- Go to Special:AbuseFilter/new
- Type added_lines irlike ("x" + rescape(summary)) into the form, but don't save
- Wait for the syntax checker to do its thing
Expected result is no warning. No matter what's in summary, this regex won't match a string not containing "x".
Actual result is a little warning triangle on the left, with the hover text "This regular expression matches the empty string, at character 41"
Were it not for the rescape(), this would make sense; we don't if there's an | in summary. But rescape() should make it "safe".