added disjunction, properly handle case T==void

davisking · Aug 5, 2023 · 97a1fc2 · 97a1fc2
1 parent 47a6a9b
commit 97a1fc2
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Showing 2 changed files with 19 additions and 6 deletions.
diff --git a/dlib/expected.h b/dlib/expected.h
@@ -685,8 +685,8 @@ namespace dlib
         template <
           class T, 
           class E,
-          bool copyable = ((std::is_void<T>::value || std::is_copy_constructible<T>::value) && std::is_copy_constructible<E>::value),
-          bool moveable = ((std::is_void<T>::value || std::is_move_constructible<T>::value) && std::is_move_constructible<E>::value)
+          bool copyable = (disjunction<std::is_void<T>, std::is_copy_constructible<T>>::value && std::is_copy_constructible<E>::value),
+          bool moveable = (disjunction<std::is_void<T>, std::is_move_constructible<T>>::value && std::is_move_constructible<E>::value)
         >
         struct expected_delete_constructors
         {
@@ -732,11 +732,13 @@ namespace dlib
         template <
           class T,
           class E,
-          bool copyable = ((std::is_void<T>::value || (std::is_copy_constructible<T>::value && std::is_copy_assignable<T>::value)) &&
-                           std::is_copy_constructible<E>::value && 
+          bool copyable = (disjunction<std::is_void<T>, std::is_copy_constructible<T>>::value   &&
+                           disjunction<std::is_void<T>, std::is_copy_assignable<T>>::value      &&
+                           std::is_copy_constructible<E>::value                                 && 
                            std::is_copy_assignable<E>::value),
-          bool moveable = ((std::is_void<T>::value || (std::is_move_constructible<T>::value && std::is_move_assignable<T>::value)) &&
-                           std::is_move_constructible<E>::value && 
+          bool moveable = (disjunction<std::is_void<T>, std::is_move_constructible<T>>::value   && 
+                           disjunction<std::is_void<T>, std::is_move_assignable<T>>::value      &&
+                           std::is_move_constructible<E>::value                                 && 
                            std::is_move_assignable<E>::value)
         >
         struct expected_delete_assign

diff --git a/dlib/type_traits.h b/dlib/type_traits.h
@@ -126,6 +126,17 @@ namespace dlib
     template<class B1, class... Bn>
     struct conjunction<B1, Bn...> : std::conditional_t<bool(B1::value), conjunction<Bn...>, B1> {};
 
+// ----------------------------------------------------------------------------------------
+
+    template<class...>
+    struct disjunction : std::false_type {};
+
+    template<class B1> 
+    struct disjunction<B1> : B1 {};
+
+    template<class B1, class... Bn>
+    struct disjunction<B1, Bn...> : std::conditional_t<bool(B1::value), B1, disjunction<Bn...>>  {};
+
 // ----------------------------------------------------------------------------------------
 
     template <typename ...Types>