LibJS: Support string literal expressions in nullish object exceptions

Author: https://github.com/trflynn89
Commit: e3ef849838
Pull-request: https://github.com/SerenityOS/serenity/pull/23802

Userland/Libraries/LibJS/Bytecode/Generator.cpp

@@ -458,6 +458,11 @@ static Optional<ByteString> expression_identifier(Expression const& expression)
         return literal.value().to_string_without_side_effects().to_byte_string();
     }
 
+    if (expression.is_string_literal()) {
+        auto const& literal = static_cast<StringLiteral const&>(expression);
+        return ByteString::formatted("'{}'", literal.value());
+    }
+
     if (expression.is_member_expression()) {
         auto const& member_expression = static_cast<MemberExpression const&>(expression);
         StringBuilder builder;

Userland/Libraries/LibJS/Tests/null-or-undefined-access.js

@@ -37,6 +37,20 @@ test("null/undefined object key", () => {
             TypeError,
             `Cannot access property "baz" on ${value} object "foo.bar"`
         );
+
+        expect(() => {
+            foo["bar"].baz;
+        }).toThrowWithMessage(
+            TypeError,
+            `Cannot access property "baz" on ${value} object "foo['bar']"`
+        );
+
+        expect(() => {
+            foo["bar"].baz = 1;
+        }).toThrowWithMessage(
+            TypeError,
+            `Cannot access property "baz" on ${value} object "foo['bar']"`
+        );
     });
 });