Cannot inherit final override toString in companion object of case class

[CoolDalek]

Compiler version

3.2.1 and 3.2.2

Minimized code

trait Companion:
  final override def toString: String = "Companion"

case class Example(value: Int)
object Example extends Companion

Output

error overriding method toString in trait Companion of type => String;
  method toString of type => String cannot override final member method toString in trait Companion
case class Example(value: Int)

Expectation

Companion object inherits toString implementation from the trait.

[odersky]

This is caused by #9165. I think #9165 should be refined to match Scala 2's behavior.

[odersky]

Another problem case:

case class Example(value: Int)
object Example {
  def toString = "Ex"
}

gives

-- [E120] Naming Error: i16879.scala:8:6 ---------------------------------------
8 |  def toString = "Ex"
  |      ^
  |Double definition:
  |override def toString: String in object Example at line 6 and
  |def toString: String in object Example at line 8
  |have the same type after erasure.
  |
  |Consider adding a @targetName annotation to one of the conflicting definitions
  |for disambiguation.