async fn foo() {
  println!("before");
  bar().await
  println!("after");
}

enum SuspendPoint { Begin, AwaitBar }

struct FooFuture {
  suspend_point: SuspendPoint,
  // local variables that live through suspend points
  _bar: BarFuture,
}

impl Future for FooFuture {
  fn poll(self, cx) {
    match self.suspend_point {
      Begin => goto BEGIN,
      AwaitBar => goto AWAIT_BAR,
    }
  BEGIN:
    println!("before");
    self._bar = bar();
  AWAIT_BAR:
    if let Pending = self._bar.poll(cx) {
      self.suspend_point = AwaitBar;
      return Pending;
    }
    drop(self._bar);
    println!("after");
    Ready
  }
}

#[opg(POST, ("some" / "path" / MySuperParamId))]
fn route_a() -> BoxedFilter<(impl warp::Reply,)> { ... }

#[opg(GET, ("another" / "path"))]
fn route_b() -> BoxedFilter<(impl warp::Reply,)> { ... }

fn docs() -> BoxedFilter<(impl warp::Reply,)> {
    let openapi = { somehow collect meta from route_a and route_b }.to_string();
    warp::path!("swagger.yaml").and(warp::get()).map(move || openapi).boxed()
}

fn api() -> .... {
    warp::serve(route_a().or(route_b()).or(docs())).run(...).await;
}

#[tokio::main]
asycn fn main() {
    foo();
}

fn foo() {
    // bar().await;
}

async fn bar() {
}