QStringRef: add missing op[]

[ChangeLog][QtCore][QStringRef] Added subscript operator.

Change-Id: Ia85d5efcb7747d2961ba55922ddabe6a46bdf20b
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/corelib/tools/qstring.cpp

@@ -8800,7 +8800,6 @@ Since this class is only used to refer to string data, and does not take
 ownership of it, no memory is freed when instances are destroyed.
 */
 
-
 /*!
     \fn int QStringRef::position() const
 
@@ -9038,6 +9037,19 @@ bool operator<(const QStringRef &s1,const QStringRef &s2) Q_DECL_NOTHROW
     (i.e., 0 <= \a position < size()).
 */
 
+/*!
+    \fn QChar QStringRef::operator[](int position) const
+    \since 5.7
+
+    Returns the character at the given index \a position in the
+    string reference.
+
+    The \a position must be a valid index position in the string
+    reference (i.e., 0 <= \a position < size()).
+
+    \sa at()
+*/
+
 /*!
     \fn void QStringRef::clear()
 

src/corelib/tools/qstring.h

@@ -1462,6 +1462,7 @@ public:
 
     inline const QChar at(int i) const
         { Q_ASSERT(uint(i) < uint(size())); return m_string->at(i + m_position); }
+    QChar operator[](int i) const { return at(i); }
 
 #if !defined(QT_NO_CAST_FROM_ASCII) && !defined(QT_RESTRICTED_CAST_FROM_ASCII)
     // ASCII compatibility

tests/auto/corelib/tools/qstringref/tst_qstringref.cpp

@@ -41,6 +41,7 @@ class tst_QStringRef : public QObject
 public slots:
     void cleanup();
 private slots:
+    void at();
     void endsWith();
     void startsWith();
     void contains();
@@ -172,6 +173,16 @@ void tst_QStringRef::cleanup()
     QLocale::setDefault(QString(QLatin1Char('C')));
 }
 
+void tst_QStringRef::at()
+{
+    const QString hw = QStringLiteral("Hello World");
+    const QStringRef ref = hw.midRef(6);
+    QCOMPARE(ref.at(0), QChar('W'));
+    QCOMPARE(ref.at(4), QChar('d'));
+    QCOMPARE(ref[0], QChar('W'));
+    QCOMPARE(ref[4], QChar('d'));
+}
+
 void tst_QStringRef::length_data()
 {
     QTest::addColumn<QString>("s1");