From e23a10f7f96cda932c605988d2d99bb5225d18a5 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Sun, 17 Jan 2021 22:36:59 +0000
Subject: [PATCH] fix corner case in `loops` (#4565)

fixes #4564
---
 lib/compress.js        |  2 +-
 test/compress/loops.js | 30 ++++++++++++++++++++++++++++++
 test/reduce.js         |  2 +-
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index d5334a95..81511535 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -6169,7 +6169,7 @@ merge(Compressor.prototype, {
                 var def = sym.definition();
                 if (def.scope !== self) {
                     var d = find_variable(sym.name);
-                    if ((d && d.redefined() || d) === def) return;
+                    if (d === def || d && d.redefined() === def) return;
                 }
                 node.object.walk(tw);
                 return true;
diff --git a/test/compress/loops.js b/test/compress/loops.js
index d76e7f74..a6d0277b 100644
--- a/test/compress/loops.js
+++ b/test/compress/loops.js
@@ -1280,3 +1280,33 @@ issue_4355: {
     }
     expect_stdout: "PASS"
 }
+
+issue_4564: {
+    options = {
+        loops: true,
+        unused: true,
+    }
+    input: {
+        try {
+            throw null;
+        } catch (a) {
+            var a;
+            (function() {
+                for (a in "foo");
+            })();
+            console.log(a);
+        }
+    }
+    expect: {
+        try {
+            throw null;
+        } catch (a) {
+            var a;
+            (function() {
+                for (a in "foo");
+            })();
+            console.log(a);
+        }
+    }
+    expect_stdout: "2"
+}
diff --git a/test/reduce.js b/test/reduce.js
index c478da5f..91df8bce 100644
--- a/test/reduce.js
+++ b/test/reduce.js
@@ -666,7 +666,7 @@ function has_loopcontrol(body, loop, label) {
 }
 
 function is_error(result) {
-    return typeof result == "object" && typeof result.name == "string" && typeof result.message == "string";
+    return result && typeof result.name == "string" && typeof result.message == "string";
 }
 
 function is_timed_out(result) {
-- 
2.34.1