What exactly is special about that DSL? I'm pressed for time, but it seems like it would be trivial to reproduce in Scala.

In Kotlin, you can write a function that takes, as its last argument, a function literal that is scoped to a specific class. Last I checked, function scoping does not work this way in Scala and you'd have to explicitly pass around objects to get the same result.

In the end, we end up with a builder DSL like this:

  div() {
      h1("header")
      p("paragraph")
      div() {
          p("another paragraph")
      }
      h2("another header")
  }

In Kotlin, each function call is properly scoped inside (unseen) classes for each level, allowing the code to generate the appropriate object tree.

In Scala, all functions would have to be visible in the local scope of the top-level function and we'd end up with a flat object tree instead.

To get the proper object tree in Scala, you'd need to pass explicit references to each containing object into the appropriate function literals, which makes it much more verbose and extremely error prone.

EDIT: not nearly as convincing without proper formatting...