Derive macro panics due to reserved node merge in invalid alternation

[redgoldlace]

More specifically, the derive macro panics when there is an invalid alternation present within a subpattern's repetition, and that subpattern is later repeated.

error: proc-macro derive panicked
 --> src\main.rs:7:10
  |
7 | #[derive(Logos)]
  |          ^^^^^
  |
  = help: message: Merging two reserved nodes! This is a bug, please report it:https://github.com/maciejhirsz/logos/issues

This is the minimum I was able to cause a panic with:

#[derive(Logos)]
#[logos(subpattern example = r"(a|)+")]
enum Example {
    #[regex("(?&example)+")]
    Subpattern,
    #[error]
    Error,
}

Notably, removing the repetition in Subpattern (like below) appears to cause compilation to hang forever:

#[derive(Logos)]
#[logos(subpattern example = r"(a|)+")]
enum Example {
    #[regex("(?&example)")]
    Subpattern,
    #[error]
    Error,
}

I was able to avoid a panic by removing the alternation:

#[derive(Logos)]
#[logos(subpattern example = r"(a)+")]
enum Example {
    #[regex("(?&example)+")]
    Subpattern,
    #[error]
    Error,
}

I've tested with both rustc 1.57.0 (f1edd0429 2021-11-29) (latest stable at time of writing) and rustc 1.58.0-nightly (c9c4b5d72 2021-11-17) (ol' reliable) and the issue appears to remain. I'm unsure if it's a compiler bug, but given the above I assume it's Logos-related. Both rustc versions are of the x86_64-pc-windows-gnu variety.