As far as I can tell, every non-nullable reference-type parameter of every non-private method is null-checked at run time (with a call to the static method kotlin.jvm.internal.Intrinsics.checkNotNull). In particular, the two-parameter method is called. I’m not at the computer right now, and I’m going on memory, so please correct me if I’m wrong.
If I’m right, does anyone know whether this could entail performance problems on Android? The following document, for example, is quite strict about what Android programmers should and shouldn’t do. From reading this, I get the impression that method calls might not be so tiny on Android.