diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index c846aada05..26c3ce2443 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -4470,6 +4470,19 @@ QDebug operator<<(QDebug dbg, const QObject *o)
     \sa QObject::objectName()
 */
 
+/*!
+    \macro QT_NO_NARROWING_CONVERSIONS_IN_CONNECT
+    \relates QObject
+    \since 5.8
+
+    Defining this macro will disable narrowing and floating-point-to-integral
+    conversions between the arguments carried by a signal and the arguments
+    accepted by a slot, when the signal and the slot are connected using the
+    PMF-based syntax.
+
+    \sa QObject::connect
+*/
+
 /*!
     \typedef QObjectList
     \relates QObject
diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index 5eae70ecc5..e94e713e1f 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -50,6 +50,8 @@
 #pragma qt_sync_stop_processing
 #endif
 
+#include <type_traits>
+
 QT_BEGIN_NAMESPACE
 
 
@@ -193,6 +195,46 @@ namespace QtPrivate {
         }
     };
 
+    /*
+        Logic that checks if the underlying type of an enum is signed or not.
+        Needs an external, explicit check that E is indeed an enum. Works
+        around the fact that it's undefined behavior to instantiate
+        std::underlying_type on non-enums (cf. §20.13.7.6 [meta.trans.other]).
+    */
+    template<typename E, typename Enable = void>
+    struct IsEnumUnderlyingTypeSigned : std::false_type
+    {
+    };
+
+    template<typename E>
+    struct IsEnumUnderlyingTypeSigned<E, typename std::enable_if<std::is_enum<E>::value>::type>
+            : std::integral_constant<bool, std::is_signed<typename std::underlying_type<E>::type>::value>
+    {
+    };
+
+    /*
+       Logic that checks if the argument of the slot does not narrow the
+       argument of the signal when used in list initialization. Cf. §8.5.4.7
+       [dcl.init.list] for the definition of narrowing.
+       For incomplete From/To types, there's no narrowing.
+    */
+    template<typename From, typename To, typename Enable = void>
+    struct AreArgumentsNarrowedBase : std::false_type
+    {
+    };
+
+    template<typename From, typename To>
+    struct AreArgumentsNarrowedBase<From, To, typename std::enable_if<sizeof(From) && sizeof(To)>::type>
+        : std::integral_constant<bool,
+              (std::is_floating_point<From>::value && std::is_integral<To>::value) ||
+              (std::is_floating_point<From>::value && std::is_floating_point<To>::value && sizeof(From) > sizeof(To)) ||
+              ((std::is_integral<From>::value || std::is_enum<From>::value) && std::is_floating_point<To>::value) ||
+              (std::is_integral<From>::value && std::is_integral<To>::value && (sizeof(From) > sizeof(To) || std::is_signed<From>::value != std::is_signed<To>::value)) ||
+              (std::is_enum<From>::value && std::is_integral<To>::value && (sizeof(From) > sizeof(To) || IsEnumUnderlyingTypeSigned<From>::value != std::is_signed<To>::value))
+              >
+    {
+    };
+
     /*
        Logic that check if the arguments of the slot matches the argument of the signal.
        To be used like this:
@@ -203,6 +245,10 @@ namespace QtPrivate {
         static char test(...);
         static const typename RemoveRef<A1>::Type &dummy();
         enum { value = sizeof(test(dummy())) == sizeof(int) };
+#ifdef QT_NO_NARROWING_CONVERSIONS_IN_CONNECT
+        struct AreArgumentsNarrowed : AreArgumentsNarrowedBase<typename RemoveRef<A1>::Type, typename RemoveRef<A2>::Type> {};
+        Q_STATIC_ASSERT_X(!AreArgumentsNarrowed::value, "Signal and slot arguments are not compatible (narrowing)");
+#endif
     };
     template<typename A1, typename A2> struct AreArgumentsCompatible<A1, A2&> { enum { value = false }; };
     template<typename A> struct AreArgumentsCompatible<A&, A&> { enum { value = true }; };
diff --git a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
index 9ee9c1f331..52bf8e9004 100644
--- a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
+++ b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
@@ -147,6 +147,7 @@ private slots:
     void noDeclarativeParentChangedOnDestruction();
     void deleteLaterInAboutToBlockHandler();
     void mutableFunctor();
+    void checkArgumentsForNarrowing();
 };
 
 struct QObjectCreatedOnShutdown
@@ -6670,6 +6671,515 @@ void tst_QObject::mutableFunctor()
     QCOMPARE(functor.count, 0); // but the original object should have been copied at connect time
 }
 
+void tst_QObject::checkArgumentsForNarrowing()
+{
+    enum UnscopedEnum {};
+    enum SignedUnscopedEnum { SignedUnscopedEnumV1 = -1, SignedUnscopedEnumV2 = 1 };
+
+    QVERIFY(sizeof(UnscopedEnum) <= sizeof(int));
+    QVERIFY(sizeof(SignedUnscopedEnum) <= sizeof(int));
+
+    // floating point to integral
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<float, bool>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, bool>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, bool>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<float, char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, char>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<float, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, short>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<float, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, int>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<float, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<float, long long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, long long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, long long>::value));
+
+
+    // floating point to a smaller floating point
+    if (sizeof(double) > sizeof(float)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<double, float>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, float>::value));
+    }
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<float, double>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<float, long double>::value));
+
+    if (sizeof(long double) > sizeof(double))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long double, float>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<double, long double>::value));
+
+
+    // integral to floating point
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, long double>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<char, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<char, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<char, long double>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, long double>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, long double>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, long double>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, long double>::value));
+
+
+    // enum to floating point
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, long double>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, float>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, double>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, long double>::value));
+
+
+    // integral to smaller integral
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<bool, bool>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<char, char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<signed char, signed char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<signed char, short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<signed char, int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<signed char, long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<signed char, long long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned char, unsigned char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned char, unsigned short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned char, unsigned int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned char, unsigned long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned char, unsigned long long>::value));
+
+    if (sizeof(bool) > sizeof(char))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, unsigned char>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<bool, unsigned char>::value));
+
+    if (sizeof(bool) > sizeof(short))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, unsigned short>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<bool, unsigned short>::value));
+
+    if (sizeof(bool) > sizeof(int))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, unsigned int>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<bool, unsigned int>::value));
+
+    if (sizeof(bool) > sizeof(long))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, unsigned long>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<bool, unsigned long>::value));
+
+    if (sizeof(bool) > sizeof(long long))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<bool, unsigned long long>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<bool, unsigned long long>::value));
+
+    if (sizeof(short) > sizeof(char)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, signed char>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, signed char>::value));
+    }
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<short, short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<short, int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<short, long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<short, long long>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned short, unsigned short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned short, unsigned int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned short, unsigned long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned short, unsigned long long>::value));
+
+    if (sizeof(int) > sizeof(short)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, unsigned short>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, unsigned short>::value));
+    }
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<int, int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<int, long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<int, long long>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned int, unsigned int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned int, unsigned long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned int, unsigned long long>::value));
+
+    if (sizeof(long) > sizeof(int)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, unsigned int>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, unsigned int>::value));
+    }
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<long, long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<long, long long>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned long, unsigned long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned long, unsigned long long>::value));
+
+    if (sizeof(long long) > sizeof(long)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, unsigned int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, long>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, unsigned long>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, unsigned int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, long>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, unsigned long>::value));
+    }
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<long long, long long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<unsigned long long, unsigned long long>::value));
+
+
+    // integral to integral with different signedness. smaller ones tested above
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<signed char, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<signed char, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<signed char, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<signed char, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<signed char, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned char, signed char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned char, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned char, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned char, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned char, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<short, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned short, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<int, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned int, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<long long, unsigned long long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<unsigned long long, long long>::value));
+
+    // enum to smaller integral
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, UnscopedEnum>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, SignedUnscopedEnum>::value));
+
+    if (std::is_signed<typename std::underlying_type<UnscopedEnum>::type>::value) {
+        if (sizeof(UnscopedEnum) > sizeof(char))
+            QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, signed char>::value));
+        else
+            QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, signed char>::value));
+
+        if (sizeof(UnscopedEnum) > sizeof(short))
+            QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, short>::value));
+        else
+            QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, short>::value));
+
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, int>::value));
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, long>::value));
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, long long>::value));
+    } else {
+        if (sizeof(UnscopedEnum) > sizeof(bool))
+            QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, bool>::value));
+        else
+            QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, bool>::value));
+
+        if (sizeof(UnscopedEnum) > sizeof(char))
+            QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned char>::value));
+        else
+            QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned char>::value));
+
+        if (sizeof(UnscopedEnum) > sizeof(short))
+            QVERIFY((QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned short>::value));
+        else
+            QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned short>::value));
+
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned int>::value));
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned long>::value));
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<UnscopedEnum, unsigned long long>::value));
+    }
+
+    QVERIFY(std::is_signed<typename std::underlying_type<SignedUnscopedEnum>::type>::value);
+
+    if (sizeof(SignedUnscopedEnum) > sizeof(char))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, signed char>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, signed char>::value));
+
+    if (sizeof(SignedUnscopedEnum) > sizeof(short))
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, short>::value));
+    else
+        QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, short>::value));
+
+    QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, int>::value));
+    QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, long>::value));
+    QVERIFY(!(QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, long long>::value));
+
+
+    enum class ScopedEnumBackedBySChar : signed char { A };
+    enum class ScopedEnumBackedByUChar : unsigned char { A };
+    enum class ScopedEnumBackedByShort : short { A };
+    enum class ScopedEnumBackedByUShort : unsigned short { A };
+    enum class ScopedEnumBackedByInt : int { A };
+    enum class ScopedEnumBackedByUInt : unsigned int { A };
+    enum class ScopedEnumBackedByLong : long { A };
+    enum class ScopedEnumBackedByULong : unsigned long { A };
+    enum class ScopedEnumBackedByLongLong : long long { A };
+    enum class ScopedEnumBackedByULongLong : unsigned long long { A };
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, ScopedEnumBackedBySChar>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, ScopedEnumBackedByUChar>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, ScopedEnumBackedByShort>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, ScopedEnumBackedByUShort>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, ScopedEnumBackedByInt>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, ScopedEnumBackedByUInt>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, ScopedEnumBackedByLong>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, ScopedEnumBackedByULong>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, ScopedEnumBackedByLongLong>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, ScopedEnumBackedByULongLong>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, signed char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, unsigned char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, unsigned short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, unsigned int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, unsigned long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, long long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, unsigned long long>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, signed char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, long long>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, unsigned char>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, unsigned short>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, unsigned int>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, unsigned long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, unsigned long long>::value));
+
+    if (sizeof(short) > sizeof(char)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, char>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, signed char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, signed char>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned char>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, unsigned char>::value));
+    }
+
+    if (sizeof(int) > sizeof(short)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, short>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned short>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, unsigned short>::value));
+    }
+
+    if (sizeof(long) > sizeof(int)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, int>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, unsigned int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned int>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, unsigned int>::value));
+    }
+
+    if (sizeof(long long) > sizeof(long)) {
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, long>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, long>::value));
+
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned long>::value));
+        QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, unsigned long>::value));
+    }
+
+    // different signedness of the underlying type
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<SignedUnscopedEnum, unsigned long long>::value));
+
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedBySChar, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByShort, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByInt, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLong, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByLongLong, unsigned long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, signed char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUChar, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, signed char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUShort, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, signed char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByUInt, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, signed char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULong, long long>::value));
+
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, signed char>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, short>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, int>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, long>::value));
+    QVERIFY((QtPrivate::AreArgumentsNarrowedBase<ScopedEnumBackedByULongLong, long long>::value));
+
+    // other types which should be always unaffected
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<void *, void *>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QString, QString>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QString &, QString &>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<const QString &, const QString &>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QObject, QObject>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QObject *, QObject *>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<const QObject *, const QObject *>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<std::nullptr_t, std::nullptr_t>::value));
+
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QString, QObject>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QString, QVariant>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QString, void *>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<QString, long long>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<bool, const QObject *&>::value));
+    QVERIFY((!QtPrivate::AreArgumentsNarrowedBase<int (*)(bool), void (QObject::*)()>::value));
+}
+
 // Test for QtPrivate::HasQ_OBJECT_Macro
 Q_STATIC_ASSERT(QtPrivate::HasQ_OBJECT_Macro<tst_QObject>::Value);
 Q_STATIC_ASSERT(!QtPrivate::HasQ_OBJECT_Macro<SiblingDeleter>::Value);