ES6 Unscopables

src/unscopables.h

Index: src/unscopables.h
diff --git a/src/unscopables.h b/src/unscopables.h
new file mode 100644
index 0000000000000000000000000000000000000000..f6e18d5cf11f033c5598c426c345c1b727fe35d5
--- /dev/null
+++ b/src/unscopables.h
@@ -0,0 +1,52 @@
+// 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.
+
+#ifndef V8_UNSCOPABLES_H_

[rossberg, 2014/08/06 09:53:02]

I don't think it's worth putting this into an extra file anymore. I'd even
prefer just inlining the function into Context::Lookup directly.

[arv (Not doing code reviews), 2014/08/06 15:08:28]

Agreed. Now that it is only used in one place.

I moved it to contexts.cc but I decided to keep it as a function for
readability's sake.

+#define V8_UNSCOPABLES_H_
+
+#include "src/isolate.h"
+#include "src/lookup.h"
+#include "src/objects.h"
+#include "src/prototype.h"
+
+namespace v8 {
+namespace internal {
+
+/**
+ * Lookups a property in an object environment, taking the unscopables into
+ * account. This is used For HasBinding spec algorithms for ObjectEnvironment.
+ */
+static Maybe<PropertyAttributes> UnscopableLookup(LookupIterator* it) {
+  Isolate* isolate = it->isolate();
+  PropertyAttributes attrs;
+  if (!JSReceiver::GetPropertyAttributes(it).ToValue(&attrs)) {

[rossberg, 2014/08/06 09:53:02]

I think it's clearer and simpler to avoid ToValue and write this e.g. as

  Maybe<PropertyAttributes> attrs = JSReceiver::GetPropertyAttributes(it);
  DCHECK(isolate->has_pending_exception() || attrs.has_value());
  if (!attrs.has_value() || attrs.value == ABSENT) return attrs;

You then can simply return attrs below.

[arv (Not doing code reviews), 2014/08/06 15:08:28]

Done.

+    DCHECK(isolate->has_pending_exception());
+    return Maybe<PropertyAttributes>();
+  }
+  if (attrs == ABSENT) return maybe(ABSENT);
+
+  Handle<Symbol> unscopables_symbol(
+      isolate->native_context()->unscopables_symbol(), isolate);
+  Handle<Object> receiver = it->GetReceiver();
+  Handle<Object> unscopables;
+  MaybeHandle<Object> maybe_unscopables =
+      Object::GetProperty(receiver, unscopables_symbol);
+  if (!maybe_unscopables.ToHandle(&unscopables)) {
+    return Maybe<PropertyAttributes>();
+  }
+  if (!unscopables->IsSpecObject()) return maybe(attrs);
+  bool blacklist;
+  if (!JSReceiver::HasProperty(Handle<JSReceiver>::cast(unscopables),
+                               it->name()).ToValue(&blacklist)) {
+    DCHECK(isolate->has_pending_exception());
+    return Maybe<PropertyAttributes>();
+  }
+  if (blacklist) return maybe(ABSENT);
+  return maybe(attrs);
+}
+}
+
+}  // namespace v8::internal
+
+#endif  // V8_UNSCOPABLES_H_