QLatin1/String/View: don't decay the arg() arguments

This turns const char[] arrays into const char* pointers and
therefore prevents the implicit conversion of string literals
to QString in QT_RESTRICTED_CAST_FROM_ASCII.

Fix by avoiding the decay.

Also simplify the template magic.

Manual conflict resolutions:
- QLatin1StringView → QLatin1String
- port away from C++17 std::disjunction

Change-Id: I88164a1866ac71b41d9cd1564f3a5e83d2d42aaa
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit ba52b29d336cc32a462306d9011b75e9948c7040)
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 3 insertions, 6 deletions

diff --git a/src/corelib/text/qstring.h b/src/corelib/text/qstring.h
index 6c365f1b0c..f1363903f5 100644
--- a/src/corelib/text/qstring.h
+++ b/src/corelib/text/qstring.h
@@ -361,14 +361,11 @@ public:
 #endif
 private:
     template <typename T>
-    struct is_convertible_to_view_or_qstring_helper
-        : std::integral_constant<bool,
+    using is_convertible_to_view_or_qstring = std::integral_constant<bool,
             std::is_convertible<T, QString>::value ||
             std::is_convertible<T, QStringView>::value ||
-            std::is_convertible<T, QLatin1String>::value> {};
-    template <typename T>
-    struct is_convertible_to_view_or_qstring
-        : is_convertible_to_view_or_qstring_helper<typename std::decay<T>::type> {};
+            std::is_convertible<T, QLatin1String>::value
+        >;
 public:
     template <typename...Args>
     Q_REQUIRED_RESULT