Beyond Scala 2.8 - A Roadmap

Consider the following program:

  trait X {
    trait A { type T >: Int <: Int }
      val x : A
      var n : x.T = 3
    }

  trait Y extends X {
    trait B { type T >: String <: String }
    lazy val x : A with B = x
    n = "foo"
  }

  new Y {}

I just used this because it is extremely simple and is just the tip of the iceberg. It is possible to exploit this in much more interesting ways and dangerous ways, but those are less concise.

It is worth noting that this is not just a simple compiler bug, but a deep flaw in the way type members and type composition interact.

That seems a little unfair. Martin Odersky has been pretty clear that he doesn't want Scala to be 'just' an academic language. In his address at Scala Days he talks about this, and about how they are investigating making Scala independent of EPFL, with possible funding from industry. Also, not all the development of Scala is done at EPFL; for example Paul Phillips (one of the key contributors to the compiler) doesn't work there (and isn't an academic so doesn't need to be concerned with publishing papers).

On another note, I don't believe that plugins for IDEs should necessarily be contributed by the 'core' Scala team. It makes more sense to me that people closer to the IDE in question are in a better position to write effective plugins. The Intellij plugin was written internally by Intellij and is perfectly usable in my opinion. Interestingly they've made the choice of not using the Scala compiler for syntax highlighting/error marking etc. which (again) in my opinion is a better choice than tieing this into the compiler.