Driving a singleton type through a brickwall

Question

Here is a very condensed version:

case class Brickwall[A](otherSide: A)
trait Monoman { def me(m: this.type): Unit }

def test(m: Monoman): Unit = m.me(Brickwall(m).otherSide)

-> error: type mismatch;
 found   : Monoman
 required: m.type

stupid brickwall doesn't let me through. any ideas how it might be possible? secret scala tunnel effects? hoping...

Answer 1

As far as I know the Scala compiler refuses to infer path dependent types, so a little type annotation helps:

def test( m: Monoman ) { m.me( Brickwall[m.type]( m ).otherSide )}

Answer 2

Yes, singleton types are never inferred by the Scala compiler.

One possibility is to add a factory method to the Monoman trait:

trait Monoman { 
  def me( m: this.type ) : Unit
  def createWall = Brickwall[this.type](this) 
}

def test( m: Monoman ) { m.me(m.createWall.otherSide) }

Maybe that's not a viable solution in your case.