Temporaries generated in alt expression have longer lifetime than expected

[brson]

{
  alt gimmeboxes() {
    _ { }
  }
  // The thing returned from gimmeboxes is still refed here
}

I would not expect it to outlive the alt expression. Will produce a better test case later.

[brson]

Test case:

resource r(i: @mutable int) {
    *i = 100;
}

fn main() {
    let i = @mutable 200;
    alt (r(i)) {
      _ { }
    }
    assert i == 100;
}

[marijnh]

I would expect that, since they are created in the block context around the alt, that is also their lifetime. Do we have some kind of policy for lifetimes? (I don't know the details of what C++ does.)