From 81312986fe07496e3d35e1d7d10d20d9aba8d1fb Mon Sep 17 00:00:00 2001
From: davidot <davidot@serenityos.org>
Date: Sun, 19 Dec 2021 20:19:15 +0100
Subject: [PATCH] LibJS: Disallow async generator functions called 'await' or
 'yield'

---
 Userland/Libraries/LibJS/Parser.cpp                       | 3 +++
 Userland/Libraries/LibJS/Tests/syntax/async-await.js      | 3 +++
 Userland/Libraries/LibJS/Tests/syntax/async-generators.js | 3 +++
 Userland/Libraries/LibJS/Tests/syntax/generators.js       | 3 +++
 4 files changed, 12 insertions(+)

diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index 30749baa65..91e643e8fc 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -2476,6 +2476,9 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
 
         check_identifier_name_for_assignment_validity(name);
 
+        if (function_kind == FunctionKind::AsyncGenerator && (name == "await"sv || name == "yield"sv))
+            syntax_error(String::formatted("async generator function is not allowed to be called '{}'", name));
+
         if (m_state.in_class_static_init_block && name == "await"sv)
             syntax_error("'await' is a reserved word");
     }
diff --git a/Userland/Libraries/LibJS/Tests/syntax/async-await.js b/Userland/Libraries/LibJS/Tests/syntax/async-await.js
index 652f0e810e..d86c9eea8e 100644
--- a/Userland/Libraries/LibJS/Tests/syntax/async-await.js
+++ b/Userland/Libraries/LibJS/Tests/syntax/async-await.js
@@ -4,6 +4,9 @@ describe("parsing freestanding async functions", () => {
         // Although it does not create an async function it is valid.
         expect(`async
         function foo() {}`).toEval();
+
+        expect(`async function await() {}`).toEval();
+        expect(`async function yield() {}`).toEval();
     });
     test("await expression", () => {
         expect(`async function foo() { await bar(); }`).toEval();
diff --git a/Userland/Libraries/LibJS/Tests/syntax/async-generators.js b/Userland/Libraries/LibJS/Tests/syntax/async-generators.js
index 68c9550dbb..ce30721efd 100644
--- a/Userland/Libraries/LibJS/Tests/syntax/async-generators.js
+++ b/Userland/Libraries/LibJS/Tests/syntax/async-generators.js
@@ -4,6 +4,9 @@ describe("parsing freestanding generators", () => {
         expect(`async function *foo() {}`).toEval();
         expect(`async function
             *foo() {}`).toEval();
+
+        expect(`async function *await() {}`).not.toEval();
+        expect(`async function *yield() {}`).not.toEval();
     });
     test("yield & await expression", () => {
         expect(`async function* foo() { yield; await 1; }`).toEval();
diff --git a/Userland/Libraries/LibJS/Tests/syntax/generators.js b/Userland/Libraries/LibJS/Tests/syntax/generators.js
index c70bc6cf72..010a1c78e5 100644
--- a/Userland/Libraries/LibJS/Tests/syntax/generators.js
+++ b/Userland/Libraries/LibJS/Tests/syntax/generators.js
@@ -4,6 +4,9 @@ describe("parsing freestanding generators", () => {
         expect(`function *foo() {}`).toEval();
         expect(`function
             *foo() {}`).toEval();
+
+        expect(`function *await() {}`).toEval();
+        expect(`function *yield() {}`).toEval();
     });
     test("yield expression", () => {
         expect(`function* foo() { yield; }`).toEval();