From 3ff0b9e0c97f9eae70756763354e59fc0d675795 Mon Sep 17 00:00:00 2001
From: Christopher Chedeau <vjeux@fb.com>
Date: Mon, 10 Aug 2015 11:22:36 -0700
Subject: [PATCH] [Fix] --define replaces SymbolRefs in LHS of assignments

See #208 for context
---
 lib/compress.js            | 10 +++++++++-
 test/compress/issue-208.js | 11 +++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 test/compress/issue-208.js

diff --git a/lib/compress.js b/lib/compress.js
index 401a1c75..ac306fc3 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2277,7 +2277,15 @@ merge(Compressor.prototype, {
     });
 
     OPT(AST_SymbolRef, function(self, compressor){
-        if (self.undeclared()) {
+        function isLHS(symbol, parent) {
+            return (
+                parent instanceof AST_Binary &&
+                parent.operator === '=' &&
+                parent.left === symbol
+            );
+        }
+
+        if (self.undeclared() && !isLHS(self, compressor.parent())) {
             var defines = compressor.option("global_defs");
             if (defines && defines.hasOwnProperty(self.name)) {
                 return make_node_from_constant(compressor, defines[self.name], self);
diff --git a/test/compress/issue-208.js b/test/compress/issue-208.js
new file mode 100644
index 00000000..14752b8a
--- /dev/null
+++ b/test/compress/issue-208.js
@@ -0,0 +1,11 @@
+do_not_update_lhs: {
+    options = { global_defs: { DEBUG: false } };
+    input: { DEBUG = false; }
+    expect: { DEBUG = false; }
+}
+
+do_update_rhs: {
+    options = { global_defs: { DEBUG: false } };
+    input: { MY_DEBUG = DEBUG; }
+    expect: { MY_DEBUG = false; }
+}
-- 
2.34.1