rustc compiler crashed when using async in loop

[fbucek]

When learning async/await feature I was struggling with running multiple tasks simultaneously.

Loop while let Some.... causes compiler to crash

https://github.com/fbucek/rust-async/blob/f6cc831c817a6b9d2f1c79182c5415b877f0da1e/actix-async/src/lib.rs#L30

Github Action crash output:

https://github.com/fbucek/rust-async/commit/f6cc831c817a6b9d2f1c79182c5415b877f0da1e/checks?check_suite_id=384856246

I expected to see this happen: Error message if something goes wrong.

Instead, this happened: Compiler crashed

Meta

Crash happens on macOS rustc 1.40 / Linux rustc 1.40 / Linux rustc 1.39 ( github actions )

rustc --version --verbose:

macOS

rustc 1.40.0 (73528e339 2019-12-16)
binary: rustc
commit-hash: 73528e339aae0f17a15ffa49a8ac608f50c6cf14
commit-date: 2019-12-16
host: x86_64-apple-darwin
release: 1.40.0
LLVM version: 9.0

Linux

rustc 1.40.0 (73528e339 2019-12-16)
binary: rustc
commit-hash: 73528e339aae0f17a15ffa49a8ac608f50c6cf14
commit-date: 2019-12-16
host: x86_64-unknown-linux-gnu
release: 1.40.0
LLVM version: 9.0

[Centril]

If you could provide an example that ICEs in e.g. the playground that would be helpful towards fixing the issue. :)

[fbucek]

Provided example is pretty small, but it is dependent on tokio and actix-web.

I do not know how to create such an example in playground, I do know know how I can replace async tokio::sync::mpsc with standard library which does not have async alternative as far as i know.

I have tried to simplify code but then crash disappear. Just putting everything into one file main.rs and crash is gone, code wont compile and reasonable errors show up.

[tmandry]

Visiting from triage.. we decided that as the first step we should reduce this reproducer to a more self-contained one.

[gilescope]

Can repro. Will try and min.

[gilescope]

Reduced version so far is here: https://github.com/gilescope/rust-async

[Aaron1011]

This no longer ICEs on the latest nightly.