Long live QtFuture::makeReadyVoidFuture() and QtFuture::makeReadyValueFuture()

[ChangeLog][QtCore][QFuture] Added QtFuture::makeReadyVoidFuture()
and QtFuture::makeReadyValueFuture().

Basically, these methods behave like QtFuture::makeReadyFuture(), but
QtFuture::makeReadyValueFuture() does not have a "const QList<T> &"
specialization returning QFuture<T> instead of QFuture<QList<T>>,
which allows it to always behave consistently.

This patch also introduces usage of the new methods around qtbase.

Task-number: QTBUG-109677
Change-Id: I89df8b26d82c192baad69efb5df517a8b182995f
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

1 files changed, 12 insertions, 15 deletions

diff --git a/src/corelib/thread/qfuture_impl.h b/src/corelib/thread/qfuture_impl.h
index 5ed7a4d27f..b282903405 100644
--- a/src/corelib/thread/qfuture_impl.h
+++ b/src/corelib/thread/qfuture_impl.h
@@ -996,8 +996,8 @@ static QFuture<ValueType> makeReadyRangeFuture(std::initializer_list<ValueType>
     return QtPrivate::makeReadyRangeFutureImpl(QList<ValueType>{values});
 }
 
-template<typename T, typename = QtPrivate::EnableForNonVoid<T>>
-static QFuture<std::decay_t<T>> makeReadyFuture(T &&value)
+template<typename T>
+static QFuture<std::decay_t<T>> makeReadyValueFuture(T &&value)
 {
     QFutureInterface<std::decay_t<T>> promise;
     promise.reportStarted();
@@ -1007,20 +1007,17 @@ static QFuture<std::decay_t<T>> makeReadyFuture(T &&value)
     return promise.future();
 }
 
-#if defined(Q_QDOC)
-static QFuture<void> makeReadyFuture()
-#else
-template<typename T = void>
-static QFuture<T> makeReadyFuture()
-#endif
-{
-    QFutureInterface<T> promise;
-    promise.reportStarted();
-    promise.reportFinished();
+Q_CORE_EXPORT QFuture<void> makeReadyVoidFuture(); // implemented in qfutureinterface.cpp
 
-    return promise.future();
+template<typename T, typename = QtPrivate::EnableForNonVoid<T>>
+static QFuture<std::decay_t<T>> makeReadyFuture(T &&value)
+{
+    return makeReadyValueFuture(std::forward<T>(value));
 }
 
+// the void specialization is moved to the end of qfuture.h, because it now
+// uses makeReadyVoidFuture() and required QFuture<void> to be defined.
+
 template<typename T>
 static QFuture<T> makeReadyFuture(const QList<T> &values)
 {
@@ -1127,7 +1124,7 @@ QFuture<OutputSequence> whenAllImpl(InputIt first, InputIt last)
 {
     const qsizetype size = std::distance(first, last);
     if (size == 0)
-        return QtFuture::makeReadyFuture(OutputSequence());
+        return QtFuture::makeReadyValueFuture(OutputSequence());
 
     const auto context = std::make_shared<QtPrivate::WhenAllContext<OutputSequence>>(size);
     context->futures.resize(size);
@@ -1166,7 +1163,7 @@ QFuture<QtFuture::WhenAnyResult<typename Future<ValueType>::type>> whenAnyImpl(I
 
     const qsizetype size = std::distance(first, last);
     if (size == 0) {
-        return QtFuture::makeReadyFuture(
+        return QtFuture::makeReadyValueFuture(
                 QtFuture::WhenAnyResult { qsizetype(-1), QFuture<PackagedType>() });
     }