/// let mut val = 12;
/// let x: Result<&mut i32, i32> = Ok(&mut val);
/// assert_eq!(x, Ok(&mut 12));
/// let copied = x.copied();
/// assert_eq!(copied, Ok(12));
/// ```
/// let mut val = 12;
/// let x: Result<&mut i32, i32> = Ok(&mut val);
/// assert_eq!(x, Ok(&mut 12));
/// let copied = x.copied();
/// assert_eq!(copied, Ok(12));
/// ```