From 812a0d3125cb89e340c59aa92cdc946862fb009d Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Sun, 7 Aug 2022 22:18:38 +0200
Subject: [PATCH] QAnyStringView: construct from any T implicitly convertible
 to QString/QByteArray

This includes QDBusReply, QProperty, and QStringBuilder expressions.

The new constructor subsumes the QStringBuilder case without requiring
jumping though hoops to delay the definition of the ctor the way we
had to for the explicit QStringBuilder constructor, so remove the
explicit QStringBuilder one again.

[ChangeLog][QtCore][QAnyStringView] Can now be constructed from
anything that implicitly converts to either QString or QByteArray.

Fixes: QTBUG-105389
Change-Id: I0e584dd3e20d591381609a3329ef47cec7356ecc
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
---
 src/corelib/kernel/qobject.cpp                |  2 +-
 src/corelib/text/qanystringview.h             | 41 +++++++++++++++----
 src/corelib/text/qstringbuilder.h             |  9 ----
 .../qanystringview/tst_qanystringview.cpp     | 10 +++++
 4 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index ac5e839eb2e..f2124678f07 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -1279,7 +1279,7 @@ void QObject::setObjectName(QAnyStringView name)
 
     d->extraData->objectName.removeBindingUnlessInWrapper();
 
-    if (d->extraData->objectName.value() != name) {
+    if (d->extraData->objectName != name) {
         d->extraData->objectName.setValueBypassingBindings(name.toString());
         d->extraData->objectName.notify(); // also emits a signal
     }
diff --git a/src/corelib/text/qanystringview.h b/src/corelib/text/qanystringview.h
index 0cd97fd54e2..36262e28e16 100644
--- a/src/corelib/text/qanystringview.h
+++ b/src/corelib/text/qanystringview.h
@@ -1,3 +1,4 @@
+// Copyright (C) 2022 The Qt Company Ltd.
 // Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 #ifndef QANYSTRINGVIEW_H
@@ -9,14 +10,22 @@
 #ifdef __cpp_impl_three_way_comparison
 #include <compare>
 #endif
+#include <QtCore/q20functional.h>
 #include <limits>
 
 class tst_QAnyStringView;
 
 QT_BEGIN_NAMESPACE
 
-template <typename, typename> class QStringBuilder;
-template <typename> struct QConcatenable;
+namespace QtPrivate {
+
+template <typename Tag, typename Result>
+struct wrapped { using type = Result; };
+
+template <typename Tag, typename Result>
+using wrapped_t = typename wrapped<Tag, Result>::type;
+
+} // namespace QtPrivate
 
 class QAnyStringView
 {
@@ -43,6 +52,19 @@ private:
         QtPrivate::IsContainerCompatibleWithQUtf8StringView<T>
     >, bool>;
 
+    template <typename QStringOrQByteArray, typename T>
+    using if_convertible_to = std::enable_if_t<std::conjunction_v<
+        // need to exclude a bunch of stuff, because we take by universal reference:
+        std::negation<std::disjunction<
+            std::is_same<q20::remove_cvref_t<T>, QAnyStringView>, // don't make a copy/move ctor
+            std::is_pointer<std::decay_t<T>>, // const char*, etc
+            std::is_same<q20::remove_cvref_t<T>, QByteArray>,
+            std::is_same<q20::remove_cvref_t<T>, QString>
+        >>,
+        // this is what we're really after:
+        std::is_convertible<T, QStringOrQByteArray>
+    >, bool>;
+
     // confirm we don't make an accidental copy constructor:
     static_assert(QtPrivate::IsContainerCompatibleWithQStringView<QAnyStringView>::value == false);
     static_assert(QtPrivate::IsContainerCompatibleWithQUtf8StringView<QAnyStringView>::value == false);
@@ -155,15 +177,20 @@ public:
     inline QAnyStringView(const QString &str) noexcept;
     inline constexpr QAnyStringView(QLatin1StringView str) noexcept;
 
-    // defined in qstringbuilder.h
-    template <typename A, typename B>
-    inline QAnyStringView(const QStringBuilder<A, B> &expr,
-                          typename QConcatenable<QStringBuilder<A, B>>::ConvertTo &&capacity = {});
-
     template <typename Container, if_compatible_container<Container> = true>
     constexpr QAnyStringView(const Container &c) noexcept
         : QAnyStringView(std::data(c), lengthHelperContainer(c)) {}
 
+    template <typename Container, if_convertible_to<QString, Container> = true>
+    constexpr QAnyStringView(Container &&c, QtPrivate::wrapped_t<Container, QString> &&capacity = {})
+            //noexcept(std::is_nothrow_constructible_v<QString, Container>)
+        : QAnyStringView(capacity = std::forward<Container>(c)) {}
+
+    template <typename Container, if_convertible_to<QByteArray, Container> = true>
+    constexpr QAnyStringView(Container &&c, QtPrivate::wrapped_t<Container, QByteArray> &&capacity = {})
+            //noexcept(std::is_nothrow_constructible_v<QByteArray, Container>)
+        : QAnyStringView(capacity = std::forward<Container>(c)) {}
+
     template <typename Char, if_compatible_char<Char> = true>
     constexpr QAnyStringView(const Char &c) noexcept
         : QAnyStringView{&c, 1} {}
diff --git a/src/corelib/text/qstringbuilder.h b/src/corelib/text/qstringbuilder.h
index f3958114dc2..4318e219edf 100644
--- a/src/corelib/text/qstringbuilder.h
+++ b/src/corelib/text/qstringbuilder.h
@@ -452,15 +452,6 @@ QString &operator+=(QString &a, const QStringBuilder<A, B> &b)
     return a;
 }
 
-//
-// inline QAnyStringView members requiring QStringBuilder:
-//
-
-template <typename A, typename B>
-QAnyStringView::QAnyStringView(const QStringBuilder<A, B> &expr,
-                               typename QConcatenable<QStringBuilder<A, B>>::ConvertTo &&capacity)
-    : QAnyStringView(capacity = expr) {}
-
 QT_END_NAMESPACE
 
 #endif // QSTRINGBUILDER_H
diff --git a/tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp b/tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp
index 4433b8efbcd..be34d9aa8cd 100644
--- a/tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp
+++ b/tests/auto/corelib/text/qanystringview/tst_qanystringview.cpp
@@ -59,6 +59,16 @@ static_assert(CanConvert<QLatin1String>);
 static_assert(CanConvert<const char*>);
 static_assert(CanConvert<QByteArray>);
 
+template <typename T>
+struct ImplicitlyConvertibleTo
+{
+    operator T() const;
+};
+
+static_assert(CanConvert<ImplicitlyConvertibleTo<QString>>);
+static_assert(CanConvert<ImplicitlyConvertibleTo<QByteArray>>);
+static_assert(!CanConvert<ImplicitlyConvertibleTo<QLatin1StringView>>);
+
 // QAnyStringView qchar_does_not_compile() { return QAnyStringView(QChar('a')); }
 // QAnyStringView qlatin1string_does_not_compile() { return QAnyStringView(QLatin1String("a")); }
 // QAnyStringView const_char_star_does_not_compile() { return QAnyStringView("a"); }