Workaround for boost::asio::basic_streambuf type check

CHANGELOG.md

@@ -1,3 +1,9 @@
+Version 45
+
+* Workaround for boost::asio::basic_streambuf type check
+
+--------------------------------------------------------------------------------
+
 Version 44
 
 * Use BOOST_THROW_EXCEPTION

include/beast/core/detail/type_traits.hpp

@@ -345,4 +345,14 @@ public:
 } // detail
 } // beast
 
+namespace boost {
+namespace asio {
+
+// for is_dynamic_buffer
+template<class Allocator>
+class basic_streambuf;
+
+} // asio
+} // boost
+
 #endif

include/beast/core/type_traits.hpp

@@ -56,17 +56,12 @@ struct is_dynamic_buffer : std::false_type {};
 template<class T>
 struct is_dynamic_buffer<T, beast::detail::void_t<
         decltype(
-    // expressions
     std::declval<std::size_t&>() =
         std::declval<T const&>().size(),
     std::declval<std::size_t&>() =
         std::declval<T const&>().max_size(),
-#if 0
-    // This check is skipped because boost::asio
-    // types are not up to date with net-ts.
     std::declval<std::size_t&>() =
         std::declval<T const&>().capacity(),
-#endif
     std::declval<T&>().commit(std::declval<std::size_t>()),
     std::declval<T&>().consume(std::declval<std::size_t>()),
         (void)0)>> : std::integral_constant<bool,
@@ -82,6 +77,14 @@ struct is_dynamic_buffer<T, beast::detail::void_t<
         >
 {
 };
+
+// Special case for Boost.Asio which doesn't adhere to
+// net-ts but still provides a read_size_helper so things work
+template<class Allocator>
+struct is_dynamic_buffer<
+    boost::asio::basic_streambuf<Allocator>> : std::true_type
+{
+};
 #endif
 
 //------------------------------------------------------------------------------