Deriving Traits

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

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
struct DrawingBuffer {
    target: [u8; 16],
    commands: Vec<String>,
}

// Many traits have simple implementations that can be generated automatically.
impl Clone for DrawingBuffer {
    fn clone(&self) -> Self {
        DrawingBuffer {
            target: self.target.clone(),
            commands: self.commands.clone(),
        }
    }
}

Many traits have trivial implementations that would be easy to mechanically write. For these traits, it’s possible to have the compiler generate the implementation for us using a derive macro.
For example, the Clone trait is commonly implemented by simply cloning all fields of the struct. If this is the behavior we want for our type, we don’t need to write out the boilerplate ourselves. Replace the manual implementation with the corresponding derive.
Derived trait implementations automatically stay in sync with your type definition. Demonstrate adding a field to DrawingBuffer and show that the derived Clone impl is automatically updated, whereas the manual impl has to be updated by hand.
Many standard library traits support being derived, and it’s common for traits defined in the ecosystem to also support this.
Traits do not support being derived by default, but you can implement derive support for your own traits with a macro. Doing so is covered in the Macros course.

references:

https://doc.rust-lang.org/reference/attributes/derive.html#r-attributes.derive

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Deriving Traits