Div. smart pointer/raii classes: mark ctors [[nodiscard]]

The following classes are smart pointers or RAII classes, whose ctors
QUIP-0019 asks to mark as [[nodiscard]]:

- QQmlMetaObjectPointer
- QQuickDeferredPointer
- QuitLockDisabler

QUIP: QUIP-0019
Fixes: QTBUG-104168
Pick-to: 6.6
Change-Id: Ia362f5d0eab7376f4536aefc61c31ceb296b1cc2
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 7 insertions, 6 deletions

diff --git a/src/plugins/qmltooling/qmldbg_preview/qqmlpreviewhandler.cpp b/src/plugins/qmltooling/qmldbg_preview/qqmlpreviewhandler.cpp
index 7601c59cac..84019826e4 100644
--- a/src/plugins/qmltooling/qmldbg_preview/qqmlpreviewhandler.cpp
+++ b/src/plugins/qmltooling/qmldbg_preview/qqmlpreviewhandler.cpp
@@ -23,7 +23,8 @@ struct QuitLockDisabler
 {
     const bool quitLockEnabled;
 
-    QuitLockDisabler() : quitLockEnabled(QCoreApplication::isQuitLockEnabled())
+    Q_NODISCARD_CTOR QuitLockDisabler()
+        : quitLockEnabled(QCoreApplication::isQuitLockEnabled())
     {
         QCoreApplication::setQuitLockEnabled(false);
     }
diff --git a/src/qml/qml/qqmlpropertycache_p.h b/src/qml/qml/qqmlpropertycache_p.h
index b261d1caca..a06a1b6e39 100644
--- a/src/qml/qml/qqmlpropertycache_p.h
+++ b/src/qml/qml/qqmlpropertycache_p.h
@@ -40,9 +40,9 @@ class QQmlVMEMetaObject;
 class QQmlMetaObjectPointer
 {
 public:
-    QQmlMetaObjectPointer() = default;
+    Q_NODISCARD_CTOR QQmlMetaObjectPointer() = default;
 
-    QQmlMetaObjectPointer(const QMetaObject *staticMetaObject)
+    Q_NODISCARD_CTOR QQmlMetaObjectPointer(const QMetaObject *staticMetaObject)
         : d(quintptr(staticMetaObject))
     {
         Q_ASSERT((d.loadRelaxed() & Shared) == 0);
@@ -57,7 +57,7 @@ public:
 
 private:
     friend class QQmlPropertyCache;
-    QQmlMetaObjectPointer(const QQmlMetaObjectPointer &other)
+    Q_NODISCARD_CTOR QQmlMetaObjectPointer(const QQmlMetaObjectPointer &other)
         : d(other.d.loadRelaxed())
     {
         // other has to survive until this ctor is done. So d cannot disappear before.
diff --git a/src/quicktemplates/qquickdeferredpointer_p_p.h b/src/quicktemplates/qquickdeferredpointer_p_p.h
index cd5a87e508..e1fa85e2ee 100644
--- a/src/quicktemplates/qquickdeferredpointer_p_p.h
+++ b/src/quicktemplates/qquickdeferredpointer_p_p.h
@@ -113,10 +113,10 @@ class QQuickDeferredPointer : public QQuickUntypedDeferredPointer
 {
     Q_DISABLE_COPY_MOVE(QQuickDeferredPointer)
 public:
-    QQuickDeferredPointer() = default;
+    Q_NODISCARD_CTOR QQuickDeferredPointer() = default;
     ~QQuickDeferredPointer() = default;
 
-    QQuickDeferredPointer(T *v) : QQuickUntypedDeferredPointer(v) {}
+    Q_NODISCARD_CTOR QQuickDeferredPointer(T *v) : QQuickUntypedDeferredPointer(v) {}
     QQuickDeferredPointer<T> &operator=(T *o) {
         QQuickUntypedDeferredPointer::operator=(o);
         return *this;