If you'd like to have two modules, `main.rs` and `foo/bar.rs`, and you want the latter to be `foo::bar`, you can do this in `main.rs` to avoid needing a foo.rs that just does `mod bar;`:

    mod foo {
        mod bar;
    }

I was just following the example from the docs, my use case is more like this:

  .
  ├── lib.rs
  └── foo/
    └── mod.rs
    └── one.rs
    └── two.rs
    └── three.rs
    └── four.rs
  └── bar/
    └── mod.rs
    └── one.rs
    └── two.rs
    └── three.rs
    └── four.rs

Which feels to me like a very common folder structure in other languages.