Implement ES6 Template Literals

src/harmony-templates.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.
+
+'use strict';
+
+function GetTemplateCallSite(cookedStrings, rawStrings) {
+  // TODO(caitp): ensure same template callsite is used for subsequent tag calls
+  var count = cookedStrings.length;
+  var siteObj = new $Array(count);
+  var rawObj = new $Array(count);
+
+  for (var index = 0; index < count; ++index) {
+    var prop = ToString(index);
+    var cookedValue = cookedStrings[index];
+    DefineArrayProperty(siteObj, prop, ToPropertyDescriptor({

[arv (Not doing code reviews), 2014/11/12 15:06:05]

I feel like this is doing too much work.

Nothing in this spec algorithm is observable since we are creating new objects
from internal structures. So given that, we should be able to do something
simpler:

function GetTemplateCallSite(siteObj, rawStrings) {
  %AddNamedProperty(siteObj, "raw", %ObjectFreeze(rawStrings),
      READ_ONLY | DONT_ENUM | DONT_DELETE);
  return %ObjectFreeze(siteObj);
}

(Even if we wanted to create new arrays we should have added the elements using
AddElement. No need to go through descriptors etc.)

[caitp (gmail), 2014/11/12 15:12:32]

Done. It's a lot tinier that way.

+      value: cookedValue,
+      configurable: false,
+      writable: false,
+      enumerable: true
+    }), false);
+    var rawValue = rawStrings[index];
+    DefineArrayProperty(rawObj, prop, ToPropertyDescriptor({
+      value: rawValue,
+      configurable: false,
+      writable: false,
+      enumerable: true
+    }), false);
+  }
+
+  DefineObjectProperty(siteObj, "raw", ToPropertyDescriptor({
+    value: %ObjectFreeze(rawObj),
+    configurable: false,
+    writable: false,
+    enumerable: false
+  }), false);
+
+  return %ObjectFreeze(siteObj);
+}