Revert "Fix #4291: Copy sticky attachments in TreeCopier"

This reverts commit 4062073.

Author: Duhemm

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -31,7 +31,7 @@ object Trees {
   @sharable var ntrees = 0
 
   /** Property key for trees with documentation strings attached */
-  val DocComment = new Property.StickyKey[Comment]
+  val DocComment = new Property.Key[Comment]
 
   @sharable private[this] var nextId = 0 // for debugging
 
@@ -910,10 +910,10 @@ object Trees {
       def postProcess(tree: Tree, copied: untpd.MemberDef): copied.ThisTree[T]
 
       def finalize(tree: Tree, copied: untpd.Tree): copied.ThisTree[T] =
-        postProcess(tree, copied.withPos(tree.pos).withAttachmentsFrom(tree))
+        postProcess(tree, copied withPos tree.pos)
 
       def finalize(tree: Tree, copied: untpd.MemberDef): copied.ThisTree[T] =
-        postProcess(tree, copied.withPos(tree.pos).withAttachmentsFrom(tree))
+        postProcess(tree, copied withPos tree.pos)
 
       def Ident(tree: Tree)(name: Name): Ident = tree match {
         case tree: BackquotedIdent =>

compiler/src/dotty/tools/dotc/util/Attachment.scala

@@ -2,12 +2,9 @@ package dotty.tools.dotc.util
 
 /** A class inheriting from Attachment.Container supports
  *  adding, removing and lookup of attachments. Attachments are typed key/value pairs.
- *
- *  Attachments whose key is an instance of `StickyKey` will be kept when the attachments
- *  are copied using `withAttachmentsFrom`.
  */
 object Attachment {
-  import Property.{Key, StickyKey}
+  import Property.Key
 
   /** An implementation trait for attachments.
    *  Clients should inherit from Container instead.
@@ -91,16 +88,6 @@ object Attachment {
   trait Container extends LinkSource {
     private[Attachment] var next: Link[_] = null
 
-    /** Copy the sticky attachments from `container` to this container. */
-    final def withAttachmentsFrom(container: Container): this.type = {
-      var current: Link[_] = container.next
-      while (current != null) {
-        if (current.key.isInstanceOf[StickyKey[_]]) pushAttachment(current.key, current.value)
-        current = current.next
-      }
-      this
-    }
-
     final def pushAttachment[V](key: Key[V], value: V): Unit = {
       assert(!getAttachment(key).isDefined, s"duplicate attachment for key $key")
       next = new Link(key, value, next)

compiler/src/dotty/tools/dotc/util/Property.scala

@@ -7,12 +7,4 @@ object Property {
 
   /** The class of keys for properties of type V */
   class Key[+V]
-
-  /**
-   * The class of keys for sticky properties of type V
-   *
-   * Sticky properties are properties that should be copied over when their container
-   * is copied.
-   */
-  class StickyKey[+V] extends Key[V]
-}
+}