Use instance type in Object::IsErrorObject().

src/objects.cc

 // Copyright 2015 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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <sstream>
 
@@ skipping 1273 matching lines @@
   RETURN_ON_EXCEPTION_VALUE(isolate, Execution::Call(isolate, setter, receiver,
                                                      arraysize(argv), argv),
                             Nothing<bool>());
   return Just(true);
 }
 
 
 // static
 bool Object::IsErrorObject(Isolate* isolate, Handle<Object> object) {
   if (!object->IsJSObject()) return false;
-  // Use stack_trace_symbol as proxy for [[ErrorData]].
-  Handle<Name> symbol = isolate->factory()->stack_trace_symbol();
-  Maybe<bool> has_stack_trace =
-      JSReceiver::HasOwnProperty(Handle<JSReceiver>::cast(object), symbol);
-  DCHECK(!has_stack_trace.IsNothing());
-  return has_stack_trace.FromJust();
+  Handle<JSReceiver> receiver = Handle<JSReceiver>::cast(object);

[Toon Verwaest, 2016/06/23 12:04:39]

since you know it's a JSObject, you might as well cast to that :)

[Franzi, 2016/06/23 14:10:19]

Done.

+  return receiver->map()->instance_type() == JS_ERROR_TYPE;
 }
 
 
 // static
 bool JSObject::AllCanRead(LookupIterator* it) {
   // Skip current iteration, it's in state ACCESS_CHECK or INTERCEPTOR, both of
   // which have already been checked.
   DCHECK(it->state() == LookupIterator::ACCESS_CHECK ||
          it->state() == LookupIterator::INTERCEPTOR);
   for (it->Next(); it->IsFound(); it->Next()) {
@@ skipping 17543 matching lines @@
   } else {
     // Old-style generators.
     int offset = continuation();
     CHECK(0 <= offset && offset < function()->code()->instruction_size());
     return function()->code()->SourcePosition(offset);
   }
 }
 
 }  // namespace internal
 }  // namespace v8