Make XmlStringRef convertible to QAnyStringView/QStringView

Both QStringView and QAnyStringView implicitly convert from any
container with a fitting value_type, and working std::data, std::size,
std::begin and std::end.

Add these missing operations (and complementary ones) to XmlStringRef,
so it implicitly converts to QStringView and QAnyStringView, too.

Add a check to that effect and remove the now-superfluous operator
QStringView().

Task-number: QTBUG-103302
Change-Id: I89d586cf64447a82022e06d546d7ee8339fc6dc7
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/serialization/qxmlstream_p.h

@@ -54,7 +54,6 @@ public:
         d.size = m_size;
         return QXmlString(std::move(d));
     }
-    operator QStringView() const { return view(); }
 
     void clear() { m_string = nullptr; m_pos = 0; m_size= 0; }
     QStringView view() const { return m_string ? QStringView(m_string->data() + m_pos, m_size) : QStringView(); }
@@ -62,6 +61,33 @@ public:
     bool isNull() const { return !m_string; }
     QString toString() const { return view().toString(); }
 
+    using value_type = QStringView::value_type;
+    using size_type = QStringView::size_type;
+    using difference_type = QStringView::difference_type;
+    using pointer = QStringView::pointer;
+    using const_pointer = QStringView::const_pointer;
+    using reference = QStringView::reference;
+    using const_reference = QStringView::const_reference;
+    using iterator = QStringView::iterator;
+    using const_iterator = QStringView::const_iterator;
+    using reverse_iterator = QStringView::reverse_iterator;
+    using const_reverse_iterator = QStringView::const_reverse_iterator;
+
+#define MAKE_MEMBER(name) \
+    auto name () const noexcept { return view(). name (); }
+    MAKE_MEMBER(data)
+    MAKE_MEMBER(size)
+    MAKE_MEMBER(empty)
+    MAKE_MEMBER(begin)
+    MAKE_MEMBER(end)
+    MAKE_MEMBER(cbegin)
+    MAKE_MEMBER(cend)
+    MAKE_MEMBER(rbegin)
+    MAKE_MEMBER(rend)
+    MAKE_MEMBER(crbegin)
+    MAKE_MEMBER(crend)
+#undef MAKE_MEMBER
+
 #define MAKE_OP(op) \
     friend auto operator op(const XmlStringRef &lhs, const XmlStringRef &rhs) noexcept { return lhs.view() op rhs.view(); } \
     /*end*/

tests/auto/corelib/text/qanystringview/CMakeLists.txt

@@ -8,6 +8,8 @@
 qt_internal_add_test(tst_qanystringview
     SOURCES
         tst_qanystringview.cpp
+    LIBRARIES
+        Qt::CorePrivate
 )
 
 ## Scopes:

tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp

@@ -7,6 +7,7 @@
 #include <QString>
 #include <QStringBuilder>
 #include <QVarLengthArray>
+#include <private/qxmlstream_p.h>
 
 #include <QTest>
 
@@ -165,6 +166,8 @@ static_assert(CanConvert<std::array<char16_t, 123>>);
 static_assert(!CanConvert<std::deque<char16_t>>);
 static_assert(!CanConvert<std::list<char16_t>>);
 
+static_assert(CanConvert<QtPrivate::XmlStringRef>);
+
 //
 // char32_t
 //

tests/auto/corelib/text/qstringview/CMakeLists.txt

@@ -10,6 +10,8 @@
 qt_internal_add_test(tst_qstringview
     SOURCES
         tst_qstringview.cpp
+    LIBRARIES
+        Qt::CorePrivate
 )
 
 ## Scopes:

tests/auto/corelib/text/qstringview/tst_qstringview.cpp

@@ -7,6 +7,7 @@
 #include <QChar>
 #include <QVarLengthArray>
 #include <QList>
+#include <private/qxmlstream_p.h>
 
 #include <QTest>
 
@@ -90,6 +91,8 @@ static_assert(CanConvert<std::array<char16_t, 123>>::value);
 static_assert(!CanConvert<std::deque<char16_t>>::value);
 static_assert(!CanConvert<std::list<char16_t>>::value);
 
+static_assert(CanConvert<QtPrivate::XmlStringRef>::value);
+
 //
 // wchar_t
 //