LibJS: Disallow shorthand properties with reserved names

Userland/Libraries/LibJS/Parser.cpp

@@ -1497,6 +1497,8 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
             auto lookahead_token = next_token();
 
             if (lookahead_token.type() != TokenType::ParenOpen && lookahead_token.type() != TokenType::Colon
+                && lookahead_token.type() != TokenType::Comma && lookahead_token.type() != TokenType::CurlyClose
+                && lookahead_token.type() != TokenType::Async
                 && !lookahead_token.trivia_contains_line_terminator()) {
                 consume(TokenType::Async);
                 function_kind = FunctionKind::Async;
@@ -1567,6 +1569,12 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
             }
             properties.append(create_ast_node<ObjectProperty>({ m_state.current_token.filename(), rule_start.position(), position() }, *property_name, parse_expression(2), property_type, false));
         } else if (property_name && property_value) {
+            if (m_state.strict_mode && is<StringLiteral>(*property_name)) {
+                auto& string_literal = static_cast<StringLiteral const&>(*property_name);
+                if (is_strict_reserved_word(string_literal.value()))
+                    syntax_error(String::formatted("'{}' is a reserved keyword", string_literal.value()));
+            }
+
             properties.append(create_ast_node<ObjectProperty>({ m_state.current_token.filename(), rule_start.position(), position() }, *property_name, *property_value, property_type, false));
         } else {
             expected("a property");

Userland/Libraries/LibJS/Tests/object-basic.js

@@ -151,6 +151,54 @@ describe("side effects", () => {
     });
 });
 
+describe("shorthanded properties with special names", () => {
+    test("keywords cannot be used", () => {
+        expect("({ function, })").not.toEval();
+        expect("({ var, })").not.toEval();
+        expect("({ const, })").not.toEval();
+        expect("({ class, })").not.toEval();
+    });
+
+    test("reserved words are allowed in non-strict mode", () => {
+        {
+            var implements = 3;
+            expect({ implements }).toEqual({ implements: 3 });
+        }
+        {
+            var public = "a";
+            expect({ public }).toEqual({ public: "a" });
+        }
+        {
+            var let = 9;
+            expect({ let }).toEqual({ let: 9 });
+        }
+        {
+            var await = 8;
+            expect({ await }).toEqual({ await: 8 });
+        }
+        {
+            var async = 7;
+            expect({ async }).toEqual({ async: 7 });
+        }
+        {
+            var yield = 6;
+            expect({ yield }).toEqual({ yield: 6 });
+        }
+    });
+
+    test("reserved words are not allowed in strict mode", () => {
+        expect('"use strict"; var implements = 3; ({ implements })').not.toEval();
+        expect("\"use strict\"; var public = 'a'; ({ public })").not.toEval();
+        expect('"use strict"; var let = 9; ({ let, })').not.toEval();
+        expect('"use strict"; var yield = 6; ({ yield, })').not.toEval();
+    });
+
+    test("special non reserved words are allowed even in strict mode", () => {
+        expect('"use strict"; var await = 8; ({ await, })').toEval();
+        expect('"use strict"; var async = 7; ({ async, })').toEval();
+    });
+});
+
 describe("errors", () => {
     test("syntax errors", () => {
         expect("({ foo: function() { super.bar; } })").not.toEval();