Additional_Tools_for_Xcode_10.dmg still have it, but 32bit version and looks like it very bugged on modern OS.

You can fix it yourself, looks like there is no reaction from Apple for years anyway :( $ sudo zsh -c 'grep -v "xcode.lang.comment.recursive" /Applications/Xcode.app/Contents/SharedFrameworks/SourceModel.framework/Versions/A/Resources/LanguageSpecifications/Swift.xclangspec > /Applications/Xcode.app/Contents/SharedFrameworks/DVTFoundation.framework/Versions/A/Resources/Swift.xclangspec' After that, there are no errors and the highlight is back.