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Asynchronous closures make trait constraint inference recursive #146399
Description
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
Activity
GrigorenkoPV commentedon Sep 10, 2025
The error used to be
before #119989
chenyukang commentedon Aug 25, 2026
here seems better? output from PR #161705