Filesystem Hierarchy

The module content can be omitted:

mod garden;

The garden module content is found at:

• src/garden.rs (modern Rust 2018 style)
• src/garden/mod.rs (older Rust 2015 style)

Similarly, a garden::vegetables module can be found at:

• src/garden/vegetables.rs (modern Rust 2018 style)
• src/garden/vegetables/mod.rs (older Rust 2015 style)

The crate root is in:

• src/lib.rs (for a library crate)

• src/main.rs (for a binary crate)

• The change from module/mod.rs to module.rs doesn’t preclude the use of submodules in Rust 2018. (It was mandatory in Rust 2015.)

  The following is valid:

  src/ ├── main.rs ├── top_module.rs └── top_module/ └── sub_module.rs

• The main reason for the change is to prevent many files named mod.rs, which can be hard to distinguish in IDEs.

• Rust will look for modules in modulename/mod.rs and modulename.rs, but this can be changed with a compiler directive:

  #[path = "some/path.rs"] mod some_module { }

  This is useful, for example, if you would like to place tests for a module in a file named some_module_test.rs, similar to the convention in Go.