bind_handler works with boost placeholders

CHANGELOG.md

@@ -2,6 +2,7 @@ Version 154:
 
 * Type check completion handlers
 * bind_handler doc update
+* bind_handler works with boost placeholders
 
 --------------------------------------------------------------------------------
 

include/boost/beast/core/detail/bind_handler.hpp

@@ -15,6 +15,7 @@
 #include <boost/asio/associated_executor.hpp>
 #include <boost/asio/handler_continuation_hook.hpp>
 #include <boost/core/ignore_unused.hpp>
+#include <boost/is_placeholder.hpp>
 #include <functional>
 #include <utility>
 
@@ -45,8 +46,10 @@ class bound_handler
     static
     typename std::enable_if<
         std::is_placeholder<typename
+            std::decay<Arg>::type>::value == 0 &&
+        boost::is_placeholder<typename
             std::decay<Arg>::type>::value == 0,
-    Arg&&>::type
+        Arg&&>::type
     extract(Arg&& arg, Vals& vals)
     {
         boost::ignore_unused(vals);
@@ -58,10 +61,10 @@ class bound_handler
     typename std::enable_if<
         std::is_placeholder<typename
             std::decay<Arg>::type>::value != 0,
-    typename std::tuple_element<
-        std::is_placeholder<
-            typename std::decay<Arg>::type>::value - 1,
-    Vals>::type&&>::type
+        typename std::tuple_element<
+            std::is_placeholder<
+                typename std::decay<Arg>::type>::value - 1,
+        Vals>>::type::type&&
     extract(Arg&&, Vals&& vals)
     {
         return std::get<std::is_placeholder<
@@ -69,6 +72,22 @@ class bound_handler
                 std::forward<Vals>(vals));
     }
 
+    template<class Arg, class Vals>
+    static
+    typename std::enable_if<
+        boost::is_placeholder<typename
+            std::decay<Arg>::type>::value != 0,
+        typename std::tuple_element<
+            boost::is_placeholder<
+                typename std::decay<Arg>::type>::value - 1,
+        Vals>>::type::type&&
+    extract(Arg&&, Vals&& vals)
+    {
+        return std::get<boost::is_placeholder<
+            typename std::decay<Arg>::type>::value - 1>(
+                std::forward<Vals>(vals));
+    }
+
     template<
         class ArgsTuple,
         std::size_t... S>