fix corner case in `reduce_vars` (#4654)

fixes #4653

1 files changed, 14 insertions, 11 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 5adeb566..b4f9c3a8 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -853,18 +853,21 @@ merge(Compressor.prototype, {
             }
             return true;
 
-            function walk_prop(node) {
-                if (node instanceof AST_Dot) {
-                    walk_prop(node.expression);
-                } else if (node instanceof AST_Sub) {
-                    walk_prop(node.expression);
-                    node.property.walk(tw);
-                } else if (node instanceof AST_SymbolRef) {
-                    var d = node.definition();
-                    push_ref(d, node);
-                    node.fixed = d.fixed;
+            function walk_prop(lhs) {
+                if (lhs instanceof AST_Dot) {
+                    walk_prop(lhs.expression);
+                } else if (lhs instanceof AST_Sub) {
+                    walk_prop(lhs.expression);
+                    lhs.property.walk(tw);
+                } else if (lhs instanceof AST_SymbolRef) {
+                    var d = lhs.definition();
+                    push_ref(d, lhs);
+                    if (d.fixed) {
+                        lhs.fixed = d.fixed;
+                        lhs.fixed.assigns = [ node ];
+                    }
                 } else {
-                    node.walk(tw);
+                    lhs.walk(tw);
                 }
             }
         });