Support move-only function objects in QObject::connect

[ChangeLog][QtCore][QObject] Added connect() support for move-only
function objects.

Task-number: QTBUG-60339
Change-Id: Iae5e48432bb64517b0607b0c2ba23931957f432e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qobject.h

@@ -304,7 +304,7 @@ public:
     static inline typename std::enable_if<QtPrivate::FunctionPointer<Func2>::ArgumentCount == -1, QMetaObject::Connection>::type
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
     {
-        return connect(sender, signal, sender, slot, Qt::DirectConnection);
+        return connect(sender, signal, sender, std::move(slot), Qt::DirectConnection);
     }
 
     //connect to a functor, with a "context" object defining in which event loop is going to be executed
@@ -334,7 +334,7 @@ public:
         return connectImpl(sender, reinterpret_cast<void **>(&signal), context, Q_NULLPTR,
                            new QtPrivate::QFunctorSlotObject<Func2, SlotArgumentCount,
                                 typename QtPrivate::List_Left<typename SignalType::Arguments, SlotArgumentCount>::Value,
-                                typename SignalType::ReturnType>(slot),
+                                typename SignalType::ReturnType>(std::move(slot)),
                            type, types, &SignalType::Object::staticMetaObject);
     }
 #endif //Q_QDOC

src/corelib/kernel/qobjectdefs_impl.h

@@ -430,7 +430,7 @@ namespace QtPrivate {
             }
         }
     public:
-        explicit QFunctorSlotObject(const Func &f) : QSlotObjectBase(&impl), function(f) {}
+        explicit QFunctorSlotObject(Func f) : QSlotObjectBase(&impl), function(std::move(f)) {}
     };
 
     // typedefs for readability for when there are no parameters

tests/auto/corelib/kernel/qobject/tst_qobject.cpp

@@ -140,6 +140,7 @@ private slots:
     void connectFunctorWithContext();
     void connectFunctorWithContextUnique();
     void connectFunctorDeadlock();
+    void connectFunctorMoveOnly();
     void connectStaticSlotWithObject();
     void disconnectDoesNotLeakFunctor();
     void contextDoesNotLeakFunctor();
@@ -6237,6 +6238,47 @@ void tst_QObject::connectFunctorDeadlock()
     sender.emitSignal1();
 }
 
+void tst_QObject::connectFunctorMoveOnly()
+{
+    struct MoveOnlyFunctor {
+        Q_DISABLE_COPY(MoveOnlyFunctor)
+        MoveOnlyFunctor(int *status) : status(status) {}
+        MoveOnlyFunctor(MoveOnlyFunctor &&o) : status(o.status) { o.status = nullptr; };
+        void operator()(int i) { *status = i; }
+        void operator()() { *status = -8; }
+        int *status;
+    };
+
+    int status = 1;
+    SenderObject obj;
+    QEventLoop e;
+
+    connect(&obj, &SenderObject::signal1, MoveOnlyFunctor(&status));
+    QCOMPARE(status, 1);
+    obj.signal1();
+    QCOMPARE(status, -8);
+
+    connect(&obj, &SenderObject::signal7, MoveOnlyFunctor(&status));
+    QCOMPARE(status, -8);
+    obj.signal7(7888, "Hello");
+    QCOMPARE(status, 7888);
+
+    // With a context
+    status = 1;
+    connect(&obj, &SenderObject::signal2, this, MoveOnlyFunctor(&status));
+    QCOMPARE(status, 1);
+    obj.signal2();
+    QCOMPARE(status, -8);
+
+    // QueuedConnection
+    status = 1;
+    connect(&obj, &SenderObject::signal3, this, MoveOnlyFunctor(&status), Qt::QueuedConnection);
+    obj.signal3();
+    QCOMPARE(status, 1);
+    QCoreApplication::processEvents();
+    QCOMPARE(status, -8);
+}
+
 static int s_static_slot_checker = 1;
 
 class StaticSlotChecker : public QObject