fix: fallback to any_state when state-specific guard fails

Author: Edvard Vasdal

include/boost/sml.hpp

@@ -1136,9 +1136,15 @@ template <class T, class, class... Ts>
 transitions<Ts...> get_state_mapping_impl(state_mappings<T, aux::type_list<Ts...>> *);
 template <class T, class TMappings, class TUnexpected>
 struct get_state_mapping {
-  using type = aux::conditional_t<aux::is_same<decltype(get_state_mapping_impl<T, TUnexpected>((TMappings *)0)), transitions<TUnexpected>>::value,
-      decltype(get_state_mapping_impl<_, TUnexpected>((TMappings *)0)),
-      decltype(get_state_mapping_impl<T, TUnexpected>((TMappings *)0))>;
+  using state_mapping = decltype(get_state_mapping_impl<T, TUnexpected>((TMappings *)0));
+  using any_state_mapping = decltype(get_state_mapping_impl<_, TUnexpected>((TMappings *)0));
+  struct type {
+    template <class TEvent, class TSm, class TDeps, class TSubs>
+    constexpr static bool execute(const TEvent& event, TSm& sm, TDeps& deps, TSubs& subs, typename TSm::state_t& current_state) {
+      return state_mapping::template execute<TEvent, TSm, TDeps, TSubs>(event, sm, deps, subs, current_state) ||
+             any_state_mapping::template execute<TEvent, TSm, TDeps, TSubs>(event, sm, deps, subs, current_state);
+    }
+  };
 };
 template <class S>
 transitions_sub<S> get_sub_state_mapping_impl(...);

test/ft/states.cpp

@@ -317,6 +317,44 @@ test any_state_nested = [] {
   expect("a1|a2|a3|" == c_.calls);
 };
 
+test any_state_fallback_when_guard_fails = [] {
+  struct c {
+    auto operator()() {
+      using namespace sml;
+      auto action1 = [this]{ calls += "a1|"; };
+      auto action2 = [this]{ calls += "a2|"; };
+      
+      auto true_guard = []{ return true; };
+      auto false_guard = []{ return false; };
+      
+      // clang-format off
+      return make_transition_table(
+        *idle + event<e1> = s1,
+        s1 + event<e2> [ false_guard ] = s2,
+
+        any + event<e1> / action1,
+        any + event<e2> / action2
+
+      );
+      // clang-format on
+    }
+
+    std::string calls{};
+  };
+
+  sml::sm<c> sm{};
+  const c& c_ = sm;
+
+  sm.process_event(e1());
+  expect(sm.is(s1));
+  sm.process_event(e1());
+  expect(sm.is(s1));
+  sm.process_event(e2());
+  expect(sm.is(s1));
+
+  expect("a1|a2|" == c_.calls);
+};
+
 #if !defined(_MSC_VER)
 test state_names = [] {
   struct c {