| An attribute is metadata applied to some module, crate or item. This metadata |
| can be used to/for: |
| |
| <!-- TODO: Link these to their respective examples --> |
| * [conditional compilation of code](/attribute/cfg.html) |
| * [set crate name, version and type (binary or library)](/attribute/crate.html) |
| * disable [lints](https://en.wikipedia.org/wiki/Lint_%28software%29) (warnings) |
| * enable compiler features (macros, glob imports, etc.) |
| * link to a foreign library |
| * mark functions as unit tests |
| * mark functions that will be part of a benchmark |
| |
| When attributes apply to a whole crate, their syntax is `#![crate_attribute]`, |
| and when they apply to a module or item, the syntax is `#[item_attribute]` |
| (notice the missing bang `!`). |
| |
| Attributes can take arguments with different syntaxes: |
| |
| * `#[attribute = "value"]` |
| * `#[attribute(key = "value")]` |
| * `#[attribute(value)]` |
