Objects leak protected inner classes

[amordahl]

Compiler version

3.6.3

Minimized code

class A:
  protected class B

// This fails to compile, as expected
// val x = A().B()

object C:
  protected val p = "protected"
  protected def getString() = "Hello!"
  protected class D

// This fails to compile
// val y = C.p

// And this also fails to compile
// val z = C.getString()

// However, this compiles just fine.
val alpha = C.D()

Output

The code compiles, even though a protected inner class is being accessed outside of the declaring object.

Expectation

I know that there isn't any point in declaring members of objects protected, since an object can't be extended. However, the way that protected inner classes are handled (which, as far as I can tell, is to ignore the protected keyword) is inconsistent with the way that protected vars/vals/defs are treated inside objects.

[som-snytt]

That is an artifact of the constructor proxy.

21 |val beta = new C.D()
   |               ^^^
   |class D cannot be accessed as a member of C.type from the top-level definitions in package <empty>.
   |  protected class D can only be accessed from object C.
1 error found

Similar to #18545