fix corner case in `reduce_vars` (#4211)

fixes #4210

1 files changed, 7 insertions, 4 deletions

diff --git a/lib/scope.js b/lib/scope.js
index abb50c4f..ef19a530 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -82,10 +82,13 @@ SymbolDef.prototype = {
     redefined: function() {
         var scope = this.defun;
         if (!scope) return;
-        var def = scope.variables.get(this.name);
-        if (!def && scope instanceof AST_Toplevel) def = scope.globals.get(this.name);
-        if (!def || def === this) return;
-        return def.redefined() || def;
+        var name = this.name;
+        var def = scope.variables.get(name)
+            || scope instanceof AST_Toplevel && scope.globals.get(name)
+            || this.orig[0] instanceof AST_SymbolConst && find_if(function(def) {
+                return def.name == name;
+            }, scope.enclosed);
+        if (def && def !== this) return def.redefined() || def;
     },
     unmangleable: function(options) {
         return this.global && !options.toplevel