From 9e40abededaae3568e6cd931268cfaa0bd0ffbc0 Mon Sep 17 00:00:00 2001
From: "Alex Lam S.L" <alexlamsl@gmail.com>
Date: Thu, 22 Oct 2020 15:19:47 +0100
Subject: [PATCH] fix corner case in `unused` (#4236)

fixes #4235
---
 lib/compress.js              |  8 +++++---
 test/compress/drop-unused.js | 27 +++++++++++++++++++++++++++
 test/compress/ie8.js         | 18 ++++++++++++++++++
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index ec9fd2a1..e4479ca8 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4774,9 +4774,11 @@ merge(Compressor.prototype, {
                     node.definitions.forEach(function(defn) {
                         var def = defn.name.definition();
                         var_defs_by_id.add(def.id, defn);
-                        var redef = def.redefined();
-                        if (redef && node instanceof AST_Var) var_defs_by_id.add(redef.id, defn);
-                        if ((!drop_vars || (node instanceof AST_Const ? redef : def.const_redefs))
+                        if (node instanceof AST_Var && def.orig[0] instanceof AST_SymbolCatch) {
+                            var redef = def.redefined();
+                            if (redef) var_defs_by_id.add(redef.id, defn);
+                        }
+                        if ((!drop_vars || (node instanceof AST_Const ? def.redefined() : def.const_redefs))
                             && !(def.id in in_use_ids)) {
                             in_use_ids[def.id] = true;
                             in_use.push(def);
diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index 257d7a76..4448bdd8 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -3085,3 +3085,30 @@ issue_4184: {
     }
     expect_stdout: "42"
 }
+
+issue_4235: {
+    options = {
+        inline: true,
+        reduce_vars: true,
+        unused: true,
+        varify: true,
+    }
+    input: {
+        (function() {
+            {
+                const f = 0;
+            }
+            (function f() {
+                var f = console.log(f);
+            })();
+        })();
+    }
+    expect: {
+        (function() {
+            f = console.log(f),
+            void 0;
+            var f;
+        })();
+    }
+    expect_stdout: "undefined"
+}
diff --git a/test/compress/ie8.js b/test/compress/ie8.js
index f2132579..2a7dace3 100644
--- a/test/compress/ie8.js
+++ b/test/compress/ie8.js
@@ -2859,3 +2859,21 @@ issue_4186: {
     }
     expect_stdout: "NaN"
 }
+
+issue_4235: {
+    options = {
+        ie8: true,
+        unused: true,
+    }
+    input: {
+        try {} catch (e) {}
+        console.log(function e() {
+            var e = 0;
+        }());
+    }
+    expect: {
+        try {} catch (e) {}
+        console.log(function e() {}());
+    }
+    expect_stdout: "undefined"
+}