presto-main/src/main/java/io/prestosql/type/UnknownOperators.java/UnknownOperators/xxHash
class UnknownOperators:    @ScalarOperator(XX_HASH_64)
    @SqlType(StandardTypes.BIGINT)
    public static long xxHash(@SqlType("unknown") boolean value)
    {
        throw new AssertionError("value of unknown type should always be NULL");
    }