mirror of https://github.com/rust-lang/rust
29 lines
666 B
Rust
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));
|
|
}
|