WIP [esnext] implement async iteration proposal

src/runtime/runtime-internal.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 <memory>
 
 #include "src/arguments.h"
 #include "src/ast/prettyprinter.h"
@@ skipping 206 matching lines @@
       NewTypeError(MessageTemplate::kIteratorResultNotAnObject, value));
 }
 
 RUNTIME_FUNCTION(Runtime_ThrowSymbolIteratorInvalid) {
   HandleScope scope(isolate);
   DCHECK_EQ(0, args.length());
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kSymbolIteratorInvalid));
 }
 
+RUNTIME_FUNCTION(Runtime_ThrowSymbolAsyncIteratorInvalid) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 0);
+  THROW_NEW_ERROR_RETURN_FAILURE(
+      isolate, NewTypeError(MessageTemplate::kSymbolAsyncIteratorInvalid));
+}
+
 RUNTIME_FUNCTION(Runtime_ThrowNotGeneric) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, arg0, 0);
   THROW_NEW_ERROR_RETURN_FAILURE(
       isolate, NewTypeError(MessageTemplate::kNotGeneric, arg0));
 }
 
 RUNTIME_FUNCTION(Runtime_ThrowGeneratorRunning) {
   HandleScope scope(isolate);
@@ skipping 248 matching lines @@
       isolate, Object::OrdinaryHasInstance(isolate, callable, object));
 }
 
 RUNTIME_FUNCTION(Runtime_Typeof) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   return *Object::TypeOf(isolate, object);
 }
 
+RUNTIME_FUNCTION(Runtime_CreateAsyncFromSyncIterator) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+
+  CONVERT_ARG_HANDLE_CHECKED(Object, sync_iterator, 0);
+
+  if (!sync_iterator->IsJSReceiver()) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kSymbolIteratorInvalid));
+  }
+
+  return *isolate->factory()->NewJSAsyncFromSyncIterator(
+      Handle<HeapObject>::cast(sync_iterator));
+}
+
 }  // namespace internal
 }  // namespace v8