Deriving

Supported traits can be automatically implemented for your custom types, as follows:

#[derive(Debug, Clone, Default)]
struct Player {
    name: String,
    strength: u8,
    hit_points: u8,
}

fn main() {
    let p1 = Player::default(); // Default trait adds `default` constructor.
    let mut p2 = p1.clone(); // Clone trait adds `clone` method.
    p2.name = String::from("EldurScrollz");
    // Debug trait adds support for printing with `{:?}`.
    println!("{p1:?} vs. {p2:?}");
}

This slide should take about 3 minutes.

Derivation is implemented with macros, and many crates provide useful derive macros to add useful functionality. For example, serde can derive serialization support for a struct using #[derive(Serialize)].
Derivation is usually provided for traits that have a common boilerplate-y implementation that is correct for most cases. For example, demonstrate how a manual Clone impl can be repetitive compared to deriving the trait:
```
impl Clone for Player {
    fn clone(&self) -> Self {
        Player {
            name: self.name.clone(),
            strength: self.strength.clone(),
            hit_points: self.hit_points.clone(),
        }
    }
}
```
Not all of the .clone()s in the above are necessary in this case, but this demonstrates the generally boilerplate-y pattern that manual impls would follow, which should help make the use of derive clear to students.

Comprehensive Rust 🦀

Deriving