[esnext] prototype runtime implementation for async functions

src/runtime/runtime-generator.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 "src/arguments.h"
 #include "src/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
 
 RUNTIME_FUNCTION(Runtime_CreateJSGeneratorObject) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 1);
-  RUNTIME_ASSERT(function->shared()->is_generator());
+  RUNTIME_ASSERT(function->shared()->is_generator() ||
+                 function->shared()->is_async());
 
   Handle<JSGeneratorObject> generator =
       isolate->factory()->NewJSGeneratorObject(function);
   generator->set_function(*function);
   generator->set_context(isolate->context());
   generator->set_receiver(*receiver);
   generator->set_operand_stack(isolate->heap()->empty_fixed_array());
   generator->set_continuation(JSGeneratorObject::kGeneratorExecuting);
   return *generator;
 }
 
 
 RUNTIME_FUNCTION(Runtime_SuspendJSGeneratorObject) {
   HandleScope handle_scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator_object, 0);
 
   JavaScriptFrameIterator stack_iterator(isolate);
   JavaScriptFrame* frame = stack_iterator.frame();
-  RUNTIME_ASSERT(frame->function()->shared()->is_generator());
+  RUNTIME_ASSERT(frame->function()->shared()->is_generator() ||
+                 frame->function()->shared()->is_async());
   DCHECK_EQ(frame->function(), generator_object->function());
   DCHECK(frame->function()->shared()->is_compiled());
   DCHECK(!frame->function()->IsOptimized());
 
   // The caller should have saved the context and continuation already.
   DCHECK_EQ(generator_object->context(), Context::cast(frame->context()));
   DCHECK_LT(0, generator_object->continuation());
 
   // We expect there to be at least two values on the operand stack: the return
   // value of the yield expression, and the arguments to this runtime call.
@@ skipping 78 matching lines @@
     int offset = generator->continuation();
     RUNTIME_ASSERT(0 <= offset && offset < code->instruction_size());
     return Smi::FromInt(code->SourcePosition(offset));
   }
 
   return isolate->heap()->undefined_value();
 }
 
 }  // namespace internal
 }  // namespace v8