From 35e005bc4fd790d41a5b5248e85bbdac33fbf043 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Vr=C3=A1til?= <dvratil@kde.org>
Date: Sat, 30 Jun 2018 13:53:03 +0200
Subject: [PATCH] Fix metatype trait for types that are both QObject and
 Q_GADGET

Fixes ambiguous template instantiation for types that derive from both
a QObject and Q_GADGET. For such types we treat them only as QObjects
as they extend the functionality of the gadget.

Task-number: QTBUG-68803
Change-Id: Ic42766034e14e5df43c4e6f7811e2c0be1dc7e74
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
---
 src/corelib/kernel/qmetatype.h                        |  4 ++--
 tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index a0969ee9082..cf68752f857 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -1413,8 +1413,8 @@ namespace QtPrivate
         static char checkType(void (X::*)());
         static void *checkType(void (T::*)());
         enum {
-            IsRealGadget = sizeof(checkType(&T::qt_check_for_QGADGET_macro)) == sizeof(void *),
-            IsGadgetOrDerivedFrom = true
+            IsRealGadget = !IsPointerToTypeDerivedFromQObject<T*>::Value && sizeof(checkType(&T::qt_check_for_QGADGET_macro)) == sizeof(void *),
+            IsGadgetOrDerivedFrom = !IsPointerToTypeDerivedFromQObject<T*>::Value
         };
     };
 
diff --git a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
index c6fd5d17c2d..e3121999806 100644
--- a/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
+++ b/tests/auto/corelib/kernel/qmetatype/tst_qmetatype.cpp
@@ -1696,11 +1696,21 @@ public:
     Q_ENUM(MyEnum)
 };
 
+class MyQObjectFromGadget : public QObject, public MyGadget
+{
+    Q_OBJECT
+public:
+    MyQObjectFromGadget(QObject *parent = 0)
+        : QObject(parent)
+    {}
+};
+
 Q_DECLARE_METATYPE(MyGadget);
 Q_DECLARE_METATYPE(MyGadget*);
 Q_DECLARE_METATYPE(const QMetaObject *);
 Q_DECLARE_METATYPE(Qt::ScrollBarPolicy);
 Q_DECLARE_METATYPE(MyGadget::MyEnum);
+Q_DECLARE_METATYPE(MyQObjectFromGadget*);
 
 void tst_QMetaType::metaObject_data()
 {
@@ -1719,6 +1729,7 @@ void tst_QMetaType::metaObject_data()
     QTest::newRow("MyGadget*") << ::qMetaTypeId<MyGadget*>() << &MyGadget::staticMetaObject << false << true << false;
     QTest::newRow("MyEnum") << ::qMetaTypeId<MyGadget::MyEnum>() <<  &MyGadget::staticMetaObject << false << false << false;
     QTest::newRow("Qt::ScrollBarPolicy") << ::qMetaTypeId<Qt::ScrollBarPolicy>() <<  &QObject::staticQtMetaObject << false << false << false;
+    QTest::newRow("MyQObjectFromGadget*") << ::qMetaTypeId<MyQObjectFromGadget*>() << &MyQObjectFromGadget::staticMetaObject << false << false << true;
 
     QTest::newRow("GadgetDerivedAndTyped<int>") << ::qMetaTypeId<GadgetDerivedAndTyped<int>>() <<  &GadgetDerivedAndTyped<int>::staticMetaObject << true << false << false;
     QTest::newRow("GadgetDerivedAndTyped<int>*") << ::qMetaTypeId<GadgetDerivedAndTyped<int>*>() <<  &GadgetDerivedAndTyped<int>::staticMetaObject << false << true << false;