Internal Compiler Error with awaited async closure within impl Future fn poll

[bionicles]

Code

Rustc panicked when I attempted to use async in poll.

I wanted to compose an async task inside my custom future

// to listen for the hello world messages, run this in a separate terminal
// ncat -k -l 8080
use anyhow::Result as AnyhowResult;
use futures::FutureExt;
use std::{
    future::Future,
    pin::Pin,
    task::{Context, Poll},
    time::Duration,
};
use tokio::{io::AsyncWriteExt, net, runtime, task};

/// A Future to print "hello world!\n" on a TCP Stream with a sleep interval and iteration number.
struct SleepyHelloWorld {
    handle: runtime::Handle,
    stream: net::TcpStream,
    sleep_millis: u64,
    n_hello: usize,
}

impl SleepyHelloWorld {
    async fn write_one(&mut self, src: &[u8]) -> AnyhowResult<()> {
        self.stream.write_all(src).await;
        Ok(())
    }
}

impl Future for SleepyHelloWorld {
    type Output = AnyhowResult<()>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let waker = cx.waker().clone();

        let n_hello = self.n_hello; // copy
        let duration = Duration::from_millis(self.sleep_millis);
        let greeting = b"hello world!\n";

        let this = Pin::get_mut(self);

        // run a task on a blocking thread (because fn poll is sync)
        let task = async move |this: &mut Self| {
            for _ in 0..n_hello {
                this.write_one(greeting).await?;
                tokio::time::sleep(duration).await;
                waker.wake();
            }
            Result::<(), anyhow::Error>::Ok(())
        };

        // move that workload into a blocking thread
        let mut owned_handle = task::spawn_blocking(move || self.handle.block_on(task(this)));
        let mut handle = Pin::new(&mut owned_handle);

        // Schedule the future to be woken up when the task is complete.
        let waker = cx.waker().clone();

        // Poll the handle to completion.
        match handle.as_mut().poll(cx) {
            Poll::Ready(result) => {
                println!("The task completed, so we're done.\nresult={result:#?}");
                match result {
                    Ok(_) => Poll::Ready(Ok(())),
                    Err(e) => Poll::Ready(Err(e.into())),
                }
            }
            Poll::Pending => {
                // The task is still running, so we need to wait.
                Poll::Pending
            }
        }
    }
}

#[tokio::main(flavor = "current_thread")]
async fn main() -> AnyhowResult<()> {
    println!("Connecting.");
    let sleepy_future = SleepyHelloWorld {
        handle: runtime::Handle::current(),
        stream: net::TcpStream::connect("127.0.0.1:8080").await?,
        sleep_millis: 350,
        n_hello: 10,
    };
    println!("Connected.");

    println!("Awaiting sleepy_future...");
    sleepy_future.await;
    println!("Awaiting sleepy_future... done.");

    Ok(())
}

Meta

rustc --version --verbose:

> rustc --version --verbose
rustc 1.80.0-nightly (7d83a4c13 2024-05-06)
binary: rustc
commit-hash: 7d83a4c131ab9ae81a74c6fd825c827d74a2881d
commit-date: 2024-05-06
host: x86_64-unknown-linux-gnu
release: 1.80.0-nightly
LLVM version: 18.1.4

Error output

error: the compiler unexpectedly panicked. this is a bug.

note: compiler flags: -Z unstable-options --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED]

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
#0 [mir_built] building MIR for `<impl at examples/with_tokio.rs:27:1: 27:33>::poll::{closure#0}::{closure#0}`
#1 [check_unsafety] unsafety-checking `<impl at examples/with_tokio.rs:27:1: 27:33>::poll`
#2 [analysis] running analysis passes on this crate
end of query stack

thread 'rustc' panicked at compiler/rustc_mir_transform/src/coroutine/by_move_body.rs:140:21:
assertion `left != right` failed: `FnOnce` coroutine-closures return coroutines that capture from their body; it will always result in a borrowck error!
  left: FnOnce
 right: FnOnce
stack backtrace:
   0:     0x7f70ebd8cb35 - std::backtrace_rs::backtrace::libunwind::trace::h918aaf6e60cc0a20
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/../../backtrace/src/backtrace/libunwind.rs:105:5
   1:     0x7f70ebd8cb35 - std::backtrace_rs::backtrace::trace_unsynchronized::h2eac6c94b93f8e3c
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f70ebd8cb35 - std::sys_common::backtrace::_print_fmt::h8e5edaeb6a4352e8
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f70ebd8cb35 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hf5cc6736d08af678
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f70ebddbcfb - core::fmt::rt::Argument::fmt::hb75c12041eb78bdc
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/core/src/fmt/rt.rs:165:63
   5:     0x7f70ebddbcfb - core::fmt::write::h3e6a6276a812b52d
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/core/src/fmt/mod.rs:1157:21
   6:     0x7f70ebd8187f - std::io::Write::write_fmt::h1eb4d2f52c7badcc
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/io/mod.rs:1835:15
   7:     0x7f70ebd8c90e - std::sys_common::backtrace::_print::h027a355b4099d109
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f70ebd8c90e - std::sys_common::backtrace::print::h9288434216016cb8
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f70ebd8f279 - std::panicking::default_hook::{{closure}}::hb774f76bb0cbe3f3
  10:     0x7f70ebd8efbd - std::panicking::default_hook::h5e6bb2fe4f610e68
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/panicking.rs:298:9
  11:     0x7f70eeeb3d1f - std[2409bda48c37ea6b]::panicking::update_hook::<alloc[e4f27f1b259856c9]::boxed::Box<rustc_driver_impl[3b65384176704029]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f70ebd8f976 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::h150247b09595b272
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/alloc/src/boxed.rs:2036:9
  13:     0x7f70ebd8f976 - std::panicking::rust_panic_with_hook::h193842b19bca8c30
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/panicking.rs:799:13
  14:     0x7f70ebd8f724 - std::panicking::begin_panic_handler::{{closure}}::h9e341f02e94749d0
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/panicking.rs:664:13
  15:     0x7f70ebd8cff9 - std::sys_common::backtrace::__rust_end_short_backtrace::ha4420d007785945b
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7f70ebd8f457 - rust_begin_unwind
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/panicking.rs:652:5
  17:     0x7f70ebdd82c3 - core::panicking::panic_fmt::h0afd8a3c11e985b9
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/core/src/panicking.rs:72:14
  18:     0x7f70ebdd888f - core::panicking::assert_failed_inner::h1ec36149f8f0af66
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/core/src/panicking.rs:403:23
  19:     0x7f70ef4abc18 - core[e58631ecc326099b]::panicking::assert_failed::<rustc_type_ir[c154581ae42d6ad0]::ClosureKind, rustc_type_ir[c154581ae42d6ad0]::ClosureKind>
  20:     0x7f70edf3dba6 - <rustc_mir_transform[ed70598d93e22d13]::coroutine::by_move_body::ByMoveBody as rustc_middle[d85377d387f08e9a]::mir::MirPass>::run_pass
  21:     0x7f70f020184d - rustc_mir_transform[ed70598d93e22d13]::pass_manager::run_passes_inner
  22:     0x7f70f04c9a28 - rustc_query_impl[f7d6eb8805e88c29]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f7d6eb8805e88c29]::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d85377d387f08e9a]::query::erase::Erased<[u8; 8usize]>>
  23:     0x7f70f0527c52 - rustc_query_system[bd604859ea317a95]::query::plumbing::try_execute_query::<rustc_query_impl[f7d6eb8805e88c29]::DynamicConfig<rustc_query_system[bd604859ea317a95]::query::caches::VecCache<rustc_span[86ddde2698e45e98]::def_id::LocalDefId, rustc_middle[d85377d387f08e9a]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[f7d6eb8805e88c29]::plumbing::QueryCtxt, true>
  24:     0x7f70f05327d6 - rustc_query_impl[f7d6eb8805e88c29]::query_impl::mir_built::get_query_incr::__rust_end_short_backtrace
  25:     0x7f70f04bec30 - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor>::visit_inner_body
  26:     0x7f70eda7eed4 - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor as rustc_middle[d85377d387f08e9a]::thir::visit::Visitor>::visit_expr
  27:     0x7f70f04bed41 - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor>::visit_inner_body
  28:     0x7f70eda7eed4 - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor as rustc_middle[d85377d387f08e9a]::thir::visit::Visitor>::visit_expr
  29:     0x7f70f09c587e - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor as rustc_middle[d85377d387f08e9a]::thir::visit::Visitor>::visit_block
  30:     0x7f70eda801cd - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor as rustc_middle[d85377d387f08e9a]::thir::visit::Visitor>::visit_expr
  31:     0x7f70eda7eed4 - <rustc_mir_build[362e64e742f0429f]::check_unsafety::UnsafetyVisitor as rustc_middle[d85377d387f08e9a]::thir::visit::Visitor>::visit_expr
  32:     0x7f70f04bbe64 - rustc_mir_build[362e64e742f0429f]::check_unsafety::check_unsafety
  33:     0x7f70f04bb911 - rustc_query_impl[f7d6eb8805e88c29]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f7d6eb8805e88c29]::query_impl::check_unsafety::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d85377d387f08e9a]::query::erase::Erased<[u8; 0usize]>>
  34:     0x7f70f053002a - rustc_query_system[bd604859ea317a95]::query::plumbing::try_execute_query::<rustc_query_impl[f7d6eb8805e88c29]::DynamicConfig<rustc_query_system[bd604859ea317a95]::query::caches::VecCache<rustc_span[86ddde2698e45e98]::def_id::LocalDefId, rustc_middle[d85377d387f08e9a]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[f7d6eb8805e88c29]::plumbing::QueryCtxt, true>
  35:     0x7f70f052fb37 - rustc_query_impl[f7d6eb8805e88c29]::query_impl::check_unsafety::get_query_incr::__rust_end_short_backtrace
  36:     0x7f70f05196ad - rustc_interface[45e847dd6c11ec07]::passes::analysis
  37:     0x7f70f0518787 - rustc_query_impl[f7d6eb8805e88c29]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[f7d6eb8805e88c29]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d85377d387f08e9a]::query::erase::Erased<[u8; 1usize]>>
  38:     0x7f70f107040a - rustc_query_system[bd604859ea317a95]::query::plumbing::try_execute_query::<rustc_query_impl[f7d6eb8805e88c29]::DynamicConfig<rustc_query_system[bd604859ea317a95]::query::caches::SingleCache<rustc_middle[d85377d387f08e9a]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[f7d6eb8805e88c29]::plumbing::QueryCtxt, true>
  39:     0x7f70f107001c - rustc_query_impl[f7d6eb8805e88c29]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  40:     0x7f70f0e270ce - rustc_interface[45e847dd6c11ec07]::interface::run_compiler::<core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>, rustc_driver_impl[3b65384176704029]::run_compiler::{closure#0}>::{closure#1}
  41:     0x7f70f0e126c9 - std[2409bda48c37ea6b]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[45e847dd6c11ec07]::util::run_in_thread_with_globals<rustc_interface[45e847dd6c11ec07]::util::run_in_thread_pool_with_globals<rustc_interface[45e847dd6c11ec07]::interface::run_compiler<core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>, rustc_driver_impl[3b65384176704029]::run_compiler::{closure#0}>::{closure#1}, core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>>::{closure#0}, core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>>
  42:     0x7f70f0e12478 - <<std[2409bda48c37ea6b]::thread::Builder>::spawn_unchecked_<rustc_interface[45e847dd6c11ec07]::util::run_in_thread_with_globals<rustc_interface[45e847dd6c11ec07]::util::run_in_thread_pool_with_globals<rustc_interface[45e847dd6c11ec07]::interface::run_compiler<core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>, rustc_driver_impl[3b65384176704029]::run_compiler::{closure#0}>::{closure#1}, core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>>::{closure#0}, core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[e58631ecc326099b]::result::Result<(), rustc_span[86ddde2698e45e98]::ErrorGuaranteed>>::{closure#2} as core[e58631ecc326099b]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  43:     0x7f70ebd997bb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h02edc3183d1b3ab4
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/alloc/src/boxed.rs:2022:9
  44:     0x7f70ebd997bb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::hd14ff6036f87e3a7
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/alloc/src/boxed.rs:2022:9
  45:     0x7f70ebd997bb - std::sys::pal::unix::thread::Thread::new::thread_start::he158ab2f3983310c
                               at /rustc/7d83a4c131ab9ae81a74c6fd825c827d74a2881d/library/std/src/sys/pal/unix/thread.rs:108:17
  46:     0x7f70ebb41ac3 - <unknown>
  47:     0x7f70ebbd3850 - <unknown>
  48:                0x0 - <unknown>

[compiler-errors]

I believe this is a duplicate of #124487, which I have a local branch to fix but which needs a bit of cleanup first.