From a6263150be9b2719105dd9b4df3fedc2dca3d9a4 Mon Sep 17 00:00:00 2001
From: davidot <david.tuin@gmail.com>
Date: Mon, 12 Jul 2021 01:32:24 +0200
Subject: [PATCH] LibJS: Disallow unqualified deletes in strict mode

---
 Userland/Libraries/LibJS/Parser.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Userland/Libraries/LibJS/Parser.cpp b/Userland/Libraries/LibJS/Parser.cpp
index 3b312146dc..7018375c5e 100644
--- a/Userland/Libraries/LibJS/Parser.cpp
+++ b/Userland/Libraries/LibJS/Parser.cpp
@@ -923,9 +923,15 @@ NonnullRefPtr<Expression> Parser::parse_unary_prefixed_expression()
     case TokenType::Void:
         consume();
         return create_ast_node<UnaryExpression>({ m_state.current_token.filename(), rule_start.position(), position() }, UnaryOp::Void, parse_expression(precedence, associativity));
-    case TokenType::Delete:
+    case TokenType::Delete: {
         consume();
-        return create_ast_node<UnaryExpression>({ m_state.current_token.filename(), rule_start.position(), position() }, UnaryOp::Delete, parse_expression(precedence, associativity));
+        auto rhs_start = position();
+        auto rhs = parse_expression(precedence, associativity);
+        if (is<Identifier>(*rhs) && m_state.strict_mode) {
+            syntax_error("Delete of an unqualified identifier in strict mode.", rhs_start);
+        }
+        return create_ast_node<UnaryExpression>({ m_state.current_token.filename(), rule_start.position(), position() }, UnaryOp::Delete, move(rhs));
+    }
     default:
         expected("primary expression");
         consume();