code: private void checkOrMarkPrivateAccess(Expression source, FieldNode fn) {
          if (fn!=null && Modifier.isPrivate(fn.getModifiers()) &&
              (fn.getDeclaringClass() != typeCheckingContext.getEnclosingClassNode() || typeCheckingContext.getEnclosingClosure()!=null) &&
              fn.getDeclaringClass().getModule() == typeCheckingContext.getEnclosingClassNode().getModule()) {
              addPrivateFieldOrMethodAccess(source, fn.getDeclaringClass(), StaticTypesMarker.PV_FIELDS_ACCESS, fn);
          }
      }
docs: Given a field node, checks if we are calling a private field from an inner class.