Extract Header qstringfwd.h

... from qstringalgorithms.h and qutf8stringview.h, in order to
centralize the declaration of the string classes, much like
qcontainerfwd.h does for Qt containers.

[ChangeLog][QtCore] Added header qstringfwd.h containing
forward-declarations of all Qt string classes.

Task-number: QTBUG-98434
Change-Id: I4cf1ede9fe6c286230f4c7e7abe379da28ce5d15
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/CMakeLists.txt

@@ -186,6 +186,7 @@ qt_internal_add_module(Core
         text/qstringbuilder.cpp text/qstringbuilder.h
         text/qstringconverter_base.h
         text/qstringconverter.cpp text/qstringconverter.h text/qstringconverter_p.h
+        text/qstringfwd.h
         text/qstringiterator_p.h
         text/qstringlist.cpp text/qstringlist.h
         text/qstringliteral.h

src/corelib/text/qstringalgorithms.h

@@ -41,6 +41,7 @@
 #define QSTRINGALGORITHMS_H
 
 #include <QtCore/qnamespace.h>
+#include <QtCore/qstringfwd.h>
 #include <QtCore/qcontainerfwd.h>
 #if 0
 #pragma qt_class(QStringAlgorithms)
@@ -48,31 +49,6 @@
 
 QT_BEGIN_NAMESPACE
 
-#if QT_VERSION >= QT_VERSION_CHECK(7, 0, 0)
-# define QT_BEGIN_HAS_CHAR8_T_NAMESPACE inline namespace q_has_char8_t {
-# define QT_BEGIN_NO_CHAR8_T_NAMESPACE namespace q_no_char8_t {
-#else
-# define QT_BEGIN_HAS_CHAR8_T_NAMESPACE namespace q_has_char8_t {
-# define QT_BEGIN_NO_CHAR8_T_NAMESPACE inline namespace q_no_char8_t {
-#endif
-#define QT_END_HAS_CHAR8_T_NAMESPACE }
-#define QT_END_NO_CHAR8_T_NAMESPACE }
-
-// declare namespaces:
-QT_BEGIN_HAS_CHAR8_T_NAMESPACE
-QT_END_HAS_CHAR8_T_NAMESPACE
-QT_BEGIN_NO_CHAR8_T_NAMESPACE
-QT_END_NO_CHAR8_T_NAMESPACE
-
-class QByteArray;
-class QLatin1String;
-class QStringView;
-template <bool> class QBasicUtf8StringView;
-class QAnyStringView;
-class QChar;
-class QRegularExpression;
-class QRegularExpressionMatch;
-
 namespace QtPrivate {
 
 [[nodiscard]] Q_CORE_EXPORT Q_DECL_PURE_FUNCTION qsizetype qustrlen(const char16_t *str) noexcept;

src/corelib/text/qstringfwd.h

@@ -0,0 +1,86 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtCore/qglobal.h>
+
+#ifndef QSTRINGFWD_H
+#define QSTRINGFWD_H
+
+QT_BEGIN_NAMESPACE
+
+#if QT_VERSION >= QT_VERSION_CHECK(7, 0, 0)
+# define QT_BEGIN_HAS_CHAR8_T_NAMESPACE inline namespace q_has_char8_t {
+# define QT_BEGIN_NO_CHAR8_T_NAMESPACE namespace q_no_char8_t {
+#else
+# define QT_BEGIN_HAS_CHAR8_T_NAMESPACE namespace q_has_char8_t {
+# define QT_BEGIN_NO_CHAR8_T_NAMESPACE inline namespace q_no_char8_t {
+#endif
+#define QT_END_HAS_CHAR8_T_NAMESPACE }
+#define QT_END_NO_CHAR8_T_NAMESPACE }
+
+// declare namespaces:
+QT_BEGIN_HAS_CHAR8_T_NAMESPACE
+QT_END_HAS_CHAR8_T_NAMESPACE
+QT_BEGIN_NO_CHAR8_T_NAMESPACE
+QT_END_NO_CHAR8_T_NAMESPACE
+
+class QByteArray;
+class QByteArrayView;
+class QLatin1String;
+class QStringView;
+template <bool> class QBasicUtf8StringView;
+class QAnyStringView;
+class QChar;
+class QRegularExpression;
+class QRegularExpressionMatch;
+
+#ifndef Q_CLANG_QDOC
+// ### Qt 7: remove the non-char8_t version of QUtf8StringView
+QT_BEGIN_NO_CHAR8_T_NAMESPACE
+using QUtf8StringView = QBasicUtf8StringView<false>;
+QT_END_NO_CHAR8_T_NAMESPACE
+
+QT_BEGIN_HAS_CHAR8_T_NAMESPACE
+using QUtf8StringView = QBasicUtf8StringView<true>;
+QT_END_HAS_CHAR8_T_NAMESPACE
+#endif // Q_CLANG_QDOC
+
+QT_END_NAMESPACE
+
+#endif // QSTRINGFWD_H

src/corelib/text/qutf8stringview.h

@@ -361,15 +361,6 @@ private:
 #else
 template <bool UseChar8T>
 Q_DECLARE_TYPEINFO_BODY(QBasicUtf8StringView<UseChar8T>, Q_PRIMITIVE_TYPE);
-
-// ### Qt 7: remove the non-char8_t version of QUtf8StringView
-QT_BEGIN_NO_CHAR8_T_NAMESPACE
-using QUtf8StringView = QBasicUtf8StringView<false>;
-QT_END_NO_CHAR8_T_NAMESPACE
-
-QT_BEGIN_HAS_CHAR8_T_NAMESPACE
-using QUtf8StringView = QBasicUtf8StringView<true>;
-QT_END_HAS_CHAR8_T_NAMESPACE
 #endif // Q_CLANG_QDOC
 
 template <typename QStringLike, std::enable_if_t<std::is_same_v<QStringLike, QByteArray>, bool> = true>