rust/tests/ui/nll/rc-loop.rs
2024-02-16 20:02:50 +00:00

29 lines
666 B
Rust

//@ run-pass
// A test for something that NLL enables. It sometimes happens that
// the `while let` pattern makes some borrows from a variable (in this
// case, `x`) that you need in order to compute the next value for
// `x`. The lexical checker makes this very painful. The NLL checker
// does not.
use std::rc::Rc;
#[derive(Debug, PartialEq, Eq)]
enum Foo {
Base(usize),
Next(Rc<Foo>),
}
fn find_base(mut x: Rc<Foo>) -> Rc<Foo> {
while let Foo::Next(n) = &*x {
x = n.clone();
}
x
}
fn main() {
let chain = Rc::new(Foo::Next(Rc::new(Foo::Base(44))));
let base = find_base(chain);
assert_eq!(&*base, &Foo::Base(44));
}