MIR Borrowck does not handle borrows of array elements

[nikomatsakis]

This example only shows 1 error, from the AST borrow checker:

#![allow(warnings)]
#![feature(rustc_attrs)]

fn use_x(_: usize) -> bool { true }

#[rustc_mir_borrowck]
fn main() {
    let mut v = [1, 2, 3];
    let p = &v[0];
    if true {
        use_x(*p);
    } else {
        use_x(22);
    }
    v[0] += 1;
}

cc @arielb1

[nikomatsakis]

I get:

Mr-Darcy. rustc +nightly -Zborrowck-mir region-liveness-basic.rs
error[E0506]: cannot assign to `v[..]` because it is borrowed (Ast)
  --> region-liveness-basic.rs:32:5
   |
26 |     let p = &v[0];
   |              ---- borrow of `v[..]` occurs here
...
32 |     v[0] += 1;
   |     ^^^^^^^^^ assignment to borrowed `v[..]` occurs here

error: aborting due to previous error

[oli-obk]

Not sure what is going on, but if -Zborrowck-mir is not passed, the error output is

error[E0506]: cannot assign to `v[..]` because it is borrowed
  --> foo.rs:15:5
   |
9  |     let p = &v[0];
   |              ---- borrow of `v[..]` occurs here
...
15 |     v[0] += 1;
   |     ^^^^^^^^^ assignment to borrowed `v[..]` occurs here

error[E0506]: cannot assign to `v` because it is borrowed (Mir)
  --> foo.rs:16:2
   |
9  |     let p = &v[0];
   |             ----- borrow of `v` occurs here
...
16 | }
   |  ^ assignment to borrowed `v` occurs here

error: aborting due to 2 previous errors