WIP [esnext] implement async iteration proposal

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 69118b31c42913b7fbd6a4cd34e705abba3c1559..27d878cbc145f07e2445eac0328fd474d22575ae 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -169,6 +169,7 @@ class Genesis BASE_EMBEDDED {
 
   void CreateStrictModeFunctionMaps(Handle<JSFunction> empty);
   void CreateIteratorMaps(Handle<JSFunction> empty);
+  void CreateAsyncIteratorMaps(Handle<JSFunction> empty);
   void CreateAsyncFunctionMaps(Handle<JSFunction> empty);
   void CreateJSProxyMaps();
 
@@ -781,6 +782,137 @@ void Genesis::CreateIteratorMaps(Handle<JSFunction> empty) {
       *generator_object_prototype_map);
 }
 
+static void InstallWithIntrinsicDefaultProto(Isolate* isolate,
+                                             Handle<JSFunction> function,
+                                             int context_index) {
+  Handle<Smi> index(Smi::FromInt(context_index), isolate);
+  JSObject::AddProperty(
+      function, isolate->factory()->native_context_index_symbol(), index, NONE);
+  isolate->native_context()->set(context_index, *function);
+}
+
+void Genesis::CreateAsyncIteratorMaps(Handle<JSFunction> empty) {
+  // Create iterator-related meta-objects.
+  Handle<JSObject> async_iterator_prototype =
+      factory()->NewJSObject(isolate()->object_function(), TENURED);
+
+  Handle<JSFunction> async_iterator_prototype_iterator = SimpleCreateFunction(
+      isolate(), factory()->NewStringFromAsciiChecked("[Symbol.asyncIterator]"),
+      Builtins::kReturnReceiver, 0, true);
+  async_iterator_prototype_iterator->shared()->set_native(true);
+
+  JSObject::AddProperty(async_iterator_prototype,
+                        factory()->async_iterator_symbol(),
+                        async_iterator_prototype_iterator, DONT_ENUM);
+
+  Handle<JSObject> async_from_sync_iterator_prototype =
+      factory()->NewJSObject(isolate()->object_function(), TENURED);
+  SimpleInstallFunction(async_from_sync_iterator_prototype,
+                        factory()->next_string(),
+                        Builtins::kAsyncFromSyncIteratorPrototypeNext, 1, true);
+  SimpleInstallFunction(
+      async_from_sync_iterator_prototype, factory()->return_string(),
+      Builtins::kAsyncFromSyncIteratorPrototypeReturn, 1, true);
+  SimpleInstallFunction(
+      async_from_sync_iterator_prototype, factory()->throw_string(),
+      Builtins::kAsyncFromSyncIteratorPrototypeThrow, 1, true);
+
+  JSObject::AddProperty(
+      async_from_sync_iterator_prototype, factory()->to_string_tag_symbol(),
+      factory()->NewStringFromAsciiChecked("Async-from-Sync Iterator"),
+      static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
+
+  JSObject::ForceSetPrototype(async_from_sync_iterator_prototype,
+                              async_iterator_prototype);
+
+  Handle<Map> async_from_sync_iterator_map = factory()->NewMap(
+      JS_ASYNC_FROM_SYNC_ITERATOR_TYPE, JSAsyncFromSyncIterator::kSize);
+  Map::SetPrototype(async_from_sync_iterator_map,
+                    async_from_sync_iterator_prototype);
+  native_context()->set_initial_async_from_sync_iterator_map(
+      *async_from_sync_iterator_map);
+
+  Handle<String> AsyncGeneratorFunction_string =
+      factory()->NewStringFromAsciiChecked("AsyncGeneratorFunction", TENURED);
+
+  static const bool kUseStrictFunctionMap = true;
+  Handle<JSObject> async_generator_object_prototype =
+      factory()->NewJSObject(isolate()->object_function(), TENURED);
+  Handle<JSObject> async_generator_function_prototype =
+      factory()->NewJSObject(isolate()->object_function(), TENURED);
+
+  Handle<JSFunction> async_generator_function = CreateFunction(
+      isolate(), AsyncGeneratorFunction_string, JS_OBJECT_TYPE,
+      JSObject::kHeaderSize, async_generator_function_prototype,
+      Builtins::kAsyncGeneratorFunctionConstructor, kUseStrictFunctionMap);
+  async_generator_function->shared()->DontAdaptArguments();
+  async_generator_function->shared()->set_length(1);
+  InstallWithIntrinsicDefaultProto(
+      isolate(), async_generator_function,
+      Context::ASYNC_GENERATOR_FUNCTION_FUNCTION_INDEX);
+
+  // %AsyncGenerator% / %AsyncGeneratorFunction%.prototype
+  JSObject::ForceSetPrototype(async_generator_function_prototype, empty);
+  JSObject::AddProperty(async_generator_function_prototype,
+                        factory()->constructor_string(),
+                        async_generator_function,
+                        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
+
+  // The value of AsyncGeneratorFunction.prototype.prototype is the
+  //     %AsyncGeneratorPrototype% intrinsic object.
+  // This property has the attributes
+  //     { [[Writable]]: false, [[Enumerable]]: false, [[Configurable]]: true }.
+  JSObject::AddProperty(async_generator_function_prototype,
+                        factory()->prototype_string(),
+                        async_generator_object_prototype,
+                        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
+  JSObject::AddProperty(async_generator_function_prototype,
+                        factory()->to_string_tag_symbol(),
+                        AsyncGeneratorFunction_string,
+                        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
+
+  // %AsyncGeneratorPrototype%
+  JSObject::ForceSetPrototype(async_generator_object_prototype,
+                              async_iterator_prototype);
+
+  JSObject::AddProperty(async_generator_object_prototype,
+                        factory()->constructor_string(),
+                        async_generator_function,
+                        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
+  JSObject::AddProperty(async_generator_object_prototype,
+                        factory()->to_string_tag_symbol(),
+                        factory()->NewStringFromAsciiChecked("AsyncGenerator"),
+                        static_cast<PropertyAttributes>(DONT_ENUM | READ_ONLY));
+  SimpleInstallFunction(async_generator_object_prototype, "next",
+                        Builtins::kAsyncGeneratorPrototypeNext, 1, true);
+  SimpleInstallFunction(async_generator_object_prototype, "return",
+                        Builtins::kAsyncGeneratorPrototypeReturn, 1, true);
+  SimpleInstallFunction(async_generator_object_prototype, "throw",
+                        Builtins::kAsyncGeneratorPrototypeThrow, 1, true);
+
+  // Create maps for async generator functions and their prototypes. Store those
+  // maps in the native context. The "prototype" property descriptor is
+  // writable, non-enumerable, and non-configurable.
+  Handle<Map> strict_function_map(strict_function_map_writable_prototype_);
+
+  // Async Generator functions do not have "caller" or "arguments" accessors in
+  // either sloppy mode or strict mode.
+  Handle<Map> async_generator_function_map =
+      Map::Copy(strict_function_map, "AsyncGeneratorFunction");
+  async_generator_function_map->set_is_constructor(false);
+  Map::SetPrototype(async_generator_function_map,
+                    async_generator_function_prototype);
+  native_context()->set_async_generator_function_map(
+      *async_generator_function_map);
+
+  Handle<JSFunction> object_function(native_context()->object_function());
+  Handle<Map> async_generator_object_prototype_map = Map::Create(isolate(), 0);
+  Map::SetPrototype(async_generator_object_prototype_map,
+                    async_generator_object_prototype);
+  native_context()->set_async_generator_object_prototype_map(
+      *async_generator_object_prototype_map);
+}
+
 void Genesis::CreateAsyncFunctionMaps(Handle<JSFunction> empty) {
   // %AsyncFunctionPrototype% intrinsic
   Handle<JSObject> async_function_prototype =
@@ -1034,15 +1166,6 @@ void Genesis::HookUpGlobalObject(Handle<JSGlobalObject> global_object) {
   TransferIndexedProperties(global_object_from_snapshot, global_object);
 }
 
-static void InstallWithIntrinsicDefaultProto(Isolate* isolate,
-                                             Handle<JSFunction> function,
-                                             int context_index) {
-  Handle<Smi> index(Smi::FromInt(context_index), isolate);
-  JSObject::AddProperty(
-      function, isolate->factory()->native_context_index_symbol(), index, NONE);
-  isolate->native_context()->set(context_index, *function);
-}
-
 static void InstallError(Isolate* isolate, Handle<JSObject> global,
                          Handle<String> name, int context_index) {
   Factory* factory = isolate->factory();
@@ -1291,6 +1414,71 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
     class_function_map_->SetConstructor(*function_fun);
   }
 
+  {
+    // --- A s y n c F r o m S y n c I t e r a t o r
+    Handle<Code> code = isolate->builtins()->AsyncIteratorValueUnwrap();
+    Handle<SharedFunctionInfo> info =
+        factory->NewSharedFunctionInfo(factory->empty_string(), code, false);
+    info->set_internal_formal_parameter_count(1);
+    info->set_length(1);
+    native_context()->set_async_iterator_value_unwrap_shared_fun(*info);
+  }
+
+  {  // --- A s y n c G e n e r a t o r ---
+    Handle<JSFunction> async_generator_function(
+        native_context()->async_generator_function_function(), isolate);
+    Handle<JSFunction> function_fun(native_context()->function_function(),
+                                    isolate);
+    JSObject::ForceSetPrototype(async_generator_function, function_fun);
+
+    async_generator_function->set_prototype_or_initial_map(
+        native_context()->async_generator_function_map());
+    async_generator_function->shared()->SetConstructStub(
+        *isolate->builtins()->AsyncGeneratorFunctionConstructor());
+    native_context()->async_generator_function_map()->SetConstructor(
+        *async_generator_function);
+
+    Handle<JSFunction> await_caught =
+        SimpleCreateFunction(isolate, factory->empty_string(),
+                             Builtins::kAsyncGeneratorAwaitCaught, 2, false);
+    InstallWithIntrinsicDefaultProto(isolate, await_caught,
+                                     Context::ASYNC_GENERATOR_AWAIT_CAUGHT);
+
+    Handle<JSFunction> await_uncaught =
+        SimpleCreateFunction(isolate, factory->empty_string(),
+                             Builtins::kAsyncGeneratorAwaitUncaught, 2, false);
+    InstallWithIntrinsicDefaultProto(isolate, await_uncaught,
+                                     Context::ASYNC_GENERATOR_AWAIT_UNCAUGHT);
+
+    Handle<JSFunction> yield =
+        SimpleCreateFunction(isolate, factory->empty_string(),
+                             Builtins::kAsyncGeneratorYield, 2, false);
+    InstallWithIntrinsicDefaultProto(isolate, yield,
+                                     Context::ASYNC_GENERATOR_YIELD);
+
+    Handle<JSFunction> raw_yield =
+        SimpleCreateFunction(isolate, factory->empty_string(),
+                             Builtins::kAsyncGeneratorRawYield, 2, false);
+    InstallWithIntrinsicDefaultProto(isolate, raw_yield,
+                                     Context::ASYNC_GENERATOR_RAW_YIELD);
+
+    Handle<Code> code =
+        isolate->builtins()->AsyncGeneratorAwaitResolveClosure();
+    Handle<SharedFunctionInfo> info =
+        factory->NewSharedFunctionInfo(factory->empty_string(), code, false);
+    info->set_internal_formal_parameter_count(1);
+    info->set_length(1);
+    native_context()->set_async_generator_await_resolve_shared_fun(*info);
+
+    code = handle(isolate->builtins()->builtin(
+                      Builtins::kAsyncGeneratorAwaitRejectClosure),
+                  isolate);
+    info = factory->NewSharedFunctionInfo(factory->empty_string(), code, false);
+    info->set_internal_formal_parameter_count(1);
+    info->set_length(1);
+    native_context()->set_async_generator_await_reject_shared_fun(*info);
+  }
+
   {  // --- A r r a y ---
     Handle<JSFunction> array_function =
         InstallFunction(global, "Array", JS_ARRAY_TYPE, JSArray::kSize,
@@ -3541,6 +3729,13 @@ void Genesis::InitializeGlobal_harmony_array_prototype_values() {
                         NONE);
 }
 
+void Genesis::InitializeGlobal_harmony_async_iteration() {
+  if (!FLAG_harmony_async_iteration) return;
+  Handle<JSFunction> symbol_fun(native_context()->symbol_function());
+  InstallConstant(isolate(), symbol_fun, "asyncIterator",
+                  factory()->async_iterator_symbol());
+}
+
 Handle<JSFunction> Genesis::InstallArrayBuffer(Handle<JSObject> target,
                                                const char* name,
                                                Builtins::Name call,
@@ -4004,6 +4199,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_trailing_commas_natives[] = {nullptr};
   static const char* harmony_class_fields_natives[] = {nullptr};
   static const char* harmony_object_spread_natives[] = {nullptr};
+  static const char* harmony_async_iteration_natives[] = {nullptr};
 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {
@@ -4605,6 +4801,7 @@ Genesis::Genesis(
     Handle<JSFunction> empty_function = CreateEmptyFunction(isolate);
     CreateStrictModeFunctionMaps(empty_function);
     CreateIteratorMaps(empty_function);
+    CreateAsyncIteratorMaps(empty_function);
     CreateAsyncFunctionMaps(empty_function);
     Handle<JSGlobalObject> global_object =
         CreateNewGlobals(global_proxy_template, global_proxy);