Lints

rustdoc provides lints to help you writing and testing your documentation. You can use them like any other lints by doing this:

#![allow(missing_docs)] // allowing the lint, no message
#![warn(missing_docs)] // warn if there is missing docs
#![deny(missing_docs)] // rustdoc will fail if there is missing docs

Here is the list of the lints provided by rustdoc:

intra_doc_link_resolution_failure

This lint warns by default and is nightly-only. This lint detects when an intra-doc link fails to get resolved. For example:

#![allow(unused_variables)]
fn main() {
/// I want to link to [`Inexistent`] but it doesn't exist!
pub fn foo() {}
}

You'll get a warning saying:

error: `[`Inexistent`]` cannot be resolved, ignoring it...

missing_docs

This lint is allowed by default. It detects items missing documentation. For example:

#![warn(missing_docs)]

pub fn undocumented() {}
fn main() {}

The undocumented function will then have the following warning:

warning: missing documentation for a function
  --> your-crate/lib.rs:3:1
   |
 3 | pub fn undocumented() {}
   | ^^^^^^^^^^^^^^^^^^^^^

missing_doc_code_examples

This lint is allowed by default. It detects when a documentation block is missing a code example. For example:

#![warn(missing_doc_code_examples)]

/// There is no code example!
pub fn no_code_example() {}
fn main() {}

The no_code_example function will then have the following warning:

warning: Missing code example in this documentation
  --> your-crate/lib.rs:3:1
   |
LL | /// There is no code example!
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To fix the lint, you need to add a code example into the documentation block:

#![allow(unused_variables)]
fn main() {
/// There is no code example!
///
/// ```
/// println!("calling no_code_example...");
/// no_code_example();
/// println!("we called no_code_example!");
/// ```
pub fn no_code_example() {}
}

private_doc_tests

This lint is allowed by default. It detects documentation tests when they are on a private item. For example:

#![warn(private_doc_tests)]

mod foo {
    /// private doc test
    ///
    /// ```
    /// assert!(false);
    /// ```
    fn bar() {}
}
fn main() {}

Which will give:

warning: Documentation test in private item
  --> your-crate/lib.rs:4:1
   |
 4 | /     /// private doc test
 5 | |     ///
 6 | |     /// ```
 7 | |     /// assert!(false);
 8 | |     /// ```
   | |___________^