/// write a function `add_one`that takes all arguments that can be converted to `&mut u64`.
/// Because [`Box<T>`] implements `AsMut<T>` `add_one` accepts arguments of type
/// `&mut Box<u64>` as well:
+///
/// ```
/// fn add_one<T: AsMut<u64>>(num: &mut T) {
/// *num.as_mut() += 1;
/// add_one(&mut boxed_num);
/// assert_eq!(*boxed_num, 1);
/// ```
-/// [`Box<T>`]: ../../std/boxed/struct.Box.html
///
+/// [`Box<T>`]: ../../std/boxed/struct.Box.html
#[stable(feature = "rust1", since = "1.0.0")]
pub trait AsMut<T: ?Sized> {
/// Performs the conversion.