Crash with lazy-initted vec

[jyasskin]

fn main() {
  let vec[int] later;
  if (true) {
    later = vec(1);
  } else {
    later = vec(2);
  }
  log later.(0);
}

crashes at runtime, apparently because the refcount of the new vector isn't getting incremented when it gets assigned to 'later'.

[graydon]

Refcount is being set, but typestate system is incorrectly judging the if and else block-ends to be the lifecycle-end of the slot 'later', so is dropping them there.

I see where the bug is (block-boundary is assuming init-in-block means owned-by-block) but it'll take a little fixing and I've got some more errands to do today. Will get at it. Thanks for the report.

[graydon]

Fix post-stmt drop calculations. Closed by b3cf793.

[graydon]

Fixed more correctly by 1843c99