Hi there. Is there some documentation on Kotlin’s synthetic constructor generation along with default arguments (bitmask used for defaulting)?

There's no documentation, but you can look at the implementation of

KCallableImpl.callDefaultMethod

which will give you a good idea what those masks mean: https://github.com/JetBrains/kotlin/blob/master/core/reflection.jvm/src/kotlin/reflect/jvm/internal/KCallableImpl.kt#L115

Thanks a lot. That’s what I did: https://github.com/spring-projects/spring-data-commons/pull/233/files#diff-0c01df5db8fdb42149d98f93c97776a1R197