Deprecate conversion functions between QList and QSet

Users should use range constructors instead to do the conversion.
Keep conversion methods between QList and QVector as these will turn
into a no-op in Qt 6, whereas forcing people to use range constructors
would lead to deep copies of the data.

Change-Id: Id9fc9e4d007044e019826da523e8418857c91283
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 22 insertions, 15 deletions

diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index ee3f7be279..be48dbc92f 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -370,10 +370,11 @@ static QList<QAbstractState *> getEffectiveTargetStates(QAbstractTransition *tra
             QList<QAbstractState*> historyConfiguration = QHistoryStatePrivate::get(historyState)->configuration;
             if (!historyConfiguration.isEmpty()) {
                 // There is a saved history, so apply that.
-                targets.unite(historyConfiguration.toSet());
+                targets.unite(QSet<QAbstractState *>(historyConfiguration.constBegin(), historyConfiguration.constEnd()));
             } else if (QAbstractTransition *defaultTransition = historyState->defaultTransition()) {
                 // No saved history, take all default transition targets.
-                targets.unite(defaultTransition->targetStates().toSet());
+                const auto &targetStates = defaultTransition->targetStates();
+                targets.unite(QSet<QAbstractState *>(targetStates.constBegin(), targetStates.constEnd()));
             } else {
                 // Woops, we found a history state without a default state. That's not valid!
                 QStateMachinePrivate *m = QStateMachinePrivate::get(historyState->machine());
@@ -384,7 +385,7 @@ static QList<QAbstractState *> getEffectiveTargetStates(QAbstractTransition *tra
         }
     }
 
-    targetsList = targets.toList();
+    targetsList = targets.values();
     cache->insert(transition, targetsList);
     return targetsList;
 }
@@ -740,7 +741,7 @@ QList<QAbstractState*> QStateMachinePrivate::computeExitSet(const QList<QAbstrac
 {
     Q_ASSERT(cache);
 
-    QList<QAbstractState*> statesToExit_sorted = computeExitSet_Unordered(enabledTransitions, cache).toList();
+    QList<QAbstractState*> statesToExit_sorted = computeExitSet_Unordered(enabledTransitions, cache).values();
     std::sort(statesToExit_sorted.begin(), statesToExit_sorted.end(), stateExitLessThan);
     return statesToExit_sorted;
 }
@@ -777,7 +778,7 @@ QSet<QAbstractState*> QStateMachinePrivate::computeExitSet_Unordered(QAbstractTr
         // makes the state machine invalid.
         if (error == QStateMachine::NoError)
             setError(QStateMachine::NoCommonAncestorForTransitionError, t->sourceState());
-        QList<QAbstractState *> lst = pendingErrorStates.toList();
+        QList<QAbstractState *> lst = pendingErrorStates.values();
         lst.prepend(t->sourceState());
 
         domain = findLCCA(lst);
@@ -879,7 +880,7 @@ QList<QAbstractState*> QStateMachinePrivate::computeEntrySet(const QList<QAbstra
         pendingErrorStatesForDefaultEntry.clear();
     }
 
-    QList<QAbstractState*> statesToEnter_sorted = statesToEnter.toList();
+    QList<QAbstractState*> statesToEnter_sorted = statesToEnter.values();
     std::sort(statesToEnter_sorted.begin(), statesToEnter_sorted.end(), stateEntryLessThan);
     return statesToEnter_sorted;
 }
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 25380d45ec..04c1f12f5f 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -403,13 +403,15 @@ public:
     inline QList<T> &operator<<(const QList<T> &l)
     { *this += l; return *this; }
 
+    static QList<T> fromVector(const QVector<T> &vector);
     QVector<T> toVector() const;
-    QSet<T> toSet() const;
 
-    static QList<T> fromVector(const QVector<T> &vector);
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
+    Q_DECL_DEPRECATED_X("Use QList<T>(set.begin(), set.end()) instead.")
     static QList<T> fromSet(const QSet<T> &set);
+    Q_DECL_DEPRECATED_X("Use QSet<T>(list.begin(), list.end()) instead.")
+    QSet<T> toSet() const;
 
-#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
     Q_DECL_DEPRECATED_X("Use QList<T>(list.begin(), list.end()) instead.")
     static inline QList<T> fromStdList(const std::list<T> &list)
     { QList<T> tmp; std::copy(list.begin(), list.end(), std::back_inserter(tmp)); return tmp; }
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index 8b31de71a9..83e574bf1c 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -245,10 +245,13 @@ public:
     inline QSet<T> operator-(const QSet<T> &other) const
         { QSet<T> result = *this; result -= other; return result; }
 
-    QList<T> toList() const;
-    inline QList<T> values() const { return toList(); }
-
+    QList<T> values() const;
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
+    Q_DECL_DEPRECATED_X("Use values() instead.")
+    QList<T> toList() const { return values(); }
+    Q_DECL_DEPRECATED_X("Use QSet<T>(list.begin(), list.end()) instead.")
     static QSet<T> fromList(const QList<T> &list);
+#endif
 
 private:
     Hash q_hash;
@@ -368,7 +371,7 @@ Q_INLINE_TEMPLATE bool QSet<T>::contains(const QSet<T> &other) const
 }
 
 template <typename T>
-Q_OUTOFLINE_TEMPLATE QList<T> QSet<T>::toList() const
+Q_OUTOFLINE_TEMPLATE QList<T> QSet<T>::values() const
 {
     QList<T> result;
     result.reserve(size());
@@ -380,6 +383,7 @@ Q_OUTOFLINE_TEMPLATE QList<T> QSet<T>::toList() const
     return result;
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
 template <typename T>
 Q_OUTOFLINE_TEMPLATE QSet<T> QList<T>::toSet() const
 {
@@ -401,6 +405,7 @@ QList<T> QList<T>::fromSet(const QSet<T> &set)
 {
     return set.toList();
 }
+#endif
 
 Q_DECLARE_SEQUENTIAL_ITERATOR(Set)
 
diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index b763d6e7e2..492afeac75 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -297,9 +297,8 @@ public:
     inline QVector<T> &operator<<(T &&t)
     { append(std::move(t)); return *this; }
 
-    QList<T> toList() const;
-
     static QVector<T> fromList(const QList<T> &list);
+    QList<T> toList() const;
 
 #if QT_VERSION < QT_VERSION_CHECK(6,0,0)
     Q_DECL_DEPRECATED_X("Use QVector<T>(vector.begin(), vector.end()) instead.")