I tried to migrate an pretty complex sbt build to mill this week and I can say I'm not disappointed.

The developer experience is so delightful compared to the other build system in the JVM land. And the task model seems just right.

I was just looking at this thinking 'this is what sbt should have looked like'...

I recommend reading the developers post http://www.lihaoyi.com/post/SowhatswrongwithSBT.html which is a balanced overview of sbt shortcomings.

I agree with you, doing this breaks almost all the advantages you have using a JVM in the first place. So you probably don't want to hack this way.

There was no real use case for trying this. Just to see if it would be possible. As you say it is just a proof of concept.

Well for this specific `add` function, no it won't :)

The hotspot compiler will generate the same code anyway (perhaps even more optimised if it is possible I don't know). Worse, this code would probably be inlined while the `native` version won't.

Not only will the native version not be inlined, the JIT will also have to insert an annoying amount of stuff round it to handle calling conventions and other fun things.