Question

consider this design of a library I need to use and cannot fix:

trait Foo

class IgnoreMe extends Foo
class A extends Foo { def bar: A = ...}
class B extends Foo { def bar: B = ...}

In my code:

object Stuff {
  type Barred = { def bar: Foo }

  def doStuff(b:Barred) = b.bar
}

Thats all well and good except that the Stuff.doStuff will accept anything conforming to the type Barred, not just the subtypes of Foo I want.

I would like to define Barred such that it is both a subtype of Foo and has a bar method, and I cannot 🙁 Help appreciated.

Answer 1

Simply

type Barred = Foo {def bar: Foo }