regression: change in async capture rules?

[Mark-Simulacrum]

https://crater-reports.s3.amazonaws.com/beta-1.74-4/beta-2023-10-21/reg/esl01-dag-0.3.0/log.txt

[INFO] [stdout] error: future cannot be sent between threads safely
[INFO] [stdout]    --> src/nameset/lazy.rs:102:9
[INFO] [stdout]     |
[INFO] [stdout] 102 | /         Box::pin(futures::stream::unfold(self, |mut state| async move {
[INFO] [stdout] 103 | |             let result = state.next().await;
[INFO] [stdout] 104 | |             result.map(|r| (r, state))
[INFO] [stdout] 105 | |         }))
[INFO] [stdout]     | |___________^ future created by async block is not `Send`
[INFO] [stdout]     |
[INFO] [stdout]     = help: the trait `Sync` is not implemented for `(dyn VertexStream<Item = std::result::Result<VertexName, DagError>> + 'static)`
[INFO] [stdout] note: future is not `Send` as this value is used across an await
[INFO] [stdout]    --> src/nameset/lazy.rs:90:72
[INFO] [stdout]     |
[INFO] [stdout] 78  |             match inner.state {
[INFO] [stdout]     |                   ----------- has type `&lazy::Inner` which is not `Send`
[INFO] [stdout] ...
[INFO] [stdout] 90  |                             if let Err(err) = inner.load_more(1, None).await {
[INFO] [stdout]     |                                                                        ^^^^^ await occurs here, with `inner.state` maybe used later
[INFO] [stdout]     = note: required for the cast from `Pin<Box<Unfold<Iter, {closure@lazy.rs:102:48}, {async block@src/nameset/lazy.rs:102:60: 105:10}>>>` to `Pin<Box<dyn VertexStream<Item = std::result::Result<VertexName, DagError>>>>`
[INFO] [stdout]     = note: the full name for the source type has been written to '/opt/rustwide/target/debug/deps/dag-bd0c9923e92e6bff.long-type-3400019024982072103.txt'
[INFO] [stdout] 

[Noratrieb]

that's probably coming from -Zdrop-tracking-mir
@cjgillot

[apiraino]

for reference: 13e6f24

Assigning priority (Zulip discussion), possibly to be adjusted after discussion.

@rustbot label -I-prioritize +P-high

[Noratrieb]

this is basically a duplicate of #116242

[lqd]

Indeed bisects to #107421 cc @cjgillot.

However, it's not obviously a duplicate of #116242 to me (nothing screams dropck here), and it is indeed not fixed by @lcnr's #117134.