From 7f35d9cee05528574a24cbdad5593403db07cbf0 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Wed, 14 Oct 2020 00:58:04 +0100
Subject: [PATCH] fix corner case in `reduce_vars` (#4219)

fixes #4218
---
 lib/compress.js        |  1 +
 test/compress/const.js | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/lib/compress.js b/lib/compress.js
index b2ed17cf..3e6218a0 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -993,6 +993,7 @@ merge(Compressor.prototype, {
                     return node.value;
                 };
                 d.fixed.assigns = [ node ];
+                if (node.name instanceof AST_SymbolConst && d.redefined()) d.single_use = false;
             } else {
                 d.fixed = false;
             }
diff --git a/test/compress/const.js b/test/compress/const.js
index 27c55ddb..8c04c6b1 100644
--- a/test/compress/const.js
+++ b/test/compress/const.js
@@ -931,6 +931,30 @@ issue_4207: {
     expect_stdout: "0"
 }
 
+issue_4218: {
+    options = {
+        reduce_funcs: true,
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        {
+            const a = function() {};
+            var b = 0 * a;
+        }
+        console.log(typeof a, b);
+    }
+    expect: {
+        {
+            const a = function() {};
+            var b = 0 * a;
+        }
+        console.log(typeof a, b);
+    }
+    expect_stdout: true
+}
+
 issue_4210: {
     options = {
         reduce_vars: true,
-- 
2.34.1