as considered harmful

[wizzwizz4]

Using the as keyword is considered harmful; it silently panics when value are out of range, and it's not explicit about it. Consider replacing:

fn main() {
    let my_number = 100;
    println!("{}", my_number as u8 as char);
}

with:

use std::convert::TryFrom;

fn main() {
    let my_number = 100;
    println!("{}", u8.try_from(my_number).unwrap() as char);
}

Since this a tutorial, I think it would be better to write:

fn main() {
    let my_number = 100 as u8;
    println!("{}", my_number as char);
}

or:

fn main() {
    let my_number: u8 = 100;
    println!("{}", my_number as char);
}

or:

fn main() {
    let my_number = 100u8;
    println!("{}", my_number as char);
}

which are all equivalent, but mean something slightly different to the original code, so you'd need to adjust the text slightly.

(None of these solutions feel good enough for inclusion. Maybe you could take a brief tangent to point out the problem with using as? But panicking hasn't been introduced yet…)

[Dhghomon]

Hi @wizzwizz4 - I've actually had it in the back of my mind to simplify the examples here to just do u8 as char since 1) the point of the examples is to just show why there are different numeric types, and 2) (something) as (something) as (something else) is probably a bit much.

So it'll probably end up with just a u8 as char example here, then move casting to a few sections down with some more advanced examples and discussion. TryFrom could work there (I've forgotten to write about it so far) and I could maybe leverage it into starting to talk about traits before the part about actually implementing them, so still in the relatively simple section but not in the super introductory part on top.