Recovery (Urgent):
* Not clear what the pipeline for errors should be
* Find better names for the many modules
* If necessary, tune performance
* What is the licensing situation?

Error messages (Medium-term):
* Agree on a strategy with other people: what should messages look like?
  What should they do: describe the context? suggest common corrections?
  Point people to grammar documentation?
* To learn what correct files look like we can probably data-mine public reason
  repositories. 
* To learn what incorrect files look like, we need some way to collect common
  errors!!!!

Completion (Long-term):
* Introduce merlin.location when there is ambiguity between concrete and
  abstract locations
