Support returning elements from an array by-value

[infinity0]

This works:

fn test_vec() -> String {
    let mut z = vec![String::from("foo"), String::from("bar")];
    z.remove(0)
}

But this fails:

fn test_array() -> String {
    let mut z = [String::from("foo"), String::from("bar")];
    z[0]
}

with a "cannot move out of" error.

(#rust-beginners advised me that this "should" intuitively work and that I should file here)

[setharnold]

Thanks infinity0; my thinking is that it would be nice to avoid the mem::swap() or mem::replace() dance to get one item out of an array if the array as a whole is going out of scope in the same statement.

Thanks

[sfackler]

This is rust-lang/rfcs#997.

[Spoonbender]

Triage: no change