Object signals not registed with QML if after nested struct with private stmt

If you add a nested struct in a class that you expose to QML and add a private: section to the struct then Qt wont expose any of the below signals to QML.

Take this simple class:

#pragma once

#include <QtCore/QObject>
#include <QtQml/QQmlEngine>

class TestObject : public QObject {
  Q_OBJECT
  QML_ELEMENT
  Q_PROPERTY(QString testString READ testString WRITE setTestString NOTIFY testStringChanged)
 public:
  struct StructThatBreaksEverything {
   private: // <--- This line breaks QML signal registration
  };
  
  TestObject(QObject *parent = nullptr);
  QString testString() const;
  void setTestString(QString testString);
  Q_SIGNAL void testStringChanged();
 private:
  QString m_testString{u"hello world"_qs};
};

That above class fails to expose the testStringChanged signal to QML because it includes a nested struct with a private: statement.

If you try to attach to the above testStringChanged signal from QML then then the application will crash if you use a onTestStringChanged handler. Connecting to the signal works fine from c++ which makes me think this is more of a QML issue rather than a straight up moc issue but I may be wrong.

It makes no difference if the struct contains actual public or private members. I ran into this issue with a more much more substantial class that happened to contain a struct with private members and it took longer than I would have liked to work out the issue.

As an extra note, if the struct is replaced with a class the above appears to work.

See the attached project for a basic qt QML project that demonstrates the above issue with some extra comments for clarity.