Allow empty arg list in rpl next/error handlers.

Telegram/SourceFiles/boxes/edit_privacy_box.cpp

@@ -288,7 +288,7 @@ void EditPrivacyBox::createWidgets() {
 	auto createExceptionLink = [this](Exception exception) {
 		exceptionLink(exception).create(this, object_ptr<Ui::LinkButton>(this, exceptionLinkText(exception)), exceptionLinkMargins());
 		exceptionLink(exception)->heightValue()
-			| rpl::start_with_next([this](int) {
+			| rpl::start_with_next([this] {
 				resizeToWidth(width());
 			}, lifetime());
 		exceptionLink(exception)->entity()->setClickedCallback([this, exception] { editExceptionUsers(exception); });

Telegram/SourceFiles/boxes/notifications_box.cpp

@@ -129,7 +129,7 @@ void NotificationsBox::prepare() {
 	_countSlider->setActiveSectionFast(_oldCount - 1);
 	_countSlider->sectionActivated()
 		| rpl::start_with_next(
-			[this](int) { countChanged(); },
+			[this] { countChanged(); },
 			lifetime());
 
 	setMouseTracking(true);

Telegram/SourceFiles/boxes/peer_list_box.cpp

@@ -52,7 +52,7 @@ void PeerListBox::createMultiSelect() {
 	_select.create(this, std::move(entity));
 	_select->heightValue()
 		| rpl::start_with_next(
-			[this](int) { updateScrollSkips(); },
+			[this] { updateScrollSkips(); },
 			lifetime());
 	_select->entity()->setSubmittedCallback([this](bool chtrlShiftEnter) { content()->submitted(); });
 	_select->entity()->setQueryChangedCallback([this](const QString &query) { searchQueryChanged(query); });

Telegram/SourceFiles/boxes/stickers_box.cpp

@@ -246,7 +246,7 @@ void StickersBox::prepare() {
 		setNoContentMargin(true);
 		_tabs->sectionActivated()
 			| rpl::start_with_next(
-				[this](int) { switchTab(); },
+				[this] { switchTab(); },
 				lifetime());
 		refreshTabs();
 	}

Telegram/SourceFiles/chat_helpers/tabbed_panel.cpp

@@ -63,7 +63,7 @@ TabbedPanel::TabbedPanel(
 		}
 	});
 	_selector->showRequests()
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->showFromSelector();
 		}, lifetime());
 

Telegram/SourceFiles/chat_helpers/tabbed_selector.cpp

@@ -609,7 +609,7 @@ void TabbedSelector::createTabsSlider() {
 	_tabsSlider->setActiveSectionFast(static_cast<int>(_currentTabType));
 	_tabsSlider->sectionActivated()
 		| rpl::start_with_next(
-			[this](int) { switchTab(); },
+			[this] { switchTab(); },
 			lifetime());
 
 	_tabsSlider->resizeToWidth(width());

Telegram/SourceFiles/info/info_layer_wrap.cpp

@@ -81,7 +81,7 @@ object_ptr<TopBar> LayerWrap::createTopBar() {
 		result.data(),
 		st::infoLayerTopBarClose));
 	close->clicks()
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			_controller->hideSpecialLayer();
 		}, close->lifetime());
 	result->setTitle(TitleValue(

Telegram/SourceFiles/info/info_narrow_wrap.cpp

@@ -94,7 +94,7 @@ object_ptr<TopBar> NarrowWrap::createTopBar() {
 		st::infoLayerTopBar);
 	result->enableBackButton(true);
 	result->backRequest()
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->controller()->showBackFromStack();
 		}, result->lifetime());
 	result->setTitle(TitleValue(

Telegram/SourceFiles/info/info_top_bar.cpp

@@ -58,7 +58,7 @@ void TopBar::pushButton(object_ptr<Ui::RpWidget> button) {
 	auto weak = Ui::AttachParentChild(this, button);
 	_buttons.push_back(std::move(button));
 	weak->widthValue()
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->updateControlsGeometry(this->width());
 		}, _lifetime);
 }

Telegram/SourceFiles/info/profile/info_profile_button.cpp

@@ -52,7 +52,7 @@ Button *Button::toggleOn(rpl::producer<bool> &&toggled) {
 		false,
 		[this] { rtlupdate(toggleRect()); });
 	clicks()
-		| rpl::start_with_next([this](auto) {
+		| rpl::start_with_next([this] {
 			_toggle->setCheckedAnimated(!_toggle->checked());
 		}, lifetime());
 	std::move(toggled)

Telegram/SourceFiles/info/profile/info_profile_cover.cpp

@@ -254,16 +254,16 @@ void Cover::initViewers() {
 	using Flag = Notify::PeerUpdate::Flag;
 	PeerUpdateValue(_peer, Flag::PhotoChanged)
 		| rpl::start_with_next(
-			[this](auto&&) { this->refreshUserpicLink(); },
+			[this] { this->refreshUserpicLink(); },
 			lifetime());
 	PeerUpdateValue(_peer, Flag::NameChanged)
 		| rpl::start_with_next(
-			[this](auto&&) { this->refreshNameText(); },
+			[this] { this->refreshNameText(); },
 			lifetime());
 	PeerUpdateValue(_peer,
 		Flag::UserOnlineChanged | Flag::MembersChanged)
 		| rpl::start_with_next(
-			[this](auto&&) { this->refreshStatusText(); },
+			[this] { this->refreshStatusText(); },
 			lifetime());
 }
 

Telegram/SourceFiles/info/profile/info_profile_icon.cpp

@@ -44,7 +44,7 @@ FloatingIcon::FloatingIcon(
 	setAttribute(Qt::WA_TransparentForMouseEvents);
 	parent->widthValue()
 		| rpl::start_with_next(
-			[this](auto&&) { moveToLeft(0, 0); },
+			[this] { moveToLeft(0, 0); },
 			lifetime());
 }
 

Telegram/SourceFiles/info/profile/info_profile_inner_widget.cpp

@@ -203,7 +203,7 @@ object_ptr<Ui::RpWidget> InnerWidget::setupMuteToggle(
 	result->toggleOn(
 		NotificationsEnabledValue(_peer)
 	)->clicks()
-		| rpl::start_with_next([this](auto) {
+		| rpl::start_with_next([this] {
 			App::main()->updateNotifySetting(
 				_peer,
 				_peer->isMuted()
@@ -239,7 +239,7 @@ void InnerWidget::setupUserButtons(
 		_controller->historyPeer.value()
 		| rpl::map($1 != user)
 	)->entity()->clicks()
-		| rpl::start_with_next([this, user](auto&&) {
+		| rpl::start_with_next([this, user] {
 			_controller->showPeerHistory(
 				user,
 				Ui::ShowWay::Forward);
@@ -250,7 +250,7 @@ void InnerWidget::setupUserButtons(
 	)->toggleOn(
 		CanAddContactValue(user)
 	)->entity()->clicks()
-		| rpl::start_with_next([user](auto&&) {
+		| rpl::start_with_next([user] {
 			auto firstName = user->firstName;
 			auto lastName = user->lastName;
 			auto phone = user->phone().isEmpty()
@@ -310,7 +310,7 @@ object_ptr<Ui::RpWidget> InnerWidget::setupSharedMedia(
 				return phrase(lt_count, count);
 			}
 		)->entity()->clicks()
-			| rpl::start_with_next([peer = _peer, type](auto&&) {
+			| rpl::start_with_next([peer = _peer, type] {
 				SharedMediaShowOverview(type, App::history(peer));
 			}, content->lifetime());
 	};
@@ -321,7 +321,7 @@ object_ptr<Ui::RpWidget> InnerWidget::setupSharedMedia(
 				return lng_profile_common_groups(lt_count, count);
 			}
 		)->entity()->clicks()
-			| rpl::start_with_next([peer = _peer](auto&&) {
+			| rpl::start_with_next([peer = _peer] {
 				App::main()->showSection(
 					::Profile::CommonGroups::SectionMemento(
 						peer->asUser()),
@@ -389,7 +389,7 @@ object_ptr<Ui::RpWidget> InnerWidget::setupUserActions(
 		)->toggleOn(
 			std::move(toggleOn)
 		)->entity()->clicks()
-			| rpl::start_with_next([callback = std::move(callback)](auto&&) {
+			| rpl::start_with_next([callback = std::move(callback)] {
 				callback();
 			}, result->lifetime());
 	};
@@ -432,7 +432,7 @@ object_ptr<Ui::RpWidget> InnerWidget::setupUserActions(
 			st::infoBlockButtonSkip));
 
 		auto text = PeerUpdateValue(user, Notify::PeerUpdate::Flag::UserIsBlocked)
-			| rpl::map([user](auto&&) -> rpl::producer<QString> {
+			| rpl::map([user]() -> rpl::producer<QString> {
 				switch (user->blockStatus()) {
 				case UserData::BlockStatus::Blocked:
 					return Lang::Viewer(lng_profile_unblock_user);

Telegram/SourceFiles/info/profile/info_profile_members.cpp

@@ -118,7 +118,7 @@ void Members::setupButtons() {
 		}, _addMember->lifetime());
 	_addMember->showOn(rpl::duplicate(addMemberShown));
 	_addMember->clicks() // TODO throttle(ripple duration)
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->addMember();
 		}, _addMember->lifetime());
 
@@ -128,18 +128,18 @@ void Members::setupButtons() {
 		| rpl::start_spawning(lifetime());
 	_search->showOn(rpl::duplicate(searchShown));
 	_search->clicks()
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->showSearch();
 		}, _search->lifetime());
 	_cancelSearch->clicks()
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->cancelSearch();
 		}, _cancelSearch->lifetime());
 
 	rpl::combine(
 		std::move(addMemberShown),
 		std::move(searchShown))
-		| rpl::start_with_next([this](auto&&) {
+		| rpl::start_with_next([this] {
 			this->resizeToWidth(width());
 		}, lifetime());
 

Telegram/SourceFiles/info/profile/info_profile_values.cpp

@@ -68,7 +68,7 @@ rpl::producer<TextWithEntities> PhoneValue(
 	return PeerUpdateValue(
 			user,
 			Notify::PeerUpdate::Flag::UserPhoneChanged)
-		| rpl::map([user](auto&&) {
+		| rpl::map([user] {
 			return App::formatPhone(user->phone());
 		})
 		| WithEmptyEntities();
@@ -79,7 +79,7 @@ rpl::producer<TextWithEntities> BioValue(
 	return PeerUpdateValue(
 			user,
 			Notify::PeerUpdate::Flag::AboutChanged)
-		| rpl::map([user](auto&&) { return user->about(); })
+		| rpl::map([user] { return user->about(); })
 		| WithEmptyEntities();
 }
 
@@ -88,7 +88,7 @@ rpl::producer<QString> PlainUsernameViewer(
 	return PeerUpdateValue(
 			peer,
 			Notify::PeerUpdate::Flag::UsernameChanged)
-		| rpl::map([peer](auto&&) {
+		| rpl::map([peer] {
 			return peer->userName();
 		});
 }
@@ -110,7 +110,7 @@ rpl::producer<TextWithEntities> AboutValue(
 		return PeerUpdateValue(
 				channel,
 				Notify::PeerUpdate::Flag::AboutChanged)
-			| rpl::map([channel](auto&&) { return channel->about(); })
+			| rpl::map([channel] { return channel->about(); })
 			| WithEmptyEntities();
 	}
 	return rpl::single(TextWithEntities{});
@@ -132,7 +132,7 @@ rpl::producer<bool> NotificationsEnabledValue(
 	return PeerUpdateValue(
 			peer,
 			Notify::PeerUpdate::Flag::NotificationsEnabled)
-		| rpl::map([peer](auto&&) { return !peer->isMuted(); });
+		| rpl::map([peer] { return !peer->isMuted(); });
 }
 
 rpl::producer<bool> IsContactValue(
@@ -140,7 +140,7 @@ rpl::producer<bool> IsContactValue(
 	return PeerUpdateValue(
 			user,
 			Notify::PeerUpdate::Flag::UserIsContact)
-		| rpl::map([user](auto&&) { return user->isContact(); });
+		| rpl::map([user] { return user->isContact(); });
 }
 
 rpl::producer<bool> CanShareContactValue(
@@ -148,7 +148,7 @@ rpl::producer<bool> CanShareContactValue(
 	return PeerUpdateValue(
 			user,
 			Notify::PeerUpdate::Flag::UserCanShareContact)
-		| rpl::map([user](auto&&) {
+		| rpl::map([user] {
 			return user->canShareThisContact();
 		});
 }
@@ -168,7 +168,7 @@ rpl::producer<int> MembersCountValue(
 		return PeerUpdateValue(
 				peer,
 				Notify::PeerUpdate::Flag::MembersChanged)
-			| rpl::map([chat](auto&&) {
+			| rpl::map([chat] {
 				return chat->amIn()
 					? qMax(chat->count, chat->participants.size())
 					: 0;
@@ -177,7 +177,7 @@ rpl::producer<int> MembersCountValue(
 		return PeerUpdateValue(
 				peer,
 				Notify::PeerUpdate::Flag::MembersChanged)
-			| rpl::map([channel](auto &&) {
+			| rpl::map([channel] {
 				auto canViewCount = channel->canViewMembers()
 					|| !channel->isMegagroup();
 				return canViewCount
@@ -215,7 +215,7 @@ rpl::producer<int> CommonGroupsCountValue(
 	return PeerUpdateValue(
 		user,
 		Notify::PeerUpdate::Flag::UserCommonChatsChanged)
-		| rpl::map([user](auto&&) {
+		| rpl::map([user] {
 			return user->commonChatsCount();
 		});
 }
@@ -226,14 +226,14 @@ rpl::producer<bool> CanAddMemberValue(
 		return PeerUpdateValue(
 			chat,
 			Notify::PeerUpdate::Flag::ChatCanEdit)
-			| rpl::map([chat](auto&&) {
+			| rpl::map([chat] {
 				return chat->canEdit();
 			});
 	} else if (auto channel = peer->asChannel()) {
 		return PeerUpdateValue(
 			channel,
 			Notify::PeerUpdate::Flag::ChannelRightsChanged)
-			| rpl::map([channel](auto&&) {
+			| rpl::map([channel] {
 				return channel->canAddMembers();
 			});
 	}

Telegram/SourceFiles/lang/lang_instance.cpp

@@ -504,7 +504,7 @@ rpl::producer<QString> Viewer(LangKey key) {
 		rpl::single(Current().getValue(key))
 		| then(
 			base::ObservableViewer(Current().updated())
-			| rpl::map([=](auto&&) {
+			| rpl::map([=] {
 				return Current().getValue(key);
 			}));
 }

Telegram/SourceFiles/mainwidget.cpp

@@ -1847,7 +1847,7 @@ void MainWidget::createPlayer() {
 		_player.create(this);
 		_player->heightValue()
 			| rpl::start_with_next(
-				[this](int) { playerHeightUpdated(); },
+				[this] { playerHeightUpdated(); },
 				lifetime());
 		_player->entity()->setCloseCallback([this] { closeBothPlayers(); });
 		_playerVolume.create(this);

Telegram/SourceFiles/rpl/details/callable.h

@@ -91,31 +91,62 @@ struct is_callable<Method>
 template <typename Method, typename Arg>
 struct is_callable<Method, Arg>
 	: std::bool_constant<
-		is_callable_plain_v<Method, Arg>
-		|| is_callable_tuple_v<Method, Arg>> {
+		is_callable_plain_v<Method, Arg> ||
+		is_callable_tuple_v<Method, Arg> ||
+		is_callable_plain_v<Method>> {
 };
 
 template <typename Method, typename ...Args>
 constexpr bool is_callable_v = is_callable<Method, Args...>::value;
 
+enum class CallableArgTag {
+	Plain,
+	Tuple,
+	Empty,
+};
+template <CallableArgTag Arg>
+using callable_arg_tag = std::integral_constant<CallableArgTag, Arg>;
+
 template <typename Method, typename Arg>
-inline decltype(auto) callable_helper(Method &&method, Arg &&arg, std::true_type) {
+inline decltype(auto) callable_helper(
+		Method &&method,
+		Arg &&arg,
+		callable_arg_tag<CallableArgTag::Plain>) {
 	return std::forward<Method>(method)(std::forward<Arg>(arg));
 }
 
 template <typename Method, typename Arg>
-inline decltype(auto) callable_helper(Method &&method, Arg &&arg, std::false_type) {
+inline decltype(auto) callable_helper(
+		Method &&method,
+		Arg &&arg,
+		callable_arg_tag<CallableArgTag::Tuple>) {
 	return std::apply(
 		std::forward<Method>(method),
 		std::forward<Arg>(arg));
 }
 
+template <typename Method, typename Arg>
+inline decltype(auto) callable_helper(
+		Method &&method,
+		Arg &&,
+		callable_arg_tag<CallableArgTag::Empty>) {
+	return std::forward<Method>(method)();
+}
+
 template <typename Method, typename Arg>
 inline decltype(auto) callable_invoke(Method &&method, Arg &&arg) {
+	// #TODO if constexpr
+	constexpr auto kTag = is_callable_plain_v<Method, Arg>
+		? CallableArgTag::Plain
+		: is_callable_tuple_v<Method, Arg>
+		? CallableArgTag::Tuple
+		: is_callable_v<Method>
+		? CallableArgTag::Empty
+		: throw "Bad callable_invoke instance.";
 	return callable_helper(
 		std::forward<Method>(method),
 		std::forward<Arg>(arg),
-		is_callable_plain<Method, Arg>());
+		callable_arg_tag<kTag>());
 }
 
 template <typename Method, typename Arg>

Telegram/SourceFiles/settings/settings_scale_widget.cpp

@@ -62,7 +62,7 @@ void ScaleWidget::createControls() {
 	_scale->setActiveSectionFast(cEvalScale(cConfigScale()) - 1);
 	_scale->sectionActivated()
 		| rpl::start_with_next(
-			[this](int) { scaleChanged(); },
+			[this] { scaleChanged(); },
 			lifetime());
 }
 

Telegram/SourceFiles/ui/wrap/vertical_layout.cpp

@@ -115,7 +115,7 @@ RpWidget *VerticalLayout::addChild(
 			width() - margins.left() - margins.right(),
 			height() - margins.top() - margins.bottom());
 		weak->heightValue()
-			| rpl::start_with_next_done([this, weak](int) {
+			| rpl::start_with_next_done([this, weak] {
 				childHeightUpdated(weak);
 			}, [this, weak] {
 				removeChild(weak);

Telegram/SourceFiles/window/top_bar_widget.cpp

@@ -119,7 +119,7 @@ TopBarWidget::TopBarWidget(
 		Auth().data().thirdSectionInfoEnabledValue(),
 		Auth().data().tabbedReplacedWithInfoValue())
 		| rpl::start_with_next(
-			[this](auto&&) { updateInfoToggleActive(); },
+			[this] { updateInfoToggleActive(); },
 			lifetime());
 
 	setCursor(style::cur_pointer);