knownEmptyContainer
ftp://ftp.de.debian.org/debian/pool/main/i/iwyu/iwyu_8.23.orig.tar.gz
head include-what-you-use-0.23/iwyu_ast_util.cc:1679:54: style: Iterating over container 'enumerator.Enumerate(arg)' that is always empty. [knownEmptyContainer]