There are 2 repositories under javac-plugin topic.
Alternative to KAPT that skips Java stub generation and therefore is as efficient as Java APT but with Kotlin
Desugar optional calls for a null safe type system with no performance hits
Java Operator Overloading Plugin
Bermuda is a modular framework for making powerful Javac compiler plugins.
Emerald is a Gradle plugin that provides an easy, automatic configuration for Javac plugins.