Incremental annotation processor example?

[ScottPeterJohnson]

I've been trying to figure out how to get a Kotlin annotation processor to produce new Kotlin source using the Filer API, which is necessary to get it to be incremental. (See here: https://docs.gradle.org/current/userguide/java_plugin.html#sec:incremental_annotation_processing )

The example code uses a direct file write:
https://github.com/Kotlin/kotlin-examples/blob/master/gradle/kotlin-code-generation/annotation-processor/src/main/java/TestAnnotationProcessor.kt#L42

Is there a way to make an annotation processor generating Kotlin incremental? I haven't found any other information about it. Naively trying to use a SOURCE_OUTPUT location with the Filer API seems not to work.