From 72805ea73a18a93793b0f3f5c64512a057d46e94 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Wed, 24 Feb 2021 21:31:12 +0000
Subject: [PATCH] fix corner case in `collapse_vars` (#4686)

fixes #4685
---
 lib/compress.js         |  4 +++-
 test/compress/arrows.js | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/compress.js b/lib/compress.js
index 5c38e407..ae96b764 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2119,7 +2119,9 @@ merge(Compressor.prototype, {
                             }
                             arg = null;
                         }
-                        if (node instanceof AST_ObjectIdentity && (fn_strict || !tw.find_parent(AST_Scope))) {
+                        if (node instanceof AST_ObjectIdentity && (fn_strict
+                            || !tw.find_parent(AST_Scope)
+                            || is_arrow(arg) && iife instanceof AST_New)) {
                             arg = null;
                             return true;
                         }
diff --git a/test/compress/arrows.js b/test/compress/arrows.js
index 096503d6..a3a46871 100644
--- a/test/compress/arrows.js
+++ b/test/compress/arrows.js
@@ -703,3 +703,24 @@ issue_4666: {
     expect_stdout: "true"
     node_version: ">=4"
 }
+
+issue_4685: {
+    options = {
+        collapse_vars: true,
+        unused: true,
+    }
+    input: {
+        new function(f) {
+            if (f() !== this)
+                console.log("PASS");
+        }(() => this);
+    }
+    expect: {
+        new function(f) {
+            if (f() !== this)
+                console.log("PASS");
+        }(() => this);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=4"
+}
-- 
2.34.1