tst_QMetaObject: change tests to forward-declared-only

The type MyUnregisteredType needs to be only forward-declared for the
trick to work. The issue is not about registration, because since commit
fa987d44417528856d5e80ed7b48ba99e19fa307 ("MetaObject: Store the
QMetaType of the methods"), we will record the meta type of the type
anyway, which will eventually allow the meta object to actually find
this type.

Instead, the tests are valid for a type that is only forward-declared.

Change-Id: I36b24183fbd041179f2ffffd1702182746f7c1b2
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

4 files changed, 42 insertions, 22 deletions

diff --git a/tests/auto/corelib/kernel/qmetaobject/CMakeLists.txt b/tests/auto/corelib/kernel/qmetaobject/CMakeLists.txt
index d0736f418d..6076f9c72c 100644
--- a/tests/auto/corelib/kernel/qmetaobject/CMakeLists.txt
+++ b/tests/auto/corelib/kernel/qmetaobject/CMakeLists.txt
@@ -1,15 +1,13 @@
-# Generated from qmetaobject.pro.
-
-#####################################################################
-## tst_qmetaobject Test:
-#####################################################################
+set(tst_qmetaobject_SOURCES
+    tst_qmetaobject.cpp
+    forwarddeclared.h
+    forwarddeclared.cpp
+)
 
 qt_internal_add_test(tst_qmetaobject
     SOURCES
-        tst_qmetaobject.cpp
+        ${tst_qmetaobject_SOURCES}
     PUBLIC_LIBRARIES
         Qt::CorePrivate
 )
 
-## Scopes:
-#####################################################################
diff --git a/tests/auto/corelib/kernel/qmetaobject/forwarddeclared.cpp b/tests/auto/corelib/kernel/qmetaobject/forwarddeclared.cpp
new file mode 100644
index 0000000000..1f81bb09f2
--- /dev/null
+++ b/tests/auto/corelib/kernel/qmetaobject/forwarddeclared.cpp
@@ -0,0 +1,12 @@
+// Copyright (C) 2022 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "forwarddeclared.h"
+
+struct MyForwardDeclaredType { };
+static const MyForwardDeclaredType t;
+
+const MyForwardDeclaredType &getForwardDeclaredType() noexcept
+{
+    return t;
+}
diff --git a/tests/auto/corelib/kernel/qmetaobject/forwarddeclared.h b/tests/auto/corelib/kernel/qmetaobject/forwarddeclared.h
new file mode 100644
index 0000000000..79db65676f
--- /dev/null
+++ b/tests/auto/corelib/kernel/qmetaobject/forwarddeclared.h
@@ -0,0 +1,11 @@
+// Copyright (C) 2022 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef FORWARDDECLARED_H
+#define FORWARDDECLARED_H
+
+struct MyForwardDeclaredType;      // and ONLY forward-declared
+
+const MyForwardDeclaredType &getForwardDeclaredType() noexcept;
+
+#endif // FORWARDDECLARED_H
diff --git a/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp b/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
index 3b2066ba5d..23c75e4422 100644
--- a/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
+++ b/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
@@ -12,6 +12,8 @@
 
 Q_DECLARE_METATYPE(const QMetaObject *)
 
+#include "forwarddeclared.h"
+
 struct MyStruct
 {
     int i;
@@ -215,8 +217,7 @@ namespace MyNamespace {
             int m_value2 = 0;
             int m_value3 = 0;
     };
-}
-
+} // namespace MyNamespace
 
 class tst_QMetaObject : public QObject
 {
@@ -435,8 +436,6 @@ void tst_QMetaObject::connectSlotsByName()
     QCOMPARE(obj2.invokeCount2, 1);
 }
 
-struct MyUnregisteredType { };
-
 static int countedStructObjectsCount = 0;
 struct CountedStruct
 {
@@ -488,8 +487,8 @@ public slots:
     void moveToThread(QThread *t)
     { QObject::moveToThread(t); }
 
-    void slotWithUnregisteredParameterType(MyUnregisteredType);
-    void slotWithOneUnregisteredParameterType(QString a1, MyUnregisteredType a2);
+    void slotWithUnregisteredParameterType(const MyForwardDeclaredType &);
+    void slotWithOneUnregisteredParameterType(QString a1, const MyForwardDeclaredType &a2);
 
     CountedStruct throwingSlot(const CountedStruct &, CountedStruct s2) {
 #ifndef QT_NO_EXCEPTIONS
@@ -584,10 +583,10 @@ void QtTestObject::testSender()
     slotResult = QString::asprintf("%p", sender());
 }
 
-void QtTestObject::slotWithUnregisteredParameterType(MyUnregisteredType)
+void QtTestObject::slotWithUnregisteredParameterType(const MyForwardDeclaredType &)
 { slotResult = "slotWithUnregisteredReturnType"; }
 
-void QtTestObject::slotWithOneUnregisteredParameterType(QString a1, MyUnregisteredType)
+void QtTestObject::slotWithOneUnregisteredParameterType(QString a1, const MyForwardDeclaredType &)
 { slotResult = "slotWithUnregisteredReturnType-" + a1; }
 
 void QtTestObject::staticFunction0()
@@ -864,19 +863,19 @@ void tst_QMetaObject::invokeQueuedMetaMember()
 
     obj.slotResult.clear();
     {
-        MyUnregisteredType t;
-        QTest::ignoreMessage(QtWarningMsg, "QMetaMethod::invoke: Unable to handle unregistered datatype 'MyUnregisteredType'");
-        QVERIFY(!QMetaObject::invokeMethod(&obj, "slotWithUnregisteredParameterType", Qt::QueuedConnection, Q_ARG(MyUnregisteredType, t)));
+        const MyForwardDeclaredType &t = getForwardDeclaredType();
+        QTest::ignoreMessage(QtWarningMsg, "QMetaMethod::invoke: Unable to handle unregistered datatype 'MyForwardDeclaredType'");
+        QVERIFY(!QMetaObject::invokeMethod(&obj, "slotWithUnregisteredParameterType", Qt::QueuedConnection, Q_ARG(MyForwardDeclaredType, t)));
         QVERIFY(obj.slotResult.isEmpty());
     }
 
     obj.slotResult.clear();
     {
         QString a1("Cannot happen");
-        MyUnregisteredType t;
-        QTest::ignoreMessage(QtWarningMsg, "QMetaMethod::invoke: Unable to handle unregistered datatype 'MyUnregisteredType'");
+        const MyForwardDeclaredType &t = getForwardDeclaredType();
+        QTest::ignoreMessage(QtWarningMsg, "QMetaMethod::invoke: Unable to handle unregistered datatype 'MyForwardDeclaredType'");
         QVERIFY(!QMetaObject::invokeMethod(&obj, "slotWithOneUnregisteredParameterType", Qt::QueuedConnection,
-                                           Q_ARG(QString, a1), Q_ARG(MyUnregisteredType, t)));
+                                           Q_ARG(QString, a1), Q_ARG(MyForwardDeclaredType, t)));
         QVERIFY(obj.slotResult.isEmpty());
     }
 }