Use qstringfwd.h when forward declaring string classes

Task-number: QTBUG-98434
Change-Id: I37b70a1b7bc164fa7dc9cb702827297ca66a6fdc
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qbytearrayview.h

@@ -40,14 +40,12 @@
 #define QBYTEARRAYVIEW_H
 
 #include <QtCore/qbytearrayalgorithms.h>
+#include <QtCore/qstringfwd.h>
 
 #include <string>
 
 QT_BEGIN_NAMESPACE
 
-class QByteArray;
-class QLatin1String;
-
 namespace QtPrivate {
 
 template <typename Byte>

src/corelib/text/qregularexpression.h

@@ -54,8 +54,6 @@ QT_REQUIRE_CONFIG(regularexpression);
 
 QT_BEGIN_NAMESPACE
 
-class QLatin1String;
-
 class QRegularExpressionMatch;
 class QRegularExpressionMatchIterator;
 struct QRegularExpressionPrivate;

src/corelib/text/qutf8stringview.h

@@ -40,6 +40,7 @@
 #define QUTF8STRINGVIEW_H
 
 #include <QtCore/qstringalgorithms.h>
+#include <QtCore/qstringfwd.h>
 #include <QtCore/qarraydata.h> // for QContainerImplHelper
 #include <QtCore/qbytearrayview.h>
 
@@ -47,10 +48,6 @@
 
 QT_BEGIN_NAMESPACE
 
-template <bool> class QBasicUtf8StringView;
-class QByteArray;
-class QLatin1String;
-
 namespace QtPrivate {
 template <typename Char>
 using IsCompatibleChar8TypeHelper = std::disjunction<

src/corelib/tools/qhashfunctions.h

@@ -42,6 +42,7 @@
 #define QHASHFUNCTIONS_H
 
 #include <QtCore/qstring.h>
+#include <QtCore/qstringfwd.h>
 #include <QtCore/qpair.h>
 
 #include <numeric> // for std::accumulate
@@ -60,9 +61,6 @@
 QT_BEGIN_NAMESPACE
 
 class QBitArray;
-class QByteArray;
-class QString;
-class QLatin1String;
 
 #if QT_DEPRECATED_SINCE(6,6)
 QT_DEPRECATED_VERSION_X_6_6("Use QHashSeed instead")

src/testlib/qtestresult_p.h

@@ -52,13 +52,11 @@
 //
 
 #include <QtTest/qttestglobal.h>
+#include <QtCore/qstringfwd.h>
 #include <QtCore/private/qglobal_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class QLatin1String;
-class QStringView;
-
 class QTestResultPrivate;
 class QTestData;