Asynchronous closures make trait constraint inference recursive

[eareimu]

I tried this code:

async fn foo() -> Vec<(&'static str, ())> {
    let mut errors = Vec::new();
    let op = async || Ok(());
    if let Err(a) = async { op().await }.await {
        errors.push(("test", a));
    }
    if let Err(a) = async { op().await }.await {
        errors.push(a);
    }
    errors
}

The code could probably be simplified further?

I expected to see this happen: ...type mismatch...

Instead, this happened:

error[E0275]: overflow evaluating the requirement `(&str, _): std::marker::Sized`
   --> genmeta-ssh3/src/config.rs:127:22
    |
127 |     let mut errors = Vec::new();
    |                      ^^^
    |
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`genmeta_ssh3`)
    = note: required because it appears within the type `(&str, (&str, _))`
    = note: required because it appears within the type `(&str, (&str, (&str, _)))`
    = note: required because it appears within the type `(&str, (&str, (&str, (&str, _))))`
    = note: required because it appears within the type `(&str, (&str, (&str, (&str, (&str, _)))))`
...... continue recursion

Meta

rustc --version --verbose:

rustc 1.91.0-nightly (7ad23f43a 2025-09-09)
binary: rustc
commit-hash: 7ad23f43a225546c095123de52cc07d8719f8e2b
commit-date: 2025-09-09
host: aarch64-apple-darwin
release: 1.91.0-nightly
LLVM version: 21.1.0

Backtrace

none

[GrigorenkoPV]

The error used to be

error[E0308]: mismatched types
 --> src/lib.rs:8:21
  |
8 |         errors.push(a);
  |                ---- ^ cyclic type of infinite size
  |                |
  |                arguments to this method are incorrect
  |

before #119989