LibJS: Parse async generator functions

Author: https://github.com/davidot
Commit: https://github.com/SerenityOS/serenity/commit/0982a73d1d8
Pull-request: https://github.com/SerenityOS/serenity/pull/10926
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Runtime/AsyncGeneratorFunctionConstructor.cpp

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2021, David Tuin <davidot@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Interpreter.h>
+#include <LibJS/Runtime/AsyncGeneratorFunctionConstructor.h>
+#include <LibJS/Runtime/ECMAScriptFunctionObject.h>
+#include <LibJS/Runtime/FunctionConstructor.h>
+#include <LibJS/Runtime/FunctionObject.h>
+#include <LibJS/Runtime/GlobalObject.h>
+
+namespace JS {
+
+AsyncGeneratorFunctionConstructor::AsyncGeneratorFunctionConstructor(GlobalObject& global_object)
+    : NativeFunction(vm().names.AsyncGeneratorFunction.as_string(), *global_object.function_prototype())
+{
+}
+
+void AsyncGeneratorFunctionConstructor::initialize(GlobalObject& global_object)
+{
+    auto& vm = this->vm();
+    NativeFunction::initialize(global_object);
+
+    // 27.4.2.2 AsyncGeneratorFunction.prototype, https://tc39.es/ecma262/#sec-asyncgeneratorfunction-prototype
+    define_direct_property(vm.names.prototype, global_object.async_generator_function_prototype(), 0);
+
+    // 27.4.2.1 AsyncGeneratorFunction.length, https://tc39.es/ecma262/#sec-asyncgeneratorfunction-length
+    define_direct_property(vm.names.length, Value(1), Attribute::Configurable);
+
+    // 27.4.2.2 AsyncGeneratorFunction.prototype, https://tc39.es/ecma262/#sec-asyncgeneratorfunction-prototype
+    define_direct_property(vm.names.prototype, global_object.async_generator_function_prototype(), 0);
+}
+
+// 27.4.1.1 AsyncGeneratorFunction ( p1, p2, … , pn, body ), https://tc39.es/ecma262/#sec-asyncgeneratorfunction
+ThrowCompletionOr<Value> AsyncGeneratorFunctionConstructor::call()
+{
+    return TRY(construct(*this));
+}
+
+// 27.4.1.1 AsyncGeneratorFunction ( p1, p2, … , pn, body ), https://tc39.es/ecma262/#sec-asyncgeneratorfunction
+ThrowCompletionOr<Object*> AsyncGeneratorFunctionConstructor::construct(FunctionObject& new_target)
+{
+    auto& vm = this->vm();
+    auto function = TRY(FunctionConstructor::create_dynamic_function_node(global_object(), new_target, FunctionKind::AsyncGenerator));
+
+    OwnPtr<Interpreter> local_interpreter;
+    Interpreter* interpreter = vm.interpreter_if_exists();
+
+    if (!interpreter) {
+        local_interpreter = Interpreter::create_with_existing_realm(*realm());
+        interpreter = local_interpreter.ptr();
+    }
+
+    VM::InterpreterExecutionScope scope(*interpreter);
+    auto result = function->execute(*interpreter, global_object());
+    if (auto* exception = vm.exception())
+        return throw_completion(exception->value());
+    VERIFY(result.is_object() && is<ECMAScriptFunctionObject>(result.as_object()));
+    return &result.as_object();
+}
+
+}