[es6] Iterators and generators should "extend" %IteratorPrototype%

test/mjsunit/es6/iterator-prototype.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.
+
+var arrayIteratorPrototype = [].entries().__proto__;
+var iteratorPrototype = arrayIteratorPrototype.__proto__;
+
+assertSame(Object.prototype, Object.getPrototypeOf(iteratorPrototype));
+assertTrue(Object.isExtensible(iteratorPrototype));
+assertSame(0, Object.getOwnPropertyNames(iteratorPrototype).length);
+assertSame(1, Object.getOwnPropertySymbols(iteratorPrototype).length);
+assertSame(Symbol.iterator,
+             Object.getOwnPropertySymbols(iteratorPrototype)[0]);
+
+var descr = Object.getOwnPropertyDescriptor(iteratorPrototype, Symbol.iterator);
+assertTrue(descr.configurable);
+assertFalse(descr.enumerable);
+assertTrue(descr.writable);
+
+var iteratorFunction = descr.value;
+assertSame('function', typeof iteratorFunction);
+assertSame(0, iteratorFunction.length);
+assertSame('[Symbol.iterator]', iteratorFunction.name);
+
+var obj = {};
+assertSame(obj, iteratorFunction.call(obj));
+assertSame(iteratorPrototype, iteratorPrototype[Symbol.iterator]());
+
+var mapIteratorPrototype = new Map().entries().__proto__;
+var setIteratorPrototype = new Set().values().__proto__;
+var stringIteratorPrototype = 'abc'[Symbol.iterator]().__proto__;
+assertSame(iteratorPrototype, mapIteratorPrototype.__proto__);
+assertSame(iteratorPrototype, setIteratorPrototype.__proto__);
+assertSame(iteratorPrototype, stringIteratorPrototype.__proto__);
+
+var typedArrays = [
+  Float32Array,
+  Float64Array,
+  Int16Array,
+  Int32Array,
+  Int8Array,
+  Uint16Array,
+  Uint32Array,
+  Uint8Array,
+  Uint8ClampedArray,
+];
+
+for (var constructor of typedArrays) {
+  var array = new constructor();
+  var iterator = array[Symbol.iterator]();
+  assertSame(iteratorPrototype, iterator.__proto__.__proto__);
+}
+
+function* gen() {}
+assertSame(iteratorPrototype, gen.prototype.__proto__.__proto__);
+var g = gen();
+assertSame(gen.prototype, g.__proto__);
+assertSame(iteratorPrototype, g.__proto__.__proto__.__proto__);