Borrow Checker allowing mutable and immutable reference out on a vec [Nightly] #41774
Description
When using array indexing, the borrow checking is allowing for both an immutable and mutable reference to be taken out on a vec.
Playground: https://play.rust-lang.org/?gist=558d7e98834c5e269eed35b335823220&version=nightly&backtrace=0
Version: rustc 1.19.0-nightly (59f1a2f 2017-05-04)
Offending Code:
#[derive(Debug)]
struct Data {
x: i32,
y: i32,
}
impl Data {
fn add(&mut self, other: &Data) -> &mut Data {
self.x += other.x;
self.y += other.y;
return self;
}
}
fn main() {
let mut v = vec![
Data{x: 0, y: 1},
Data{x: 2, y: 3},
Data{x: 4, y: 5},
];
v[0].add(v[1].add(&v[2]));
println!("{:?}", v);
}
Expected Result:
error[E0499]: cannot borrow `v` as mutable more than once at a time
--> <anon>:21:14
|
21 | v[0].add(v[1].add(&v[2]));
| - ^ - first borrow ends here
| | |
| | second mutable borrow occurs here
| first mutable borrow occurs here
error[E0502]: cannot borrow `v` as immutable because it is also borrowed as mutable
--> <anon>:21:24
|
21 | v[0].add(v[1].add(&v[2]));
| - ^ - mutable borrow ends here
| | |
| | immutable borrow occurs here
| mutable borrow occurs here
Actual Result:
[Data { x: 6, y: 9 }, Data { x: 6, y: 8 }, Data { x: 4, y: 5 }]