Improve error reporting when requesting unsupported native interface

By switching out the static_assert for an enable_if we end up producing
a clearer error, at the call site:

/qt/qtbase/examples/gui/rasterwindow/main.cpp:69:9: error: no matching member
      function for call to 'nativeInterface'
    app.nativeInterface<QNativeInterface::QCocoaGLContext>();
    ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/qt/qtbase/src/gui/kernel/qguiapplication.h:176:5: note:
      candidate template ignored: requirement
      'NativeInterface<QNativeInterface::QCocoaGLContext>::isCompatibleWith<QGuiApplication>'
      was not satisfied [with NativeInterface = QNativeInterface::QCocoaGLContext, TypeInfo =
      QNativeInterface::Private::NativeInterface<QNativeInterface::QCocoaGLContext>, BaseType =
      QGuiApplication]
    QT_DECLARE_NATIVE_INTERFACE_ACCESSOR(QGuiApplication)
    ^
By using SFINAE for the TypeInfo we can also ensure that it works for
types that are not native interfaces, such as if the user tries to
call nativeInterface<QString>().

Since we can no longer use decltype(*this) to resolve the base type
we need to change QT_DECLARE_NATIVE_INTERFACE_ACCESSOR to take the
type as an argument, as we do for other QT_DECLARE_FOO macros.

Pick-to: 6.2
Change-Id: Ie3f7e01ab7c3eb3dcc2ef730834f268bb9e81e0c
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 14 insertions, 1 deletions

diff --git a/tests/auto/corelib/global/qnativeinterface/tst_qnativeinterface.cpp b/tests/auto/corelib/global/qnativeinterface/tst_qnativeinterface.cpp
index 0da3108817..dfd8d4fca1 100644
--- a/tests/auto/corelib/global/qnativeinterface/tst_qnativeinterface.cpp
+++ b/tests/auto/corelib/global/qnativeinterface/tst_qnativeinterface.cpp
@@ -44,7 +44,7 @@ struct InterfaceImplementation;
 struct PublicClass
 {
     PublicClass();
-    QT_DECLARE_NATIVE_INTERFACE_ACCESSOR
+    QT_DECLARE_NATIVE_INTERFACE_ACCESSOR(PublicClass)
     std::unique_ptr<InterfaceImplementation> m_implementation;
 };
 
@@ -66,6 +66,15 @@ QT_DEFINE_NATIVE_INTERFACE(Interface);
 QT_DEFINE_NATIVE_INTERFACE(OtherInterface);
 QT_END_NAMESPACE
 
+struct NotInterface {};
+
+struct AlmostInterface
+{
+    struct TypeInfo {
+        // Missing required members
+    };
+};
+
 using namespace QNativeInterface;
 
 struct InterfaceImplementation : public Interface
@@ -89,6 +98,10 @@ void tst_QNativeInterface::typeInfo() const
 {
     using namespace QNativeInterface::Private;
 
+    QCOMPARE(TypeInfo<Interface>::haveTypeInfo, true);
+    QCOMPARE(TypeInfo<NotInterface>::haveTypeInfo, false);
+    QCOMPARE(TypeInfo<AlmostInterface>::haveTypeInfo, false);
+
     QCOMPARE(TypeInfo<Interface>::isCompatibleWith<PublicClass>, true);
     QCOMPARE(TypeInfo<Interface>::isCompatibleWith<QObject>, false);
     QCOMPARE(TypeInfo<Interface>::isCompatibleWith<int>, false);