Hands-On Concurrency with Rust

Static and dynamic dispatch

Trait objects likewise have no statically known size in Rust. Trait objects are the mechanism by which Rust performs dynamic dispatch. Preferentially, Rust is a static dispatch language as there are increased opportunities for inlining and optimization—the compiler simply knows more. Consider the following code:

use std::ops::Add;

fn sd_add<T: Add<Output=T>>(x: T, y: T) -> T {
    x + y
}

fn main() {
    assert_eq!(48, sd_add(16 as u8, 32 as u8));
    assert_eq!(48, sd_add(16 as u64, 32 as u64));
}

Here, we define a function, sd_add<T: Add<Output=T>>(x: T, y: T) -> T. Rust, like C++, will perform monomorphization at compile time, emitting two sd_add functions, one for u8 and the other for u64. Like C++, this potentially increases ...