Missing iterations

[samueltardieu]

The following code prints "foo" 4 times with stable and beta, but prints nothing with rustc 1.33.0-nightly (93c2f05 2018-12-15).

fn main() {
    std::iter::once(0).cycle().skip(1).take(4).for_each(|_| println!("foo"));
}

Replacing once() by something else or replacing for_each() with map() exhibits the same behaviour.

[bluss]

It looks like the try_fold impl for Cycle in commit fbe5aa5 is is not correct, this is probably the cause. PR #56630

[samueltardieu]

Indeed, it looks like if you try to fold after you have just exhausted a copy of your original iterator, you are out of luck and will exit immediately with the initial value.