What we have lost ?

[Remi Forax]

Hi everybody,
it seems to me that the current design has reached a kind of local maximum, which is nice and not nice at the same time,
so i would like to take the time to reflect on what we have sacrificed when moving to the current design.

What is missing/not supported by the current model is value classes that should not be used by reference,
either because it will cause performance issues or because the user will not get the semantics he think he will get.

Here is a list of such value types:
- unit types, value types like by example Nothing (which mean that a method never returns) with no fields.
  Because creating a ref on it creates something :)

- wrappers/monads that modify the semantics, by example a generic value class Atomic that plays the same role as an AtomicReference, AtomicInteger, etc
  the problem here is that the default semantics is not the semantics the user want.
  
- SIMD vectors, if those are nullable, the VM/JIT will insert implicit null checks which are not usually a problem apart in thigh loop like users write with SIMD vectors.

- existing value classes in Scala or Kotlin, those are not nullable by default but in the current design, getClass() will happily reflect them with a nullable class making Scala/Kotlin second class citizens of the Java platform.

Those are my 4 tent poles, they are maybe others, but currently we fail to provide a good answer for those cases.

regards,
Rémi