can't move out nested boxes

[goffrie]

The following code seems like it should work, but it produces a cryptic error:

fn main() {
    let f = box Some((box 1i, box 2i));
    let g = match f { box Some((a, b)) => (*b, *a), _ => (0,0) };
    println!("{}", g);
}

<anon>:3:36: 3:37 error: use of partially moved value: `f#0#1`
<anon>:3     let g = match f { box Some((a, b)) => (*b, *a), _ => (0,0) };
                                            ^
<anon>:3:33: 3:34 note: `f#0#0` moved here because it has type `Box<int>`, which is moved by default (use `ref` to override)
<anon>:3     let g = match f { box Some((a, b)) => (*b, *a), _ => (0,0) };
                                         ^
error: aborting due to previous error

However, removing the outermost box works:

fn main() {
    let f = Some((box 1i, box 2i));
    let g = match f { Some((a, b)) => (*b, *a), _ => (0,0) };
    println!("{}", g); // => (2, 1)
}

Alternatively, matching on an rvalue also works:

fn main() {
    let f = box Some((box 1i, box 2i));
    let g = match f.clone() { box Some((a, b)) => (*b, *a), _ => (0,0) };
    println!("{}", g); // => (2, 1)
}

[alexcrichton]

This may be a dupe of #16223, but I'm not sure. cc @zwarich

[goffrie]

Oops, yeah, I'm pretty sure this is a dupe.