Hey Everybody,
I just pushed a preview release of Mirah using the new self hosted AST and typer. Because more of the compiler is self hosted, it should be noticeably faster and that rocks. I've really noticed the difference running the mirah test suite.
It works best on JRuby 1.6.7-8. It has some problems on 1.7.0 that we hope to resolve before doing a final release.
You can download it on JRuby by running
gem install mirah --pre