Expose completion as DSL event token

include/boost/sml.hpp

@@ -3254,7 +3254,7 @@ front::event<back::unexpected_event<TEvent>> unexpected_event __BOOST_SML_VT_INI
 template <class T>
 front::event<back::exception<T>> exception __BOOST_SML_VT_INIT;
 template <class TEvent>
-using completion = back::completion<TEvent>;
+__BOOST_SML_UNUSED front::event<back::completion<TEvent>> completion __BOOST_SML_VT_INIT;
 using anonymous = back::anonymous;
 using initial = back::initial;
 #if !(defined(_MSC_VER) && !defined(__clang__))

test/ft/actions_process_n_defer.cpp

@@ -142,7 +142,7 @@ test process_queue_runs_completion_for_popped_event_type = [] {
       return make_transition_table(
         *q0_state + event<trigger> / (process(queued1{}), process(queued2{})) = q1_state
         , q1_state + event<queued1> = q2_state
-        , q2_state + event<completion<queued1>> = q3_state
+        , q2_state + completion<queued1> = q3_state
         , q2_state + event<queued2> = wrong_state
         , q3_state + event<queued2> = done_state
       );
@@ -178,8 +178,8 @@ test defer_queue_runs_completion_for_popped_event_type = [] {
         *d0_state + event<deferred> / defer
         , d0_state + event<release> = d1_state
         , d1_state + event<deferred> = d2_state
-        , d2_state + event<completion<deferred>> = done_state
-        , d2_state + event<completion<release>> = wrong_state
+        , d2_state + completion<deferred> = done_state
+        , d2_state + completion<release> = wrong_state
       );
       // clang-format on
     }

test/ft/transitions.cpp

@@ -95,7 +95,7 @@ test completion_transition_runs_before_anonymous = [] {
       // clang-format off
       return make_transition_table(
          *idle + event<e1> = s1
-        ,s1 + event<completion<e1>> / [this] { calls += "completion|"; } = s2
+        ,s1 + completion<e1> / [this] { calls += "completion|"; } = s2
         ,s1 / [this] { calls += "anonymous_s1|"; } = s3
         ,s2 / [this] { calls += "anonymous_s2|"; } = s4
       );