poem: type annotations needed

[lcnr]

[INFO] [stdout] error[E0282]: type annotations needed
[INFO] [stdout]    --> /opt/rustwide/cargo-home/registry/src/index.crates.io-1949cf8c6b5b557f/poem-3.0.4/src/route/router_method.rs:186:33
[INFO] [stdout]     |
[INFO] [stdout] 186 | ...                   let mut resp = self.call(req).await?;
[INFO] [stdout]     |                           ^^^^^^^^
[INFO] [stdout] 187 | ...                   resp.set_body(());
[INFO] [stdout]     |                            -------- type must be known at this point
[INFO] [stdout]     |
[INFO] [stdout] help: consider giving `resp` an explicit type
[INFO] [stdout]     |
[INFO] [stdout] 186 |                             let mut resp: /* Type */ = self.call(req).await?;
[INFO] [stdout]     |                                         ++++++++++++
[INFO] [stdout] 
[INFO] [stdout] 
[INFO] [stdout] error[E0271]: type mismatch resolving `impl Future<Output = Result<<RouteMethod as Endpoint>::Output, Error>> + Send normalizes-to _`
[INFO] [stdout]    --> /opt/rustwide/cargo-home/registry/src/index.crates.io-1949cf8c6b5b557f/poem-3.0.4/src/route/router_method.rs:186:44
[INFO] [stdout]     |
[INFO] [stdout] 186 | ...                   let mut resp = self.call(req).await?;
[INFO] [stdout]     |                                      ^^^^^^^^^^^^^^ types differ
[INFO] [stdout] 

[lcnr]

it encounters a debug assert

trait Trait<'a> {}
impl<'a, T: Send> Trait<'a> for T {}

fn needs_trait<T: for<'a> Trait<'a>>(_: T) {}
fn main() {
    let x = ();
    needs_trait(async { x });
}

[lcnr]

fixing that issue, given us the actual bug here

use std::future::Future;
fn call() -> impl Future<Output = String> {
    Box::pin(async {
        let mut resp = call().await;
        resp.len();
        resp
    })
}

[lcnr]

with iterator

fn iterator(b: bool) -> impl Iterator<Item = String> {
    if b {
        for i in iterator(false) {
            i.len();
        }
    }

    vec![].into_iter()
}