From c0cc12b92685a54c5def768c86003d2a04191058 Mon Sep 17 00:00:00 2001
From: nsfisis <nsfisis@gmail.com>
Date: Sun, 10 Mar 2024 22:50:45 +0900
Subject: [PATCH] Fix acorn-optimizer error when destructuring array including
 empty element in function parameters

It will fix a problem similar to #20843.

#20843 fixed this case:

```javascript
[, a] = x;
```

This commit will fix this case:

```javascript
function ([, a]) { }
```
---
 test/optimizer/JSDCE-objectPattern-output.js | 2 +-
 test/optimizer/JSDCE-objectPattern.js        | 2 +-
 tools/acorn-optimizer.mjs                    | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/test/optimizer/JSDCE-objectPattern-output.js b/test/optimizer/JSDCE-objectPattern-output.js
index 7aa8f6136f2fb..a797a6a24bc89 100644
--- a/test/optimizer/JSDCE-objectPattern-output.js
+++ b/test/optimizer/JSDCE-objectPattern-output.js
@@ -2,7 +2,7 @@ let d = 40;
 
 let z = 50;
 
-globalThis.f = function(r) {
+globalThis.f = function([, r]) {
  let {a: a, b: b} = r;
  let {z: c} = r;
  let [, i, {foo: p, bar: q}] = r;
diff --git a/test/optimizer/JSDCE-objectPattern.js b/test/optimizer/JSDCE-objectPattern.js
index 934791538ab69..4d26827f47ada 100644
--- a/test/optimizer/JSDCE-objectPattern.js
+++ b/test/optimizer/JSDCE-objectPattern.js
@@ -10,7 +10,7 @@ let d = 40;
 // z.
 let z = 50;
 
-globalThis.f = function(r) {
+globalThis.f = function([/*empty*/, r]) {
   let { a, b } = r;
   let { z: c } = r;
   let [/*empty*/, i, {foo : p, bar : q}] = r;
diff --git a/tools/acorn-optimizer.mjs b/tools/acorn-optimizer.mjs
index f877761d636eb..e808a0058ac89 100755
--- a/tools/acorn-optimizer.mjs
+++ b/tools/acorn-optimizer.mjs
@@ -388,7 +388,7 @@ function runJSDCE(ast, aggressive) {
         }
         if (param.type === 'ArrayPattern') {
           for (var elem of param.elements) {
-            traverse(elem);
+            if (elem) traverse(elem);
           }
         } else if (param.type === 'ObjectPattern') {
           for (var prop of param.properties) {