assert_eq! macro

This crate provides a custom assert_eq! macro that gives detailed error messages when comparing complex data structures. It supports nested structures, collections, and provides a path to the first point of difference.

A quick example:

use assert_eq::AssertEq;
#[derive(AssertEq, Debug)]
struct A {
    x: String,
    y: Vec<i32>,
}

#[derive(AssertEq, Debug)]
struct B {
    x: A,
    y: Vec<i32>,
}

let x = B {
    x: A {
        x: "hello".to_string(),
        y: vec![1, 2, 3],
    },
    y: vec![4, 5, 6],
};

let y = B {
    x: A {
        x: "hello".to_string(),
        y: vec![1, 2, 8],
    },
    y: vec![4, 5, 6],
};

assert_eq::assert_eq!(x, y); // at .x → .y → [2] left: 3 right: 8

Running this code will panic with the following message:

assertion `left == right` failed: at .x → .y → [2]
  left: 3
 right: 8
assert_eq! called initially on:
  left: B { x: A { x: "hello", y: [1, 2, 3] }, y: [4, 5, 6] }
 right: B { x: A { x: "hello", y: [1, 2, 8] }, y: [4, 5, 6] }

It is no_std compatible, but requires the alloc crate.