[modules] Implement @@iterator on namespace objects.

src/builtins/builtins-iterator.cc

 // Copyright 2016 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/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
-#include "src/builtins/builtins-utils.h"
+#include "src/frames-inl.h"
 
 namespace v8 {
 namespace internal {
 
 void Builtins::Generate_IteratorPrototypeIterator(
     CodeStubAssembler* assembler) {
   assembler->Return(assembler->Parameter(0));
 }
 
+BUILTIN(ModuleNamespaceIterator) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  Handle<Object> receiver = args.at<Object>(0);
+
+  if (!receiver->IsJSModuleNamespace()) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kIncompatibleMethodReceiver,
+                              isolate->factory()->iterator_symbol(), receiver));
+  }
+  auto ns = Handle<JSModuleNamespace>::cast(receiver);
+
+  Handle<FixedArray> names =
+      KeyAccumulator::GetKeys(ns, KeyCollectionMode::kOwnOnly, SKIP_SYMBOLS)
+          .ToHandleChecked();
+  return *isolate->factory()->NewJSFixedArrayIterator(names);
+}
+
+BUILTIN(FixedArrayIteratorNext) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  Handle<Object> receiver = args.at<Object>(0);
+
+  // It is an error if this function is called on anything other than the
+  // particular iterator object for which the function was created.
+  if (!receiver->IsJSFixedArrayIterator() ||
+      Handle<JSFixedArrayIterator>::cast(receiver)->initial_next() !=
+          *args.target<JSFunction>()) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kIncompatibleMethodReceiver,
+                              isolate->factory()->next_string(), receiver));
+  }
+
+  auto iterator = Handle<JSFixedArrayIterator>::cast(receiver);
+  Handle<Object> value;
+  bool done;
+
+  int index = iterator->index();
+  if (index < iterator->array()->length()) {
+    value = handle(iterator->array()->get(index), isolate);
+    done = false;
+    iterator->set_index(index + 1);
+  } else {
+    value = isolate->factory()->undefined_value();
+    done = true;
+  }
+
+  return *isolate->factory()->NewJSIteratorResult(value, done);
+}
+
 }  // namespace internal
 }  // namespace v8