It's still a gotcha in Rust, I've seen code like:

  #[non_exhaustive]
  pub enum Protocol {
    Tcp,
    Udp,
    Other(u16),
  }

It allows you to still match on the unrecognized case (like `Protocol::Other(1)`, which is nice), but an additional enum variant may eliminate that case, if our enum gets extended to:

  #[non_exhaustive]
  pub enum Protocol {
    Tcp,
    Udp,
    Icmp,
    Other(u16),
  }

Even though we can add additional variants in a semver-nonbreaking way due to `#[non_exhaustive]`, other people's code may now be broken until they've changed `Protocol::Other(1)` to `Protocol::Icmp`.

Having had this in the back of my head for quite some time, I think instead of an `Other` case there should be two methods, one returns an `Option<Protocol>` and the other one returns the `u16` representation. Unless there's a match on one of your expected cases your default branch would inspect the raw numeric type, which would keep working even if that case is added to the enum.