Tracking issue for "reached the type-length limit" in interop crate

[djc]

This seems to be an instance of rust-lang/rust#54540 which apparently has gotten worse due to rust-lang/rust#75443 (which has been on nightly since 2020-08-14 and is now also a part of 1.46.0-beta.5. There seems to be an interaction with tracing, described in tokio-rs/tracing#616.

First noticed in CI, for example https://github.com/djc/quinn/pull/837/checks?check_run_id=1017422950.

[Ralith]

The error appears to reference this code:

    let results = future::join_all(peers.into_iter().map(|peer| async move {
        let span = info_span!("peer", name = peer.name.as_str());
        let result = run(&peer, keylog).instrument(span).await;
        (peer, result)
    }));

Maybe info_span! is expanding to something wildly complex? Can't otherwise see how this would have anything to do with tracing (or indeed be an issue at all).

[tmandry]

cc rust-lang/rust#64496

[djc]

Fixed (well, worked around) in #844.