Common Standard Traits

Standard library traits appear everywhere. Know Debug, Display, Clone, Copy, Eq, Ord, Hash, Default, From/Into, and Deref.

Recipe

use std::collections::HashMap;
 
#[derive(Debug, Clone, PartialEq, Eq, Hash, Default)]
struct UserId(u64);
 
fn main() {
    let mut m = HashMap::new();
    m.insert(UserId(1), "Ada");
    let id: UserId = 2u64.into();
    println!("{:?} {}", UserId::default(), id.0);
}

When to reach for this: Collections keys, logging, conversions, and smart pointer ergonomics.

Working Example

#[derive(Debug, Default, PartialEq)]
struct Config { timeout_ms: u64, retries: u32 }
 
impl From<u64> for Config {
    fn from(timeout_ms: u64) -> Self {
        Self { timeout_ms, ..Default::default() }
    }
}
 
fn main() {
    let c: Config = 5000.into();
    assert_eq!(c.timeout_ms, 5000);
}

What this demonstrates:

• Default + From for ergonomic construction
• Into auto from From
• PartialEq for tests
• Debug for diagnostics

Deep Dive

Gotchas

• Derive Ord on floats - Not total. Fix: Wrapper or integer cents.
• Hash without Eq - Derive pairing. Fix: Both together for maps.
• Display not derivable - Manual impl needed. Fix: Use Debug or write fmt.
• Default wrong sentinel - Zero values misleading. Fix: new() constructor instead.
• From overlap - Only one From<T> per type. Fix: Newtype for ambiguous sources.

Alternatives

FAQs

Related

• Deriving Traits
• Operator Overloading
• Deref & Deref Coercion
• Traits Basics

Stack versions: This page was written for Rust 1.97.0 (edition 2024), Tokio 1.x, Axum 0.8, serde 1.0, sqlx 0.8, clap 4, and Polars 0.46+.