Bindings in structural self types are not picked up correctly.

[odersky]

The following typechecks:

trait TS { type T = Int }
trait T { self: TS =>
  type T
  def lift(x: Int): T = x
}

But this variant doesn't:

trait T { self: { type T = Int } =>
  type T
  def lift(x: Int): T = x  // error: expected T, found: Int
}

The two should behave the same.