LibRegex: Use correct source characters for Unicode identity escapes

Tests/LibRegex/Regex.cpp

@@ -557,6 +557,8 @@ TEST_CASE(ECMA262_parse)
         { "[\\0]"sv, regex::Error::NoError, combine_flags(ECMAScriptFlags::Unicode, ECMAScriptFlags::BrowserExtended) },
         { "[\\00]"sv, regex::Error::NoError, ECMAScriptFlags::BrowserExtended },
         { "[\\00]"sv, regex::Error::InvalidPattern, combine_flags(ECMAScriptFlags::Unicode, ECMAScriptFlags::BrowserExtended) },
+        { "\\^\\$\\\\\\.\\*\\+\\?\\(\\)\\[\\]\\{\\}\\|\\/"sv, regex::Error::NoError, ECMAScriptFlags::Unicode },
+        { "[\\^\\$\\\\\\.\\*\\+\\?\\(\\)\\[\\]\\{\\}\\|\\/]"sv, regex::Error::NoError, ECMAScriptFlags::Unicode },
     };
 
     for (auto& test : tests) {
@@ -605,6 +607,8 @@ TEST_CASE(ECMA262_match)
         { "((...)X)+"sv, "fooXbarXbazX"sv, true },
         { "(?:)"sv, ""sv, true },
         { "\\^"sv, "^"sv },
+        { "\\^\\$\\\\\\.\\*\\+\\?\\(\\)\\[\\]\\{\\}\\|\\/"sv, "^$\\.*+?()[]{}|/"sv, true, ECMAScriptFlags::Unicode },
+        { "[\\^\\$\\\\\\.\\*\\+\\?\\(\\)\\[\\]\\{\\}\\|\\/]{15}"sv, "^$\\.*+?()[]{}|/"sv, true, ECMAScriptFlags::Unicode },
         // ECMA262, B.1.4. Regular Expression Pattern extensions for browsers
         { "{"sv, "{"sv, true, ECMAScriptFlags::BrowserExtended },
         { "\\5"sv, "\5"sv, true, ECMAScriptFlags::BrowserExtended },

Userland/Libraries/LibRegex/RegexParser.cpp

@@ -20,6 +20,15 @@ static constexpr size_t s_maximum_repetition_count = 1024 * 1024;
 static constexpr auto s_alphabetic_characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"sv;
 static constexpr auto s_decimal_characters = "0123456789"sv;
 
+static constexpr StringView identity_escape_characters(bool unicode, bool browser_extended)
+{
+    if (unicode)
+        return "^$\\.*+?()[]{}|/"sv;
+    if (browser_extended)
+        return "^$\\.*+?()[|"sv;
+    return "^$\\.*+?()[]{}|"sv;
+}
+
 ALWAYS_INLINE bool Parser::set_error(Error error)
 {
     if (m_parser_state.error == Error::NoError) {
@@ -1530,8 +1539,7 @@ bool ECMA262Parser::parse_atom_escape(ByteCode& stack, size_t& match_length_mini
     }
 
     // IdentityEscape
-    auto source_characters = m_should_use_browser_extended_grammar ? "^$\\.*+?()[|"sv : "^$\\.*+?()[]{}|"sv;
-    for (auto ch : source_characters) {
+    for (auto ch : identity_escape_characters(unicode, m_should_use_browser_extended_grammar)) {
         if (try_skip({ &ch, 1 })) {
             match_length_minimum += 1;
             stack.insert_bytecode_compare_values({ { CharacterCompareType::Char, (ByteCodeValueType)ch } });
@@ -1840,6 +1848,12 @@ bool ECMA262Parser::parse_nonempty_class_ranges(Vector<CompareTypeAndValuePair>&
                 }
             }
 
+            // IdentityEscape
+            for (auto ch : identity_escape_characters(unicode, m_should_use_browser_extended_grammar)) {
+                if (try_skip({ &ch, 1 }))
+                    return { CharClassRangeElement { .code_point = (u32)ch, .is_character_class = false } };
+            }
+
             if (unicode) {
                 if (try_skip("-"))
                     return { CharClassRangeElement { .code_point = '-', .is_character_class = false } };