Note that I still don't understand why you can use...

# announcements

[jbnizet]

Note that I still don't understand why you can use a lambda expression to create an instance of a Java functional interface, but not to create an instance of a Kotlin functional interface. I understand that Kotlin has functions, but interfaces with a single method don't look like a bad idea to me (being able to document the contract of the interface is a good enough reason to use one), and when mixing Kotlin and Java, this difference is annoying, IMO.