From 77f7ae5ba2449c38751c444263106603edb587ef Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Mon, 15 Nov 2021 13:35:54 +0000
Subject: [PATCH] fix corner case in `join_vars` (#5176)

fixes #5175
---
 lib/compress.js            |  2 +-
 test/compress/join_vars.js | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/compress.js b/lib/compress.js
index 2f5233bb..a4232ed2 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -3500,7 +3500,7 @@ merge(Compressor.prototype, {
             var exprs = extract_exprs(body);
             if (!exprs) return;
             var trimmed = false;
-            for (var i = exprs.length; --i >= 0;) {
+            for (var i = exprs.length - (keep || 0); --i >= 0;) {
                 var expr = exprs[i];
                 if (!can_trim(expr)) continue;
                 var tail;
diff --git a/test/compress/join_vars.js b/test/compress/join_vars.js
index 94612c4b..e2c54be1 100644
--- a/test/compress/join_vars.js
+++ b/test/compress/join_vars.js
@@ -1293,3 +1293,26 @@ assign_sequence_var: {
         "1 2 3",
     ]
 }
+
+issue_5175: {
+    options = {
+        join_vars: true,
+    }
+    input: {
+        function log(f) {
+            console.log(f(), A.p);
+        }
+        log(function() {
+            return (A = {}).p = "PASS";
+        });
+    }
+    expect: {
+        function log(f) {
+            console.log(f(), A.p);
+        }
+        log(function() {
+            return (A = {}).p = "PASS";
+        });
+    }
+    expect_stdout: "PASS PASS"
+}