tst_QCompare: restore some test coverage to QPartialOrdering

When I split Qt::partial_ordering off of QPartialOrdering, O
duplicated the partialOrdering() test, but lost the conversion() part
of the tests.

This patch brings them back.

Because we maintained the test coverage for Qt::partial_ordering, it
suffices to check that QPartialOrdering::X correctly maps to
std::partial_ordering::x. The rest follows from transtivity of
equality.

We're still lacking conversions of QPartialOrdering to Qt::_ordering
types. That will be the subject of a follow-up patch.

Amends 4b6f757020382ed157bf6beb572549f05e881359.

Change-Id: I1938d09f696ed8d58143dbacccb72cfd54ca12dd
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

1 files changed, 22 insertions, 0 deletions

diff --git a/tests/auto/corelib/global/qcompare/tst_qcompare.cpp b/tests/auto/corelib/global/qcompare/tst_qcompare.cpp
index 7561fbdc38..ba382d57fb 100644
--- a/tests/auto/corelib/global/qcompare/tst_qcompare.cpp
+++ b/tests/auto/corelib/global/qcompare/tst_qcompare.cpp
@@ -13,6 +13,7 @@ class tst_QCompare: public QObject
     Q_OBJECT
 private slots:
     void legacyPartialOrdering();
+    void legacyConversions();
     void stdQtBinaryCompatibility();
     void partialOrdering();
     void weakOrdering();
@@ -131,6 +132,27 @@ void tst_QCompare::legacyPartialOrdering()
     static_assert(!(0 >= QPartialOrdering::Greater));
 }
 
+void tst_QCompare::legacyConversions()
+{
+#define CHECK_CONVERTS(Lhs, Rhs) static_assert(std::is_convertible_v<Lhs, Rhs>)
+#define CHECK_ALL(NS) do { \
+        CHECK_CONVERTS(QPartialOrdering, NS ::partial_ordering); \
+        static_assert(QPartialOrdering::Less == NS ::partial_ordering::less); \
+        static_assert(QPartialOrdering::Greater == NS ::partial_ordering::greater); \
+        static_assert(QPartialOrdering::Equivalent == NS ::partial_ordering::equivalent); \
+        static_assert(QPartialOrdering::Unordered == NS ::partial_ordering::unordered); \
+        \
+        CHECK_CONVERTS(NS ::partial_ordering, QPartialOrdering); \
+    } while (false)
+
+#ifdef __cpp_lib_three_way_comparison
+    CHECK_ALL(std);
+#endif // __cpp_lib_three_way_comparison
+
+#undef CHECK_ALL
+#undef CHECK_CONVERTS
+}
+
 void tst_QCompare::stdQtBinaryCompatibility()
 {
 #ifndef __cpp_lib_three_way_comparison