non_repeating_rand.rs

use rand; // 0.8.3
use rand::Rng;
use std::iter::successors;

fn non_repeating<T: std::cmp::PartialEq + Clone>(src: &[T]) -> impl Iterator<Item = &T> + '_ {
    let mut rng = rand::thread_rng();
    successors(Some(&src[rng.gen_range(0..src.len())]), move |n| {
        let mut next = &src[rng.gen_range(0..src.len())];
        while *next == **n {
            next = &src[rng.gen_range(0..src.len())];
        }
        Some(next)
    })
}
fn main() {
    for i in non_repeating(&["a", "b"]).take(10) {
        println!("{}", i)
    }
}