Fix deprecations and compile warnings (#34)

- Use std::invoke_result, fallback to std::result_of on C++11/14.
- Use RVO instead of std::move (GCC warning: redundant-move).
- Replace QSharedPointer with std::shared_ptr (GCC warning: unititialized value).
- QLinkedList is deprecated in Qt 5.15.

src/qtpromise/qpromise_p.h

@@ -34,6 +34,14 @@ class QPromiseReject;
 
 namespace QtPromisePrivate {
 
+// Use std::invoke_result for C++17 and beyond
+#if (__cplusplus >= 201703L) || defined(_MSVC_LANG) && (_MSVC_LANG >= 201703L)
+using std::invoke_result;
+#else
+template<class F, class... ArgTypes>
+using invoke_result = std::result_of<F(ArgTypes...)>;
+#endif
+
 // https://stackoverflow.com/a/21653558
 template<typename F>
 static void qtpromise_defer(F&& f, const QPointer<QThread>& thread)
@@ -138,7 +146,7 @@ struct PromiseDeduce<QtPromise::QPromise<T>> : public PromiseDeduce<T>
 template<typename Functor, typename... Args>
 struct PromiseFunctor
 {
-    using ResultType = typename std::result_of<Functor(Args...)>::type;
+    using ResultType = typename invoke_result<Functor, Args...>::type;
     using PromiseType = typename PromiseDeduce<ResultType>::Type;
 };
 
@@ -231,7 +239,7 @@ struct PromiseDispatch<void>
 template<typename T, typename THandler, typename TArg = typename ArgsOf<THandler>::first>
 struct PromiseHandler
 {
-    using ResType = typename std::result_of<THandler(T)>::type;
+    using ResType = typename invoke_result<THandler, T>::type;
     using Promise = typename PromiseDeduce<ResType>::Type;
 
     template<typename TResolve, typename TReject>
@@ -247,7 +255,7 @@ struct PromiseHandler
 template<typename T, typename THandler>
 struct PromiseHandler<T, THandler, void>
 {
-    using ResType = typename std::result_of<THandler()>::type;
+    using ResType = typename invoke_result<THandler>::type;
     using Promise = typename PromiseDeduce<ResType>::Type;
 
     template<typename TResolve, typename TReject>
@@ -263,7 +271,7 @@ struct PromiseHandler<T, THandler, void>
 template<typename THandler>
 struct PromiseHandler<void, THandler, void>
 {
-    using ResType = typename std::result_of<THandler()>::type;
+    using ResType = typename invoke_result<THandler>::type;
     using Promise = typename PromiseDeduce<ResType>::Type;
 
     template<typename TResolve, typename TReject>
@@ -312,7 +320,7 @@ struct PromiseHandler<void, std::nullptr_t, void>
 template<typename T, typename THandler, typename TArg = typename ArgsOf<THandler>::first>
 struct PromiseCatcher
 {
-    using ResType = typename std::result_of<THandler(TArg)>::type;
+    using ResType = typename invoke_result<THandler, TArg>::type;
 
     template<typename TResolve, typename TReject>
     static std::function<void(const PromiseError&)>
@@ -333,7 +341,7 @@ struct PromiseCatcher
 template<typename T, typename THandler>
 struct PromiseCatcher<T, THandler, void>
 {
-    using ResType = typename std::result_of<THandler()>::type;
+    using ResType = typename invoke_result<THandler>::type;
 
     template<typename TResolve, typename TReject>
     static std::function<void(const PromiseError&)>
@@ -371,7 +379,7 @@ struct PromiseMapper
 template<typename T, typename F, template<typename, typename...> class Sequence, typename... Args>
 struct PromiseMapper<Sequence<T, Args...>, F>
 {
-    using ReturnType = typename std::result_of<F(T, int)>::type;
+    using ReturnType = typename invoke_result<F, T, int>::type;
     using ResultType = QVector<typename PromiseDeduce<ReturnType>::Type::Type>;
     using PromiseType = QtPromise::QPromise<ResultType>;
 };

src/qtpromise/qpromiseconnections.h

@@ -8,14 +8,15 @@
 #ifndef QTPROMISE_QPROMISECONNECTIONS_H
 #define QTPROMISE_QPROMISECONNECTIONS_H
 
-#include <QtCore/QSharedPointer>
+#include <QtCore/QObject>
+#include <memory>
 
 namespace QtPromise {
 
 class QPromiseConnections
 {
 public:
-    QPromiseConnections() : m_d(QSharedPointer<Data>::create()) { }
+    QPromiseConnections() : m_d(std::make_shared<Data>()) { }
 
     int count() const { return m_d->connections.count(); }
 
@@ -48,7 +49,7 @@ private:
         }
     };
 
-    QSharedPointer<Data> m_d;
+    std::shared_ptr<Data> m_d;
 };
 
 } // namespace QtPromise

src/qtpromise/qpromisehelpers.h

@@ -32,7 +32,7 @@ static inline typename QtPromisePrivate::PromiseDeduce<T>::Type resolve(T&& valu
 template<typename T>
 static inline QPromise<T> resolve(QPromise<T> value)
 {
-    return std::move(value);
+    return value;
 }
 
 static inline QPromise<void> resolve()

tests/auto/qtpromise/helpers/tst_reduce.cpp

@@ -290,7 +290,10 @@ void tst_helpers_reduce::functorThrows()
 
 void tst_helpers_reduce::sequenceTypes()
 {
+#if (QT_VERSION < QT_VERSION_CHECK(5, 15, 0))
+    // QLinkedList is deprecated since Qt 5.15.
     SequenceTester<QLinkedList<QPromise<int>>>::exec();
+#endif
     SequenceTester<QList<QPromise<int>>>::exec();
     SequenceTester<QVector<QPromise<int>>>::exec();
     SequenceTester<std::list<QPromise<int>>>::exec();

tests/auto/qtpromise/qpromise/tst_reduce.cpp

@@ -283,7 +283,10 @@ void tst_qpromise_reduce::functorThrows()
 
 void tst_qpromise_reduce::sequenceTypes()
 {
+#if (QT_VERSION < QT_VERSION_CHECK(5, 15, 0))
+    // QLinkedList is deprecated since Qt 5.15.
     SequenceTester<QLinkedList<QPromise<int>>>::exec();
+#endif
     SequenceTester<QList<QPromise<int>>>::exec();
     SequenceTester<QVector<QPromise<int>>>::exec();
     SequenceTester<std::list<QPromise<int>>>::exec();