Overriding qualified private or protected members doesn't work

[scabug]

class A {
  protected def x = 0
  protected[A] def y = 0
}

class B extends A {
  override def x = 1
  println(super[A].y)
  override def y = 1
}

gives the following compile error:

P.scala:9: error: method y overrides nothing
  override def y = 1
               ^
one error found

This is either a misleading error message, since A.y is definitely visible in B or as I think a plain error. Section 5.1.4 of the spec doesn't disallow this.

The same applies for qualified private members as in:

class A {
  class B {
    private[A] def x = 0
  }

  class C extends B {
    override def x = 1
  }
}

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-1994?orig=1
Reporter: @ingoem

[scabug]

@paulp said:
This is mostly a duplicate of #1352. The issue is not that you can't override them, but that you can't widen the visibility to public. This works:

class A {
  class B {
    private[A] def x = 0
  }

  class C extends B {
    override private[A] def x = 1
    // or even this works
    // override protected[A] def x = 1
  }
}

My "mostly" qualifier above is because it doesn't look like you can override def y in your first example, because A is not an enclosing class inside B:

//   override protected[A] def y = 1
a.scala:9: error: A is not an enclosing class
  override protected[A] def y = 1
                            ^
//   override protected def y = 1
a.scala:9: error: method y overrides nothing
  override protected def y = 1
                         ^
//   override protected[B] def y = 1
a.scala:9: error: method B$$$$y overrides nothing
  override protected[B] def y = 1
                            ^

[scabug]

@dragos said:
This has to do with the mangling scheme for class protected members, which needs to be changed. Contributions are welcome.