> I don’t know scala 3 well, but if it can make nonnullable types (that’s what “exempt null from ordinary types” means, isn’t it?), that’s not something the JVM

> I don’t know scala 3 well, but if it can make nonnullable types (that’s what “exempt null from ordinary types” means, isn’t it?), that’s not something the JVM knows about (although that may be changing with the addition of value types to the JVM) Haskell or Rust compiles to machine code, which can have invalid/null pointers as well they don’t know about. Nullness is a so-called trivial property, the compiler can prove the absence of NPEs in code output by it, so you only have to check at the boundaries (e.g. every java method will return a nullable type) I don’t know why would these map badly to java types. Scala unifies primitives with their boxed versions and tries to smartly optimize between them, so it doesn’t have the kind of distinction as Java. Value classes require runtime support so the only thing Scala can do is to alias a primitive as another class, but optimize it away. Of course this is a leaky abstraction, but this is a fact of life on managed runtimes. Re multiple inheritance: doesn’t map natively, but this also doesn’t need native support. At worst, scala can always just go the Groovy way and intercept any call to/from every such object of theirs and then they can literally do any form of call indirection. Re reflection: as far as I know Scala doesn’t really require frequent use of reflection, as it can circumvent it at most times through metaprogramming/more expressive language features. Also, type erasure is the norm — most runtimes don’t store type infos.