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// regression test of https://github.com/rust-lang/rust/pull/133572#issuecomment-2543007164
// see also the test for UniqueRc` in variance-uniquerc.rs
//
// inline comments explain how this code *would* compile if UniqueArc was still covariant
#![feature(unique_rc_arc)]
use std::sync::UniqueArc;
fn extend_lifetime<'a, 'b>(x: &'a str) -> &'b str {
let r = UniqueArc::new(""); // UniqueArc<&'static str>
let w = UniqueArc::downgrade(&r); // Weak<&'static str>
let mut r = r; // [IF COVARIANT]: ==>> UniqueArc<&'a str>
*r = x; // assign the &'a str
let _r = UniqueArc::into_arc(r); // Arc<&'a str>, but we only care to activate the weak
let r = w.upgrade().unwrap(); // Arc<&'static str>
*r // &'static str, coerces to &'b str
//~^ ERROR lifetime may not live long enough
}
fn main() {
let s = String::from("Hello World!");
let r = extend_lifetime(&s);
println!("{r}");
drop(s);
println!("{r}");
}
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