Bug 1055472 - Part 3: Make the Object constructor properly subclassable. (r=Waldo)

js/src/builtin/Object.cpp

@@ -33,7 +33,12 @@ js::obj_construct(JSContext* cx, unsigned argc, Value* vp)
     CallArgs args = CallArgsFromVp(argc, vp);
 
     RootedObject obj(cx, nullptr);
-    if (args.length() > 0 && !args[0].isNullOrUndefined()) {
+    if (args.isConstructing() && (&args.newTarget().toObject() != &args.callee())) {
+        RootedObject newTarget(cx, &args.newTarget().toObject());
+        obj = CreateThis(cx, &PlainObject::class_, newTarget);
+        if (!obj)
+            return false;
+    } else if (args.length() > 0 && !args[0].isNullOrUndefined()) {
         obj = ToObject(cx, args[0]);
         if (!obj)
             return false;

js/src/tests/ecma_6/Class/extendBuiltinConstructors.js

@@ -16,6 +16,7 @@ function testBuiltin(builtin) {
 
 
 testBuiltin(Function);
+testBuiltin(Object);
 
 `;
 

js/src/tests/ecma_6/Class/superCallBaseInvoked.js

@@ -53,8 +53,6 @@ testBase(p);
 handler.construct = (target, args, nt) => Reflect.construct(target, args, nt);
 testBase(p);
 
-// Object will have to wait for fixed builtins.
-
 `;
 
 if (classesEnabled())