QTextStream: add missing op<<(QStringRef)

It simply is missing. We could wait for QStringView to come around, but
I need this function in uic _now_, so let's add it.

[ChangeLog][QtCore][QTextStream] Can now stream QStringRef without converting
to a QString first.

Change-Id: Idd178e0ba8a89c025f4533d46de912cbdb3883d5
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/corelib/io/qtextstream.cpp

@@ -2519,6 +2519,21 @@ QTextStream &QTextStream::operator<<(QLatin1String string)
     return *this;
 }
 
+/*!
+    \since 5.6
+    \overload
+
+    Writes \a string to the stream, and returns a reference to the
+    QTextStream.
+*/
+QTextStream &QTextStream::operator<<(const QStringRef &string)
+{
+    Q_D(QTextStream);
+    CHECK_VALID_STREAM(*this);
+    d->putString(string.data(), string.size());
+    return *this;
+}
+
 /*!
     \overload
 

src/corelib/io/qtextstream.h

@@ -179,6 +179,7 @@ public:
     QTextStream &operator<<(double f);
     QTextStream &operator<<(const QString &s);
     QTextStream &operator<<(QLatin1String s);
+    QTextStream &operator<<(const QStringRef &s);
     QTextStream &operator<<(const QByteArray &array);
     QTextStream &operator<<(const char *c);
     QTextStream &operator<<(const void *ptr);

tests/auto/corelib/io/qtextstream/tst_qtextstream.cpp

@@ -163,6 +163,7 @@ private slots:
     void string_write_operator_ToDevice_data();
     void string_write_operator_ToDevice();
     void latin1String_write_operator_ToDevice();
+    void stringref_write_operator_ToDevice();
 
     // other
     void skipWhiteSpace_data();
@@ -2554,6 +2555,22 @@ void tst_QTextStream::latin1String_write_operator_ToDevice()
     QCOMPARE(buf.buffer().constData(), "No explicit lengthExplicit length");
 }
 
+void tst_QTextStream::stringref_write_operator_ToDevice()
+{
+    QBuffer buf;
+    buf.open(QBuffer::WriteOnly);
+    QTextStream stream(&buf);
+    stream.setCodec(QTextCodec::codecForName("ISO-8859-1"));
+    stream.setAutoDetectUnicode(true);
+
+    const QString expected = "No explicit lengthExplicit length";
+
+    stream << expected.leftRef(18);
+    stream << expected.midRef(18);
+    stream.flush();
+    QCOMPARE(buf.buffer().constData(), "No explicit lengthExplicit length");
+}
+
 // ------------------------------------------------------------------------------
 void tst_QTextStream::useCase1()
 {