Add friendship support to require_concept CPO.

chip5441 · Jan 6, 2021 · 962a85f · 962a85f
1 parent a3992b6
commit 962a85f
Showing 1 changed file with 61 additions and 23 deletions.
diff --git a/asio/include/asio/require_concept.hpp b/asio/include/asio/require_concept.hpp
@@ -107,6 +107,7 @@ struct require_concept_result
 
 namespace asio_require_concept_fn {
 
+using asio::conditional;
 using asio::decay;
 using asio::declval;
 using asio::enable_if;
@@ -125,7 +126,7 @@ enum overload_type
   ill_formed
 };
 
-template <typename T, typename Properties, typename = void,
+template <typename Impl, typename T, typename Properties, typename = void,
     typename = void, typename = void, typename = void, typename = void>
 struct call_traits
 {
@@ -134,8 +135,8 @@ struct call_traits
   typedef void result_type;
 };
 
-template <typename T, typename Property>
-struct call_traits<T, void(Property),
+template <typename Impl, typename T, typename Property>
+struct call_traits<Impl, T, void(Property),
   typename enable_if<
     is_applicable_property<
       typename decay<T>::type,
@@ -154,8 +155,8 @@ struct call_traits<T, void(Property),
   typedef ASIO_MOVE_ARG(T) result_type;
 };
 
-template <typename T, typename Property>
-struct call_traits<T, void(Property),
+template <typename Impl, typename T, typename Property>
+struct call_traits<Impl, T, void(Property),
   typename enable_if<
     is_applicable_property<
       typename decay<T>::type,
@@ -169,15 +170,21 @@ struct call_traits<T, void(Property),
     !static_require_concept<T, Property>::is_valid
   >::type,
   typename enable_if<
-    require_concept_member<T, Property>::is_valid
+    require_concept_member<
+      typename Impl::template proxy<T>::type,
+      Property
+    >::is_valid
   >::type> :
-  require_concept_member<T, Property>
+  require_concept_member<
+    typename Impl::template proxy<T>::type,
+    Property
+  >
 {
   ASIO_STATIC_CONSTEXPR(overload_type, overload = call_member);
 };
 
-template <typename T, typename Property>
-struct call_traits<T, void(Property),
+template <typename Impl, typename T, typename Property>
+struct call_traits<Impl, T, void(Property),
   typename enable_if<
     is_applicable_property<
       typename decay<T>::type,
@@ -191,7 +198,10 @@ struct call_traits<T, void(Property),
     !static_require_concept<T, Property>::is_valid
   >::type,
   typename enable_if<
-    !require_concept_member<T, Property>::is_valid
+    !require_concept_member<
+      typename Impl::template proxy<T>::type,
+      Property
+    >::is_valid
   >::type,
   typename enable_if<
     require_concept_free<T, Property>::is_valid
@@ -203,45 +213,69 @@ struct call_traits<T, void(Property),
 
 struct impl
 {
+  template <typename T>
+  struct proxy
+  {
+#if defined(ASIO_HAS_DEDUCED_REQUIRE_CONCEPT_MEMBER_TRAIT)
+    struct type
+    {
+      template <typename P>
+      auto require_concept(ASIO_MOVE_ARG(P) p)
+        noexcept(
+          noexcept(
+            declval<typename conditional<true, T, P>::type>().require_concept(
+              ASIO_MOVE_CAST(P)(p))
+          )
+        )
+        -> decltype(
+          declval<typename conditional<true, T, P>::type>().require_concept(
+            ASIO_MOVE_CAST(P)(p))
+        );
+    };
+#else // defined(ASIO_HAS_DEDUCED_REQUIRE_CONCEPT_MEMBER_TRAIT)
+    typedef T type;
+#endif // defined(ASIO_HAS_DEDUCED_REQUIRE_CONCEPT_MEMBER_TRAIT)
+  };
+
   template <typename T, typename Property>
   ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
-    call_traits<T, void(Property)>::overload == identity,
-    typename call_traits<T, void(Property)>::result_type
+    call_traits<impl, T, void(Property)>::overload == identity,
+    typename call_traits<impl, T, void(Property)>::result_type
   >::type
   operator()(
       ASIO_MOVE_ARG(T) t,
       ASIO_MOVE_ARG(Property)) const
     ASIO_NOEXCEPT_IF((
-      call_traits<T, void(Property)>::is_noexcept))
+      call_traits<impl, T, void(Property)>::is_noexcept))
   {
     return ASIO_MOVE_CAST(T)(t);
   }
 
   template <typename T, typename Property>
   ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
-    call_traits<T, void(Property)>::overload == call_member,
-    typename call_traits<T, void(Property)>::result_type
+    call_traits<impl, T, void(Property)>::overload == call_member,
+    typename call_traits<impl, T, void(Property)>::result_type
   >::type
   operator()(
       ASIO_MOVE_ARG(T) t,
       ASIO_MOVE_ARG(Property) p) const
     ASIO_NOEXCEPT_IF((
-      call_traits<T, void(Property)>::is_noexcept))
+      call_traits<impl, T, void(Property)>::is_noexcept))
   {
     return ASIO_MOVE_CAST(T)(t).require_concept(
         ASIO_MOVE_CAST(Property)(p));
   }
 
   template <typename T, typename Property>
   ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
-    call_traits<T, void(Property)>::overload == call_free,
-    typename call_traits<T, void(Property)>::result_type
+    call_traits<impl, T, void(Property)>::overload == call_free,
+    typename call_traits<impl, T, void(Property)>::result_type
   >::type
   operator()(
       ASIO_MOVE_ARG(T) t,
       ASIO_MOVE_ARG(Property) p) const
     ASIO_NOEXCEPT_IF((
-      call_traits<T, void(Property)>::is_noexcept))
+      call_traits<impl, T, void(Property)>::is_noexcept))
   {
     return require_concept(
         ASIO_MOVE_CAST(T)(t),
@@ -267,11 +301,14 @@ static ASIO_CONSTEXPR const asio_require_concept_fn::impl&
 
 } // namespace
 
+typedef asio_require_concept_fn::impl require_concept_t;
+
 template <typename T, typename Property>
 struct can_require_concept :
   integral_constant<bool,
-    asio_require_concept_fn::call_traits<T, void(Property)>::overload !=
-      asio_require_concept_fn::ill_formed>
+    asio_require_concept_fn::call_traits<
+      require_concept_t, T, void(Property)>::overload !=
+        asio_require_concept_fn::ill_formed>
 {
 };
 
@@ -286,7 +323,8 @@ constexpr bool can_require_concept_v
 template <typename T, typename Property>
 struct is_nothrow_require_concept :
   integral_constant<bool,
-    asio_require_concept_fn::call_traits<T, void(Property)>::is_noexcept>
+    asio_require_concept_fn::call_traits<
+      require_concept_t, T, void(Property)>::is_noexcept>
 {
 };
 
@@ -302,7 +340,7 @@ template <typename T, typename Property>
 struct require_concept_result
 {
   typedef typename asio_require_concept_fn::call_traits<
-      T, void(Property)>::result_type type;
+      require_concept_t, T, void(Property)>::result_type type;
 };
 
 } // namespace asio