---

name: rustdoc description: Rust documentation conventions (RFC 1574). Apply when writing doc comments on Rust items. Covers summary sentences, section headings, type references, and examples.

Rust Documentation Conventions (RFC 1574)

Apply these rules when writing doc comments (///) on public and private Rust items.

Summary Sentence

Every doc comment starts with a single-line summary sentence.

Copy// DO: third person singular present indicative, never ends with period
/// Returns the length of the string
/// Creates a new instance with default settings
/// Parses the input and returns the result

// DON'T: imperative, missing period, or verbose
/// Return the length of the string
/// This function creates a new instance with default settings.
/// Use this to parse the input and get the result back.

Comment Style

Use line comments, not block comments.

Copy// DO
/// Summary sentence here
///
/// More details if needed.

// DON'T
/**
 * Summary sentence here
 *
 * More details if needed.
 */

Use //! only for crate-level and module-level docs at the top of the file.

Section Headings

Use these exact headings (always plural):

Copy/// Summary sentence
///
/// # Examples
///
/// # Panics
///
/// # Errors
///
/// # Safety
///
/// # Aborts
///
/// # Undefined Behavior

Copy// DO
/// # Examples

// DON'T
/// # Example
/// ## Examples
/// **Examples:**

Type References

Use full generic forms and link with reference-style markdown.

Copy// DO
/// Returns [`Option<T>`] if the value exists.
///
/// [`Option<T>`]: std::option::Option

// DON'T
/// Returns `Option` if the value exists.
/// Returns an optional value.

Examples

Every public item should have examples showing usage.

Copy/// Adds two numbers together
///
/// # Examples
///
/// ```
/// let result = my_crate::add(2, 3);
/// assert_eq!(result, 5);
/// ```
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

For multiple patterns:

Copy/// Parses a string into a number
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let n: i32 = my_crate::parse("42").unwrap();
/// assert_eq!(n, 42);
/// ```
///
/// Handling errors:
///
/// ```
/// let result = my_crate::parse::<i32>("not a number");
/// assert!(result.is_err());
/// ```

Errors Section

Document what errors can be returned and when.

Copy/// Reads a file from disk
///
/// # Errors
///
/// Returns [`io::Error`] if the file does not exist or cannot be read.
///
/// [`io::Error`]: std::io::Error

Panics Section

Document conditions that cause panics.

Copy/// Divides two numbers
///
/// # Panics
///
/// Panics if `divisor` is zero.
pub fn divide(dividend: i32, divisor: i32) -> i32 {
    assert!(divisor != 0, "divisor must not be zero");
    dividend / divisor
}

Safety Section

Required for unsafe functions.

Copy/// Dereferences a raw pointer
///
/// # Safety
///
/// The pointer must be non-null and properly aligned.
/// The pointed-to memory must be valid for the lifetime `'a`.
pub unsafe fn deref<'a, T>(ptr: *const T) -> &'a T {
    &*ptr
}

Module vs Type Docs

• Module docs (//!): high-level summaries, when to use this module
• Type docs (///): comprehensive, self-contained

Some duplication is acceptable.

Language

Use American English spelling: "color" not "colour", "serialize" not "serialise".