borrow check doesn't distinguish different tuple elements in match expression

[thestinger]

enum Foo {
    X, Y(uint, uint)
}

fn main() {
    // works
    let mut x = (1, 2);
    let (ref _k, ref mut _v) = x;

    // doesn't work
    let mut y = Y(1, 2);
    match y {
      Y(ref _v, ref mut _k) => {}

      // error: loan of enum content as mutable conflicts with prior loan
      // Y(ref _v, ref mut _k) => {}
      //           ^~~~~~~~~~~
      // note: prior loan as immutable granted here
      // Y(ref _v, ref mut _k) => {}
      //   ^~~~~~~

      X => ()
    }
}

[nikomatsakis]

problem is that the mem_categorization structures don't consider the index into a tuple

[bstrie]

Still reproduces, but try again once the new borrowck lands.

[nikomatsakis]

This is not yet fixed, but it would be easy to do so. I was trying to avoid making the patch bigger than otherwise necessary.

[nikomatsakis]

Fixed now.