Cautious variant of take_while.

take_while_eq.rs

use std::iter::{from_fn, Peekable};

fn take_while_eq<I>(it: &mut Peekable<I>, eq: I::Item) -> impl Iterator<Item = I::Item> + '_
where
    I: Iterator,
    I::Item: Eq,
{
    from_fn(move || it.next_if_eq(&eq))
}