From fd45278eaa3004e5450f011102fe0d55ae6ed8b3 Mon Sep 17 00:00:00 2001
From: Mikolaj Boc <mikolaj.boc@qt.io>
Date: Thu, 7 Jul 2022 11:32:01 +0200
Subject: [PATCH] Specialize MetaObjectForType for non-pointer QObject-derived
 types

QMetaTypeInterfaceWrapper tries to find the metaObjectFunction using
the MetaObjectForType template. Using SFINAE, for a QObject, it should
resolve to a suitable specialization.

Such a specialization doesn't yet exist. It had to be created.

The following path returns nullptr for registered meta types:

  auto metatype = QMetaType(typeId);
  requestedTestType.metaObject() -> returns nullptr since a bad template
  argument is fed to MetaObjectForType<T> in
  QMetaTypeInterfaceWrapper<IneritingFromQObject>::metaType's static initializer.

Change-Id: I8b31c51e12cb19c333e00480b0177354b910ce1e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/kernel/qmetatype.h                        | 7 ++++++-
 tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index 2e97e1892d..24d1de4a28 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -901,7 +901,12 @@ namespace QtPrivate
         static constexpr const QMetaObject *metaObjectFunction(const QMetaTypeInterface *) { return &T::staticMetaObject; }
     };
     template<typename T>
-    struct MetaObjectForType<T, typename std::enable_if<IsGadgetHelper<T>::IsGadgetOrDerivedFrom>::type>
+    struct MetaObjectForType<T, std::enable_if_t<
+        std::disjunction_v<
+            std::bool_constant<IsGadgetHelper<T>::IsGadgetOrDerivedFrom>,
+            std::is_base_of<QObject, T>
+        >
+    >>
     {
         static constexpr const QMetaObject *value() { return &T::staticMetaObject; }
         static constexpr const QMetaObject *metaObjectFunction(const QMetaTypeInterface *) { return &T::staticMetaObject; }
diff --git a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
index ed413107c0..053408997c 100644
--- a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
+++ b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
@@ -1999,6 +1999,7 @@ void tst_QMetaType::metaObject_data()
     QTest::newRow("unknown-type") << int(QMetaType::UnknownType) << static_cast<const QMetaObject *>(0) << false << false << false;
     QTest::newRow("QObject") << int(QMetaType::QObjectStar) << &QObject::staticMetaObject << false << false << true;
     QTest::newRow("QFile*") << ::qMetaTypeId<QFile*>() << &QFile::staticMetaObject << false << false << true;
+    QTest::newRow("MyObject") << ::qMetaTypeId<MyObject>() << &MyObject::staticMetaObject << false << false << false;
     QTest::newRow("MyObject*") << ::qMetaTypeId<MyObject*>() << &MyObject::staticMetaObject << false << false << true;
     QTest::newRow("int") << int(QMetaType::Int) << static_cast<const QMetaObject *>(0) << false << false << false;
     QTest::newRow("QEasingCurve") << ::qMetaTypeId<QEasingCurve>() <<  &QEasingCurve::staticMetaObject << true << false << false;