Private fields

src/runtime/runtime-classes.cc

 // 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.
 
 #include "src/runtime/runtime-utils.h"
 
 #include <stdlib.h>
 #include <limits>
 
 #include "src/arguments.h"
@@ skipping 57 matching lines @@
 RUNTIME_FUNCTION(Runtime_ThrowIfStaticPrototype) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Name, name, 0);
   if (Name::Equals(name, isolate->factory()->prototype_string())) {
     return ThrowStaticPrototypeError(isolate);
   }
   return *name;
 }
 
+RUNTIME_FUNCTION(Runtime_ThrowIfMissingPrivateField) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 2);
+  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
+  CONVERT_ARG_HANDLE_CHECKED(Name, name, 1);
+  if (!object->IsJSReceiver() ||
+      !JSReceiver::HasOwnProperty(Handle<JSReceiver>::cast(object), name)
+           .FromMaybe(false)) {  // TODO(bakkot) check this doesn't trigger a
+                                 // proxy trap

[Dan Ehrenberg, 2016/09/10 04:30:28]

Proxy traps aren't triggered on private symbol lookups. You could make a DCHECK
failure to ensure that there's no failure related to this. Probably it's worth
adding a test with the super return trick adding private state to a Proxy,
ensuring that it works and also no Proxy traps are hit.

[bakkot, 2016/09/13 22:05:04]

Added such a test.

+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kMissingPrivateField));
+  }
+  return *object;
+}
 
 RUNTIME_FUNCTION(Runtime_HomeObjectSymbol) {
   DCHECK(args.length() == 0);
   return isolate->heap()->home_object_symbol();
 }
 
 static MaybeHandle<Object> DefineClass(Isolate* isolate,
                                        Handle<Object> super_class,
                                        Handle<JSFunction> constructor,
                                        int start_position, int end_position) {
@@ skipping 302 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_GetSuperConstructor) {
   SealHandleScope shs(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_CHECKED(JSFunction, active_function, 0);
   return active_function->map()->prototype();
 }
 
 }  // namespace internal
 }  // namespace v8