Fix QMetaObject::invokeMethod for free functions and std::bind

Amends 3bf5b5f8944dd417530b09dd6f1cd568717c8cc1, after which free
functions and std::bind could no longer be used as callables in
QMetaMethod::invokeMethod.

For free functions to work we need to decay to function pointers when
choosing what type QtPrivate::Callable aliases.

And std::bind has operator() overloads and the return type cannot be
deduced. So simplify the definition of the ZeroArgFunctor - we know
the function prototype if we know the return type.

Add testcase for calling std::bind and free function, and remove the
now unneeded helpers for functor argument and return type deduction.

Change-Id: I54aac5cb6d660267e6b2f5ab05d583e8826cdf9a
Reviewed-by: Zoltan Gera <zoltan.gera@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 45 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp b/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
index 4c3bb8532b..926f3d1d60 100644
--- a/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
+++ b/tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp
@@ -302,6 +302,8 @@ private slots:
     void invokeTypedefTypes();
     void invokeException();
     void invokeQueuedAutoRegister();
+    void invokeFreeFunction();
+    void invokeBind();
     void qtMetaObjectInheritance();
     void normalizedSignature_data();
     void normalizedSignature();
@@ -1997,6 +1999,49 @@ void tst_QMetaObject::invokeQueuedAutoRegister()
              QString("slotWithRegistrableArgument:myShared-myShared-myShared-myShared-00"));
 }
 
+namespace FunctionTest {
+    static void function0() {}
+    static int functionNoExcept() noexcept
+    {
+        return 42;
+    }
+}
+
+void tst_QMetaObject::invokeFreeFunction()
+{
+    using namespace FunctionTest;
+    QtTestObject obj;
+    QMetaObject::invokeMethod(&obj, function0);
+    int retInt = -1;
+    QMetaObject::invokeMethod(&obj, functionNoExcept, &retInt);
+    QCOMPARE(retInt, functionNoExcept());
+}
+
+void tst_QMetaObject::invokeBind()
+{
+    QtTestObject obj;
+
+    struct {
+        int number;
+        QString string;
+    } results;
+
+    const auto function = [&results](int number, const QString &string) -> bool {
+        results.number = number;
+        results.string = string;
+        return true;
+    };
+
+    const int number = 42;
+    const QString string("Test");
+    const auto binding = std::bind(function, number, string);
+    bool ret = false;
+    QMetaObject::invokeMethod(&obj, binding, &ret);
+    QVERIFY(ret);
+    QCOMPARE(results.number, number);
+    QCOMPARE(results.string, string);
+}
+
 void tst_QMetaObject::normalizedSignature_data()
 {
     QTest::addColumn<QString>("signature");