Ensure _.map rewrite handles objects with non-numeric length properties correctly.

Former-commit-id: 60a4f322dcd284db5bb8ad4d8d5138e52e14cce3

test/test.js

@@ -41,6 +41,9 @@
   /** Shortcut used to make object properties immutable */
   var freeze = Object.freeze;
 
+  /** Used to set property descriptors */
+  var setDescriptor = Object.defineProperty;
+
   /** Shortcut used to convert array-like objects to arrays */
   var slice = [].slice;
 
@@ -946,6 +949,16 @@
       });
       deepEqual(actual, [1, 2, 3]);
     });
+
+    test('should handle object arguments with non-numeric length properties', function() {
+      if (setDescriptor) {
+        var object = {};
+        setDescriptor(object, 'length', { 'value': 'x' });
+        deepEqual(_.map(object, _.identity), []);
+      } else {
+        skipTest();
+      }
+    });
   }());
 
   /*--------------------------------------------------------------------------*/