We currently use 1.9. ATM Gradle is up to 2.3.

I played with this a little bit locally. I tried 2.3, but ran into a problem where the Antlr plugin is not picking up our grammars and processing them into java sources or is not adjusting the javac sources properly. Either way, when running compilation fails because the Antlr-generated classes are not found.

I tried 2.0 which worked fine. I tried 2.1 which worked fine also. I tried 2.2 which also worked fine. The issue seems to be in 2.3 specifically. Still need to go through its release notes...