This is a nice counterexample to the wisdom that production compilers all use hand-written parsers. Of course, the current parser does suck, but...
What is/was the problem with the current parser?
Helpful error messages have not been my experience.
On the other hand type error messages are simply awesome.
The days of Error: Syntax error. may be numbered
They move from a auto-generated compiler that sucks to another one (whose quality is yet to be seen).
Even if it proves to be great, it would still be an outlier.