Rollup merge of #130820 - 91khr:fix-coroutine-unit-arg, r=compiler-errors

Fix diagnostics for coroutines with () as input.

This may be a more real-life example to trigger the diagnostic:

```rust
#![features(try_blocks, coroutine_trait, coroutines)]

use std::ops::Coroutine;

struct Request;
struct Response;
fn get_args() -> Result<String, String> { todo!() }
fn build_request(_arg: String) -> Request { todo!() }
fn work() -> impl Coroutine<Option<Response>, Yield = Request> {
    #[coroutine]
    |_| {
        let r: Result<(), String> = try {
            let req = get_args()?;
            yield build_request(req)
        };
        if let Err(msg) = r {
            eprintln!("Error: {msg}");
        }
    }
}
```

0 files changed, 0 insertions, 0 deletions