tst_QVariant: add a test contrasting Qt 5/6 isNull behavior

A null QString used to make a QVariant containing it null in Qt 5, but
this is no longer the case. Add a test that get_if works as expected.

Task-number: QTBUG-111598
Change-Id: I0f3511e1b33f4a9d67755269455680feda22ddca
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
index cbe3f90b94..6667d95e0d 100644
--- a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
+++ b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
@@ -381,6 +381,7 @@ private slots:
     void getIf_int() { getIf_impl(42); }
     void getIf_QString() { getIf_impl(u"string"_s); };
     void getIf_NonDefaultConstructible();
+    void getIfSpecial();
 
     void get_int() { get_impl(42); }
     void get_QString() { get_impl(u"string"_s); }
@@ -5724,6 +5725,12 @@ void tst_QVariant::getIf_NonDefaultConstructible()
     getIf_impl(NonDefaultConstructible{42});
 }
 
+void tst_QVariant::getIfSpecial()
+{
+    QVariant v{QString{}}; // used to be a null QVariant in Qt 5
+    QCOMPARE_NE(get_if<QString>(&v), nullptr); // not anymore...
+}
+
 void tst_QVariant::get_NonDefaultConstructible()
 {
     get_impl(NonDefaultConstructible{42});