i don't want to divert attention from the above, so please read benjy's message. i posted two PRs just now, one that makes

@rule

parse errors much better and have the location and text of the offending

yield

statement (https://github.com/pantsbuild/pants/pull/7023), and another that makes the visualized rule graph much, much nicer to read, i think (https://github.com/pantsbuild/pants/pull/7024).