obfd: could not resolve upvar

[lcnr]

https://github.com/The-Noah/obfd/tree/32ba2512d01b2e45b61cba55cd172450dd8aef0a

https://crater-reports.s3.amazonaws.com/pr-133502-9/try%232bef413807188d2b84cd7cc67c6e5bc4a5952d95/gh/The-Noah.obfd/log.txt

[INFO] [stdout] error: internal compiler error: compiler/rustc_mir_build/src/builder/expr/as_place.rs:260:67: could not resolve upvar: LocalVarId(HirId(DefId(0:17 ~ obfd[57aa]::walk_dir).9)) + [Deref]
[INFO] [stdout]   --> src/main.rs:72:39
[INFO] [stdout]    |
[INFO] [stdout] 72 | async fn walk_dir<'a, C>(path: &Path, cb: &C)
[INFO] [stdout]    |                                       ^^
[INFO] [stdout] 

[compiler-errors]

Non-defining revealing recursive use:

use std::pin::Pin;

async fn walk_dir<C>(cb: &C)
where
    C: Fn() -> Pin<Box<dyn Future<Output = ()> + 'static>>,
{
    async move {
        walk_dir(cb).await;
    }
    .await
}

fn main() {}

This is expected to result in a infinite/recursive/cyclical opaque error, but not an ICE.

Unfortunately it would also be very interesting to understand why this code does not ICE:

use std::pin::Pin;

async fn walk_dir<C>(cb: &C)
where
    C: Fn() -> Pin<Box<dyn Future<Output = ()> + 'static>>,
{
    async move {
        Box::pin(walk_dir(cb)).await; // <- box pin!
    }
    .await
}

fn main() {}

[compiler-errors]

lmao:

async fn walk_dir(cb: &()) {
    let fut = walk_dir(cb);
}

fn main() {}

[lcnr]

fixed by rust-lang/rust#140678