policy 是一个 Scala 编译器的改进版。其目标是解决 Scala 中的一些问题。
改变包括：
an extensive sbt-driven build system
(reluctantly) brought partest back from separate repository, minor improvements
deletion of lots of the worst and/or least necessary code
deletion of tons of useless and unmaintained compiler log messages
eliminated scala-reflect jar (I intend to eliminate the entire useless scala-reflect layer)
eliminated asm fork in favor of standard asm dependency[*]
trailing commas! I think that’s the only “feature”.
