`-Xsource-features:infer-override` stricter than Scala 3

[lrytz]

Follow-up for https://github.com/scala/bug/issues/12975.

The example doesn't compile with 2.13.13 under -Xsource:3-cross (-Xsource-features:infer-override on 2.13.14). The inferred type for final val companion = Editor is taken from the parent.

It compiles with 3.4.1.

trait EditableCellsCompanion {
  type Editor <: CellEditor

  val Editor: CellEditorCompanion

  trait CellEditorCompanion {
    type CellInfo
  }

  trait CellEditor {
    val companion: CellEditorCompanion

    def componentFor(cellInfo: companion.CellInfo): Object
  }
}

sealed trait TreeEditors extends EditableCellsCompanion {
  object Editor extends CellEditorCompanion {
    class CellInfo

    def apply(editor: Editor): Editor = new Editor {
      override def componentFor(info: companion.CellInfo): Object = {
        editor.componentFor(info)
      }
    }
  }
  abstract class Editor extends CellEditor {
    final val companion = Editor
    // final val companion: Editor.type = Editor
  }
}

Maybe it's a bug in Scala 3 though?

Scala 3.4.1 -Vprint:typer:

    abstract class Editor() extends Object(), TreeEditors.this.CellEditor {
      final val companion: TreeEditors.this.Editor.type = TreeEditors.this.Editor
    }

Scala 2.13.13 -Xsource:3-cross -Vprint:typer:

    abstract class Editor extends AnyRef with TreeEditors.this.CellEditor {
      final <stable> <accessor> def companion: TreeEditors.this.CellEditorCompanion = Editor.this.companion
   }