Deprecate constructing QFlags from a pointer

This was used to support QFlags f = 0 initialization, but with 0 used
as a pointer literal now considered bad form, it had been changed many
places to QFlags f = nullptr, which is meaningless and confusing.

Change-Id: I4bc592151c255dc5cab1a232615caecc520f02e8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

16 files changed, 35 insertions, 20 deletions

diff --git a/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp b/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
index eb75a29ca2..a540b88247 100644
--- a/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
+++ b/src/corelib/doc/snippets/code/src_corelib_global_qglobal.cpp
@@ -50,6 +50,7 @@
 
 //! [0]
 label->setAlignment(Qt::AlignLeft | Qt::AlignTop);
+label->setAlignment({ });
 //! [0]
 
 
diff --git a/src/corelib/global/qflags.h b/src/corelib/global/qflags.h
index bd3c219968..4f46de5eaa 100644
--- a/src/corelib/global/qflags.h
+++ b/src/corelib/global/qflags.h
@@ -93,8 +93,10 @@ class QFlags
                       "long long will overflow.");
     Q_STATIC_ASSERT_X((std::is_enum<Enum>::value), "QFlags is only usable on enumeration types.");
 
+#if QT_DEPRECATED_SINCE(5,15)
     struct Private;
     typedef int (Private::*Zero);
+#endif
     template <typename E> friend QDataStream &operator>>(QDataStream &, QFlags<E> &);
     template <typename E> friend QDataStream &operator<<(QDataStream &, QFlags<E>);
 public:
@@ -115,8 +117,11 @@ public:
     Q_DECL_CONSTEXPR inline QFlags(const QFlags &other);
     Q_DECL_CONSTEXPR inline QFlags &operator=(const QFlags &other);
 #endif
+    Q_DECL_CONSTEXPR inline QFlags() noexcept : i(0) {}
     Q_DECL_CONSTEXPR inline QFlags(Enum flags) noexcept : i(Int(flags)) {}
-    Q_DECL_CONSTEXPR inline QFlags(Zero = nullptr) noexcept : i(0) {}
+#if QT_DEPRECATED_SINCE(5,15)
+    QT_DEPRECATED_X("Use default constructor instead") Q_DECL_CONSTEXPR inline QFlags(Zero) noexcept : i(0) {}
+#endif
     Q_DECL_CONSTEXPR inline QFlags(QFlag flag) noexcept : i(flag) {}
 
     Q_DECL_CONSTEXPR inline QFlags(std::initializer_list<Enum> flags) noexcept
diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 4ab5bd2edb..d95cc786ab 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -250,7 +250,7 @@ Q_STATIC_ASSERT((std::is_same<qsizetype, qptrdiff>::value));
     Qt::Alignment type is simply a typedef for
     QFlags<Qt::AlignmentFlag>. QLabel::setAlignment() takes a
     Qt::Alignment parameter, which means that any combination of
-    Qt::AlignmentFlag values, or 0, is legal:
+    Qt::AlignmentFlag values, or \c{{ }}, is legal:
 
     \snippet code/src_corelib_global_qglobal.cpp 0
 
@@ -318,10 +318,20 @@ Q_STATIC_ASSERT((std::is_same<qsizetype, qptrdiff>::value));
 */
 
 /*!
+    \fn template <typename Enum> QFlags<Enum>::QFlags()
+    \since 5.15
+
+    Constructs a QFlags object with no flags set.
+*/
+
+/*!
     \fn template <typename Enum> QFlags<Enum>::QFlags(Zero)
+    \deprecated
 
     Constructs a QFlags object with no flags set. The parameter must be a
     literal 0 value.
+
+    Deprecated, use default constructor instead.
 */
 
 /*!
diff --git a/src/corelib/io/qabstractfileengine.cpp b/src/corelib/io/qabstractfileengine.cpp
index 8a1679c5af..070139b608 100644
--- a/src/corelib/io/qabstractfileengine.cpp
+++ b/src/corelib/io/qabstractfileengine.cpp
@@ -658,7 +658,7 @@ QStringList QAbstractFileEngine::entryList(QDir::Filters filters, const QStringL
 QAbstractFileEngine::FileFlags QAbstractFileEngine::fileFlags(FileFlags type) const
 {
     Q_UNUSED(type);
-    return nullptr;
+    return {};
 }
 
 /*!
diff --git a/src/corelib/io/qfileinfo.cpp b/src/corelib/io/qfileinfo.cpp
index 93696c1320..3fe1aec41f 100644
--- a/src/corelib/io/qfileinfo.cpp
+++ b/src/corelib/io/qfileinfo.cpp
@@ -134,7 +134,7 @@ uint QFileInfoPrivate::getFileFlags(QAbstractFileEngine::FileFlags request) cons
     // extra syscall. Bundle detecton on Mac can be slow, expecially on network
     // paths, so we separate out that as well.
 
-    QAbstractFileEngine::FileFlags req = nullptr;
+    QAbstractFileEngine::FileFlags req;
     uint cachedFlags = 0;
 
     if (request & (QAbstractFileEngine::FlagsMask | QAbstractFileEngine::TypesMask)) {
diff --git a/src/corelib/io/qfilesystemmetadata_p.h b/src/corelib/io/qfilesystemmetadata_p.h
index 275a4bf8d0..3154658e5c 100644
--- a/src/corelib/io/qfilesystemmetadata_p.h
+++ b/src/corelib/io/qfilesystemmetadata_p.h
@@ -76,8 +76,7 @@ class Q_AUTOTEST_EXPORT QFileSystemMetaData
 {
 public:
     QFileSystemMetaData()
-        : knownFlagsMask(nullptr),
-          size_(-1)
+        : size_(-1)
     {
     }
 
@@ -186,7 +185,7 @@ public:
 
     void clear()
     {
-        knownFlagsMask = nullptr;
+        knownFlagsMask = {};
     }
 
     void clearFlags(MetaDataFlags flags = AllMetaDataFlags)
diff --git a/src/corelib/io/qfsfileengine_win.cpp b/src/corelib/io/qfsfileengine_win.cpp
index 5b868cc447..dd4882a2bc 100644
--- a/src/corelib/io/qfsfileengine_win.cpp
+++ b/src/corelib/io/qfsfileengine_win.cpp
@@ -591,14 +591,14 @@ QAbstractFileEngine::FileFlags QFSFileEngine::fileFlags(QAbstractFileEngine::Fil
     if (type & Refresh)
         d->metaData.clear();
 
-    QAbstractFileEngine::FileFlags ret = 0;
+    QAbstractFileEngine::FileFlags ret;
 
     if (type & FlagsMask)
         ret |= LocalDiskFlag;
 
     bool exists;
     {
-        QFileSystemMetaData::MetaDataFlags queryFlags = 0;
+        QFileSystemMetaData::MetaDataFlags queryFlags;
 
         queryFlags |= QFileSystemMetaData::MetaDataFlags(uint(type))
                 & QFileSystemMetaData::Permissions;
diff --git a/src/corelib/io/qresource.cpp b/src/corelib/io/qresource.cpp
index 22c22ce711..0a145b2be4 100644
--- a/src/corelib/io/qresource.cpp
+++ b/src/corelib/io/qresource.cpp
@@ -1492,7 +1492,7 @@ bool QResourceFileEngine::isSequential() const
 QAbstractFileEngine::FileFlags QResourceFileEngine::fileFlags(QAbstractFileEngine::FileFlags type) const
 {
     Q_D(const QResourceFileEngine);
-    QAbstractFileEngine::FileFlags ret = 0;
+    QAbstractFileEngine::FileFlags ret;
     if(!d->resource.isValid())
         return ret;
 
diff --git a/src/corelib/io/qurl.cpp b/src/corelib/io/qurl.cpp
index 878e007fb0..659552b72f 100644
--- a/src/corelib/io/qurl.cpp
+++ b/src/corelib/io/qurl.cpp
@@ -823,7 +823,7 @@ recodeFromUser(const QString &input, const ushort *actions, int from, int to)
     QString output;
     const QChar *begin = input.constData() + from;
     const QChar *end = input.constData() + to;
-    if (qt_urlRecode(output, begin, end, nullptr, actions))
+    if (qt_urlRecode(output, begin, end, {}, actions))
         return output;
 
     return input.mid(from, to - from);
diff --git a/src/corelib/itemmodels/qabstractitemmodel.cpp b/src/corelib/itemmodels/qabstractitemmodel.cpp
index 88555f9572..fa975ce117 100644
--- a/src/corelib/itemmodels/qabstractitemmodel.cpp
+++ b/src/corelib/itemmodels/qabstractitemmodel.cpp
@@ -432,7 +432,7 @@ Qt::ItemFlags QPersistentModelIndex::flags() const
 {
     if (d)
         return d->index.flags();
-    return 0;
+    return { };
 }
 
 /*!
@@ -2296,7 +2296,7 @@ Qt::ItemFlags QAbstractItemModel::flags(const QModelIndex &index) const
 {
     Q_D(const QAbstractItemModel);
     if (!d->indexValid(index))
-        return 0;
+        return { };
 
     return Qt::ItemIsSelectable|Qt::ItemIsEnabled;
 }
diff --git a/src/corelib/plugin/qlibrary_p.h b/src/corelib/plugin/qlibrary_p.h
index db5afac98e..a58547a2c3 100644
--- a/src/corelib/plugin/qlibrary_p.h
+++ b/src/corelib/plugin/qlibrary_p.h
@@ -96,7 +96,7 @@ public:
     void setLoadHints(QLibrary::LoadHints lh);
 
     static QLibraryPrivate *findOrCreate(const QString &fileName, const QString &version = QString(),
-                                         QLibrary::LoadHints loadHints = nullptr);
+                                         QLibrary::LoadHints loadHints = { });
     static QStringList suffixes_sys(const QString &fullVersion);
     static QStringList prefixes_sys();
 
diff --git a/src/corelib/text/qregularexpression.cpp b/src/corelib/text/qregularexpression.cpp
index 8d2187eb28..d0bdc0d45c 100644
--- a/src/corelib/text/qregularexpression.cpp
+++ b/src/corelib/text/qregularexpression.cpp
@@ -912,7 +912,7 @@ QRegularExpression::QRegularExpression(QRegularExpressionPrivate &dd)
 */
 QRegularExpressionPrivate::QRegularExpressionPrivate()
     : QSharedData(),
-      patternOptions(0),
+      patternOptions(),
       pattern(),
       mutex(),
       compiledPattern(nullptr),
diff --git a/src/corelib/text/qtextboundaryfinder.cpp b/src/corelib/text/qtextboundaryfinder.cpp
index 67dd15377b..070b041220 100644
--- a/src/corelib/text/qtextboundaryfinder.cpp
+++ b/src/corelib/text/qtextboundaryfinder.cpp
@@ -71,7 +71,7 @@ static void init(QTextBoundaryFinder::BoundaryType type, const QChar *chars, int
         }
     }
 
-    QUnicodeTools::CharAttributeOptions options = 0;
+    QUnicodeTools::CharAttributeOptions options;
     switch (type) {
     case QTextBoundaryFinder::Grapheme: options |= QUnicodeTools::GraphemeBreaks; break;
     case QTextBoundaryFinder::Word: options |= QUnicodeTools::WordBreaks; break;
diff --git a/src/corelib/time/qdatetime.cpp b/src/corelib/time/qdatetime.cpp
index 878a2c1e46..accaea988e 100644
--- a/src/corelib/time/qdatetime.cpp
+++ b/src/corelib/time/qdatetime.cpp
@@ -3266,7 +3266,7 @@ inline QDateTime::Data::Data(Qt::TimeSpec spec)
         // the structure is too small, we need to detach
         d = new QDateTimePrivate;
         d->ref.ref();
-        d->m_status = mergeSpec(nullptr, spec);
+        d->m_status = mergeSpec({}, spec);
     }
 }
 
diff --git a/src/corelib/time/qdatetimeparser.cpp b/src/corelib/time/qdatetimeparser.cpp
index 2c566e3584..70d6f280bf 100644
--- a/src/corelib/time/qdatetimeparser.cpp
+++ b/src/corelib/time/qdatetimeparser.cpp
@@ -407,7 +407,7 @@ bool QDateTimeParser::parseFormat(const QString &newFormat)
     QDTPDEBUGN("parseFormat: %s", newFormat.toLatin1().constData());
 
     QVector<SectionNode> newSectionNodes;
-    Sections newDisplay = 0;
+    Sections newDisplay;
     QStringList newSeparators;
     int i, index = 0;
     int add = 0;
@@ -1799,7 +1799,7 @@ int QDateTimeParser::SectionNode::maxChange() const
 
 QDateTimeParser::FieldInfo QDateTimeParser::fieldInfo(int index) const
 {
-    FieldInfo ret = 0;
+    FieldInfo ret;
     const SectionNode &sn = sectionNode(index);
     switch (sn.type) {
     case MSecSection:
diff --git a/src/corelib/time/qdatetimeparser_p.h b/src/corelib/time/qdatetimeparser_p.h
index e9f1455380..ec4e4e4df2 100644
--- a/src/corelib/time/qdatetimeparser_p.h
+++ b/src/corelib/time/qdatetimeparser_p.h
@@ -84,7 +84,7 @@ public:
         DateTimeEdit
     };
     QDateTimeParser(QVariant::Type t, Context ctx, const QCalendar &cal = QCalendar())
-        : currentSectionIndex(-1), display(nullptr), cachedDay(-1), parserType(t),
+        : currentSectionIndex(-1), cachedDay(-1), parserType(t),
         fixday(false), spec(Qt::LocalTime), context(ctx), calendar(cal)
     {
         defaultLocale = QLocale::system();