QMetaType: fix typenameHelper() for types in the QtPrivate namespace

GCC at some point decided that it wouldn't include the full namespace
expansion in __PRETTY_FUNCTION__ for any type that is in the same
namespace as the template function being expanded (that is, the
QtPrivate) namespace. I don't know how long this behavior has been in
place, but it can be seen with GCC 13, where the expansion of that macro
inside QtPrivate::typenameHelper<QtPrivate::ModelIndex>() is:

 constexpr auto QtPrivate::typenameHelper() [with T = ModelIndex]

This can be easily worked around by using a different namespace.

Fixes: QTBUG-119650
Pick-to: 6.6 6.5 6.2
Change-Id: Ica7a43f6147b49c187ccfffd179df309e43a70cb
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp
index c0650c7b1a..bde4e19907 100644
--- a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp
+++ b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype2.cpp
@@ -640,6 +640,21 @@ void tst_QMetaType::typeNameNormalization()
     }
 }
 
+QT_BEGIN_NAMESPACE
+namespace QtPrivate { struct tst_QMetaType_TestType {}; }
+QT_END_NAMESPACE
+
+void tst_QMetaType::typeNameInQtPrivate()
+{
+    using T = QT_PREPEND_NAMESPACE(QtPrivate::tst_QMetaType_TestType);
+
+    // some compilers (GCC) are known to suppress the namespace prefix if the
+    // type and the function where it is expanded on are on the same namespace
+    static constexpr char expectedName[] = "QtPrivate::tst_QMetaType_TestType";
+    QMetaType mt = QMetaType::fromType<T>();
+    QCOMPARE(mt.name(), expectedName);
+}
+
 #if QT_DEPRECATED_SINCE(6, 0)
 void tst_QMetaType::testDeprecatedGetters()
 {