Double bind in alt causes assert in trans #3038

fn main()
{
    let pt = {x: 1, y: 2};
    let _x = alt pt {
        {x, x} { x }
    };
}

fn main()
{
    let pt = {x: 1, y: 2};
    let pt2 = {x: 1, y: 2};
    let _x = alt (pt, pt2) {
       ({x, y}, {x, y}) { x }
    };
}

fn main()
{
    let _z = alt (1, 2) {
        (x, x) { x }
    };
}

rust: task failed at 'Assertion cx.fcx.lllocals.contains_key(nid) failed', /Users/jruderman/code/rust/src/rustc/middle/trans/base.rs:2438