Change access boundary of protected[this]

Should be `base`, was the class enclosing the definition.

Author: odersky

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -805,7 +805,7 @@ object SymDenotations {
      */
     final def accessBoundary(base: Symbol)(implicit ctx: Context): Symbol = {
       val fs = flags
-      if (fs is PrivateOrLocal) owner
+      if (fs is Private) owner
       else if (fs is StaticProtected) defn.RootClass
       else if (privateWithin.exists && !ctx.phase.erasedTypes) privateWithin
       else if (fs is Protected) base