Apply q20::remove_cvref_t around the code

Found in API review. It's not BC-critical, but let's get this into 6.5
to minimize the diff to our future LTS.

Pick-to: 6.5
Change-Id: Iaa63afad1d31f6edef29e1185897d925f47a094d
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qmetatype.h

@@ -26,7 +26,7 @@
 #include <map>
 #include <functional>
 #include <optional>
-#include <type_traits>
+#include <QtCore/q20type_traits.h>
 
 #ifdef Bool
 #error qmetatype.h must be included before any header file that defines Bool
@@ -606,8 +606,7 @@ public:
             const From *f = static_cast<const From *>(from);
             To *t = static_cast<To *>(to);
             auto &&r = function(*f);
-            if constexpr (std::is_same_v<std::remove_cv_t<std::remove_reference_t<decltype(r)>>,
-                                         std::optional<To>>) {
+            if constexpr (std::is_same_v<q20::remove_cvref_t<decltype(r)>, std::optional<To>>) {
                 if (!r)
                     return false;
                 *t = *std::forward<decltype(r)>(r);

src/corelib/text/qbytearrayview.h

@@ -8,6 +8,7 @@
 #include <QtCore/qarraydata.h>
 
 #include <string>
+#include <QtCore/q20type_traits.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -23,8 +24,7 @@ struct IsCompatibleByteTypeHelper
 
 template <typename Byte>
 struct IsCompatibleByteType
-    : IsCompatibleByteTypeHelper<
-              typename std::remove_cv_t<typename std::remove_reference_t<Byte>>> {};
+    : IsCompatibleByteTypeHelper<q20::remove_cvref_t<Byte>> {};
 
 template <typename Pointer>
 struct IsCompatibleByteArrayPointerHelper : std::false_type {};
@@ -33,8 +33,7 @@ struct IsCompatibleByteArrayPointerHelper<Byte *>
     : IsCompatibleByteType<Byte> {};
 template<typename Pointer>
 struct IsCompatibleByteArrayPointer
-    : IsCompatibleByteArrayPointerHelper<
-              typename std::remove_cv_t<typename std::remove_reference_t<Pointer>>> {};
+    : IsCompatibleByteArrayPointerHelper<q20::remove_cvref_t<Pointer>> {};
 
 template <typename T, typename Enable = void>
 struct IsContainerCompatibleWithQByteArrayView : std::false_type {};

src/corelib/text/qstringview.h

@@ -11,6 +11,7 @@
 #include <QtCore/qutf8stringview.h>
 
 #include <string>
+#include <QtCore/q20type_traits.h>
 
 #if defined(Q_OS_DARWIN) || defined(Q_QDOC)
 Q_FORWARD_DECLARE_CF_TYPE(CFString);
@@ -34,7 +35,7 @@ struct IsCompatibleCharTypeHelper
                              (std::is_same<Char, wchar_t>::value && sizeof(wchar_t) == sizeof(QChar))> {};
 template <typename Char>
 struct IsCompatibleCharType
-    : IsCompatibleCharTypeHelper<typename std::remove_cv<typename std::remove_reference<Char>::type>::type> {};
+    : IsCompatibleCharTypeHelper<q20::remove_cvref_t<Char>> {};
 
 template <typename Pointer>
 struct IsCompatiblePointerHelper : std::false_type {};
@@ -43,7 +44,7 @@ struct IsCompatiblePointerHelper<Char*>
     : IsCompatibleCharType<Char> {};
 template <typename Pointer>
 struct IsCompatiblePointer
-    : IsCompatiblePointerHelper<typename std::remove_cv<typename std::remove_reference<Pointer>::type>::type> {};
+    : IsCompatiblePointerHelper<q20::remove_cvref_t<Pointer>> {};
 
 template <typename T, typename Enable = void>
 struct IsContainerCompatibleWithQStringView : std::false_type {};

src/corelib/text/qutf8stringview.h

@@ -13,6 +13,7 @@
 #include <QtCore/qbytearrayview.h>
 
 #include <string>
+#include <QtCore/q20type_traits.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -28,7 +29,7 @@ using IsCompatibleChar8TypeHelper = std::disjunction<
     >;
 template <typename Char>
 using IsCompatibleChar8Type
-    = IsCompatibleChar8TypeHelper<std::remove_cv_t<std::remove_reference_t<Char>>>;
+    = IsCompatibleChar8TypeHelper<q20::remove_cvref_t<Char>>;
 
 template <typename Pointer>
 struct IsCompatiblePointer8Helper : std::false_type {};
@@ -37,7 +38,7 @@ struct IsCompatiblePointer8Helper<Char*>
     : IsCompatibleChar8Type<Char> {};
 template <typename Pointer>
 using IsCompatiblePointer8
-    = IsCompatiblePointer8Helper<std::remove_cv_t<std::remove_reference_t<Pointer>>>;
+    = IsCompatiblePointer8Helper<q20::remove_cvref_t<Pointer>>;
 
 template <typename T, typename Enable = void>
 struct IsContainerCompatibleWithQUtf8StringView : std::false_type {};