Use type member as self-type

I'm having a problem with a recursive self-type that should correspond to a type member:

trait Elem { me =>
  type Peer

  import me.{Peer => Peer0}

  type This <: Elem { type Peer = Peer0 }

  def mkCopy(): This
}

Now I want to define a convenient trait:

trait ImmutableImpl extends Elem {
  _ : This =>

  def mkCopy(): This = this
}

This doesn't work, because "error: not found: type This" :(

Next attempt:

trait ImmutableImpl[Repr] extends Elem {
  _ : Repr =>

  type This = Repr

  def mkCopy(): This = this
}

This fails with "Error: overriding type This ... This has incompatible type".

I can do only this abomination:

trait ImmutableImpl[Peer0, Repr <: Elem { type Peer = Peer0 }] extends Elem {
  _ : Repr =>

  type Peer = Peer0
  type This = Repr

  override def mkCopy(): This = this
}

class IntElem extends ImmutableImpl[Int, IntElem]

In the real case I have more type members, so that makes this last approach useless, as it's much more boiler plate that implementing the mkCopy by hand each time.

Any ideas?

My workaround is to relax the refinement on This, as it appears to not be required in my API in the end:

trait Elem { me =>
  type Peer

  // import me.{Peer => Peer0}

  type This <: Elem // { type Peer = Peer0 }

  def mkCopy(): This
}

trait ImmutableImpl[Repr <: Elem] extends Elem {
  _ : Repr =>

  override type This = Repr

  def mkCopy(): This = this
}

class IntElem extends ImmutableImpl[IntElem] {
  type Peer = Int
}