From c91327645b1a659a5b749264d7fb3447c9c43c3f Mon Sep 17 00:00:00 2001
From: Jarek Kobus <jaroslaw.kobus@qt.io>
Date: Wed, 30 Sep 2020 21:01:36 +0200
Subject: [PATCH] QtConcurrent: Reuse ArgResolver from qfuture_impl.h

Task-number: QTBUG-83331
Change-Id: I572f68f6d3be4a50970d8d77d070f175be3ec785
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
---
 src/concurrent/qtconcurrentrun.h  | 104 ++----------------------------
 src/corelib/thread/qfuture_impl.h |  46 +++++++++++++
 2 files changed, 50 insertions(+), 100 deletions(-)

diff --git a/src/concurrent/qtconcurrentrun.h b/src/concurrent/qtconcurrentrun.h
index 5804393e25..79322b925f 100644
--- a/src/concurrent/qtconcurrentrun.h
+++ b/src/concurrent/qtconcurrentrun.h
@@ -73,102 +73,6 @@ namespace QtConcurrent {
 
 namespace QtConcurrent {
 
-// Note: It's a copy taken from qfuture_impl.h with some specialization added
-// TODO: Get rid of the code repetition and unify this for both purposes, see QTBUG-83331
-template<typename...>
-struct ArgsType;
-
-template<typename Arg, typename... Args>
-struct ArgsType<Arg, Args...>
-{
-    using PromiseType = void;
-    static const bool IsPromise = false;
-};
-
-// Note: this specialization was added
-template<typename Arg, typename... Args>
-struct ArgsType<QPromise<Arg> &, Args...>
-{
-    using PromiseType = Arg;
-    static const bool IsPromise = true;
-};
-
-template<>
-struct ArgsType<>
-{
-    using PromiseType = void;
-    static const bool IsPromise = false;
-};
-
-template<typename F>
-struct ArgResolver : ArgResolver<decltype(&std::decay_t<F>::operator())>
-{
-};
-
-// Note: this specialization was added, see callableObjectWithState() test in qtconcurrentrun
-template<typename F>
-struct ArgResolver<std::reference_wrapper<F>> : ArgResolver<decltype(&std::decay_t<F>::operator())>
-{
-};
-
-template<typename R, typename... Args>
-struct ArgResolver<R(Args...)> : public ArgsType<Args...>
-{
-};
-
-template<typename R, typename... Args>
-struct ArgResolver<R (*)(Args...)> : public ArgsType<Args...>
-{
-};
-
-// Note: this specialization was added, see light() test in qtconcurrentrun
-template<typename R, typename... Args>
-struct ArgResolver<R (*&)(Args...)> : public ArgsType<Args...>
-{
-};
-
-// Note: this specialization was added, see light() test in qtconcurrentrun
-template<typename R, typename... Args>
-struct ArgResolver<R (* const)(Args...)> : public ArgsType<Args...>
-{
-};
-
-template<typename R, typename... Args>
-struct ArgResolver<R (&)(Args...)> : public ArgsType<Args...>
-{
-};
-
-template<typename Class, typename R, typename... Args>
-struct ArgResolver<R (Class::*)(Args...)> : public ArgsType<Args...>
-{
-};
-
-template<typename Class, typename R, typename... Args>
-struct ArgResolver<R (Class::*)(Args...) noexcept> : public ArgsType<Args...>
-{
-};
-
-template<typename Class, typename R, typename... Args>
-struct ArgResolver<R (Class::*)(Args...) const> : public ArgsType<Args...>
-{
-};
-
-template<typename Class, typename R, typename... Args>
-struct ArgResolver<R (Class::*)(Args...) const noexcept> : public ArgsType<Args...>
-{
-};
-
-// Note: this specialization was added, see crefFunction() test in qtconcurrentrun
-template<typename Class, typename R, typename... Args>
-struct ArgResolver<R (Class::* const)(Args...) const> : public ArgsType<Args...>
-{
-};
-
-template<typename Class, typename R, typename... Args>
-struct ArgResolver<R (Class::* const)(Args...) const noexcept> : public ArgsType<Args...>
-{
-};
-
 template <class Function, class ...Args>
 [[nodiscard]]
 auto run(QThreadPool *pool, Function &&f, Args &&...args)
@@ -196,8 +100,8 @@ template <class Function, class ...Args>
 [[nodiscard]]
 auto runWithPromise(QThreadPool *pool, Function &&f, Args &&...args)
 {
-    static_assert(ArgResolver<Function>::IsPromise, "The first argument of passed callable object isn't a QPromise<T> & type.");
-    using PromiseType = typename ArgResolver<Function>::PromiseType;
+    static_assert(QtPrivate::ArgResolver<Function>::IsPromise, "The first argument of passed callable object isn't a QPromise<T> & type.");
+    using PromiseType = typename QtPrivate::ArgResolver<Function>::PromiseType;
     return runWithPromise<PromiseType>(pool, std::forward<Function>(f), std::forward<Args>(args)...);
 }
 
@@ -205,8 +109,8 @@ template <class Function, class ...Args>
 [[nodiscard]]
 auto runWithPromise(QThreadPool *pool, std::reference_wrapper<const Function> &&functionWrapper, Args &&...args)
 {
-    static_assert(ArgResolver<const Function>::IsPromise, "The first argument of passed callable object isn't a QPromise<T> & type.");
-    using PromiseType = typename ArgResolver<const Function>::PromiseType;
+    static_assert(QtPrivate::ArgResolver<const Function>::IsPromise, "The first argument of passed callable object isn't a QPromise<T> & type.");
+    using PromiseType = typename QtPrivate::ArgResolver<const Function>::PromiseType;
     return runWithPromise<PromiseType>(pool, std::forward<const Function>(functionWrapper.get()), std::forward<Args>(args)...);
 }
 
diff --git a/src/corelib/thread/qfuture_impl.h b/src/corelib/thread/qfuture_impl.h
index 883f8d4f09..bd3976f990 100644
--- a/src/corelib/thread/qfuture_impl.h
+++ b/src/corelib/thread/qfuture_impl.h
@@ -59,6 +59,8 @@ template<class T>
 class QFuture;
 template<class T>
 class QFutureInterface;
+template<class T>
+class QPromise;
 
 namespace QtFuture {
 enum class Launch { Sync, Async, Inherit };
@@ -121,6 +123,8 @@ template<typename Arg, typename... Args>
 struct ArgsType<Arg, Args...>
 {
     using First = Arg;
+    using PromiseType = void;
+    static const bool IsPromise = false;
     static const bool HasExtraArgs = (sizeof...(Args) > 0);
     using AllArgs =
             std::conditional_t<HasExtraArgs, std::tuple<std::decay_t<Arg>, std::decay_t<Args>...>,
@@ -130,10 +134,27 @@ struct ArgsType<Arg, Args...>
     static const bool CanInvokeWithArgs = std::is_invocable_v<Callable, Class, Arg, Args...>;
 };
 
+template<typename Arg, typename... Args>
+struct ArgsType<QPromise<Arg> &, Args...>
+{
+    using First = QPromise<Arg> &;
+    using PromiseType = Arg;
+    static const bool IsPromise = true;
+    static const bool HasExtraArgs = (sizeof...(Args) > 0);
+    using AllArgs =
+            std::conditional_t<HasExtraArgs, std::tuple<std::decay_t<QPromise<Arg> &>, std::decay_t<Args>...>,
+                               std::decay_t<QPromise<Arg> &>>;
+
+    template<class Class, class Callable>
+    static const bool CanInvokeWithArgs = std::is_invocable_v<Callable, Class, QPromise<Arg> &, Args...>;
+};
+
 template<>
 struct ArgsType<>
 {
     using First = void;
+    using PromiseType = void;
+    static const bool IsPromise = false;
     static const bool HasExtraArgs = false;
     using AllArgs = void;
 
@@ -146,6 +167,11 @@ struct ArgResolver : ArgResolver<decltype(&std::decay_t<F>::operator())>
 {
 };
 
+template<typename F>
+struct ArgResolver<std::reference_wrapper<F>> : ArgResolver<decltype(&std::decay_t<F>::operator())>
+{
+};
+
 template<typename R, typename... Args>
 struct ArgResolver<R(Args...)> : public ArgsType<Args...>
 {
@@ -156,6 +182,16 @@ struct ArgResolver<R (*)(Args...)> : public ArgsType<Args...>
 {
 };
 
+template<typename R, typename... Args>
+struct ArgResolver<R (*&)(Args...)> : public ArgsType<Args...>
+{
+};
+
+template<typename R, typename... Args>
+struct ArgResolver<R (* const)(Args...)> : public ArgsType<Args...>
+{
+};
+
 template<typename R, typename... Args>
 struct ArgResolver<R (&)(Args...)> : public ArgsType<Args...>
 {
@@ -181,6 +217,16 @@ struct ArgResolver<R (Class::*)(Args...) const noexcept> : public ArgsType<Args.
 {
 };
 
+template<typename Class, typename R, typename... Args>
+struct ArgResolver<R (Class::* const)(Args...) const> : public ArgsType<Args...>
+{
+};
+
+template<typename Class, typename R, typename... Args>
+struct ArgResolver<R (Class::* const)(Args...) const noexcept> : public ArgsType<Args...>
+{
+};
+
 template<class Class, class Callable>
 using EnableIfInvocable = std::enable_if_t<
         QtPrivate::ArgResolver<Callable>::template CanInvokeWithArgs<Class, Callable>>;