LibRegex: Fix lookup table-based range checks in Compare

The lowercase version of a range is not required to be a valid range,
instead of casefolding the range and making it invalid, check twice with
both cases of the input character (which are the same as the input if
not insensitive).
This time includes an actual test :^)

1 files changed, 6 insertions, 7 deletions

diff --git a/Userland/Libraries/LibRegex/RegexByteCode.cpp b/Userland/Libraries/LibRegex/RegexByteCode.cpp
index de7ce26444..cccdb93982 100644
--- a/Userland/Libraries/LibRegex/RegexByteCode.cpp
+++ b/Userland/Libraries/LibRegex/RegexByteCode.cpp
@@ -531,16 +531,15 @@ ALWAYS_INLINE ExecutionResult OpCode_Compare::execute(MatchInput const& input, M
             auto ch = input.view.substring_view(state.string_position, 1)[0];
 
             auto const* matching_range = binary_search(range_data, ch, nullptr, [insensitive = input.regex_options & AllFlags::Insensitive](auto needle, CharRange range) {
-                auto from = range.from;
-                auto to = range.to;
+                auto upper_case_needle = needle;
+                auto lower_case_needle = needle;
                 if (insensitive) {
-                    from = to_ascii_lowercase(from);
-                    to = to_ascii_lowercase(to);
-                    needle = to_ascii_lowercase(needle);
+                    upper_case_needle = to_ascii_uppercase(needle);
+                    lower_case_needle = to_ascii_lowercase(needle);
                 }
-                if (needle > to)
+                if (lower_case_needle > range.to && upper_case_needle > range.to)
                     return 1;
-                if (needle < from)
+                if (lower_case_needle < range.from && upper_case_needle < range.from)
                     return -1;
                 return 0;
             });