From c800e96523d4561f5ac08b5d570ca5e2f5d2a25b Mon Sep 17 00:00:00 2001
From: Ulf Hermann <ulf.hermann@qt.io>
Date: Fri, 16 Oct 2020 12:08:54 +0200
Subject: [PATCH] qtypeinfo.h: We only need a const reference for most
 operator<<

If we require a value, then we need a dtor, too. This is not always the
case. For example QSessionManager has a private dtor, leading to
failures.

Change-Id: I3f715848ff5c63b2ea2773c17bced21e7a814ca9
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
---
 src/corelib/global/qtypeinfo.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/corelib/global/qtypeinfo.h b/src/corelib/global/qtypeinfo.h
index 4b29d0bf53..d7cdb8b5d4 100644
--- a/src/corelib/global/qtypeinfo.h
+++ b/src/corelib/global/qtypeinfo.h
@@ -356,7 +356,7 @@ using compare_lt_result = std::enable_if_t<std::conjunction_v<QTypeTraits::has_o
 namespace detail {
 
 template<typename T>
-const T const_value();
+const T &const_reference();
 template<typename T>
 T &reference();
 
@@ -365,7 +365,7 @@ T &reference();
 template <typename Stream, typename, typename = void>
 struct has_ostream_operator : std::false_type {};
 template <typename Stream, typename T>
-struct has_ostream_operator<Stream, T, std::void_t<decltype(detail::reference<Stream>() << detail::const_value<T>())>>
+struct has_ostream_operator<Stream, T, std::void_t<decltype(detail::reference<Stream>() << detail::const_reference<T>())>>
         : std::true_type {};
 template <typename Stream, typename T>
 constexpr bool has_ostream_operator_v = has_ostream_operator<Stream, T>::value;