From 8334f86f30074c51ae53f4f69399119fbdd7e273 Mon Sep 17 00:00:00 2001
From: alexlamsl <alexlamsl@gmail.com>
Date: Thu, 2 Nov 2017 18:59:01 +0800
Subject: [PATCH] handle `AST_SymbolFunarg`

---
 lib/compress.js              |  7 +++---
 test/compress/reduce_vars.js | 48 +++++++++++++++++++++++++++++++++++-
 2 files changed, 51 insertions(+), 4 deletions(-)

diff --git a/lib/compress.js b/lib/compress.js
index d7b986df..f09f2b9b 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4217,9 +4217,10 @@ merge(Compressor.prototype, {
             if (fixed && d.should_replace === undefined) {
                 var init;
                 if (fixed instanceof AST_This) {
-                    if (all(d.references, function(ref) {
-                        return d.scope === ref.scope;
-                    })) {
+                    if (!(d.orig[0] instanceof AST_SymbolFunarg)
+                        && all(d.references, function(ref) {
+                            return d.scope === ref.scope;
+                        })) {
                         init = fixed;
                     }
                 } else {
diff --git a/test/compress/reduce_vars.js b/test/compress/reduce_vars.js
index 13e469da..5ec5bfde 100644
--- a/test/compress/reduce_vars.js
+++ b/test/compress/reduce_vars.js
@@ -3296,7 +3296,7 @@ escaped_prop: {
     expect_stdout: "2"
 }
 
-issue_2420: {
+issue_2420_1: {
     options = {
         reduce_vars: true,
         unused: true,
@@ -3337,3 +3337,49 @@ issue_2420: {
         "foo",
     ]
 }
+
+issue_2420_2: {
+    options = {
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var t = this;
+            if (t.bar)
+                t.foo();
+            else
+                !function(t) {
+                    console.log(this === t);
+                }(this);
+        }
+        var o = {
+            bar: 1,
+            foo: function() { console.log("foo", this.bar); },
+        };
+        f.call(o);
+        o.bar = 0;
+        f.call(o);
+    }
+    expect: {
+        function f() {
+            if (this.bar)
+                this.foo();
+            else
+                !function(t) {
+                    console.log(this === t);
+                }(this);
+        }
+        var o = {
+            bar: 1,
+            foo: function() { console.log("foo", this.bar); },
+        };
+        f.call(o);
+        o.bar = 0;
+        f.call(o);
+    }
+    expect_stdout: [
+        "foo 1",
+        "false",
+    ]
+}