Introduce QMetaType::UnknownType.

QMetaType::Void was ambiguous, it was pointing to a valid type (void)
and in the same time it was signaling errors in QMetaType. There was
no clean way to check if returned type was valid void or some
unregistered type.

This feature will be used by new QMetaObject revision which will
store type ids instead of type names. So it will be easy to
distinguish between:
 void mySlot();
 MyUnregisteredType mySlot();

Change-Id: I73ff097f75585a95e12df74d50c6f3141153e771
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

1 files changed, 23 insertions, 6 deletions

diff --git a/src/corelib/kernel/qvariant_p.h b/src/corelib/kernel/qvariant_p.h
index a754bc4363..b28aaf3c20 100644
--- a/src/corelib/kernel/qvariant_p.h
+++ b/src/corelib/kernel/qvariant_p.h
@@ -187,7 +187,11 @@ public:
         return FilteredComparator<T>::compare(m_a, m_b);
     }
 
-    bool delegate(const void*) { return true; }
+    bool delegate(const void*) { Q_ASSERT(false); return true; }
+    bool delegate(const QMetaTypeSwitcher::UnknownType*)
+    {
+        return true; // for historical reason invalid variant == invalid variant
+    }
     bool delegate(const QMetaTypeSwitcher::NotBuiltinType*) { return false; }
 protected:
     const QVariant::Private *m_a;
@@ -281,7 +285,8 @@ public:
         return CallIsNull<T>::isNull(m_d);
     }
     // we need that as sizof(void) is undefined and it is needed in HasIsNullMethod
-    bool delegate(const void *) { return m_d->is_null; }
+    bool delegate(const void *) { Q_ASSERT(false); return m_d->is_null; }
+    bool delegate(const QMetaTypeSwitcher::UnknownType *) { return m_d->is_null; }
     bool delegate(const QMetaTypeSwitcher::NotBuiltinType *) { return m_d->is_null; }
 protected:
     const QVariant::Private *m_d;
@@ -354,8 +359,18 @@ public:
 
     void delegate(const void*)
     {
-        // QMetaType::Void == QVariant::Invalid, creating an invalid value creates invalid QVariant
-        // TODO it might go away, check is needed
+        qWarning("Trying to create a QVariant instance of QMetaType::Void type, an invalid QVariant will be constructed instead");
+        m_x->type = QMetaType::UnknownType;
+        m_x->is_shared = false;
+        m_x->is_null = !m_copy;
+    }
+
+    void delegate(const QMetaTypeSwitcher::UnknownType*)
+    {
+        if (m_x->type != QMetaType::UnknownType) {
+            qWarning("Trying to construct an instance of an invalid type, type id: %i", m_x->type);
+            m_x->type = QMetaType::UnknownType;
+        }
         m_x->is_shared = false;
         m_x->is_null = !m_copy;
     }
@@ -401,7 +416,8 @@ public:
         qWarning("Trying to destruct an instance of an invalid type, type id: %i", m_d->type);
     }
     // Ignore nonconstructible type
-    void delegate(const void*) {}
+    void delegate(const QMetaTypeSwitcher::UnknownType*) {}
+    void delegate(const void*) { Q_ASSERT(false); }
 private:
     QVariant::Private *m_d;
 };
@@ -446,10 +462,11 @@ public:
     {
         qWarning("Trying to stream an instance of an invalid type, type id: %i", m_d->type);
     }
-    void delegate(const void*)
+    void delegate(const QMetaTypeSwitcher::UnknownType*)
     {
         m_debugStream.nospace() << "QVariant::Invalid";
     }
+    void delegate(const void*) { Q_ASSERT(false); }
 private:
     QDebug m_debugStream;
     QVariant::Private *m_d;