there is some statement that the aim is to have build times in Kotlin as in Java. I personally won’t care if build times were longer as long as you don’t have to rebuild the whole thing once you changed some method in the IDE. But it makes me think whether build times scale with the size of the code base, because the experience with Scala was not fun in this way and it was a lot of time to get into this feature-loaded language.
Do you have something like test cases with some intricate code where you know you are on the safe side as what build time scalability is concerned if those intricate/artificial/contrived/etc. test cases don’t make the compiler run wild? That would then make me feel quite comfortable ;-).
We have a few big projects and we monitor build time (informally so far). There's a lot to work on in this direction: many things should be optimized in the compiler.
A full rebuild to APK for Android Rivers (which contains 50% Java) now takes in low 2 minutes (8 GB RAM, Slow HD Windows 7 64 bit). In the early days, this type of operation would have taken me in the 3 minutes mark. I have no reference though about the full rebuild speed for a full Java program in similar size.
Just in order to point out: my initial question was not about compilation time of Java code compared to Kotlin code. It was about scalable build times with the size of the code growing. This is to me the decisive issue (I mentioned those problems with Scala). When the Kotlin compiler somewhen achieves some level of incremental compilation, compilation times at development time won't be that much of an issue as full builds need not be done that often.