The Flag enum is missing entries for ANONCONSTR_BASED and POTENTIALLY_AMBIGUOUS, resulting in an assertion failure if those flags are passed to `Flags#asFlagSet`.
compiler-dev thread: http://mail.openjdk.java.net/pipermail/compiler-dev/2018-September/012472.html
compiler-dev thread: http://mail.openjdk.java.net/pipermail/compiler-dev/2018-September/012472.html