add support for importable attachments

Previously attachments weren't imported by importTree. Now a new marker
trait has been added that lets attachments to import themselves to the
new universe together with all their innards. Additionally a simpler
subtrait is defined to mark attachments that can be imported as-is.

3 files changed, 19 insertions, 5 deletions

diff --git a/src/reflect/scala/reflect/internal/Importers.scala b/src/reflect/scala/reflect/internal/Importers.scala
index 72c8ccfa62..cc6e55192f 100644
--- a/src/reflect/scala/reflect/internal/Importers.scala
+++ b/src/reflect/scala/reflect/internal/Importers.scala
@@ -8,6 +8,16 @@ import scala.ref.WeakReference
 // SI-6241: move importers to a mirror
 trait Importers extends api.Importers { to: SymbolTable =>
 
+  /** Attachment that knows how to import itself into another universe. */
+  trait ImportableAttachment {
+    def importAttachment(importer: Importer): this.type
+  }
+
+  /** Attachment that doesn't contain any reflection artificats and can be imported as-is. */
+  trait PlainAttachment extends ImportableAttachment {
+    def importAttachment(importer: Importer): this.type = this
+  }
+
   def mkImporter(from0: api.Universe): Importer { val from: from0.type } = (
     if (to eq from0) {
       new Importer {
@@ -417,11 +427,15 @@ trait Importers extends api.Importers { to: SymbolTable =>
           my.setPos(importPosition(their.pos))
         }
       }
+      importAttachments(their.attachments.all).foreach { my.updateAttachment(_) }
       my
     }
 
     // ============== MISCELLANEOUS ==============
 
+    def importAttachments(attachments: Set[Any]): Set[Any] =
+      attachments.collect { case ia: ImportableAttachment => ia.importAttachment(this) }
+
     def importAnnotationInfo(ann: from.AnnotationInfo): AnnotationInfo = {
       val atp1 = importType(ann.atp)
       val args1 = ann.args map importTree
diff --git a/src/reflect/scala/reflect/internal/StdAttachments.scala b/src/reflect/scala/reflect/internal/StdAttachments.scala
index 2e89ffca56..fe4438015d 100644
--- a/src/reflect/scala/reflect/internal/StdAttachments.scala
+++ b/src/reflect/scala/reflect/internal/StdAttachments.scala
@@ -22,13 +22,13 @@ trait StdAttachments {
     def setPos(newpos: Position): this.type = { pos = newpos; this }
   }
 
-  /** When present, indicates that the host `Ident` has been created from a backquoted identifier.
-   */
-  case object BackquotedIdentifierAttachment
-
   /** Stores the trees that give rise to a refined type to be used in reification.
    *  Unfortunately typed `CompoundTypeTree` is lacking essential info, and the reifier cannot use `CompoundTypeTree.tpe`.
    *  Therefore we need this hack (see `Reshape.toPreTyperTypeTree` for a detailed explanation).
    */
   case class CompoundTypeTreeOriginalAttachment(parents: List[Tree], stats: List[Tree])
+
+  /** When present, indicates that the host `Ident` has been created from a backquoted identifier.
+   */
+  case object BackquotedIdentifierAttachment extends PlainAttachment
 }
diff --git a/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala b/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala
index 4d69a6673c..26091b84a1 100644
--- a/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala
+++ b/src/reflect/scala/reflect/runtime/JavaUniverseForce.scala
@@ -53,8 +53,8 @@ trait JavaUniverseForce { self: runtime.JavaUniverse  =>
     this.perRunCaches
     this.FixedMirrorTreeCreator
     this.FixedMirrorTypeCreator
-    this.BackquotedIdentifierAttachment
     this.CompoundTypeTreeOriginalAttachment
+    this.BackquotedIdentifierAttachment
     this.noPrint
     this.typeDebug
     // inaccessible: this.maxFree