SerializedAsyncContin:getAcquiredQutexHistory returns rval ref

This ensures that the caller takes ownership.

include/serializedAsynchronousContinuation.h

@@ -38,7 +38,8 @@ public:
 	}
 
 	// Return list of all qutexes in predecessors' LockSets; excludes self.
-	std::unique_ptr<std::forward_list<std::reference_wrapper<Qutex>>>
+	[[nodiscard]]
+	std::unique_ptr<std::forward_list<std::reference_wrapper<Qutex>>>&&
 	getAcquiredQutexHistory() const;
 
 public:

smocore/serializedAsynchronousContinuation.cpp

@@ -182,7 +182,7 @@ SerializedAsynchronousContinuation<OriginalCbFnT>
 #endif
 
 template <class OriginalCbFnT>
-std::unique_ptr<std::forward_list<std::reference_wrapper<Qutex>>>
+std::unique_ptr<std::forward_list<std::reference_wrapper<Qutex>>>&&
 SerializedAsynchronousContinuation<OriginalCbFnT>::getAcquiredQutexHistory()
 const
 {
@@ -213,7 +213,7 @@ const
 		}
 	}
 
-	return heldLocks;
+	return std::move(heldLocks);
 }
 
 // Explicit template instantiations for the types we need