fix corner case with `collapse_vars` & `ie8` (#3469)

fixes #3468

2 files changed, 3 insertions, 2 deletions

diff --git a/lib/compress.js b/lib/compress.js
index 29ef07c3..06ba43c0 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -896,8 +896,7 @@ merge(Compressor.prototype, {
         if (lhs instanceof AST_This) return true;
         if (lhs instanceof AST_SymbolRef) {
             var def = lhs.definition();
-            return def.orig[0] instanceof AST_SymbolLambda
-                || compressor.exposed(def) && identifier_atom[def.name];
+            return def.lambda || compressor.exposed(def) && identifier_atom[def.name];
         }
         if (lhs instanceof AST_PropAccess) {
             lhs = lhs.expression;
diff --git a/lib/scope.js b/lib/scope.js
index 08c9efd8..83df3fde 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -55,6 +55,7 @@ function SymbolDef(scope, orig, init) {
     this.mangled_name = null;
     this.undeclared = false;
     this.id = SymbolDef.next_id++;
+    this.lambda = orig instanceof AST_SymbolLambda;
 }
 
 SymbolDef.next_id = 1;
@@ -210,6 +211,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
             node.thedef = new_def;
             node.reference(options);
         });
+        if (old_def.lambda) new_def.lambda = true;
     }
 });