Fixes issue 712 causing non-configurable accessors to be overwritable by usin...

src/v8natives.js

Index: src/v8natives.js
===================================================================
--- src/v8natives.js	(revision 4684)
+++ src/v8natives.js	(working copy)
@@ -434,6 +434,11 @@
 }
 
 
+PropertyDescriptor.prototype.hasWritable = function() {
+  return this.hasWritable_;
+}
+
+
 PropertyDescriptor.prototype.setConfigurable = function(configurable) {
   this.configurable_ = configurable;
   this.hasConfigurable_ = true;
@@ -537,6 +542,22 @@
     throw MakeTypeError("define_disallowed", ["defineProperty"]);
 
   if (!IS_UNDEFINED(current) && !current.isConfigurable()) {
+      // Step 5 and 6
+     if ((!desc.hasEnumerable() || 
+          SameValue(desc.isEnumerable() && current.isEnumerable())) &&
+         (!desc.hasConfigurable() || 
+          SameValue(desc.isConfigurable(), current.isConfigurable())) &&
+         (!desc.hasWritable() || 
+          SameValue(desc.isWritable(), current.isWritable())) &&
+         (!desc.hasValue() ||
+          SameValue(desc.getValue(), current.getValue())) &&
+         (!desc.hasGetter() ||
+          SameValue(desc.getGet(), current.getGet())) &&
+         (!desc.hasSetter() ||
+          SameValue(desc.getSet(), current.getSet()))) {
+       return true;
+     }
+			
     // Step 7
     if (desc.isConfigurable() ||  desc.isEnumerable() != current.isEnumerable())
       throw MakeTypeError("redefine_disallowed", ["defineProperty"]);
@@ -673,8 +694,9 @@
 // ES5 section 15.2.3.6.
 function ObjectDefineProperty(obj, p, attributes) {
   if ((!IS_SPEC_OBJECT_OR_NULL(obj) || IS_NULL_OR_UNDEFINED(obj)) &&
-      !IS_UNDETECTABLE(obj))
+      !IS_UNDETECTABLE(obj)) {
     throw MakeTypeError("obj_ctor_property_non_object", ["defineProperty"]);
+  }
   var name = ToString(p);
   var desc = ToPropertyDescriptor(attributes);
   DefineOwnProperty(obj, name, desc, true);