impl Trait causes "borrowed value does not live long enough" #50823
Description
This code:
fn main() {
println!("{:?}", max());
}
fn max() -> Option<i32> {
let v = vec![1, 2, 3];
iter(&v).max()
}
fn iter(a: &[i32]) -> impl Iterator<Item = i32> + '_ {
a.iter().cloned()
}gives this error:
error[E0597]: `v` does not live long enough
--> src/main.rs:7:11
|
7 | iter(&v).max()
| ^ borrowed value does not live long enough
8 | }
| - `v` dropped here while still borrowed
|
= note: values in a scope are dropped in the opposite order they are created
But if I change the return type to an explicit std::iter::Cloned<std::slice::Iter<'_, i32>>, then it's fine. It's also fine if I bind that result before returning it, like: let m = iter(&v).max(); m
And it works with #![feature(nll)], so maybe I just have to hope for that to stabilize soon... 🙏