Can't use [] to get slice of &mut Vec

[comex]

let val = &mut vec!(1u);
let slice1 = val.as_slice(); // OK
let slice2 = val[]; // error: cannot take a slice of a value with type `&mut collections::vec::Vec<uint>`

(If I use core::ops::Slice, as_slice_() works but as_slice() stops working. I don't understand how that works either.)

The RFC says "uses of this notation will auto-deref just as if they were method invocations", so I think this is a bug.

[steveklabnik]

Today, this code looks like

fn main() {
    let val = &mut vec!(1);
    let slice1 = val.as_slice(); // OK
    let slice2 = &val[]; // er
}

and compiles just fine. Note the last &.