Okay so the problem seems to be that `ObservableSo...

# android

[robin]

Okay so the problem seems to be that ObservableSource and BiFunction are both SAM types. It looks like if you want to replace the BiFunction parameter with a lambda, Kotlin forces you to also replace the other SAM-type parameters with a lambda or at least a Kotlin function type, it doesn't let you do this with one and not the other. I'm not sure if that's a technical limitation or just a bug.