made in gimp, with <3

Context for actual rust programmers

I was having massive beef with the rust compiler yesterday, every cargo check takes 20 seconds.

And then look at the three functions below, only one of them are Send, if you know why, please let me know.

(Note: value that is not Send cannot be held across an await point, and Box<dyn Error> is not Send)

async fn one() {
    let res: Result<(), Box<dyn Error>> = do_stuff();
    if let Err(err) = res {
        let content = err.to_string();
        let _ = do_stuff(content).await;
    }
}

async fn two() {
    let res: Result<(), Box<dyn Error>> = do_stuff();
    let content = if let Err(err) = res {
        Some(err.to_string())
    } else {
        None
    };
    drop(res);
    if let Some(content) = content {
        let _ = do_stuff(content).await;
    }
}

async fn three() {
    let content = {
        let res: Result<(), Box<dyn Error>> = do_stuff();
        if let Err(err) = res {
            Some(err.to_string())
        } else {
            None
        }
    };
    if let Some(content) = content {
        let _ = do_stuff(content).await;
    }
}
  • edinbruh@feddit.itEnglish
    111·
    2 days ago

    Yeah, like, who would ever want to

    stuff1()?.map(stuff2);

    It’s much better to just:

    err, value = stuff1();
if err == nil 
    return err, nil;
if value != nil
    stuff2(value);

    And you might even:

    for a in vec {
    vec[a]
}
    • Ethan@programming.devEnglish
      4·
      2 days ago

      I totally agree, that Go snippet is absolutely more maintainable. Though you forgot the curly braces and the semicolons are unnecessary.

      • AeonFelis@lemmy.world
        2·
        2 days ago

        Though you forgot the curly braces and the semicolons are unnecessary.

        Yup. These are pretty big issues. But there are also some minor, trivial, purely-preference-based issues - like returning an error if err == nil instead of when it isn’t.