The following code compiles and runs in Scala 2:

trait SomeTrait {
  val myName: String
}

class SomeClass() extends SomeTrait {
  override val myName: String = "Billy Banana"
}

val someClass = new SomeClass()
println(someClass.myName)

val extendedTrait = new SomeTrait {
  override val myName: String = "Amy Apples"
  def printName(): Unit = println(myName)
}

extendedTrait.printName()

However in Scala 3, there is a compilation error at this line:

extendedTrait.printName()

What in the Scala 3 docs references this change?