Rustdoc suggests notable trait for &mut when given shared reference

[carbotaniuman]

I can't tell what version this is, but I was browsing the HashMap documentation here and came across this block for fn key(&self).

Notable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F 
where
    F: Unpin + Future + ?Sized, 
    type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I 
where
    I: Iterator + ?Sized, 
    type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W