ES6: Tighten up Object.prototype.__proto__

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index 24b0c51c19f6b2c43a025e09003d9174ef6cb0fd..34f5d903a14d262d33cb1d48fe555e5d36e1938c 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -1384,15 +1384,19 @@ function ObjectIs(obj1, obj2) {
 }
 
 
-// Harmony __proto__ getter.
+// ECMA-262, Edition 6, section B.2.2.1.1
 function ObjectGetProto() {
-  return %GetPrototype(this);
+  return %GetPrototype(ToObject(this));
 }
 
 
-// Harmony __proto__ setter.
-function ObjectSetProto(obj) {
-  return %SetPrototype(this, obj);
+// ECMA-262, Edition 6, section B.2.2.1.2
+function ObjectSetProto(proto) {
+  CHECK_OBJECT_COERCIBLE(this, "Object.prototype.__proto__");
+
+  if (IS_SPEC_OBJECT(proto) || IS_NULL(proto) && IS_SPEC_OBJECT(this)) {
+    %SetPrototype(this, proto);
+  }
 }