is_completion_handler, type_traits.hpp are deprecated (API Change):

* is_completion_handler is deprecated
* type_traits.hpp is a deprecated include

These items will be removed in the next version

* Include the new header file for the types needed:
  - stream_traits.hpp
  - file_base.hpp
* Use std::is_invocable instead of is_completion_handler

test/beast/core/file_stdio.cpp

@@ -12,7 +12,6 @@
 
 #include "file_test.hpp"
 
-#include <boost/beast/core/type_traits.hpp>
 #include <boost/beast/_experimental/unit_test/suite.hpp>
 
 namespace boost {