Closed as not planned
Description
I tried this code:
fn bar<T>(_i: T) -> impl Iterator<Item = usize> + 'static {
std::iter::once(3)
}
fn bar2<T: ?Sized>(_i: &T) -> impl Iterator<Item = usize> + 'static {
std::iter::once(3)
}
fn main() {
let mut b;
{
let a = 1;
// doesn't work
b = bar(&a);
// this works
// b = bar2(&a);
}
println!("{}", b.next().unwrap());
}I expected to see this happen:
Both bar and bar2 should compile successfully, since both outputs have 'static bounds.
Instead, this happened:
The version that calls bar2 successfully compiles, whereas calling bar results in the following error:
error[[E0597]](https://doc.rust-lang.org/nightly/error-index.html#E0597): `a` does not live long enough
--> src/main.rs:27:19
|
27 | b = bar(&a);
| ^^ borrowed value does not live long enough
28 | }
| - `a` dropped here while still borrowed
29 | println!("{}", b.next().unwrap());
| -------- borrow later used here
Using a TAIT as the return type of bar seems to not capture any lifetimes from T.
#![feature(type_alias_impl_trait)]
type Iter = impl Iterator<Item = usize> + 'static;
fn bar<T>(_i: T) -> Iter {
std::iter::once(3)
}
fn main() {
let mut b;
{
let a = 1;
// this works fine
b = bar(&a);
}
println!("{}", b.next().unwrap());
}Meta
rustc --version --verbose:
rustc 1.68.0-nightly (0442fbabe 2023-01-10)
This is also present on the latest stable version: rustc 1.66.1.