[SOLVED] Need help to understand error message related to async move closure

help
1

Hi there, Im trying to write scraping async library for rust, learning on the go and just now got blocked by an error that I don't understand. Here is my public api:

    let mut crabweb = CrabWeb::new();

    crabweb.on_html("td.title > a.storylink", |request: &mut Request, a: &Element| async move {
        println!("found a link");
        if let Some(href) = a.attr("href") {
            println!("Found link {} on {}", href, request.url);
            request.navigate(href).await?;
        }

        Ok(())
    }).await;

    crabweb.navigate("https://news.ycombinator.com/").await?;

    let worker = crabweb.new_worker();
    let handle = tokio::spawn(async move { worker.start().await; });
    crabweb.run().await?;
    handle.await?;

Here is my crawler struct definition:

pub struct CrabWeb<Fut, F>
    where Fut: Future<Output=Result<()>>,
          F: Fn(&mut Request, &Element) -> Fut {

    on_html_callbacks: HashMap<&'static str, F>,
    navigate_ch: Channels<String>, // async_std channels

    // ... some other crap
}

I get following error that makes almost no sense to me:

error: borrowed data cannot be stored outside of its closure
  --> src/main.rs:40:95
   |
38 |       let mut crabweb = CrabWeb::new();
   |           ----------- borrowed data cannot be stored into here...
39 |
40 |       crabweb.on_html("td.title > a.storylink", |request: &mut Request, a: &Element| async move {
   |  _______________________________________________------------------------------------____________^
   | |                                               |
   | |                                               ...because it cannot outlive this closure
41 | |         println!("found a link");
42 | |         if let Some(href) = a.attr("href") {
43 | |             let href = href.clone();
...  |
48 | |         Ok(())
49 | |     }).await;
   | |_____^ cannot be stored outside of its closure

error: aborting due to previous error

I do not capture anything from outside of this closure, request does share channels with CrabWeb struct, I'm a bit puzzled on how to solve this issue.

Thanks in advance!

2

I solved this problem by copying Request and Element (arguments to closure). This way I dont have borrow mess and this seems to be working.