Lints - The rustdoc book

# 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)]
    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)]
    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 | |     /// ```
       | |___________^