Implement comments as attachments instead of tree members

3 files changed, 15 insertions, 18 deletions

diff --git a/src/dotty/tools/dotc/ast/Trees.scala b/src/dotty/tools/dotc/ast/Trees.scala
index eb5ab15e3..be3e2eb5f 100644
--- a/src/dotty/tools/dotc/ast/Trees.scala
+++ b/src/dotty/tools/dotc/ast/Trees.scala
@@ -29,6 +29,9 @@ object Trees {
   /** The total number of created tree nodes, maintained if Stats.enabled */
   @sharable var ntrees = 0
 
+  /** Attachment key for trees with documentation strings attached */
+  val DocComment = new Attachment.Key[String]
+
   /** Modifiers and annotations for definitions
    *  @param flags          The set flags
    *  @param privateWithin  If a private or protected has is followed by a
@@ -321,9 +324,7 @@ object Trees {
     private[ast] def rawMods: Modifiers[T] =
       if (myMods == null) genericEmptyModifiers else myMods
 
-    private[this] var myComment: Option[String] = None
-
-    def rawComment: Option[String] = myComment
+    def rawComment: Option[String] = getAttachment(DocComment)
 
     def withMods(mods: Modifiers[Untyped]): ThisTree[Untyped] = {
       val tree = if (myMods == null || (myMods == mods)) this else clone.asInstanceOf[MemberDef[Untyped]]
@@ -333,8 +334,8 @@ object Trees {
 
     def withFlags(flags: FlagSet): ThisTree[Untyped] = withMods(Modifiers(flags))
 
-    def withComment(cmt: Option[String]): ThisTree[Untyped] = {
-      myComment = cmt
+    def setComment(comment: Option[String]): ThisTree[Untyped] = {
+      comment.map(putAttachment(DocComment, _))
       asInstanceOf[ThisTree[Untyped]]
     }
 
diff --git a/src/dotty/tools/dotc/parsing/Parsers.scala b/src/dotty/tools/dotc/parsing/Parsers.scala
index dad618381..cdfc366a7 100644
--- a/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -1782,9 +1782,9 @@ object Parsers {
           }
         } else EmptyTree
       lhs match {
-        case (id @ Ident(name: TermName)) :: Nil =>
-          cpy.ValDef(id)(name, tpt, rhs).withMods(mods).withComment(docstring)
-        case _ =>
+        case (id @ Ident(name: TermName)) :: Nil => {
+          cpy.ValDef(id)(name, tpt, rhs).withMods(mods).setComment(docstring)
+        } case _ =>
           PatDef(mods, lhs, tpt, rhs)
       }
     }
@@ -1835,7 +1835,7 @@ object Parsers {
             accept(EQUALS)
             expr()
           }
-        DefDef(name, tparams, vparamss, tpt, rhs).withMods(mods1).withComment(docstring)
+        DefDef(name, tparams, vparamss, tpt, rhs).withMods(mods1).setComment(docstring)
       }
     }
 
@@ -1877,7 +1877,7 @@ object Parsers {
         in.token match {
           case EQUALS =>
             in.nextToken()
-            TypeDef(name, tparams, typ()).withMods(mods).withComment(docstring)
+            TypeDef(name, tparams, typ()).withMods(mods).setComment(docstring)
           case SUPERTYPE | SUBTYPE | SEMI | NEWLINE | NEWLINES | COMMA | RBRACE | EOF =>
             TypeDef(name, tparams, typeBounds()).withMods(mods)
           case _ =>
@@ -1923,9 +1923,7 @@ object Parsers {
       }
       val templ = templateOpt(constr)
 
-      TypeDef(name, templ)
-        .withMods(mods)
-        .withComment(docstring)
+      TypeDef(name, templ).withMods(mods).setComment(docstring)
     }
 
     /** ConstrMods        ::=  AccessModifier
@@ -1945,9 +1943,7 @@ object Parsers {
       val name = ident()
       val template = templateOpt(emptyConstructor())
 
-      ModuleDef(name, template)
-        .withMods(mods)
-        .withComment(docstring)
+      ModuleDef(name, template).withMods(mods).setComment(docstring)
     }
 
 /* -------- TEMPLATES ------------------------------------------- */
diff --git a/src/dotty/tools/dotc/parsing/Scanners.scala b/src/dotty/tools/dotc/parsing/Scanners.scala
index 5ec6823e4..4211b6275 100644
--- a/src/dotty/tools/dotc/parsing/Scanners.scala
+++ b/src/dotty/tools/dotc/parsing/Scanners.scala
@@ -180,12 +180,12 @@ object Scanners {
     /** All comments in the reverse order of their position in the source.
      *  set only when `keepComments` is true.
      */
-    var revComments: List[Comment] = Nil
+    private[this] var revComments: List[Comment] = Nil
 
     /** All doc comments as encountered, each list contains doc comments from
      *  the same block level. Starting with the deepest level and going upward
      */
-    var docsPerBlockStack: List[List[Comment]] = List(List())
+    private[this] var docsPerBlockStack: List[List[Comment]] = List(List())
 
     /** Adds level of nesting to docstrings */
     def enterBlock(): Unit =