What Is the Copy Trait and Which Types Implement It?

The Copy trait indicates that a type can be duplicated by simply copying its bits, meaning assignment does not move ownership. Primitive types like integers (i32, u64), floating-point numbers (f32, f64), booleans (bool), and characters (char) implement Copy by default, as do tuples and structs composed entirely of Copy types. You can derive this trait for your own structs using #[derive(Copy, Clone)] if all fields are also Copy.

#[derive(Copy, Clone)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let p1 = Point { x: 1, y: 2 };
    let p2 = p1; // p1 is copied, not moved; both p1 and p2 are valid
    println!("p1: {:?}, p2: {:?}", p1, p2);
}

The Copy trait tells Rust that a type is cheap to duplicate, so assigning it to a new variable creates a full copy instead of transferring ownership. This applies to simple data like numbers and booleans, similar to how copying a number on a piece of paper doesn't erase the original. You use it when you need to pass values around without worrying about who owns the original data.