Implement DefineOwnProperty for TypedArrays

test/mjsunit/element-accessor.js

 // Copyright 2015 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: --allow-natives-syntax
 
 (function () {
   var o = [];
   o.__proto__ = {};
 
@@ skipping 11 matching lines @@
   Object.defineProperty(o, "3", {
     get:function() { return 100; },
     set:function(v) { set = v; }});
 
   store(o, 3, 1000);
   assertEquals(1000, set);
   assertEquals(100, o[3]);
 })();
 
 (function () {
-  var o = new Int32Array();
-  Object.defineProperty(o, "0", {get: function(){}});
+  var o = new Int32Array(1);

[Henrique Ferreiro, 2016/11/15 13:07:55]

I assumed that we are checking particularly for accessors, not an out-of-bounds
index

[caitp, 2016/11/15 15:10:57]

Why not test both?

[Henrique Ferreiro, 2016/11/15 22:03:13]

Well, this test is called element-accessor.js, there are already tests for that
in mjsunit/es6/indexed-integer-exotics.js.

+  assertThrows('Object.defineProperty(o, "0", {get: function(){}})');
   assertEquals(undefined, Object.getOwnPropertyDescriptor(o, "0"));

[caitp, 2016/11/15 15:10:57]

isn't this assertion going to fail with this change?

[Henrique Ferreiro, 2016/11/15 22:03:13]

It returns 'undefined', as it used to do. I don't understand why that would
change.

[caitp, 2016/11/15 22:13:50]

It shouldn't return undefined, because it _should_ be `{ value: 0, writable:
true, enumerable: true, configurable: false }`, based on the logic in
https://tc39.github.io/ecma262/#sec-integer-indexed-exotic-objects-getownprop...

[caitp, 2016/11/15 22:17:01]

in detail, the typed array is created via
https://tc39.github.io/ecma262/#sec-typedarray-length, so it has a length of 1,
so "0"'s canonical numeric index is less than length, so it returns this
predefined descriptor.

If it's returning undefined, then something is wrong in this code

 })();
 
 (function() {
   function f() {
     var a = new Array();
     a[1] = 1.5;
     return a;
   }
 
   f();
   f();
   %OptimizeFunctionOnNextCall(f);
   var a = f();
   a[2] = 2;
   assertEquals(3, a.length);
 })();