PreParser: track variable declarations and parameters

test/mjsunit/lazy-inner-functions.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --lazy-inner-functions
+
 (function TestLazyInnerFunctionCallsEval() {
   var i = (function eager_outer() {
-    var a = 41; // Should be context-allocated
+    var outer_var = 41; // Should be context-allocated
     function lazy_inner() {
-      return eval("a");
+      return eval("outer_var");
     }
     return lazy_inner;
   })();
+  assertEquals(41, i());
+})();
+
+(function TestLazyInnerFunctionDestructuring() {
+  var i = (function eager_outer() {
+    var outer_var = 41; // Should be context-allocated
+    function lazy_inner() {
+      // This introduces b and refers to outer_var.
+      var {outer_var : b} = {outer_var};
+      return b;
+    }
+    return lazy_inner;
+  })();
   assertEquals(41, i());
 })();