Fix bind_cancellation_slot to not require async_result::return_type.

felipealmeida · Aug 1, 2023 · 9009036 · 9009036
1 parent f042b0b
commit 9009036
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Showing 2 changed files with 27 additions and 9 deletions.
diff --git a/include/boost/asio/bind_cancellation_slot.hpp b/include/boost/asio/bind_cancellation_slot.hpp
@@ -474,20 +474,40 @@ namespace detail {
 
 template <typename TargetAsyncResult,
   typename CancellationSlot, typename = void>
-struct cancellation_slot_binder_async_result_completion_handler_type
+class cancellation_slot_binder_completion_handler_async_result
 {
+public:
+  template <typename T>
+  explicit cancellation_slot_binder_completion_handler_async_result(T&)
+  {
+  }
 };
 
 template <typename TargetAsyncResult, typename CancellationSlot>
-struct cancellation_slot_binder_async_result_completion_handler_type<
+class cancellation_slot_binder_completion_handler_async_result<
   TargetAsyncResult, CancellationSlot,
   typename void_type<
     typename TargetAsyncResult::completion_handler_type
   >::type>
 {
+public:
   typedef cancellation_slot_binder<
     typename TargetAsyncResult::completion_handler_type, CancellationSlot>
       completion_handler_type;
+
+  explicit cancellation_slot_binder_completion_handler_async_result(
+      typename TargetAsyncResult::completion_handler_type& handler)
+    : target_(handler)
+  {
+  }
+
+  typename TargetAsyncResult::return_type get()
+  {
+    return target_.get();
+  }
+
+private:
+  TargetAsyncResult target_;
 };
 
 template <typename TargetAsyncResult, typename = void>
@@ -509,22 +529,18 @@ struct cancellation_slot_binder_async_result_return_type<
 
 template <typename T, typename CancellationSlot, typename Signature>
 class async_result<cancellation_slot_binder<T, CancellationSlot>, Signature> :
-  public detail::cancellation_slot_binder_async_result_completion_handler_type<
+  public detail::cancellation_slot_binder_completion_handler_async_result<
     async_result<T, Signature>, CancellationSlot>,
   public detail::cancellation_slot_binder_async_result_return_type<
     async_result<T, Signature> >
 {
 public:
   explicit async_result(cancellation_slot_binder<T, CancellationSlot>& b)
-    : target_(b.get())
+    : detail::cancellation_slot_binder_completion_handler_async_result<
+        async_result<T, Signature>, CancellationSlot>(b.get())
   {
   }
 
-  typename async_result<T, Signature>::return_type get()
-  {
-    return target_.get();
-  }
-
   template <typename Initiation>
   struct init_wrapper
   {

diff --git a/test/bind_cancellation_slot.cpp b/test/bind_cancellation_slot.cpp
@@ -149,7 +149,9 @@ template <>
 class async_result<incrementer_token_v2, void(boost::system::error_code)>
 {
 public:
+#if !defined(BOOST_ASIO_HAS_RETURN_TYPE_DEDUCTION)
   typedef void return_type;
+#endif // !defined(BOOST_ASIO_HAS_RETURN_TYPE_DEDUCTION)
 
 #if defined(BOOST_ASIO_HAS_VARIADIC_TEMPLATES)