From 91e1e8e647ae2e70fb7a3319af7a5eda4c52d925 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Thu, 12 Jun 2025 17:19:57 +0100
Subject: [PATCH 1/2] [acorn-opt] Use walkPattern for variable declarators too

---
 tools/acorn-optimizer.mjs | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/tools/acorn-optimizer.mjs b/tools/acorn-optimizer.mjs
index 5d8c3fe61bd96..22271d61befb9 100755
--- a/tools/acorn-optimizer.mjs
+++ b/tools/acorn-optimizer.mjs
@@ -243,17 +243,16 @@ function JSDCE(ast, aggressive) {
           let removedHere = 0;
           node.declarations = node.declarations.filter((node) => {
             assert(node.type === 'VariableDeclarator');
-            const id = node.id;
-            if (id.type === 'ObjectPattern' || id.type === 'ArrayPattern') {
-              // TODO: DCE into object patterns, that is, things like
-              //         let { a, b } = ..
-              //         let [ a, b ] = ..
-              return true;
-            }
-            assert(id.type === 'Identifier');
-            const curr = id.name;
-            const value = node.init;
-            const keep = !names.has(curr) || (value && hasSideEffects(value));
+            let keep = node.init && hasSideEffects(node.init);
+            walkPattern(
+              node.id,
+              (value) => {
+                keep ||= hasSideEffects(value);
+              },
+              (boundName) => {
+                keep ||= !names.has(boundName);
+              },
+            );
             if (!keep) removedHere = 1;
             return keep;
           });

From 4ca0dafc45de3604b05059bf02386233516b2169 Mon Sep 17 00:00:00 2001
From: Ingvar Stepanyan <me@rreverser.com>
Date: Thu, 12 Jun 2025 19:37:29 +0100
Subject: [PATCH 2/2] Update JSDCE-objectPattern-output.js

---
 test/js_optimizer/JSDCE-objectPattern-output.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test/js_optimizer/JSDCE-objectPattern-output.js b/test/js_optimizer/JSDCE-objectPattern-output.js
index 18601ccdea310..c4c7893aeb8b4 100644
--- a/test/js_optimizer/JSDCE-objectPattern-output.js
+++ b/test/js_optimizer/JSDCE-objectPattern-output.js
@@ -5,7 +5,6 @@ let z = 50;
 globalThis.f = function([, r]) {
   let {a, b} = r;
   let {z: c} = r;
-  let [, i, {foo: p, bar: q}] = r;
   return g(a, b, c, d, z);
 };