From 2a053710bdafde88c305d318ed2e0196d5dcdfc7 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Wed, 16 Sep 2020 20:11:57 +0100
Subject: fix corner case in `merge_vars` (#4116)

fixes #4115
---
 lib/compress.js             |  6 ++++++
 test/compress/merge_vars.js | 26 ++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/lib/compress.js b/lib/compress.js
index a79b909d..e3139054 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4376,6 +4376,12 @@ merge(Compressor.prototype, {
                 pop();
                 return true;
             }
+            if (node instanceof AST_LabeledStatement) {
+                push();
+                node.body.walk(tw);
+                pop();
+                return true;
+            }
             if (node instanceof AST_Scope) {
                 if (node instanceof AST_Lambda) {
                     references[node.variables.get("arguments").id] = false;
diff --git a/test/compress/merge_vars.js b/test/compress/merge_vars.js
index fd650f9d..c63f33d0 100644
--- a/test/compress/merge_vars.js
+++ b/test/compress/merge_vars.js
@@ -486,3 +486,29 @@ issue_4112: {
     }
     expect_stdout: "function"
 }
+
+issue_4115: {
+    options = {
+        merge_vars: true,
+        toplevel: true,
+    }
+    input: {
+        L: {
+            var o = typeof console;
+            for (var k in o)
+                break L;
+            var a = 0;
+        }
+        console.log(typeof a);
+    }
+    expect: {
+        L: {
+            var o = typeof console;
+            for (var k in o)
+                break L;
+            var a = 0;
+        }
+        console.log(typeof a);
+    }
+    expect_stdout: "undefined"
+}
-- 
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