qualified private and protected not rendered by tree printers

[retronym]

class D {
  class C {
    protected[D] def a = 0
    private[D]   def b = 0
  }
}

% ./bin/dotc -Xprint:frontend sandbox/test.scala
result of sandbox/test.scala after frontend:
package <empty> {
  class D() extends Object() {
    class C() extends Object() {
      protected def a: Int = 0
      def b: Int = 0
    }
  }
}

I was trying to test whether access was properly propagated from constructor params to param accessors, but this but made that difficult. Once this is fixed, it would be good to systematically review derivation of accessors, case- implicit-class factories, etc. to make sure access is coherent.

This is another area where you shouldn't assume the scalac is doing the right thing, e.g. implicit classes get a factory method that circumvents the access of the constructor.

scalac -Xprint:typer sandbox/test.scala
[[syntax trees at end of                     typer]] // test.scala
package <empty> {
  object O extends scala.AnyRef {
    def <init>(): O.type = {
      O.super.<init>();
      ()
    };
    implicit class C extends scala.AnyRef {
      <paramaccessor> private[this] val a: Any = _;
      private[O] def <init>(a: Any): O.C = {
        C.super.<init>();
        ()
      }
    };
    implicit <synthetic> def C(a: Any): O.C = new C(a)
  }
}

[retronym]

Followup from #617, /cc @smarter

[DarkDimius]

AFAIK qualified private and protected aren't supposed to work at all, as we are considering removing them.