/// }

/// ```

///

/// This still allows the use of `async fn` within impls of the trait.

/// However, it also means that the trait will never be compatible with

/// impls where the returned [`Future`] of the method does not implement

/// `Send`.

///

/// Conversely, if the trait is used only locally, if it is never used in

/// generic functions, or if it is only used in single-threaded contexts

/// that do not care whether the returned [`Future`] implements [auto traits]

/// such as [`Send`], then the lint may be suppressed.

/// that do not care whether the returned [`Future`] implements [`Send`],

/// then the lint may be suppressed.

///

/// [`Future`]: https://doc.rust-lang.org/core/future/trait.Future.html

/// [`Send`]: https://doc.rust-lang.org/core/marker/trait.Send.html