Module rayon::compile_fail::must_use::try_fold

First sanity check that the expression is OK.

#![deny(unused_must_use)]

use rayon::prelude::*;

let v: Vec<_> = (0..100).map(Some).collect();
let _ =
 v.par_iter().try_fold(|| 0, |x, _| Some(x)); 

Now trigger the must_use.

#![deny(unused_must_use)]

use rayon::prelude::*;

let v: Vec<_> = (0..100).map(Some).collect();
 v.par_iter().try_fold(|| 0, |x, _| Some(x));