Scala 2.13.6 Breaks Compilation of Extending Java Interfaces Defining Clone as public

[jrduncans]

reproduction steps

using Scala 2.13.6,

object CloneTest extends javax.naming.directory.Attribute {
  override def getAll(): javax.naming.NamingEnumeration[_ <: Object] = ???
  override def get(): Object = ???
  override def size(): Int = ???
  override def getID(): String = ???
  override def contains(x$1: Object): Boolean = ???
  override def add(x$1: Object): Boolean = ???
  override def remove(x$1: Object): Boolean = ???
  override def clear(): Unit = ???
  override def getAttributeSyntaxDefinition(): javax.naming.directory.DirContext = ???
  override def getAttributeDefinition(): javax.naming.directory.DirContext = ???
  override def isOrdered(): Boolean = ???
  override def get(x$1: Int): Object = ???
  override def remove(x$1: Int): Object = ???
  override def add(x$1: Int, x$2: Object): Unit = ???
  override def set(x$1: Int, x$2: Object): Object = ???
}

results in

[error] ...weaker access privileges in overriding
[error] def clone(): Object (defined in trait Attribute)
[error]   override should be public;
[error]   (note that def clone(): Object (defined in trait Attribute) is abstract,
[error]   and is therefore overridden by concrete protected[package lang] def clone(): Object (defined in class Object))
[error] object CloneTest extends Attribute {

problem

In Scala 2.13.5 this compiles successfully. The above is a minimal reproduction; I actually face this problem using ScalaMock to mock javax.naming.directory.Attribute.

[SethTisue]

Please have a look at scala/scala#9525 and let us know what you think afterwards. cc @lrytz @kynthus

[jrduncans]

If it's caused by that, it seems to be an unintentional impact. Unlike the statement "They are all about overriding public or package-private Java members with protected, protected[something] or private[something] in Scala.", this is caused by the Java interface setting the visibility to public, contravening the Object type as protected. And unlike the fixes found for community builds, I don't see any way to work around this while still extending such a Java interface.

[lrytz]

Java

interface A {
  public Object clone();
}

Scala

class C extends A

Test.scala:1: error: weaker access privileges in overriding
def clone(): Object (defined in trait A)
  override should be public;
  (note that def clone(): Object (defined in trait A) is abstract,
  and is therefore overridden by concrete protected[package lang] def clone(): Object (defined in class Object))
class C extends A
      ^
1 error

The mssage seems correct to me, the concrete method overrides the abstract one, and it cannot have weaker access privileges. Java agrees, with

public class B implements A { }

you get

B.java:1: error: clone() in Object cannot implement clone() in A
public class B implements A {
       ^
  attempting to assign weaker access privileges; was public
1 error

[jrduncans]

I see now, I'll file a bug with ScalaMock to produce something that compiles.