uncaptured lifetimes required to live as long as the opaque type

[aliemjay]

The following valid code stopped compiling since v1.67, most likely due to #103491:

fn opaque<'a: 'a>(_: &'a str) -> *mut impl Sized {
    &mut ()
}

fn main() {
    let x = opaque(&String::new()); //~ ERROR temporary value dropped while borrowed
    drop(x);
}

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-medium