chore: fix mandatory binary incompatibilities between Scala 2 and Scala 3

Author: hamzaremmal

project/Scala2LibraryBootstrappedMiMaFilters.scala

@@ -74,8 +74,6 @@ object Scala2LibraryBootstrappedMiMaFilters {
         "scala.collection.mutable.PriorityQueue#ResizableArrayAccess.this",
         "scala.concurrent.BatchingExecutor#AbstractBatch.this",
         "scala.concurrent.Channel#LinkedList.this",
-        "scala.Enumeration#ValueOrdering.this",
-        "scala.io.Source#RelaxedPosition.this",
         "scala.collection.IterableOnceOps#Maximized.this", // New in 2.13.11: private inner class
         "scala.util.Properties.<clinit>",
         "scala.util.Sorting.scala$util$Sorting$$mergeSort$default$5",

scala2-library-bootstrapped/src/scala/Enumeration.scala

@@ -272,6 +272,12 @@ abstract class Enumeration (initial: Int) extends Serializable {
 
   /** An ordering by id for values of this set */
   implicit object ValueOrdering extends Ordering[Value] {
+
+    // IMPORTANT: 
+    // Scala 3 removes unnecessary outer pointers while Scala 2 doesn't
+    // This is important to capture the outer pointer when compiling with
+    // dotc to maintain our binary compatibility requirements
+    private val _ = Enumeration.this
     def compare(x: Value, y: Value): Int = x compare y
   }
 

scala2-library-bootstrapped/src/scala/io/Source.scala

@@ -292,6 +292,13 @@ abstract class Source extends Iterator[Char] with Closeable {
    */
   @nowarn("cat=deprecation")
   object RelaxedPosition extends Position {
+
+    // IMPORTANT: 
+    // Scala 3 removes unnecessary outer pointers while Scala 2 doesn't
+    // This is important to capture the outer pointer when compiling with
+    // dotc to maintain our binary compatibility requirements
+    private val _ = Source.this
+
     def checkInput(line: Int, column: Int): Unit = ()
   }
   object RelaxedPositioner extends Positioner(RelaxedPosition) { }