Update compiler/src/dotty/tools/dotc/ast/Positioned.scala

Co-authored-by: Nicolas Stucki <nicolas.stucki@gmail.com>

Author: odersky

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

@@ -245,7 +245,7 @@ object Positioned {
 
   def init(using Context): Unit =
     debugId = ctx.settings.YdebugTreeWithId.value
-    if ctx.settings.YshowTreeIds.value
+    if ids == null && ctx.settings.YshowTreeIds.value
        || debugId != ctx.settings.YdebugTreeWithId.default
     then
       ids = java.util.WeakHashMap()