_ replacement suggestion when returning async closures is broken #148493
Description
Code
fn ord() -> _ { async || {} }Current output
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types --> src/lib.rs:1:13 | 1 | fn ord() -> _ { | ^ not allowed in type signatures | help: replace with the correct return type | 1 - fn ord() -> _ { 1 + fn ord() -> {async closure@src/lib.rs:2:5: 2:13} { |Desired output
error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types --> src/lib.rs:1:13 | 1 | fn ord() -> _ { | ^ not allowed in type signatures | help: replace with the correct return type | 1 - fn ord() -> _ { 1 + fn ord() -> impl AsyncFn() { |Rationale and extra context
This works correctly if you remove either async or ||.
Found from #148488.
Other cases
Rust Version
Nightly version: 1.93.0-nightly (2025-11-03 20383c9f1d84eb9b9c66)Anything else?
No response