Enum to int casting fails with subtype mismatch

[franziskuskiefer]

enum E {
    One = 1,
    Five = 5,
}

fn fun(e: E) -> i32 {
    e as i32
}

fails with a subtype mismatch

subtype mismatch:
  bool (a.k.a. bool) vs:
  bool_t (a.k.a. bool_t)