dyn_partial_eq

PartialEq for trait objects

This crate provides macros for deriving PartialEq for Box<dyn Trait>, removing the boilerplate of having to provide your own implementations. Inspired by this blog post: https://dev.to/magnusstrale/rust-trait-objects-in-a-vector-non-trivial-4co5

Add the crate to your project:

cargo add dyn_partial_eq

use dyn_partial_eq::*;

// Use this to add a DynPartialEq supertrait and implement PartialEq for your trait.
#[dyn_partial_eq]
trait SomeTrait {}

// Derive DynPartialEq and PartialEq on your types that implement your trait.
#[derive(DynPartialEq, PartialEq)]
struct A(usize);
impl SomeTrait for A {}

#[derive(DynPartialEq, PartialEq)]
struct B((usize, usize));
impl SomeTrait for B {}

And voila:

let boxed_a_zero: Box<dyn SomeTrait> = Box::new(A(0));
let boxed_a_one: Box<dyn SomeTrait> = Box::new(A(1));
let boxed_b: Box<dyn SomeTrait> = Box::new(B((1, 2)));

assert_eq!(&boxed_a_zero == &boxed_a_zero, true);
assert_eq!(&boxed_a_zero == &boxed_a_one, false);
assert_eq!(&boxed_a_zero == &boxed_b, false);

assert_eq!(&boxed_a_one == &boxed_a_zero, false);
assert_eq!(&boxed_a_one == &boxed_a_one, true);
assert_eq!(&boxed_a_one == &boxed_b, false);

assert_eq!(&boxed_b == &boxed_a_zero, false);
assert_eq!(&boxed_b == &boxed_a_one, false);
assert_eq!(&boxed_b == &boxed_b, true);