    //=============================================================================
    //  MuseScore
    //  Music Composition & Notation
    //
    //  Copyright (C) 2010-2011 Werner Schweer
    //
    //  This program is free software; you can redistribute it and/or modify
    //  it under the terms of the GNU General Public License version 2
    //  as published by the Free Software Foundation and appearing in
    //  the file LICENCE.GPL
    //=============================================================================

    #ifndef __TEXTFRAME_H__
    #define __TEXTFRAME_H__

    #include "box.h"

    namespace Ms {

    class Text;

    //---------------------------------------------------------
    //   @@ TBox
    ///    Text frame.
    //---------------------------------------------------------

    class TBox : public VBox {
          Q_GADGET
          Text* _text;

       public:
          TBox(Score* score);
          TBox(const TBox&);
          ~TBox();
          virtual TBox* clone() const        { return new TBox(*this); }
          virtual ElementType type() const { return ElementType::TBOX;       }
          virtual void write(XmlWriter&) const override;
          using VBox::write;
          virtual void read(XmlReader&) override;
          virtual Element* drop(EditData&) override;
          virtual void add(Element* e) override;
          virtual void remove(Element* el) override;

          virtual void layout();
          virtual void scanElements(void* data, void (*func)(void*, Element*), bool all=true);
          Text* text()                        { return _text; }
          };

    }     // namespace Ms
    #endif

↑ V690 The 'TBox' class implements a copy constructor, but lacks the '=' operator. It is dangerous to use such a class.