cannot move into irrefutable slice patterns with multiple elements

[oli-obk]

let arr = [Box::new(1), Box::new(2), Box::new(3)];
let [a, b, c] = arr;

fails with

<anon>:5:13: 5:14 error: use of moved value: `arr[..]` [E0382]
<anon>:5     let [a, b, c] = arr;
                     ^
<anon>:5:10: 5:11 note: `arr[..]` moved here because it has type `Box<i32>`, which is moved by default
<anon>:5     let [a, b, c] = arr;
                  ^
<anon>:5:10: 5:11 help: use `ref` to override

while the following work fine:

let arr = [Box::new(1)];
let [a] = arr;

enum Dummy<T> {
    Val([T; 2]),
}
let arr = [Box::new(1), Box::new(2)];
let Dummy::Val([a, b]) = Dummy::Val(arr);

[arielb1]

Slice patterns are broken.

[oli-obk]

yes they are, is there any consensus on whether to report bugs and fix it or simply rewrite it from scratch?

[steveklabnik]

Triage; no change on slice patterns

[mikhail-m1]

works with -Z borrowck=mir, hope it will be soon by default

[ZoeyR]

This is still happening on stable as of the 1.26 release. This may cause confusion for people trying to use slice patterns since the release notes show an example of them. The only way the release notes get away with it is because they use numbers which are Copy.

[andersk]

These work fine as parameter patterns, so here’s an annoying but functional workaround while we’re waiting for MIR borrowck:

let arr = [Box::new(1), Box::new(2), Box::new(3)];
let (a, b, c) = (|[a, b, c]: [Box<i32>; 3]| (a, b, c))(arr);