Update comments for parser; remove unnecessary checks

Author: noti0na1

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

@@ -524,7 +524,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def makeRetaining(parent: Tree, refs: List[Tree], annotName: TypeName)(using Context): Annotated =
     Annotated(parent, New(scalaAnnotationDot(annotName), List(refs)))
 
-  def makeCapsOf(tp: Tree)(using Context): Tree =
+  def makeCapsOf(tp: RefTree)(using Context): Tree =
     TypeApply(Select(scalaDot(nme.caps), nme.capsOf), tp :: Nil)
 
   def makeCapsBound()(using Context): Tree =

compiler/src/dotty/tools/dotc/cc/CaptureOps.scala

@@ -194,8 +194,7 @@ extension (tp: Type)
       true
     case tp: TermRef =>
       ((tp.prefix eq NoPrefix)
-      || tp.symbol.isField && !tp.symbol.isStatic && (
-        tp.prefix.isThisTypeOf(tp.symbol.owner) || tp.prefix.isTrackableRef)
+      || tp.symbol.isField && !tp.symbol.isStatic && tp.prefix.isTrackableRef
       || tp.isRootCapability
       ) && !tp.symbol.isOneOf(UnstableValueFlags)
     case tp: TypeRef =>

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1559,22 +1559,20 @@ object Parsers {
       case _ => None
     }
 
-    /** CaptureRef  ::=  (ident | `this`) [`*` | `^`]
+    /** CaptureRef  ::=  SimpleRef { `.` id } [`*` | `^`]
      */
     def captureRef(): Tree =
-      val ref = singleton()
+      val ref = dotSelectors(simpleRef())
       if isIdent(nme.raw.STAR) then
         in.nextToken()
         atSpan(startOffset(ref)):
           PostfixOp(ref, Ident(nme.CC_REACH))
       else if isIdent(nme.UPARROW) then
         in.nextToken()
-        def toTypeSel(r: Tree): Tree = r match
-          case id: Ident => cpy.Ident(id)(id.name.toTypeName)
-          case Select(qual, id) => Select(qual, id.toTypeName)
-          case _ => r
         atSpan(startOffset(ref)):
-          makeCapsOf(toTypeSel(ref))
+          convertToTypeId(ref) match
+            case ref: RefTree => makeCapsOf(ref)
+            case ref => ref
       else ref
 
     /**  CaptureSet ::=  `{` CaptureRef {`,` CaptureRef} `}`    -- under captureChecking