Fix bug in dep resolution when requesting a "const T*" after providing a "T*"

Before this fix, if a T* was injected as depedency, requesting a const T* will result in a invalid nullptr.
Four unit tests added.

(cherry picked from commit 7ca4d03)

Author: marcobergamin

Diff for: include/boost/sml.hpp

@@ -230,6 +230,16 @@ struct remove_reference<T &&> {
 };
 template <class T>
 using remove_reference_t = typename remove_reference<T>::type;
+template <class T>
+struct remove_pointer {
+  using type = T;
+};
+template <class T>
+struct remove_pointer<T *> {
+  using type = T;
+};
+template <class T>
+using remove_pointer_t = typename remove_pointer<T>::type;
 }  // namespace aux
 namespace aux {
 using swallow = int[];
@@ -401,6 +411,14 @@ template <class T>
 constexpr T &try_get(const pool_type<T &> *object) {
   return object->value;
 }
+template <class T>
+const T *try_get(const pool_type<const T *> *object) {
+  return object->value;
+}
+template <class T>
+T *try_get(const pool_type<T *> *object) {
+  return object->value;
+}
 template <class T, class TPool>
 constexpr T &get(TPool &p) {
   return static_cast<pool_type<T> &>(p).value;
@@ -409,13 +427,22 @@ template <class T, class TPool>
 constexpr const T &cget(const TPool &p) {
   return static_cast<const pool_type<T> &>(p).value;
 }
+template <class T, class TPool>
+T *get(TPool *p) {
+  return static_cast<pool_type<T> &>(p).value;
+}
+template <class T, class TPool>
+const T *cget(const TPool *p) {
+  return static_cast<const pool_type<T> &>(p).value;
+}
 template <class... Ts>
 struct pool : pool_type<Ts>... {
   using boost_di_inject__ = type_list<Ts...>;
   constexpr pool() = default;
   constexpr explicit pool(Ts... ts) : pool_type<Ts>(ts)... {}
   template <class... TArgs>
-  constexpr pool(init, const pool<TArgs...> &p) : pool_type<Ts>(try_get<aux::remove_const_t<aux::remove_reference_t<Ts>>>(&p))... {}
+  constexpr pool(init, const pool<TArgs...> &p)
+      : pool_type<Ts>(try_get<aux::remove_const_t<aux::remove_reference_t<aux::remove_pointer_t<Ts>>>>(&p))... {}
   template <class... TArgs>
   constexpr pool(const pool<TArgs...> &p) : pool_type<Ts>(init{}, p)... {}
 };

Diff for: test/ft/dependencies.cpp

@@ -179,6 +179,90 @@ test dependencies_smart_ptrs = [] {
   expect(sm.is(sml::X));
 };
 
+test dependencies_with_reference = [] {
+  struct Data {
+    int m_member { 42 };
+  };
+
+  struct c {
+    auto operator()() noexcept {
+      const auto action = [](Data& data) { expect(data.m_member == 42); };
+
+      using namespace sml;
+      return make_transition_table(*idle + event<e1> / action = X);
+    }
+  };
+
+  Data data;
+  sml::sm<c> sm{data};
+  sm.process_event(e1{});
+  expect(sm.is(sml::X));
+};
+
+test dependencies_with_const_reference = [] {
+  struct Data {
+    int m_member { 42 };
+  };
+
+  struct c {
+    auto operator()() noexcept {
+      const auto action = [](const Data& data) {
+        expect(data.m_member == 42);
+      };
+
+      using namespace sml;
+      return make_transition_table(*idle + event<e1> / action = X);
+    }
+  };
+
+  Data data;
+  sml::sm<c> sm{data};
+  sm.process_event(e1{});
+  expect(sm.is(sml::X));
+};
+
+test dependencies_with_pointer = [] {
+  struct Data {
+    int m_member { 42 };
+  };
+
+  struct c {
+    auto operator()() noexcept {
+      const auto action = [](Data* data) { expect(data->m_member == 42); };
+
+      using namespace sml;
+      return make_transition_table(*idle + event<e1> / action = X);
+    }
+  };
+
+  Data data;
+  sml::sm<c> sm{&data};
+  sm.process_event(e1{});
+  expect(sm.is(sml::X));
+};
+
+test dependencies_with_const_pointer = [] {
+  struct Data {
+    int m_member { 42 };
+  };
+
+  struct c {
+    auto operator()() noexcept {
+      const auto action = [](const Data* data) {
+        expect(data->m_member == 42);
+      };
+
+      using namespace sml;
+      return make_transition_table(*idle + event<e1> / action = X);
+    }
+  };
+
+  Data data;
+  sml::sm<c> sm{&data};
+  sm.process_event(e1{});
+  expect(sm.is(sml::X));
+};
+
 #if (_MSC_VER >= 1910)  // MSVC 2017
 test dependencies_multiple_subs = [] {
   struct update {