visit_diff: analyzing structural differences in Rust

This is a library for easily comparing Rust data structures to detect differences. This is useful, for example, when reporting a test failure.

The simplest use case:

1. Put a #[derive(Diff)] annotation on your type.

2. Replace assert_eq! with assert_eq_diff!.

Now your error messages will highlight diffs instead of making you hunt for them manually.

See the API docs on the module for more.