exhaustiveness checking and trans fail on this pattern

[nikomatsakis]

This test case:

fn foo(a: option<uint>, b: option<uint>) {
  alt (a,b) {
    (some(a), some(b)) if a == b { }
    (some(_), none) |
    (none, some(_)) { }
  }
}

when compiled (1) does not fail exhaustiveness checking (it should) and (2) causes an option::get() failure in trans (possibly as a result of problem #1?)

[marijnh]

That patch makes the check much more reliable, but has some false positives. Not merging it for now.

[catamorphism]

Correctly rejected with a non-exhaustive pattern error as of 6/21/2012. Added test case; closing.