Integrate the remaining job of AugmentScala2Traits into Scala2Unpickler.

This allows to entirely get rid of the phase as well as the
`Scala2xAugmented` flag.

Author: sjrd

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -86,7 +86,6 @@ class Compiler {
          new LiftTry,                // Put try expressions that might execute on non-empty stacks into their own methods
          new CollectNullableFields,  // Collect fields that can be nulled out after use in lazy initialization
          new ElimOuterSelect,        // Expand outer selections
-         new AugmentScala2Traits,    // Augments Scala2 traits so that super accessors are made non-private
          new ResolveSuper,           // Implement super accessors
          new FunctionXXLForwarders,  // Add forwarders for FunctionXXL apply method
          new ParamForwarding,        // Add forwarders for aliases of superclass parameters

compiler/src/dotty/tools/dotc/core/Flags.scala

@@ -378,12 +378,8 @@ object Flags {
   /** Children were queried on this class */
   val (_, _, ChildrenQueried @ _) = newFlags(56, "<children-queried>")
 
-  /** A module variable (Scala 2.x only)
-   *    /
-   *  A Scala 2.x trait that has been augmented.
-   *  This is set in `AugmentScala2Trait` when the trait is augmented.
-   */
-  val (_, Scala2ModuleVar @ _, Scala2xAugmented @ _) = newFlags(57, "<modulevar>", "<scala-2.x-augmented>")
+  /** A module variable (Scala 2.x only) */
+  val (_, Scala2ModuleVar @ _, _) = newFlags(57, "<modulevar>")
 
   /** A macro */
   val (Macro @ _, _, _) = newFlags(58, "<macro>")

compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

@@ -455,8 +455,12 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
       flags = flags &~ Scala2ExpandedName
     }
     if (flags.is(Scala2SuperAccessor)) {
-      name = name.asTermName.unmangle(SuperAccessorName)
-      flags = flags &~ Scala2SuperAccessor
+      /* Scala 2 super accessors are pickled as private, but are compiled as public expanded.
+       * Dotty super accessors, however, are already pickled as public expanded.
+       * We bridge the gap right now.
+       */
+      name = name.asTermName.unmangle(SuperAccessorName).expandedName(owner)
+      flags = flags &~ (Scala2SuperAccessor | Private)
     }
     name = name.mapLast(_.decode)
 
@@ -1308,4 +1312,3 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
         errorBadSignature("expected an TypeDef (" + other + ")")
     }
 }
-

compiler/src/dotty/tools/dotc/transform/AugmentScala2Traits.scala

@@ -34,7 +34,6 @@ class ResolveSuper extends MiniPhase with IdentityDenotTransformer { thisPhase =
   override def phaseName: String = ResolveSuper.name
 
   override def runsAfter: Set[String] = Set(ElimByName.name, // verified empirically, need to figure out what the reason is.
-                               AugmentScala2Traits.name,
                                PruneErasedDefs.name) // Erased decls make `isCurrent` work incorrectly
 
   override def changesMembers: Boolean = true // the phase adds super accessors