WIP [esnext] implement async iteration proposal

src/builtins/builtins-function.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/code-factory.h"
 #include "src/code-stub-assembler.h"
 #include "src/compiler.h"
 #include "src/string-builder.h"
@@ skipping 145 matching lines @@
   // Do not lazily compute eval position for AsyncFunction, as they may not be
   // determined after the function is resumed.
   Handle<JSFunction> func = Handle<JSFunction>::cast(maybe_func);
   Handle<Script> script = handle(Script::cast(func->shared()->script()));
   int position = script->GetEvalPosition();
   USE(position);
 
   return *func;
 }
 
+BUILTIN(AsyncGeneratorFunctionConstructor) {
+  HandleScope scope(isolate);
+  Handle<Object> maybe_func;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, maybe_func,
+      CreateDynamicFunction(isolate, args, "async function*"));
+  if (!maybe_func->IsJSFunction()) return *maybe_func;
+
+  // Do not lazily compute eval position for AsyncFunction, as they may not be
+  // determined after the function is resumed.
+  Handle<JSFunction> func = Handle<JSFunction>::cast(maybe_func);
+  Handle<Script> script = handle(Script::cast(func->shared()->script()));
+  int position = script->GetEvalPosition();
+  USE(position);
+
+  return *func;
+}
+
 namespace {
 
 Object* DoFunctionBind(Isolate* isolate, BuiltinArguments args) {
   HandleScope scope(isolate);
   DCHECK_LE(1, args.length());
   if (!args.receiver()->IsCallable()) {
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate, NewTypeError(MessageTemplate::kFunctionBind));
   }
 
@@ skipping 290 matching lines @@
 
   Node* f = assembler.Parameter(0);
   Node* v = assembler.Parameter(1);
   Node* context = assembler.Parameter(4);
   Node* result = assembler.OrdinaryHasInstance(context, f, v);
   assembler.Return(result);
 }
 
 }  // namespace internal
 }  // namespace v8