Add @@iterator support for strings

test/mjsunit/harmony/string-iterator.js

+// Copyright 2014 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: --harmony-iteration
+
+
+function TestStringPrototypeIterator() {
+  assertTrue(String.prototype.hasOwnProperty(Symbol.iterator));
+  assertFalse("".hasOwnProperty(Symbol.iterator));
+  assertFalse("".propertyIsEnumerable(Symbol.iterator));
+}
+TestStringPrototypeIterator();
+
+
+function assertIteratorResult(value, done, result) {
+  assertEquals({value: value, done: done}, result);
+}
+
+
+function TestManualIteration() {
+  var string = "abc";
+  var iterator = string[Symbol.iterator]();
+  assertIteratorResult('a', false, iterator.next());
+  assertIteratorResult('b', false, iterator.next());
+  assertIteratorResult('c', false, iterator.next());
+  assertIteratorResult(void 0, true, iterator.next());
+  assertIteratorResult(void 0, true, iterator.next());
+}
+TestManualIteration();
+
+
+function TestSurrogatePairs() {
+  var lo = "\uD834";
+  var hi = "\uDF06";
+  var pair = lo + hi;
+  var string = "abc" + pair + "def" + lo + pair + hi + lo;
+  var iterator = string[Symbol.iterator]();
+  assertIteratorResult('a', false, iterator.next());
+  assertIteratorResult('b', false, iterator.next());
+  assertIteratorResult('c', false, iterator.next());
+  assertIteratorResult(pair, false, iterator.next());
+  assertIteratorResult('d', false, iterator.next());
+  assertIteratorResult('e', false, iterator.next());
+  assertIteratorResult('f', false, iterator.next());
+  assertIteratorResult(lo, false, iterator.next());
+  assertIteratorResult(pair, false, iterator.next());
+  assertIteratorResult(hi, false, iterator.next());
+  assertIteratorResult(lo, false, iterator.next());
+  assertIteratorResult(void 0, true, iterator.next());
+  assertIteratorResult(void 0, true, iterator.next());
+}
+TestSurrogatePairs();
+
+
+function TestStringIteratorPrototype() {
+  var iterator = ""[Symbol.iterator]();
+  var StringIteratorPrototype = iterator.__proto__;
+  assertFalse(StringIteratorPrototype.hasOwnProperty('constructor'));
+  assertEquals(StringIteratorPrototype.__proto__, Object.prototype);
+  assertArrayEquals(['next'],
+      Object.getOwnPropertyNames(StringIteratorPrototype));
+  assertEquals('[object String Iterator]', "" + iterator);
+}
+TestStringIteratorPrototype();
+
+
+function TestForOf() {
+  var lo = "\uD834";
+  var hi = "\uDF06";
+  var pair = lo + hi;
+  var string = "abc" + pair + "def" + lo + pair + hi + lo;
+  var expected = ['a', 'b', 'c', pair, 'd', 'e', 'f', lo, pair, hi, lo];
+
+  var i = 0;
+  for (var char of string) {
+    assertEquals(expected[i++], char);
+  }
+
+  assertEquals(expected.length, i);
+}
+TestForOf();
+
+
+function TestNonOwnSlots() {
+  var iterator = ""[Symbol.iterator]();
+  var object = {__proto__: iterator};
+
+  assertThrows(function() {
+    object.next();

[rossberg, 2014/06/18 09:33:19]

Nit: fits on one line

+  }, TypeError);
+}
+TestNonOwnSlots();