Replace custom type traits with std one's

Remove most type traits from qtypetraits.h, but keep the custom
implementation of is_signed/is_unsigned. This gets rid of
BSD-3 licensed code from Google in a public header (hugh!).

The custom implementations for is_signed/is_unsigned are kept
because the implementations in gcc's standard headers do not
work as we expect for enums - both is_signed and is_unsigned
always returns false there - see also
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59027

[ChangeLog][QtCore][General] Qt now relies on type traits from
the C++ standard library.

Change-Id: I3f2188b46949f04ca4482a6ac9afd3482103f0e1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

5 files changed, 20 insertions, 21 deletions

diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index 9e2a5bf75d..29e60b0eb5 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -46,7 +46,6 @@
 #include <QtCore/qbytearray.h>
 #include <QtCore/qvarlengtharray.h>
 #include <QtCore/qisenum.h>
-#include <QtCore/qtypetraits.h>
 #ifndef QT_NO_QOBJECT
 #include <QtCore/qobjectdefs.h>
 #endif
@@ -887,7 +886,7 @@ private:
     // is void* to avoid overloads conflicts. We do it by injecting unaccessible Dummy
     // type as part of the overload signature.
     struct Dummy {};
-    typedef typename QtPrivate::if_<QtPrivate::is_same<value_type, void*>::value, Dummy, value_type>::type value_type_OR_Dummy;
+    typedef typename std::conditional<std::is_same<value_type, void*>::value, Dummy, value_type>::type value_type_OR_Dummy;
 public:
     static void assign(void **ptr, const value_type_OR_Dummy *iterator )
     {
@@ -1092,7 +1091,7 @@ struct QSequentialIterableConvertFunctor
 }
 
 namespace QtMetaTypePrivate {
-template<typename T, bool = QtPrivate::is_same<typename T::const_iterator::value_type, typename T::mapped_type>::value>
+template<typename T, bool = std::is_same<typename T::const_iterator::value_type, typename T::mapped_type>::value>
 struct AssociativeContainerAccessor
 {
     static const typename T::key_type& getKey(const typename T::const_iterator &it)
@@ -1106,7 +1105,7 @@ struct AssociativeContainerAccessor
     }
 };
 
-template<typename T, bool = QtPrivate::is_same<typename T::const_iterator::value_type, std::pair<const typename T::key_type, typename T::mapped_type> >::value>
+template<typename T, bool = std::is_same<typename T::const_iterator::value_type, std::pair<const typename T::key_type, typename T::mapped_type> >::value>
 struct StlStyleAssociativeContainerAccessor;
 
 template<typename T>
@@ -1787,7 +1786,7 @@ template <typename T>
 struct QMetaTypeIdQObject<T, QMetaType::IsGadget>
 {
     enum {
-        Defined = QtPrivate::is_default_constructible<T>::value
+        Defined = std::is_default_constructible<T>::value
     };
 
     static int qt_metatype_id()
diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index 3cec9802dc..69b70ad6ec 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -155,14 +155,14 @@ public:
     template<typename T>
     inline T findChild(const QString &aName = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
-        typedef typename QtPrivate::remove_cv<typename QtPrivate::remove_pointer<T>::type>::type ObjType;
+        typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
         return static_cast<T>(qt_qFindChild_helper(this, aName, ObjType::staticMetaObject, options));
     }
 
     template<typename T>
     inline QList<T> findChildren(const QString &aName = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
-        typedef typename QtPrivate::remove_cv<typename QtPrivate::remove_pointer<T>::type>::type ObjType;
+        typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
         QList<T> list;
         qt_qFindChildren_helper(this, aName, ObjType::staticMetaObject,
                                 reinterpret_cast<QList<void *> *>(&list), options);
@@ -173,7 +173,7 @@ public:
     template<typename T>
     inline QList<T> findChildren(const QRegExp &re, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
-        typedef typename QtPrivate::remove_cv<typename QtPrivate::remove_pointer<T>::type>::type ObjType;
+        typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
         QList<T> list;
         qt_qFindChildren_helper(this, re, ObjType::staticMetaObject,
                                 reinterpret_cast<QList<void *> *>(&list), options);
@@ -185,7 +185,7 @@ public:
     template<typename T>
     inline QList<T> findChildren(const QRegularExpression &re, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
-        typedef typename QtPrivate::remove_cv<typename QtPrivate::remove_pointer<T>::type>::type ObjType;
+        typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
         QList<T> list;
         qt_qFindChildren_helper(this, re, ObjType::staticMetaObject,
                                 reinterpret_cast<QList<void *> *>(&list), options);
@@ -493,7 +493,7 @@ inline QT_DEPRECATED QList<T> qFindChildren(const QObject *o, const QRegExp &re)
 template <class T>
 inline T qobject_cast(QObject *object)
 {
-    typedef typename QtPrivate::remove_cv<typename QtPrivate::remove_pointer<T>::type>::type ObjType;
+    typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
     Q_STATIC_ASSERT_X(QtPrivate::HasQ_OBJECT_Macro<ObjType>::Value,
                     "qobject_cast requires the type to have a Q_OBJECT macro");
     return static_cast<T>(ObjType::staticMetaObject.cast(object));
@@ -502,7 +502,7 @@ inline T qobject_cast(QObject *object)
 template <class T>
 inline T qobject_cast(const QObject *object)
 {
-    typedef typename QtPrivate::remove_cv<typename QtPrivate::remove_pointer<T>::type>::type ObjType;
+    typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
     Q_STATIC_ASSERT_X(QtPrivate::HasQ_OBJECT_Macro<ObjType>::Value,
                       "qobject_cast requires the type to have a Q_OBJECT macro");
     return static_cast<T>(ObjType::staticMetaObject.cast(object));
diff --git a/src/corelib/kernel/qpointer.h b/src/corelib/kernel/qpointer.h
index b5c17ad394..b2b3cda4ab 100644
--- a/src/corelib/kernel/qpointer.h
+++ b/src/corelib/kernel/qpointer.h
@@ -52,7 +52,7 @@ class QVariant;
 template <class T>
 class QPointer
 {
-    Q_STATIC_ASSERT_X(!QtPrivate::is_pointer<T>::value, "QPointer's template type must not be a pointer type");
+    Q_STATIC_ASSERT_X(!std::is_pointer<T>::value, "QPointer's template type must not be a pointer type");
 
     template<typename U>
     struct TypeSelector
diff --git a/src/corelib/kernel/qtimer.h b/src/corelib/kernel/qtimer.h
index 4f934d0367..96c7efd8f5 100644
--- a/src/corelib/kernel/qtimer.h
+++ b/src/corelib/kernel/qtimer.h
@@ -119,14 +119,14 @@ public:
     // singleShot to a functor or function pointer (without context)
     template <typename Duration, typename Func1>
     static inline typename QtPrivate::QEnableIf<!QtPrivate::FunctionPointer<Func1>::IsPointerToMemberFunction &&
-                                                !QtPrivate::is_same<const char*, Func1>::value, void>::Type
+                                                !std::is_same<const char*, Func1>::value, void>::Type
             singleShot(Duration interval, Func1 slot)
     {
         singleShot(interval, defaultTypeFor(interval), nullptr, slot);
     }
     template <typename Duration, typename Func1>
     static inline typename QtPrivate::QEnableIf<!QtPrivate::FunctionPointer<Func1>::IsPointerToMemberFunction &&
-                                                !QtPrivate::is_same<const char*, Func1>::value, void>::Type
+                                                !std::is_same<const char*, Func1>::value, void>::Type
             singleShot(Duration interval, Qt::TimerType timerType, Func1 slot)
     {
         singleShot(interval, timerType, nullptr, slot);
@@ -134,14 +134,14 @@ public:
     // singleShot to a functor or function pointer (with context)
     template <typename Duration, typename Func1>
     static inline typename QtPrivate::QEnableIf<!QtPrivate::FunctionPointer<Func1>::IsPointerToMemberFunction &&
-                                                !QtPrivate::is_same<const char*, Func1>::value, void>::Type
+                                                !std::is_same<const char*, Func1>::value, void>::Type
             singleShot(Duration interval, QObject *context, Func1 slot)
     {
         singleShot(interval, defaultTypeFor(interval), context, slot);
     }
     template <typename Duration, typename Func1>
     static inline typename QtPrivate::QEnableIf<!QtPrivate::FunctionPointer<Func1>::IsPointerToMemberFunction &&
-                                                !QtPrivate::is_same<const char*, Func1>::value, void>::Type
+                                                !std::is_same<const char*, Func1>::value, void>::Type
             singleShot(Duration interval, Qt::TimerType timerType, QObject *context, Func1 slot)
     {
         //compilation error if the slot has arguments.
diff --git a/src/corelib/kernel/qvariant_p.h b/src/corelib/kernel/qvariant_p.h
index d01f386032..ec87e20656 100644
--- a/src/corelib/kernel/qvariant_p.h
+++ b/src/corelib/kernel/qvariant_p.h
@@ -66,7 +66,7 @@ struct QVariantIntegrator
 {
     static const bool CanUseInternalSpace = sizeof(T) <= sizeof(QVariant::Private::Data)
                                             && ((QTypeInfoQuery<T>::isRelocatable) || Q_IS_ENUM(T));
-    typedef QtPrivate::integral_constant<bool, CanUseInternalSpace> CanUseInternalSpace_t;
+    typedef std::integral_constant<bool, CanUseInternalSpace> CanUseInternalSpace_t;
 };
 Q_STATIC_ASSERT(QVariantIntegrator<double>::CanUseInternalSpace);
 Q_STATIC_ASSERT(QVariantIntegrator<long int>::CanUseInternalSpace);
@@ -118,28 +118,28 @@ private:
 };
 
 template <class T>
-inline void v_construct_helper(QVariant::Private *x, const T &t, QtPrivate::true_type)
+inline void v_construct_helper(QVariant::Private *x, const T &t, std::true_type)
 {
     new (&x->data) T(t);
     x->is_shared = false;
 }
 
 template <class T>
-inline void v_construct_helper(QVariant::Private *x, const T &t, QtPrivate::false_type)
+inline void v_construct_helper(QVariant::Private *x, const T &t, std::false_type)
 {
     x->data.shared = new QVariantPrivateSharedEx<T>(t);
     x->is_shared = true;
 }
 
 template <class T>
-inline void v_construct_helper(QVariant::Private *x, QtPrivate::true_type)
+inline void v_construct_helper(QVariant::Private *x, std::true_type)
 {
     new (&x->data) T();
     x->is_shared = false;
 }
 
 template <class T>
-inline void v_construct_helper(QVariant::Private *x, QtPrivate::false_type)
+inline void v_construct_helper(QVariant::Private *x, std::false_type)
 {
     x->data.shared = new QVariantPrivateSharedEx<T>;
     x->is_shared = true;