From aec1edfe40f44394f50332d306ee7aa6c86d2222 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Wed, 29 May 2024 09:33:39 +0200
Subject: [PATCH] qtypeinfo.h: move QTypeTraits part to qttypetraits.h

Makes sense to collect the stuff in a similarly-named header, and it's
not like any of the QTypeTraits stuff was needed for QTypeInfo.

Makes #include <qtypeinfo.h> _much_ lighter again, at the expense of
qminmax.h now getting <variant>, <tuple> and <optional> instead, but
qminmax.h is much easier to avoid in Qt headers (just use the std
versions) than qtypeinfo.h.

[ChangeLog][QtCore][Potentially Source-Incompatible Changes] The
qtypeinfo.h header no longer transitively includes <optional>, <tuple>
and <variant>.

Task-number: QTBUG-97601
Change-Id: Ied96113f38c1232fef3ec79847ee62f06c68f268
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit b2eb422699118f4ae8370519b4c7bb3fe121beb2)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/global/qttypetraits.h             | 189 +++++++++++++++++
 src/corelib/global/qtypeinfo.h                | 195 ------------------
 src/corelib/io/qdebug.h                       |   1 +
 src/corelib/kernel/qmetatype.h                |   1 +
 src/corelib/kernel/qproperty.h                |   1 +
 src/corelib/kernel/qpropertyprivate.h         |   1 +
 src/corelib/serialization/qdatastream.h       |   1 +
 src/corelib/tools/qcontiguouscache.h          |   1 +
 src/corelib/tools/qhash.h                     |   1 +
 src/corelib/tools/qlist.h                     |   1 +
 src/corelib/tools/qmap.h                      |   1 +
 src/corelib/tools/qset.h                      |   1 +
 src/corelib/tools/qvarlengtharray.h           |   1 +
 src/testlib/qtesttostring.h                   |   2 +
 .../corelib/kernel/qvariant/tst_qvariant.cpp  |   2 +
 15 files changed, 204 insertions(+), 195 deletions(-)

diff --git a/src/corelib/global/qttypetraits.h b/src/corelib/global/qttypetraits.h
index 35dfad155bf..2cd68c73cbe 100644
--- a/src/corelib/global/qttypetraits.h
+++ b/src/corelib/global/qttypetraits.h
@@ -7,8 +7,11 @@
 #include <QtCore/qtconfigmacros.h>
 #include <QtCore/qtdeprecationmarkers.h>
 
+#include <optional>
+#include <tuple>
 #include <type_traits>
 #include <utility>
+#include <variant>
 
 #if 0
 #pragma qt_class(QtTypeTraits)
@@ -78,6 +81,192 @@ struct Promoted
 template <typename T, typename U>
 using Promoted = typename detail::Promoted<T, U>::type;
 
+/*
+    The templates below aim to find out whether one can safely instantiate an operator==() or
+    operator<() for a type.
+
+    This is tricky for containers, as most containers have unconstrained comparison operators, even though they
+    rely on the corresponding operators for its content.
+    This is especially true for all of the STL template classes that have a comparison operator defined, and
+    leads to the situation, that the compiler would try to instantiate the operator, and fail if any
+    of its template arguments does not have the operator implemented.
+
+    The code tries to cover the relevant cases for Qt and the STL, by checking (recusrsively) the value_type
+    of a container (if it exists), and checking the template arguments of pair, tuple and variant.
+*/
+namespace detail {
+
+// find out whether T is a conteiner
+// this is required to check the value type of containers for the existence of the comparison operator
+template <typename, typename = void>
+struct is_container : std::false_type {};
+template <typename T>
+struct is_container<T, std::void_t<
+        typename T::value_type,
+        std::is_convertible<decltype(std::declval<T>().begin() != std::declval<T>().end()), bool>
+>> : std::true_type {};
+
+
+// Checks the existence of the comparison operator for the class itself
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_FLOAT_COMPARE
+template <typename, typename = void>
+struct has_operator_equal : std::false_type {};
+template <typename T>
+struct has_operator_equal<T, std::void_t<decltype(bool(std::declval<const T&>() == std::declval<const T&>()))>>
+        : std::true_type {};
+QT_WARNING_POP
+
+// Two forward declarations
+template<typename T, bool = is_container<T>::value>
+struct expand_operator_equal_container;
+template<typename T>
+struct expand_operator_equal_tuple;
+
+// the entry point for the public method
+template<typename T>
+using expand_operator_equal = expand_operator_equal_container<T>;
+
+// if T isn't a container check if it's a tuple like object
+template<typename T, bool>
+struct expand_operator_equal_container : expand_operator_equal_tuple<T> {};
+// if T::value_type exists, check first T::value_type, then T itself
+template<typename T>
+struct expand_operator_equal_container<T, true> :
+        std::conjunction<
+        std::disjunction<
+            std::is_same<T, typename T::value_type>, // avoid endless recursion
+            expand_operator_equal<typename T::value_type>
+        >, expand_operator_equal_tuple<T>> {};
+
+// recursively check the template arguments of a tuple like object
+template<typename ...T>
+using expand_operator_equal_recursive = std::conjunction<expand_operator_equal<T>...>;
+
+template<typename T>
+struct expand_operator_equal_tuple : has_operator_equal<T> {};
+template<typename T>
+struct expand_operator_equal_tuple<std::optional<T>> : expand_operator_equal_recursive<T> {};
+template<typename T1, typename T2>
+struct expand_operator_equal_tuple<std::pair<T1, T2>> : expand_operator_equal_recursive<T1, T2> {};
+template<typename ...T>
+struct expand_operator_equal_tuple<std::tuple<T...>> : expand_operator_equal_recursive<T...> {};
+template<typename ...T>
+struct expand_operator_equal_tuple<std::variant<T...>> : expand_operator_equal_recursive<T...> {};
+
+// the same for operator<(), see above for explanations
+template <typename, typename = void>
+struct has_operator_less_than : std::false_type{};
+template <typename T>
+struct has_operator_less_than<T, std::void_t<decltype(bool(std::declval<const T&>() < std::declval<const T&>()))>>
+        : std::true_type{};
+
+template<typename T, bool = is_container<T>::value>
+struct expand_operator_less_than_container;
+template<typename T>
+struct expand_operator_less_than_tuple;
+
+template<typename T>
+using expand_operator_less_than = expand_operator_less_than_container<T>;
+
+template<typename T, bool>
+struct expand_operator_less_than_container : expand_operator_less_than_tuple<T> {};
+template<typename T>
+struct expand_operator_less_than_container<T, true> :
+        std::conjunction<
+            std::disjunction<
+                std::is_same<T, typename T::value_type>,
+                expand_operator_less_than<typename T::value_type>
+            >, expand_operator_less_than_tuple<T>
+        > {};
+
+template<typename ...T>
+using expand_operator_less_than_recursive = std::conjunction<expand_operator_less_than<T>...>;
+
+template<typename T>
+struct expand_operator_less_than_tuple : has_operator_less_than<T> {};
+template<typename T>
+struct expand_operator_less_than_tuple<std::optional<T>> : expand_operator_less_than_recursive<T> {};
+template<typename T1, typename T2>
+struct expand_operator_less_than_tuple<std::pair<T1, T2>> : expand_operator_less_than_recursive<T1, T2> {};
+template<typename ...T>
+struct expand_operator_less_than_tuple<std::tuple<T...>> : expand_operator_less_than_recursive<T...> {};
+template<typename ...T>
+struct expand_operator_less_than_tuple<std::variant<T...>> : expand_operator_less_than_recursive<T...> {};
+
+}
+
+template<typename T, typename = void>
+struct is_dereferenceable : std::false_type {};
+
+template<typename T>
+struct is_dereferenceable<T, std::void_t<decltype(std::declval<T>().operator->())> >
+    : std::true_type {};
+
+template <typename T>
+inline constexpr bool is_dereferenceable_v = is_dereferenceable<T>::value;
+
+template<typename T>
+struct has_operator_equal : detail::expand_operator_equal<T> {};
+template<typename T>
+inline constexpr bool has_operator_equal_v = has_operator_equal<T>::value;
+
+template <typename Container, typename T>
+using has_operator_equal_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_operator_equal<T>>;
+
+template<typename T>
+struct has_operator_less_than : detail::expand_operator_less_than<T> {};
+template<typename T>
+inline constexpr bool has_operator_less_than_v = has_operator_less_than<T>::value;
+
+template <typename Container, typename T>
+using has_operator_less_than_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_operator_less_than<T>>;
+
+template <typename ...T>
+using compare_eq_result = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_equal<T>...>, bool>;
+
+template <typename Container, typename ...T>
+using compare_eq_result_container = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_equal_container<Container, T>...>, bool>;
+
+template <typename ...T>
+using compare_lt_result = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_less_than<T>...>, bool>;
+
+template <typename Container, typename ...T>
+using compare_lt_result_container = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_less_than_container<Container, T>...>, bool>;
+
+namespace detail {
+
+template<typename T>
+const T &const_reference();
+template<typename T>
+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_reference<T>())>>
+        : std::true_type {};
+template <typename Stream, typename T>
+inline constexpr bool has_ostream_operator_v = has_ostream_operator<Stream, T>::value;
+
+template <typename Stream, typename Container, typename T>
+using has_ostream_operator_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_ostream_operator<Stream, T>>;
+
+template <typename Stream, typename, typename = void>
+struct has_istream_operator : std::false_type {};
+template <typename Stream, typename T>
+struct has_istream_operator<Stream, T, std::void_t<decltype(detail::reference<Stream>() >> detail::reference<T>())>>
+        : std::true_type {};
+template <typename Stream, typename T>
+inline constexpr bool has_istream_operator_v = has_istream_operator<Stream, T>::value;
+template <typename Stream, typename Container, typename T>
+using has_istream_operator_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_istream_operator<Stream, T>>;
+
+template <typename Stream, typename T>
+inline constexpr bool has_stream_operator_v = has_ostream_operator_v<Stream, T> && has_istream_operator_v<Stream, T>;
+
 } // namespace QTypeTraits
 
 QT_END_NAMESPACE
diff --git a/src/corelib/global/qtypeinfo.h b/src/corelib/global/qtypeinfo.h
index 255a2b33c61..e9dfbc34a4f 100644
--- a/src/corelib/global/qtypeinfo.h
+++ b/src/corelib/global/qtypeinfo.h
@@ -8,9 +8,6 @@
 #include <QtCore/qcompilerdetection.h>
 #include <QtCore/qcontainerfwd.h>
 
-#include <variant>
-#include <optional>
-#include <tuple>
 #include <type_traits>
 
 QT_BEGIN_NAMESPACE
@@ -186,197 +183,5 @@ template<typename T> class QFlags;
 template<typename T>
 Q_DECLARE_TYPEINFO_BODY(QFlags<T>, Q_PRIMITIVE_TYPE);
 
-namespace QTypeTraits
-{
-
-/*
-    The templates below aim to find out whether one can safely instantiate an operator==() or
-    operator<() for a type.
-
-    This is tricky for containers, as most containers have unconstrained comparison operators, even though they
-    rely on the corresponding operators for its content.
-    This is especially true for all of the STL template classes that have a comparison operator defined, and
-    leads to the situation, that the compiler would try to instantiate the operator, and fail if any
-    of its template arguments does not have the operator implemented.
-
-    The code tries to cover the relevant cases for Qt and the STL, by checking (recusrsively) the value_type
-    of a container (if it exists), and checking the template arguments of pair, tuple and variant.
-*/
-namespace detail {
-
-// find out whether T is a conteiner
-// this is required to check the value type of containers for the existence of the comparison operator
-template <typename, typename = void>
-struct is_container : std::false_type {};
-template <typename T>
-struct is_container<T, std::void_t<
-        typename T::value_type,
-        std::is_convertible<decltype(std::declval<T>().begin() != std::declval<T>().end()), bool>
->> : std::true_type {};
-
-
-// Checks the existence of the comparison operator for the class itself
-QT_WARNING_PUSH
-QT_WARNING_DISABLE_FLOAT_COMPARE
-template <typename, typename = void>
-struct has_operator_equal : std::false_type {};
-template <typename T>
-struct has_operator_equal<T, std::void_t<decltype(bool(std::declval<const T&>() == std::declval<const T&>()))>>
-        : std::true_type {};
-QT_WARNING_POP
-
-// Two forward declarations
-template<typename T, bool = is_container<T>::value>
-struct expand_operator_equal_container;
-template<typename T>
-struct expand_operator_equal_tuple;
-
-// the entry point for the public method
-template<typename T>
-using expand_operator_equal = expand_operator_equal_container<T>;
-
-// if T isn't a container check if it's a tuple like object
-template<typename T, bool>
-struct expand_operator_equal_container : expand_operator_equal_tuple<T> {};
-// if T::value_type exists, check first T::value_type, then T itself
-template<typename T>
-struct expand_operator_equal_container<T, true> :
-        std::conjunction<
-        std::disjunction<
-            std::is_same<T, typename T::value_type>, // avoid endless recursion
-            expand_operator_equal<typename T::value_type>
-        >, expand_operator_equal_tuple<T>> {};
-
-// recursively check the template arguments of a tuple like object
-template<typename ...T>
-using expand_operator_equal_recursive = std::conjunction<expand_operator_equal<T>...>;
-
-template<typename T>
-struct expand_operator_equal_tuple : has_operator_equal<T> {};
-template<typename T>
-struct expand_operator_equal_tuple<std::optional<T>> : expand_operator_equal_recursive<T> {};
-template<typename T1, typename T2>
-struct expand_operator_equal_tuple<std::pair<T1, T2>> : expand_operator_equal_recursive<T1, T2> {};
-template<typename ...T>
-struct expand_operator_equal_tuple<std::tuple<T...>> : expand_operator_equal_recursive<T...> {};
-template<typename ...T>
-struct expand_operator_equal_tuple<std::variant<T...>> : expand_operator_equal_recursive<T...> {};
-
-// the same for operator<(), see above for explanations
-template <typename, typename = void>
-struct has_operator_less_than : std::false_type{};
-template <typename T>
-struct has_operator_less_than<T, std::void_t<decltype(bool(std::declval<const T&>() < std::declval<const T&>()))>>
-        : std::true_type{};
-
-template<typename T, bool = is_container<T>::value>
-struct expand_operator_less_than_container;
-template<typename T>
-struct expand_operator_less_than_tuple;
-
-template<typename T>
-using expand_operator_less_than = expand_operator_less_than_container<T>;
-
-template<typename T, bool>
-struct expand_operator_less_than_container : expand_operator_less_than_tuple<T> {};
-template<typename T>
-struct expand_operator_less_than_container<T, true> :
-        std::conjunction<
-            std::disjunction<
-                std::is_same<T, typename T::value_type>,
-                expand_operator_less_than<typename T::value_type>
-            >, expand_operator_less_than_tuple<T>
-        > {};
-
-template<typename ...T>
-using expand_operator_less_than_recursive = std::conjunction<expand_operator_less_than<T>...>;
-
-template<typename T>
-struct expand_operator_less_than_tuple : has_operator_less_than<T> {};
-template<typename T>
-struct expand_operator_less_than_tuple<std::optional<T>> : expand_operator_less_than_recursive<T> {};
-template<typename T1, typename T2>
-struct expand_operator_less_than_tuple<std::pair<T1, T2>> : expand_operator_less_than_recursive<T1, T2> {};
-template<typename ...T>
-struct expand_operator_less_than_tuple<std::tuple<T...>> : expand_operator_less_than_recursive<T...> {};
-template<typename ...T>
-struct expand_operator_less_than_tuple<std::variant<T...>> : expand_operator_less_than_recursive<T...> {};
-
-}
-
-template<typename T, typename = void>
-struct is_dereferenceable : std::false_type {};
-
-template<typename T>
-struct is_dereferenceable<T, std::void_t<decltype(std::declval<T>().operator->())> >
-    : std::true_type {};
-
-template <typename T>
-inline constexpr bool is_dereferenceable_v = is_dereferenceable<T>::value;
-
-template<typename T>
-struct has_operator_equal : detail::expand_operator_equal<T> {};
-template<typename T>
-inline constexpr bool has_operator_equal_v = has_operator_equal<T>::value;
-
-template <typename Container, typename T>
-using has_operator_equal_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_operator_equal<T>>;
-
-template<typename T>
-struct has_operator_less_than : detail::expand_operator_less_than<T> {};
-template<typename T>
-inline constexpr bool has_operator_less_than_v = has_operator_less_than<T>::value;
-
-template <typename Container, typename T>
-using has_operator_less_than_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_operator_less_than<T>>;
-
-template <typename ...T>
-using compare_eq_result = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_equal<T>...>, bool>;
-
-template <typename Container, typename ...T>
-using compare_eq_result_container = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_equal_container<Container, T>...>, bool>;
-
-template <typename ...T>
-using compare_lt_result = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_less_than<T>...>, bool>;
-
-template <typename Container, typename ...T>
-using compare_lt_result_container = std::enable_if_t<std::conjunction_v<QTypeTraits::has_operator_less_than_container<Container, T>...>, bool>;
-
-namespace detail {
-
-template<typename T>
-const T &const_reference();
-template<typename T>
-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_reference<T>())>>
-        : std::true_type {};
-template <typename Stream, typename T>
-inline constexpr bool has_ostream_operator_v = has_ostream_operator<Stream, T>::value;
-
-template <typename Stream, typename Container, typename T>
-using has_ostream_operator_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_ostream_operator<Stream, T>>;
-
-template <typename Stream, typename, typename = void>
-struct has_istream_operator : std::false_type {};
-template <typename Stream, typename T>
-struct has_istream_operator<Stream, T, std::void_t<decltype(detail::reference<Stream>() >> detail::reference<T>())>>
-        : std::true_type {};
-template <typename Stream, typename T>
-inline constexpr bool has_istream_operator_v = has_istream_operator<Stream, T>::value;
-template <typename Stream, typename Container, typename T>
-using has_istream_operator_container = std::disjunction<std::is_base_of<Container, T>, QTypeTraits::has_istream_operator<Stream, T>>;
-
-template <typename Stream, typename T>
-inline constexpr bool has_stream_operator_v = has_ostream_operator_v<Stream, T> && has_istream_operator_v<Stream, T>;
-
-}
-
-
 QT_END_NAMESPACE
 #endif // QTYPEINFO_H
diff --git a/src/corelib/io/qdebug.h b/src/corelib/io/qdebug.h
index 4797bcd169f..44c3dea804b 100644
--- a/src/corelib/io/qdebug.h
+++ b/src/corelib/io/qdebug.h
@@ -11,6 +11,7 @@
 
 #include <QtCore/qcontainerfwd.h>
 #include <QtCore/qtextstream.h>
+#include <QtCore/qttypetraits.h>
 #include <QtCore/qtypes.h>
 #include <QtCore/qstring.h>
 #include <QtCore/qcontiguouscache.h>
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index 12a67aef584..1e944660c61 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -18,6 +18,7 @@
 #include <QtCore/qobjectdefs.h>
 #endif
 #include <QtCore/qscopeguard.h>
+#include <QtCore/qttypetraits.h>
 
 #include <array>
 #include <new>
diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index 0373867a661..8c4b13cf5e8 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -7,6 +7,7 @@
 #include <QtCore/qglobal.h>
 #include <QtCore/qshareddata.h>
 #include <QtCore/qstring.h>
+#include <QtCore/qttypetraits.h>
 #include <QtCore/qbindingstorage.h>
 
 #include <type_traits>
diff --git a/src/corelib/kernel/qpropertyprivate.h b/src/corelib/kernel/qpropertyprivate.h
index a8456721d05..c4a73f2c912 100644
--- a/src/corelib/kernel/qpropertyprivate.h
+++ b/src/corelib/kernel/qpropertyprivate.h
@@ -19,6 +19,7 @@
 #include <QtCore/qtaggedpointer.h>
 #include <QtCore/qmetatype.h>
 #include <QtCore/qcontainerfwd.h>
+#include <QtCore/qttypetraits.h>
 
 #include <functional>
 
diff --git a/src/corelib/serialization/qdatastream.h b/src/corelib/serialization/qdatastream.h
index cf37df71d75..e094d76c13e 100644
--- a/src/corelib/serialization/qdatastream.h
+++ b/src/corelib/serialization/qdatastream.h
@@ -8,6 +8,7 @@
 #include <QtCore/qiodevicebase.h>
 #include <QtCore/qcontainerfwd.h>
 #include <QtCore/qnamespace.h>
+#include <QtCore/qttypetraits.h>
 
 #include <iterator>         // std::distance(), std::next()
 
diff --git a/src/corelib/tools/qcontiguouscache.h b/src/corelib/tools/qcontiguouscache.h
index c01dbb9390f..e3f98c30de6 100644
--- a/src/corelib/tools/qcontiguouscache.h
+++ b/src/corelib/tools/qcontiguouscache.h
@@ -8,6 +8,7 @@
 #include <QtCore/qassert.h>
 #include <QtCore/qtclasshelpermacros.h>
 #include <QtCore/qtcoreexports.h>
+#include <QtCore/qttypetraits.h>
 #include <QtCore/qtypeinfo.h>
 
 #include <climits>
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index e7cd4123fb4..9cc6fbf30bc 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -11,6 +11,7 @@
 #include <QtCore/qiterator.h>
 #include <QtCore/qlist.h>
 #include <QtCore/qrefcount.h>
+#include <QtCore/qttypetraits.h>
 
 #include <initializer_list>
 #include <functional> // for std::hash
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 89e0e3f380f..1cced5acc2d 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -11,6 +11,7 @@
 #include <QtCore/qiterator.h>
 #include <QtCore/qcontainertools_impl.h>
 #include <QtCore/qnamespace.h>
+#include <QtCore/qttypetraits.h>
 
 #include <functional>
 #include <limits>
diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index 7ee0be1e519..326ae7d8a51 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -12,6 +12,7 @@
 #include <QtCore/qpair.h>
 #include <QtCore/qshareddata.h>
 #include <QtCore/qshareddata_impl.h>
+#include <QtCore/qttypetraits.h>
 
 #include <functional>
 #include <initializer_list>
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index 7330b5e91cc..6eaeb8fc417 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -6,6 +6,7 @@
 
 #include <QtCore/qhash.h>
 #include <QtCore/qcontainertools_impl.h>
+#include <QtCore/qttypetraits.h>
 
 #include <initializer_list>
 #include <iterator>
diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index 0a579bf4873..78d5a276277 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -14,6 +14,7 @@
 #include <QtCore/qalgorithms.h>
 #include <QtCore/qcontainertools_impl.h>
 #include <QtCore/qhashfunctions.h>
+#include <QtCore/qttypetraits.h>
 
 #include <algorithm>
 #include <initializer_list>
diff --git a/src/testlib/qtesttostring.h b/src/testlib/qtesttostring.h
index 18262332ba3..a1ee4f69258 100644
--- a/src/testlib/qtesttostring.h
+++ b/src/testlib/qtesttostring.h
@@ -7,6 +7,8 @@
 
 #include <QtTest/qttestglobal.h>
 
+#include <QtCore/qttypetraits.h>
+
 #if QT_CONFIG(itemmodel)
 #  include <QtCore/qabstractitemmodel.h>
 #endif
diff --git a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
index a8e2c7bda37..d79e0e82f8a 100644
--- a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
+++ b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
@@ -5,6 +5,8 @@
 
 #include <qvariant.h>
 
+#include <QtCore/qttypetraits.h>
+
 // don't assume <type_traits>
 template <typename T, typename U>
 constexpr inline bool my_is_same_v = false;