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  1. Qt
  2. QTBUG-82415

[REG 5.14->5.15] QShortcut constructor call fails to compile if called with ambiguousMember=nullptr (or 0)

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    • e1920f65936fe7d712441e88c023746ab5c21cee (qt/qtbase/5.15)

    Description

      Calls to "new QShortcut" fail to compile with Qt 5.15.0-alpha.

      Simple (and trimmed down to the point that it is bogus, but still shows the error) test case:

      #include <QShortcut>
      #include <QKeySequence>
      int main(int argc, char **argv) {
              QShortcut x(QKeySequence(QObject::tr("Ctrl+L", "File|Load")), nullptr, SLOT(someSlotHere()), nullptr);
      }
      

      Result:

      In file included from test.cpp:1:
      In file included from /usr/include/qt5/QtWidgets/QShortcut:1:
      /usr/include/qt5/QtWidgets/qshortcut.h:101:9: error: no matching member function for call to 'connect'
              connect(this, &QShortcut::activated, object1, std::move(slot1));
              ^~~~~~~
      test.cpp:4:12: note: in instantiation of function template specialization 'QShortcut::QShortcut<char, nullptr_t>' requested here
              QShortcut x(QKeySequence(QObject::tr("Ctrl+L", "File|Load")), nullptr, SLOT(someSlotHere()), nullptr);
                        ^
      /usr/include/qt5/QtCore/qobject.h:283:13: note: candidate function template not viable: no known conversion from 'const char *' to 'const QObject *' for 3rd argument
                  connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, const QObject *context, Func2 slot,
                  ^
      /usr/include/qt5/QtCore/qobject.h:322:13: note: candidate function template not viable: no known conversion from 'const char *' to 'const QObject *' for 3rd argument
                  connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, const QObject *context, Func2 slot,
                  ^
      /usr/include/qt5/QtCore/qobject.h:222:36: note: candidate function not viable: no known conversion from 'void (QShortcut::*)()' to 'const char *' for 2nd argument
          static QMetaObject::Connection connect(const QObject *sender, const char *signal,
                                         ^
      /usr/include/qt5/QtCore/qobject.h:481:41: note: candidate function not viable: no known conversion from 'void (QShortcut::*)()' to 'const char *' for 2nd argument
      inline QMetaObject::Connection QObject::connect(const QObject *asender, const char *asignal,
                                              ^
      /usr/include/qt5/QtCore/qobject.h:225:36: note: candidate function not viable: no known conversion from 'void (QShortcut::*)()' to 'const QMetaMethod' for 2nd argument
          static QMetaObject::Connection connect(const QObject *sender, const QMetaMethod &signal,
                                         ^
      /usr/include/qt5/QtCore/qobject.h:242:43: note: candidate template ignored: substitution failure [with Func1 = void (QShortcut::*)(), Func2 = nullptr_t]: no type named 'Object' in 'QtPrivate::FunctionPointer<nullptr_t>'
          static inline QMetaObject::Connection connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal,
                                                ^
      /usr/include/qt5/QtCore/qobject.h:274:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided
                  connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
                  ^
      /usr/include/qt5/QtCore/qobject.h:314:13: note: candidate function template not viable: requires 3 arguments, but 4 were provided
                  connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
                  ^
      1 error generated.
      

      Real world (and valid) uses of QShortcut that break can be found in KDE lokalize 19.12.2 and kvirc (with WebKit enabled).

      Tested with clang 10.0-rc2 and a current gcc 10 snapshot.

      Workaround:
      Passing any slot (valid or not) instead of nullptr or 0 as ambiguousMember works

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              chehrlic Christian Ehrlicher
              bero Bernhard Rosenkränzer
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                Updated:
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