From bfd0ac7f4bd8d5062b480c904c302a56946d7c2a Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Wed, 24 Nov 2021 09:29:26 +0000
Subject: [PATCH] fix corner case in `ie` (#5193)

fixes #5192
---
 lib/compress.js                 |  2 +-
 test/compress/default-values.js | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/lib/compress.js b/lib/compress.js
index 115408d0..b28ac5e2 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -456,7 +456,7 @@ merge(Compressor.prototype, {
     }
 
     function can_drop_symbol(ref, compressor, keep_lambda) {
-        var def = ref.definition();
+        var def = ref.redef || ref.definition();
         if (ref.in_arg && is_funarg(def)) return false;
         return all(def.orig, function(sym) {
             if (sym instanceof AST_SymbolConst || sym instanceof AST_SymbolLet) {
diff --git a/test/compress/default-values.js b/test/compress/default-values.js
index 3a4d1640..a7c0ed27 100644
--- a/test/compress/default-values.js
+++ b/test/compress/default-values.js
@@ -1938,3 +1938,22 @@ issue_5138_2: {
     expect_stdout: "PASS"
     node_version: ">=6"
 }
+
+issue_5192: {
+    options = {
+        dead_code: true,
+        ie: true,
+    }
+    input: {
+        (function a(a,  [] = a = "PASS") {
+            console.log(a);
+        })("FAIL");
+    }
+    expect: {
+        (function a(a,  [] = a = "PASS") {
+            console.log(a);
+        })("FAIL");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}