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  4. error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to'
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error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to'

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  • A Alcor

    Hi Everybody, This is my first post on this forum. Forgive me if it's a repeat post. I am using Qt6.5 with Visual Studio 2022. I am trying to build an old piece of code in Qt Creator. There is no issue with any source file of the code. But I am getting this error.
    "error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to'"

    Full details.

    C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.36.32532\include\type_traits:334: error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to'
    C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.36.32532\include\type_traits(334): error C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to'
    C:\Qt\6.5.1\msvc2019_64\include\QtCore/qstringview.h(22): note: see declaration of 'QString'
    C:\Qt\6.5.1\msvc2019_64\include\QtCore/qanystringview.h(82): note: see reference to class template instantiation 'std::is_convertible<QStringTokenizerBaseBase::tokenizer_state &,QString>' being compiled
    C:\Qt\6.5.1\msvc2019_64\include\QtCore/qanystringview.h(82): note: see reference to variable template 'const bool conjunction_v<std::negation<std::disjunction<std::is_same<QStringTokenizerBaseBase::tokenizer_state,enum QAnyStringView::Tag>,std::is_sameQStringTokenizerBaseBase::tokenizer_state,QAnyStringView,std::is_pointerQStringTokenizerBaseBase::tokenizer_state,std::is_sameQStringTokenizerBaseBase::tokenizer_state,QByteArray,std::is_sameQStringTokenizerBaseBase::tokenizer_state,QString > >,std::is_convertible<QStringTokenizerBaseBase::tokenizer_state &,QString> >' being compiled
    C:\Qt\6.5.1\msvc2019_64\include\QtCore/qanystringview.h(216): note: see reference to alias template instantiation 'QAnyStringView::if_convertible_to<QString,QStringTokenizerBaseBase::tokenizer_state&>' being compiled

    I have also attached the screenshot of the Qt Creator Screen. Please help me as I have no clue about it.

    Screenshot 2023-07-17 104102.jpg

    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by
    #2

    @Alcor
    In your original code, prior to whatever line causes the error, do you have something like #include <QString> or equivalent other #include which will lead to this?

    A 1 Reply Last reply
    0
    • JonBJ JonB

      @Alcor
      In your original code, prior to whatever line causes the error, do you have something like #include <QString> or equivalent other #include which will lead to this?

      A Offline
      A Offline
      Alcor
      wrote on last edited by
      #3

      @JonB

      "In your original code, prior to whatever line causes the error, do you have something like...."

      How do I find which line in which file of my code is causing this error?

      SGaistS kkoehneK 2 Replies Last reply
      0
      • A Alcor

        @JonB

        "In your original code, prior to whatever line causes the error, do you have something like...."

        How do I find which line in which file of my code is causing this error?

        SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #4

        @Alcor hi and welcome to devnet,

        Where in your code is QString used ?
        Do all the files that do something with it contain the proper include ?

        Interested in AI ? www.idiap.ch
        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

        A 1 Reply Last reply
        0
        • SGaistS SGaist

          @Alcor hi and welcome to devnet,

          Where in your code is QString used ?
          Do all the files that do something with it contain the proper include ?

          A Offline
          A Offline
          Alcor
          wrote on last edited by
          #5

          @SGaist

          There are many source code files that are using QString such as those given below. But none of these files have directive #include<QString>. I thought adding the line #include<QString> will make the error go away but it unfortunately it stays.

          "
          foreach(const QString &preset, presets)
          {
          QStringList temp = preset.split(";");
          m_ui->presetComboBox->addItem(temp[0], temp[1] + ":" + temp[2]);
          }

          "

          or
          "
          void DateTimeWidget::on_utcOffsetDoubleSpinBox_valueChanged(double d)
          {
          QString prefix("UTC");
          if(d >= 0.0)
          prefix.append("+");

          m_ui->utcOffsetDoubleSpinBox->setPrefix(prefix);
             
          autoApply();
          

          }

          "

          or
          "
          void CollapsibleDockWidget::updateWindowTitle(QString windowTitle)
          {
          if(_titleBar)
          _titleBar->setWindowTitle(windowTitle);
          }

          "

          SGaistS 1 Reply Last reply
          0
          • A Alcor

            @SGaist

            There are many source code files that are using QString such as those given below. But none of these files have directive #include<QString>. I thought adding the line #include<QString> will make the error go away but it unfortunately it stays.

            "
            foreach(const QString &preset, presets)
            {
            QStringList temp = preset.split(";");
            m_ui->presetComboBox->addItem(temp[0], temp[1] + ":" + temp[2]);
            }

            "

            or
            "
            void DateTimeWidget::on_utcOffsetDoubleSpinBox_valueChanged(double d)
            {
            QString prefix("UTC");
            if(d >= 0.0)
            prefix.append("+");

            m_ui->utcOffsetDoubleSpinBox->setPrefix(prefix);
               
            autoApply();
            

            }

            "

            or
            "
            void CollapsibleDockWidget::updateWindowTitle(QString windowTitle)
            {
            if(_titleBar)
            _titleBar->setWindowTitle(windowTitle);
            }

            "

            SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #6

            Are you using Qt's QStringBuilder ?

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

            A 1 Reply Last reply
            0
            • SGaistS SGaist

              Are you using Qt's QStringBuilder ?

              A Offline
              A Offline
              Alcor
              wrote on last edited by Alcor
              #7

              @SGaist
              No. Not to the best of my understanding of the code that I am working with. By the way, if it helps, the code I am working with was originally written (compiled and executed successfully for Qt4.8).

              Just now I found one file with include directive #Include <QtCore/QString>.

              JonBJ 1 Reply Last reply
              0
              • A Alcor

                @JonB

                "In your original code, prior to whatever line causes the error, do you have something like...."

                How do I find which line in which file of my code is causing this error?

                kkoehneK Offline
                kkoehneK Offline
                kkoehne
                Moderators
                wrote on last edited by
                #8

                @Alcor said in error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to':

                How do I find which line in which file of my code is causing this error?

                Go to the 'Compile Output' pane in Qt Creator. Look for the first "error C2139" . There should be a line with "cl.exe" (the MSVC compiler) before , and that line should contain the name of the source file.

                Director R&D, The Qt Company

                1 Reply Last reply
                2
                • A Alcor

                  @SGaist
                  No. Not to the best of my understanding of the code that I am working with. By the way, if it helps, the code I am working with was originally written (compiled and executed successfully for Qt4.8).

                  Just now I found one file with include directive #Include <QtCore/QString>.

                  JonBJ Offline
                  JonBJ Offline
                  JonB
                  wrote on last edited by
                  #9

                  @Alcor
                  First please follow @kkoehne's suggestion.

                  It might be time now for you to create a brand new, standalone project in Creator. Keep it tiny, put #include <QString> at the head of the .cpp file and QString temp; somewhere inside a function. As little else as possible. Try to just compile. Does that work or generate errors?

                  1 Reply Last reply
                  0
                  • W Offline
                    W Offline
                    WWebber
                    wrote on last edited by WWebber
                    #10

                    I ran into exactly the same problem!
                    Porting from V5.12.x (VS2019) to V6.5.3 (VS2022).
                    How did you fix this?
                    The project works perfect with VS2019!
                    The problem is that the error message does not point to any useful source file than "type_traits".

                    1 Reply Last reply
                    0
                    • aha_1980A Offline
                      aha_1980A Offline
                      aha_1980
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      @WWebber: Have you tried the suggestion from @kkoehne in https://forum.qt.io/post/765260 ?

                      Qt has to stay free or it will die.

                      W 1 Reply Last reply
                      0
                      • aha_1980A aha_1980

                        @WWebber: Have you tried the suggestion from @kkoehne in https://forum.qt.io/post/765260 ?

                        W Offline
                        W Offline
                        WWebber
                        wrote on last edited by
                        #12

                        @aha_1980 said in error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to':

                        @WWebber: Have you tried the suggestion from @kkoehne in https://forum.qt.io/post/765260 ?

                        It points to 'type_traits' and to exactly this line:

                        struct is_convertible : bool_constant<__is_convertible_to(_From, _To)> {
                        // determine whether _From is convertible to _To
                        };

                        1>C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.43.34808\include\type_traits(323,39): error C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to'
                        1>(compiling source file '../QT/test.cpp')
                        1> c:\Qt6\6.5.3\msvc2019_64\include\QtCore\qcontainerfwd.h(30,7):
                        1> see declaration of 'QString'
                        1> C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.43.34808\include\type_traits(323,39):
                        1> the template instantiation context (the oldest one first) is
                        1> c:\Qt6\6.5.3\msvc2019_64\include\QtCore\qstringtokenizer.h(27,30):
                        1> while compiling class template member function 'QAnyStringView::QAnyStringView(Container &&,wrapped<Container,QString>::type &&)'
                        1> c:\Qt6\6.5.3\msvc2019_64\include\QtCore\qstringtokenizer.h(27,30):
                        1> while processing the default template argument of 'QAnyStringView::QAnyStringView(Container &&,wrapped<Container,QString>::type &&)'
                        1> c:\Qt6\6.5.3\msvc2019_64\include\QtCore\qanystringview.h(216,35):
                        1> see reference to alias template instantiation 'QAnyStringView::if_convertible_to<QString,QStringTokenizerBaseBase::tokenizer_state&>' being compiled
                        1> c:\Qt6\6.5.3\msvc2019_64\include\QtCore\qanystringview.h(82,53):
                        1> see reference to variable template 'const bool conjunction_v<std::negation<std::disjunction<std::is_same<QStringTokenizerBaseBase::tokenizer_state,enum QAnyStringView::Tag>,std::is_sameQStringTokenizerBaseBase::tokenizer_state,QAnyStringView,std::is_pointerQStringTokenizerBaseBase::tokenizer_state,std::is_sameQStringTokenizerBaseBase::tokenizer_state,QByteArray,std::is_sameQStringTokenizerBaseBase::tokenizer_state,QString > >,std::is_convertible<QStringTokenizerBaseBase::tokenizer_state &,QString> >' being compiled
                        1> c:\Qt6\6.5.3\msvc2019_64\include\QtCore\qanystringview.h(82,53):
                        1> see reference to class template instantiation 'std::is_convertible<QStringTokenizerBaseBase::tokenizer_state &,QString>' being compiled

                        1 Reply Last reply
                        0
                        • W Offline
                          W Offline
                          WWebber
                          wrote on last edited by
                          #13

                          The error shows up with an empty CPP file holding just this single line:
                          #include <qdialog.h>

                          1 Reply Last reply
                          0
                          • Christian EhrlicherC Offline
                            Christian EhrlicherC Offline
                            Christian Ehrlicher
                            Lifetime Qt Champion
                            wrote on last edited by
                            #14

                            Use a recent Qt version and add the include to QString before.

                            Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                            Visit the Qt Academy at https://academy.qt.io/catalog

                            W 1 Reply Last reply
                            0
                            • Christian EhrlicherC Christian Ehrlicher

                              Use a recent Qt version and add the include to QString before.

                              W Offline
                              W Offline
                              WWebber
                              wrote on last edited by
                              #15

                              @Christian-Ehrlicher said in error: C2139: 'QString': an undefined class is not allowed as an argument to compiler intrinsic type trait '__is_convertible_to':

                              Use a recent Qt version and add the include to QString before.

                              This is unfortunately not an option as I write a DLL for a main application using V6.5.3.
                              Even when I just include <qstring> in the testcpp, I'm gettig the same error.

                              1 Reply Last reply
                              0
                              • Christian EhrlicherC Offline
                                Christian EhrlicherC Offline
                                Christian Ehrlicher
                                Lifetime Qt Champion
                                wrote on last edited by
                                #16

                                Simply try a recent version to see if it works...

                                Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                                Visit the Qt Academy at https://academy.qt.io/catalog

                                1 Reply Last reply
                                0
                                • W Offline
                                  W Offline
                                  WWebber
                                  wrote on last edited by
                                  #17

                                  Tested with the latest 6.x version - same error.
                                  I suspect it has to do with the latest QT Tools..

                                  1 Reply Last reply
                                  0
                                  • Christian EhrlicherC Offline
                                    Christian EhrlicherC Offline
                                    Christian Ehrlicher
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #18

                                    Try it with a simple CMakeLists.txt on thee visual studio command line.

                                    Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                                    Visit the Qt Academy at https://academy.qt.io/catalog

                                    1 Reply Last reply
                                    0
                                    • W Offline
                                      W Offline
                                      WWebber
                                      wrote on last edited by
                                      #19

                                      Found it!
                                      This error was caused by the compiler option "/Zc:hiddenFriend-" !

                                      1 Reply Last reply
                                      2
                                      • SGaistS SGaist has marked this topic as solved on

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