This request is for an alternative to

  trait B[T <: B[T]] requires T {}

that uses virtual types instead of generics.



I've raised the issue on the mailing list and haven't heard that there is an alternative.
http://article.gmane.org/gmane.comp.lang.scala.user/202
http://article.gmane.org/gmane.comp.lang.scala.user/211




Here is one possible syntax, with the error it currently generates

trait B
{
     type T >: this.type <: B


     // compile-time check: have we achieved our objective?
     def test: T = this
}


error: type mismatch;
 found   : B
 required: B.this.T
     def test: T = this
                   ^