QDateTime: use new comparison helper macros

The unit-tests were already ported to the new comparison helper
functions from QTestPrivate.

Task-number: QTBUG-104111
Change-Id: I95fccb33433b3bbf1167545e347a271140727f23
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/compat/removed_api.cpp

@@ -692,6 +692,11 @@ void QDateTime::setTimeZone(const QTimeZone &toZone)
     setTimeZone(toZone, TransitionResolution::LegacyBehavior);
 }
 
+bool QDateTime::precedes(const QDateTime &other) const
+{
+    return compareThreeWay(*this, other) < 0;
+}
+
 #include "qdatastream.h"
 
 QDataStream &QDataStream::readBytes(char *&s, uint &l)

src/corelib/time/qdatetime.cpp

@@ -5067,26 +5067,19 @@ bool QDateTime::equals(const QDateTime &other) const
     \sa operator==()
 */
 
-/*!
+Qt::weak_ordering compareThreeWay(const QDateTime &lhs, const QDateTime &rhs)
-    \internal
-    Returns \c true if \a lhs is earlier than the \a rhs
-    datetime; otherwise returns \c false.
-
-    \sa equals(), operator<()
-*/
-
-bool QDateTime::precedes(const QDateTime &other) const
 {
-    if (!isValid())
+    if (!lhs.isValid())
-        return other.isValid();
+        return rhs.isValid() ? Qt::weak_ordering::less : Qt::weak_ordering::equivalent;
-    if (!other.isValid())
-        return false;
 
-    if (usesSameOffset(d, other.d))
+    if (!rhs.isValid())
-        return getMSecs(d) < getMSecs(other.d);
+        return Qt::weak_ordering::greater; // we know that lhs is valid here
+
+    if (usesSameOffset(lhs.d, rhs.d))
+        return Qt::compareThreeWay(getMSecs(lhs.d), getMSecs(rhs.d));
 
     // Convert to UTC and compare
-    return toMSecsSinceEpoch() < other.toMSecsSinceEpoch();
+    return Qt::compareThreeWay(lhs.toMSecsSinceEpoch(), rhs.toMSecsSinceEpoch());
 }
 
 /*!

src/corelib/time/qdatetime.h

@@ -547,17 +547,18 @@ public:
 
 private:
     bool equals(const QDateTime &other) const;
+#if QT_CORE_REMOVED_SINCE(6, 7)
     bool precedes(const QDateTime &other) const;
+#endif
     friend class QDateTimePrivate;
 
     Data d;
 
-    friend bool operator==(const QDateTime &lhs, const QDateTime &rhs) { return lhs.equals(rhs); }
+    friend bool comparesEqual(const QDateTime &lhs, const QDateTime &rhs)
-    friend bool operator!=(const QDateTime &lhs, const QDateTime &rhs) { return !(lhs == rhs); }
+    { return lhs.equals(rhs); }
-    friend bool operator<(const QDateTime &lhs, const QDateTime &rhs) { return lhs.precedes(rhs); }
+    friend Q_CORE_EXPORT Qt::weak_ordering
-    friend bool operator<=(const QDateTime &lhs, const QDateTime &rhs) { return !(rhs < lhs); }
+    compareThreeWay(const QDateTime &lhs, const QDateTime &rhs);
-    friend bool operator>(const QDateTime &lhs, const QDateTime &rhs) { return rhs.precedes(lhs); }
+    Q_DECLARE_WEAKLY_ORDERED(QDateTime)
-    friend bool operator>=(const QDateTime &lhs, const QDateTime &rhs) { return !(lhs < rhs); }
 
 #ifndef QT_NO_DATASTREAM
     friend Q_CORE_EXPORT QDataStream &operator<<(QDataStream &, const QDateTime &);