flags descriptor-flags {
    /// Read mode: Data can be read.
    read,
    /// Write mode: Data can be written to.
    write,

    // ...

    /// Mutating directories mode: Directory contents may be mutated.
    ///
    /// When this flag is unset on a descriptor, operations using the
    /// descriptor which would create, rename, delete, modify the data or
    /// metadata of filesystem objects, or obtain another handle which
    /// would permit any of those, shall fail with `error-code::read-only` if
    /// they would otherwise succeed.
    ///
    /// This may only be set on directories.
    mutate-directory,
}