I’m new to Rust and implementing a list library for familiarisation. So far the normal unit tests run correctly, but when I started writing doc tests, they resulted in what seems to be a runtime error.

I use the command cargo test --doc to kick it off, but it results in the following error:

error: doctest failed, to rerun pass `--doc`

Caused by:
  process didn't exit successfully: `rustdoc --edition=2021 --crate-type lib --crate-name cons_list --test src/lib.rs --test-run-directory ... -L dependency=... --extern cons_list=... -C embed-bitcode=no --error-format human`

signal: 5, SIGTRAP: trace/breakpoint trap)

Doctests seem to run but the moment I try introducing my own type, rustdoc fails. so e.g. a test like assert_eq!(1, 1); works fine, but the moment I start referring to my own type it seems to result in rustdoc failing.

List definition

#[derive(Debug, Default, PartialEq, PartialOrd)]
pub enum List<T> {
    #[default]
    Nil,
    Cons(T, Box<List<T>>),
}

The test in question

Even one line doesn’t work, let alone adding any asserts

    /// Creates a new empty list of type List<T>
    /// ```
    /// let list: List<i32> = List::new();
    /// ```
    pub fn new() -> List<T> {
        Nil
    }

I’m really not certain what to do here. Any ideas?