Support rest element pattern with user-defined iterable

test/mjsunit/harmony/destructuring-assignment.js

Index: test/mjsunit/harmony/destructuring-assignment.js
diff --git a/test/mjsunit/harmony/destructuring-assignment.js b/test/mjsunit/harmony/destructuring-assignment.js
index bc8c424d8b48f4085e2e9c88a9ef03a837221d1f..1aff4ee2c0ec439b8c587b2a391b8b72b5963c75 100644
--- a/test/mjsunit/harmony/destructuring-assignment.js
+++ b/test/mjsunit/harmony/destructuring-assignment.js
@@ -405,6 +405,28 @@ assertEquals(oz, [1, 2, 3, 4, 5]);
     assertEquals([undefined, undefined, undefined], z);
     assertEquals(9, count);
   })();
+
+  (function cstm() {
+    var idx = 0;
+    var iterable = {};
+    var iterator = {
+      next: function() {
+        idx += 1;
+        return {
+          value: idx,
+          done: idx > 3
+        };
+      }
+    };
+    iterable[Symbol.iterator] = function() {
+      return iterator;
+    };
+    var result;
+
+    [...result] = iterable;
+
+    assertEquals([1, 2, 3], result);
+  })();
 })();
 
 (function testRequireObjectCoercible() {