst orig_expr + | isEmptySubst subst = orig_expr + | otherwise = -- pprTrace "enter subst-expr" (doc $$ ppr orig_expr) $ + subst_expr subst orig_expr + +substExpr :: SDoc -> Subst -> CoreExpr -> CoreExpr +substExpr _doc subst orig_expr = subst_expr subst orig_expr + +subst_expr :: Subst -> CoreExpr -> CoreExpr +subst_expr subst expr = go expr where - go (Var v) = lookupIdSubst subst v + go (Var v) = lookupIdSubst (text "subst_expr") subst v go (Type ty) = Type (substTy subst ty) go (Lit lit) = Lit lit go (App fun arg) = App (go fun) (go arg) go (Note note e) = Note (go_note note) (go e) - go (Cast e co) = Cast (go e) (optCoercion (getTvSubst subst) co) + go (Cast e co) + | isIdentityCoercion co' = go e + | otherwise = Cast (go e) co' + where + co' = optCoercion (getTvSubst subst) co -- Optimise coercions as we go; this is good, for example -- in the RHS of rules, which are only substituted in - go (Lam bndr body) = Lam bndr' (substExpr subst' body) + go (Lam bndr body) = Lam bndr' (subst_expr subst' body) where (subst', bndr') = substBndr subst bndr - go (Let bind body) = Let bind' (substExpr subst' body) + go (Let bind body) = Let bind' (subst_expr subst' body) where (subst', bind') = substBind subst bind @@ -307,7 +325,7 @@ substExpr subst expr where (subst', bndr') = substBndr subst bndr - go_alt subst (con, bndrs, rhs) = (con, bndrs', substExpr subst' rhs) + go_alt subst (con, bndrs, rhs) = (con, bndrs', subst_expr subst' rhs) where (subst', bndrs') = substBndrs subst bndrs @@ -315,16 +333,32 @@ substExpr subst expr -- | Apply a substititon to an entire 'CoreBind', additionally returning an updated 'Subst' -- that should be used by subsequent substitutons. -substBind :: Subst -> CoreBind -> (Subst, CoreBind) -substBind subst (NonRec bndr rhs) = (subst', NonRec bndr' (substExpr subst rhs)) +substBind, substBindSC :: Subst -> CoreBind -> (Subst, CoreBind) + +substBindSC subst bind -- Short-cut if the substitution is empty + | not (isEmptySubst subst) + = substBind subst bind + | otherwise + = case bind of + NonRec bndr rhs -> (subst', NonRec bndr' rhs) + where + (subst', bndr') = substBndr subst bndr + Rec pairs -> (subst', Rec (bndrs' `zip` rhss')) + where + (bndrs, rhss) = unzip pairs + (subst', bndrs') = substRecBndrs subst bndrs + rhss' | isEmptySubst subst' = rhss + | otherwise = map (subst_expr subst') rhss + +substBind subst (NonRec bndr rhs) = (subst', NonRec bndr' (subst_expr subst rhs)) where (subst', bndr') = substBndr subst bndr -substBind subst (Rec pairs) = (subst', Rec pairs') +substBind subst (Rec pairs) = (subst', Rec (bndrs' `zip` rhss')) where - (subst', bndrs') = substRecBndrs subst (map fst pairs) - pairs' = bndrs' `zip` rhss' - rhss' = map (substExpr subst' . snd) pairs + (bndrs, rhss) = unzip pairs + (subst', bndrs') = substRecBndrs subst bndrs + rhss' = map (subst_expr subst') rhss \end{code} \begin{code} @@ -359,8 +393,8 @@ preserve occ info in rules. -- 'IdInfo' is preserved by this process, although it is substituted into appropriately. substBndr :: Subst -> Var -> (Subst, Var) substBndr subst bndr - | isTyVar bndr = substTyVarBndr subst bndr - | otherwise = substIdBndr subst subst bndr + | isTyCoVar bndr = substTyVarBndr subst bndr + | otherwise = substIdBndr (text "var-bndr") subst subst bndr -- | Applies 'substBndr' to a number of 'Var's, accumulating a new 'Subst' left-to-right substBndrs :: Subst -> [Var] -> (Subst, [Var]) @@ -371,18 +405,20 @@ substRecBndrs :: Subst -> [Id] -> (Subst, [Id]) substRecBndrs subst bndrs = (new_subst, new_bndrs) where -- Here's the reason we need to pass rec_subst to subst_id - (new_subst, new_bndrs) = mapAccumL (substIdBndr new_subst) subst bndrs + (new_subst, new_bndrs) = mapAccumL (substIdBndr (text "rec-bndr") new_subst) subst bndrs \end{code} \begin{code} -substIdBndr :: Subst -- ^ Substitution to use for the IdInfo +substIdBndr :: SDoc + -> Subst -- ^ Substitution to use for the IdInfo -> Subst -> Id -- ^ Substitition and Id to transform -> (Subst, Id) -- ^ Transformed pair -- NB: unfolding may be zapped -substIdBndr rec_subst subst@(Subst in_scope env tvs) old_id - = (Subst (in_scope `extendInScopeSet` new_id) new_env tvs, new_id) +substIdBndr _doc rec_subst subst@(Subst in_scope env tvs) old_id + = -- pprTrace "substIdBndr" (doc $$ ppr old_id $$ ppr in_scope) $ + (Subst (in_scope `extendInScopeSet` new_id) new_env tvs, new_id) where id1 = uniqAway in_scope old_id -- id1 is cloned if necessary id2 | no_type_change = id1 @@ -414,7 +450,7 @@ It also unconditionally zaps the OccInfo. \begin{code} -- | Very similar to 'substBndr', but it always allocates a new 'Unique' for --- each variable in its output and removes all 'IdInfo' +-- each variable in its output. It substitutes the IdInfo though. cloneIdBndr :: Subst -> UniqSupply -> Id -> (Subst, Id) cloneIdBndr subst us old_id = clone_id subst subst (old_id, uniqFromSupply us) @@ -493,7 +529,6 @@ substIdType subst@(Subst _ _ tv_env) id ------------------ -- | Substitute into some 'IdInfo' with regard to the supplied new 'Id'. --- Always zaps the unfolding, to save substitution work substIdInfo :: Subst -> Id -> IdInfo -> Maybe IdInfo substIdInfo subst new_id info | nothing_to_do = Nothing @@ -507,22 +542,27 @@ substIdInfo subst new_id info ------------------ -- | Substitutes for the 'Id's within an unfolding -substUnfolding :: Subst -> Unfolding -> Unfolding +substUnfolding, substUnfoldingSC :: Subst -> Unfolding -> Unfolding -- Seq'ing on the returned Unfolding is enough to cause -- all the substitutions to happen completely -substUnfolding subst (DFunUnfolding con args) - = DFunUnfolding con (map (substExpr subst) args) + +substUnfoldingSC subst unf -- Short-cut version + | isEmptySubst subst = unf + | otherwise = substUnfolding subst unf + +substUnfolding subst (DFunUnfolding ar con args) + = DFunUnfolding ar con (map (substExpr (text "dfun-unf") subst) args) substUnfolding subst unf@(CoreUnfolding { uf_tmpl = tmpl, uf_src = src }) -- Retain an InlineRule! - | not (isInlineRuleSource src) -- Always zap a CoreUnfolding, to save substitution work + | not (isStableSource src) -- Zap an unstable unfolding, to save substitution work = NoUnfolding - | otherwise -- But keep an InlineRule! + | otherwise -- But keep a stable one! = seqExpr new_tmpl `seq` new_src `seq` unf { uf_tmpl = new_tmpl, uf_src = new_src } where - new_tmpl = substExpr subst tmpl + new_tmpl = substExpr (text "subst-unf") subst tmpl new_src = substUnfoldingSource subst src substUnfolding _ unf = unf -- NoUnfolding, OtherCon @@ -533,24 +573,25 @@ substUnfoldingSource (Subst in_scope ids _) (InlineWrapper wkr) | Just wkr_expr <- lookupVarEnv ids wkr = case wkr_expr of Var w1 -> InlineWrapper w1 - _other -> WARN( True, text "Interesting! CoreSubst.substWorker1:" <+> ppr wkr - <+> equals <+> ppr wkr_expr ) -- Note [Worker inlining] - InlineRule -- It's not a wrapper any more, but still inline it! + _other -> -- WARN( True, text "Interesting! CoreSubst.substWorker1:" <+> ppr wkr + -- <+> ifPprDebug (equals <+> ppr wkr_expr) ) + -- Note [Worker inlining] + InlineStable -- It's not a wrapper any more, but still inline it! | Just w1 <- lookupInScope in_scope wkr = InlineWrapper w1 - | otherwise = WARN( True, text "Interesting! CoreSubst.substWorker2:" <+> ppr wkr ) + | otherwise = -- WARN( True, text "Interesting! CoreSubst.substWorker2:" <+> ppr wkr ) -- This can legitimately happen. The worker has been inlined and -- dropped as dead code, because we don't treat the UnfoldingSource -- as an "occurrence". -- Note [Worker inlining] - InlineRule + InlineStable substUnfoldingSource _ src = src ------------------ substIdOcc :: Subst -> Id -> Id -- These Ids should not be substituted to non-Ids -substIdOcc subst v = case lookupIdSubst subst v of +substIdOcc subst v = case lookupIdSubst (text "substIdOcc") subst v of Var v' -> v' other -> pprPanic "substIdOcc" (vcat [ppr v <+> ppr other, ppr subst]) @@ -567,7 +608,9 @@ substSpec subst new_id (SpecInfo rules rhs_fvs) ------------------ substRulesForImportedIds :: Subst -> [CoreRule] -> [CoreRule] substRulesForImportedIds subst rules - = map (substRule subst (\name -> name)) rules + = map (substRule subst not_needed) rules + where + not_needed name = pprPanic "substRulesForImportedIds" (ppr name) ------------------ substRule :: Subst -> (Name -> Name) -> CoreRule -> CoreRule @@ -581,11 +624,14 @@ substRule :: Subst -> (Name -> Name) -> CoreRule -> CoreRule substRule _ _ rule@(BuiltinRule {}) = rule substRule subst subst_ru_fn rule@(Rule { ru_bndrs = bndrs, ru_args = args - , ru_fn = fn_name, ru_rhs = rhs }) + , ru_fn = fn_name, ru_rhs = rhs + , ru_local = is_local }) = rule { ru_bndrs = bndrs', - ru_fn = subst_ru_fn fn_name, - ru_args = map (substExpr subst') args, - ru_rhs = substExpr subst' rhs } + ru_fn = if is_local + then subst_ru_fn fn_name + else fn_name, + ru_args = map (substExpr (text "subst-rule" <+> ppr fn_name) subst') args, + ru_rhs = substExpr (text "subst-rule" <+> ppr fn_name) subst' rhs } where (subst', bndrs') = substBndrs subst bndrs @@ -595,7 +641,7 @@ substVarSet subst fvs = foldVarSet (unionVarSet . subst_fv subst) emptyVarSet fvs where subst_fv subst fv - | isId fv = exprFreeVars (lookupIdSubst subst fv) + | isId fv = exprFreeVars (lookupIdSubst (text "substVarSet") subst fv) | otherwise = Type.tyVarsOfType (lookupTvSubst subst fv) \end{code} @@ -629,7 +675,8 @@ simpleOptExpr :: CoreExpr -> CoreExpr -- may change radically simpleOptExpr expr - = go init_subst (occurAnalyseExpr expr) + = -- pprTrace "simpleOptExpr" (ppr init_subst $$ ppr expr) + simple_opt_expr init_subst (occurAnalyseExpr expr) where init_subst = mkEmptySubst (mkInScopeSet (exprFreeVars expr)) -- It's potentially important to make a proper in-scope set @@ -642,74 +689,173 @@ simpleOptExpr expr -- It's a bit painful to call exprFreeVars, because it makes -- three passes instead of two (occ-anal, and go) - go subst (Var v) = lookupIdSubst subst v - go subst (App e1 e2) = App (go subst e1) (go subst e2) - go subst (Type ty) = Type (substTy subst ty) - go _ (Lit lit) = Lit lit - go subst (Note note e) = Note note (go subst e) - go subst (Cast e co) = Cast (go subst e) (substTy subst co) - go subst (Let bind body) = go_let subst bind body - go subst (Lam bndr body) = Lam bndr' (go subst' body) - where - (subst', bndr') = substBndr subst bndr +---------------------- +simpleOptPgm :: DynFlags -> [CoreBind] -> [CoreRule] -> IO ([CoreBind], [CoreRule]) +simpleOptPgm dflags binds rules + = do { dumpIfSet_dyn dflags Opt_D_dump_occur_anal "Occurrence analysis" + (pprCoreBindings occ_anald_binds); - go subst (Case e b ty as) = Case (go subst e) b' - (substTy subst ty) - (map (go_alt subst') as) - where - (subst', b') = substBndr subst b - - - ---------------------- - go_alt subst (con, bndrs, rhs) = (con, bndrs', go subst' rhs) - where - (subst', bndrs') = substBndrs subst bndrs + ; return (reverse binds', substRulesForImportedIds subst' rules) } + where + occ_anald_binds = occurAnalysePgm binds rules + (subst', binds') = foldl do_one (emptySubst, []) occ_anald_binds + + do_one (subst, binds') bind + = case simple_opt_bind subst bind of + (subst', Nothing) -> (subst', binds') + (subst', Just bind') -> (subst', bind':binds') + +---------------------- +type InVar = Var +type OutVar = Var +type InId = Id +type OutId = Id +type InExpr = CoreExpr +type OutExpr = CoreExpr + +-- In these functions the substitution maps InVar -> OutExpr + +---------------------- +simple_opt_expr :: Subst -> InExpr -> OutExpr +simple_opt_expr subst expr + = go expr + where + go (Var v) = lookupIdSubst (text "simpleOptExpr") subst v + go (App e1 e2) = App (go e1) (go e2) + go (Type ty) = Type (substTy subst ty) + go (Lit lit) = Lit lit + go (Note note e) = Note note (go e) + go (Cast e co) | isIdentityCoercion co' = go e + | otherwise = Cast (go e) co' + where + co' = substTy subst co + + go (Let bind body) = maybeLet mb_bind (simple_opt_expr subst' body) + where + (subst', mb_bind) = simple_opt_bind subst bind + go lam@(Lam {}) = go_lam [] subst lam + go (Case e b ty as) = Case (go e) b' (substTy subst ty) + (map (go_alt subst') as) + where + (subst', b') = subst_opt_bndr subst b ---------------------- - go_let subst (Rec prs) body - = Let (Rec (reverse rev_prs')) (go subst'' body) + go_alt subst (con, bndrs, rhs) + = (con, bndrs', simple_opt_expr subst' rhs) where - (subst', bndrs') = substRecBndrs subst (map fst prs) - (subst'', rev_prs') = foldl do_pr (subst', []) (prs `zip` bndrs') - do_pr (subst, prs) ((b,r), b') = case go_bind subst b r of - Left subst' -> (subst', prs) - Right r' -> (subst, (b',r'):prs) - - go_let subst (NonRec b r) body - = case go_bind subst b r of - Left subst' -> go subst' body - Right r' -> Let (NonRec b' r') (go subst' body) - where - (subst', b') = substBndr subst b - + (subst', bndrs') = subst_opt_bndrs subst bndrs ---------------------- - go_bind :: Subst -> Var -> CoreExpr -> Either Subst CoreExpr - -- (go_bind subst old_var old_rhs) - -- either extends subst with (old_var -> new_rhs) - -- or return new_rhs for a binding new_var = new_rhs - go_bind subst b r - | Type ty <- r - , isTyVar b -- let a::* = TYPE ty in - = Left (extendTvSubst subst b (substTy subst ty)) - - | isId b -- let x = e in - , safe_to_inline (idOccInfo b) || exprIsTrivial r' - , isAlwaysActive (idInlineActivation b) -- Note [Inline prag in simplOpt] - = Left (extendIdSubst subst b r') - - | otherwise - = Right r' - where - r' = go subst r + -- go_lam tries eta reduction + go_lam bs' subst (Lam b e) + = go_lam (b':bs') subst' e + where + (subst', b') = subst_opt_bndr subst b + go_lam bs' subst e + | Just etad_e <- tryEtaReduce bs e' = etad_e + | otherwise = mkLams bs e' + where + bs = reverse bs' + e' = simple_opt_expr subst e + +---------------------- +simple_opt_bind :: Subst -> CoreBind -> (Subst, Maybe CoreBind) +simple_opt_bind subst (Rec prs) + = (subst'', Just (Rec (reverse rev_prs'))) + where + (subst', bndrs') = subst_opt_bndrs subst (map fst prs) + (subst'', rev_prs') = foldl do_pr (subst', []) (prs `zip` bndrs') + do_pr (subst, prs) ((b,r), b') = case simple_opt_pair subst b r of + Left subst' -> (subst', prs) + Right r' -> (subst, (b2,r'):prs) + where + b2 = add_info subst b b' + +simple_opt_bind subst (NonRec b r) + = case simple_opt_pair subst b r of + Left ext_subst -> (ext_subst, Nothing) + Right r' -> (subst', Just (NonRec b2 r')) + where + (subst', b') = subst_opt_bndr subst b + b2 = add_info subst' b b' + +---------------------- +simple_opt_pair :: Subst -> InVar -> InExpr -> Either Subst OutExpr + -- (simple_opt_pair subst in_var in_rhs) + -- either extends subst with (in_var -> out_rhs) + -- or return out_rhs for a binding out_var = out_rhs +simple_opt_pair subst b r + | Type ty <- r -- let a::* = TYPE ty in + = ASSERT( isTyCoVar b ) + Left (extendTvSubst subst b (substTy subst ty)) + + | isId b -- let x = e in + , safe_to_inline (idOccInfo b) + , isAlwaysActive (idInlineActivation b) -- Note [Inline prag in simplOpt] + , not (isStableUnfolding (idUnfolding b)) + , not (isExportedId b) + = Left (extendIdSubst subst b r') + + | otherwise + = Right r' + where + r' = simple_opt_expr subst r - ---------------------- -- Unconditionally safe to inline safe_to_inline :: OccInfo -> Bool - safe_to_inline IAmDead = True - safe_to_inline (OneOcc in_lam one_br _) = not in_lam && one_br safe_to_inline (IAmALoopBreaker {}) = False - safe_to_inline NoOccInfo = False + safe_to_inline IAmDead = True + safe_to_inline (OneOcc in_lam one_br _) = (not in_lam && one_br) || exprIsTrivial r' + safe_to_inline NoOccInfo = exprIsTrivial r' + +---------------------- +subst_opt_bndr :: Subst -> InVar -> (Subst, OutVar) +subst_opt_bndr subst bndr + | isTyCoVar bndr = substTyVarBndr subst bndr + | otherwise = subst_opt_id_bndr subst bndr + +subst_opt_id_bndr :: Subst -> InId -> (Subst, OutId) +-- Nuke all fragile IdInfo, unfolding, and RULES; +-- it gets added back later by add_info +-- Rather like SimplEnv.substIdBndr +-- +-- It's important to zap fragile OccInfo (which CoreSubst.SubstIdBndr +-- carefully does not do) because simplOptExpr invalidates it + +subst_opt_id_bndr subst@(Subst in_scope id_subst tv_subst) old_id + = (Subst new_in_scope new_id_subst tv_subst, new_id) + where + id1 = uniqAway in_scope old_id + id2 = setIdType id1 (substTy subst (idType old_id)) + new_id = zapFragileIdInfo id2 -- Zaps rules, worker-info, unfolding + -- and fragile OccInfo + new_in_scope = in_scope `extendInScopeSet` new_id + + -- Extend the substitution if the unique has changed, + -- or there's some useful occurrence information + -- See the notes with substTyVarBndr for the delSubstEnv + new_id_subst | new_id /= old_id + = extendVarEnv id_subst old_id (Var new_id) + | otherwise + = delVarEnv id_subst old_id + +---------------------- +subst_opt_bndrs :: Subst -> [InVar] -> (Subst, [OutVar]) +subst_opt_bndrs subst bndrs + = mapAccumL subst_opt_bndr subst bndrs + +---------------------- +add_info :: Subst -> InVar -> OutVar -> OutVar +add_info subst old_bndr new_bndr + | isTyCoVar old_bndr = new_bndr + | otherwise = maybeModifyIdInfo mb_new_info new_bndr + where + mb_new_info = substIdInfo subst new_bndr (idInfo old_bndr) + +---------------------- +maybeLet :: Maybe CoreBind -> CoreExpr -> CoreExpr +maybeLet Nothing e = e +maybeLet (Just b) e = Let b e \end{code} Note [Inline prag in simplOpt] @@ -729,4 +875,5 @@ we don't know what phase we're in. Here's an example bar n = foo n 1 When inlining 'foo' in 'bar' we want the let-binding for 'inner' -to remain visible until Phase 1 \ No newline at end of file +to remain visible until Phase 1 +