Hash

Performing a hash on a type.

Derivable: ✅

// Copyright 2025 Google LLC
// SPDX-License-Identifier: Apache-2.0

use std::collections::HashMap;

#[derive(PartialEq, Eq, Hash)]
pub struct User {
    id: u32,
    name: String,
}

fn main() {
    let user = User { id: 1, name: "Alice".into() };
    let mut map = HashMap::new();
    map.insert(user, "value");
}

  • Allows a type to be used in hash algorithms, most commonly used with data structures like HashMap.

  • Makes it very easy for us to use custom types as the keys in a HashMap!

  • Hash doesn’t define any of the hashing logic itself, instead it just feeds the type’s data into a Hasher. This allows us to use different hash algorithms without changing a type’s Hash impl.