diff --git a/include/iris/x4/core/detail/parse_alternative.hpp b/include/iris/x4/core/detail/parse_alternative.hpp
index 0cb5f9203..7162d07ec 100644
--- a/include/iris/x4/core/detail/parse_alternative.hpp
+++ b/include/iris/x4/core/detail/parse_alternative.hpp
@@ -230,7 +230,7 @@ struct parse_into_container_impl<alternative<Left, Right>>
     using parser_type = alternative<Left, Right>;
 
     template<std::forward_iterator It, std::sentinel_for<It> Se, class Context, X4Attribute Attr>
-        requires traits::is_variant_v<traits::container_value_t<Attr>>
+        requires traits::is_variant_v<typename traits::container_value<Attr>::type>
     [[nodiscard]] static constexpr bool
     call(
         parser_type const& parser,
@@ -242,7 +242,7 @@ struct parse_into_container_impl<alternative<Left, Right>>
     }
 
     template<std::forward_iterator It, std::sentinel_for<It> Se, class Context, X4Attribute Attr>
-        requires (!traits::is_variant_v<traits::container_value_t<Attr>>)
+        requires (!traits::is_variant_v<typename traits::container_value<Attr>::type>)
     [[nodiscard]] static constexpr bool
     call(
         parser_type const& parser,
diff --git a/include/iris/x4/core/detail/parse_into_container.hpp b/include/iris/x4/core/detail/parse_into_container.hpp
index 0da6f707a..2593828b7 100644
--- a/include/iris/x4/core/detail/parse_into_container.hpp
+++ b/include/iris/x4/core/detail/parse_into_container.hpp
@@ -48,8 +48,7 @@ struct parse_into_container_base_impl
     {
         static_assert(!std::same_as<std::remove_const_t<Attr>, unused_container_type>);
 
-        using value_type = traits::container_value_t<unwrap_recursive_type<Attr>>;
-        value_type val; // default-initialize
+        typename traits::container_value<unwrap_recursive_type<Attr>>::type val{}; // value-initialize
 
         //static_assert(Parsable<Parser, It, Se, Context, value_type>);
         if (!parser.parse(first, last, ctx, val)) return false;
@@ -149,7 +148,7 @@ struct parse_into_container_impl<Parser>
                 It, Se, Context,
                 typename parser_traits<Parser>::attribute_type
             >::actual_type,
-            traits::container_value_t<Attr>
+            typename traits::container_value<Attr>::type
         >>
     >;
 
@@ -217,7 +216,7 @@ parse_into_container(
         using attribute_type = parser_traits<Parser>::attribute_type;
 
         // e.g. `std::string` when the attribute_type is `char`
-        using substitute_type = traits::variant_find_substitute_t<Attr, traits::build_container_t<attribute_type>>;
+        using substitute_type = traits::variant_find_substitute_t<Attr, typename traits::build_container<attribute_type>::type>;
 
         // instead of creating a temporary `substitute_type`, append directly into the emplaced alternative
         auto& variant_alt = attr.template emplace<substitute_type>();
diff --git a/include/iris/x4/core/detail/parse_sequence.hpp b/include/iris/x4/core/detail/parse_sequence.hpp
index 28df3abf1..61242686f 100644
--- a/include/iris/x4/core/detail/parse_sequence.hpp
+++ b/include/iris/x4/core/detail/parse_sequence.hpp
@@ -284,7 +284,7 @@ struct parse_into_container_impl<sequence<Left, Right>>
     template<X4Attribute Attr>
     static constexpr bool is_container_substitute = traits::is_substitute_v<
         typename sequence<Left, Right>::attribute_type,
-        traits::container_value_t<Attr>
+        typename traits::container_value<Attr>::type
     >;
 
     template<std::forward_iterator It, std::sentinel_for<It> Se, class Context, X4Attribute Attr>
diff --git a/include/iris/x4/directive/repeat.hpp b/include/iris/x4/directive/repeat.hpp
index 9dc8db3c2..5bf43d63d 100644
--- a/include/iris/x4/directive/repeat.hpp
+++ b/include/iris/x4/directive/repeat.hpp
@@ -87,7 +87,7 @@ template<class Subject, detail::RepeatBounds Bounds>
 struct repeat_directive : proxy_parser<Subject, repeat_directive<Subject, Bounds>>
 {
     using base_type = proxy_parser<Subject, repeat_directive>;
-    using attribute_type = traits::build_container_t<typename parser_traits<Subject>::attribute_type>;
+    using attribute_type = traits::build_container<typename parser_traits<Subject>::attribute_type>::type;
 
     static constexpr bool handles_container = true;
 
diff --git a/include/iris/x4/operator/alternative.hpp b/include/iris/x4/operator/alternative.hpp
index 03015241a..2746a15e5 100644
--- a/include/iris/x4/operator/alternative.hpp
+++ b/include/iris/x4/operator/alternative.hpp
@@ -29,6 +29,27 @@
 
 namespace iris::x4 {
 
+namespace detail {
+
+template<bool IsBothSameAttribute, class Left, class Right>
+struct alternative_attribute_impl;
+
+// Both same attribute
+template<class Left, class Right>
+struct alternative_attribute_impl<true, Left, Right>
+{
+    using type = parser_traits<Left>::attribute_type;
+};
+
+// Not same attribute
+template<class Left, class Right>
+struct alternative_attribute_impl<false, Left, Right>
+{
+    using type = traits::detail::attribute_of_alternative<Left, Right>::type;
+};
+
+} // detail
+
 template<class Left, class Right>
 struct alternative : binary_parser<Left, Right, alternative<Left, Right>>
 {
@@ -40,10 +61,8 @@ struct alternative : binary_parser<Left, Right, alternative<Left, Right>>
 
 public:
     // Canonicalize `rvariant<X, X>` to `X`
-    using attribute_type = std::conditional_t<
-        is_both_same_attribute,
-        std::type_identity<typename parser_traits<Left>::attribute_type>,
-        traits::attribute_of_binary<iris::rvariant, Left, Right>
+    using attribute_type = detail::alternative_attribute_impl<
+        is_both_same_attribute, Left, Right
     >::type;
 
     // If canonicalized, proxy the underlying `sequence_size`. In other words:
diff --git a/include/iris/x4/operator/kleene.hpp b/include/iris/x4/operator/kleene.hpp
index 1785f3935..0289ce968 100644
--- a/include/iris/x4/operator/kleene.hpp
+++ b/include/iris/x4/operator/kleene.hpp
@@ -28,7 +28,7 @@ namespace iris::x4 {
 template<class Subject>
 struct kleene : unary_parser<Subject, kleene<Subject>>
 {
-    using attribute_type = traits::build_container_t<typename parser_traits<Subject>::attribute_type>;
+    using attribute_type = traits::build_container<typename parser_traits<Subject>::attribute_type>::type;
 
     static constexpr bool handles_container = true;
 
diff --git a/include/iris/x4/operator/list.hpp b/include/iris/x4/operator/list.hpp
index 9270aa6d7..c6d9039b9 100644
--- a/include/iris/x4/operator/list.hpp
+++ b/include/iris/x4/operator/list.hpp
@@ -28,7 +28,7 @@ namespace iris::x4 {
 template<class Left, class Right>
 struct list : binary_parser<Left, Right, list<Left, Right>>
 {
-    using attribute_type = traits::build_container_t<typename parser_traits<Left>::attribute_type>;
+    using attribute_type = traits::build_container<typename parser_traits<Left>::attribute_type>::type;
 
     static constexpr bool handles_container = true;
 
diff --git a/include/iris/x4/operator/optional.hpp b/include/iris/x4/operator/optional.hpp
index a259a33fa..498b30f87 100644
--- a/include/iris/x4/operator/optional.hpp
+++ b/include/iris/x4/operator/optional.hpp
@@ -30,7 +30,7 @@ namespace iris::x4 {
 template<class Subject>
 struct optional : unary_parser<Subject, optional<Subject>>
 {
-    using attribute_type = traits::build_optional_t<typename parser_traits<Subject>::attribute_type>;
+    using attribute_type = traits::build_optional<typename parser_traits<Subject>::attribute_type>::type;
 
     static constexpr bool handles_container = true;
 
@@ -82,15 +82,13 @@ struct optional : unary_parser<Subject, optional<Subject>>
     [[nodiscard]] constexpr bool
     parse(It& first, Se const& last, Context const& ctx, Attr& attr) const
         noexcept(
-            std::is_nothrow_default_constructible_v<x4::traits::optional_value_t<Attr>> &&
-            is_nothrow_parsable_v<Subject, It, Se, Context, x4::traits::optional_value_t<Attr>> &&
-            noexcept(x4::move_to(std::declval<x4::traits::optional_value_t<Attr>&&>(), attr))
+            std::is_nothrow_default_constructible_v<typename traits::optional_value<Attr>::type> &&
+            is_nothrow_parsable_v<Subject, It, Se, Context, typename traits::optional_value<Attr>::type> &&
+            noexcept(x4::move_to(std::declval<typename traits::optional_value<Attr>::type&&>(), attr))
         )
     {
-        using value_type = x4::traits::optional_value_t<Attr>;
-        value_type val; // default-initialize
+        typename traits::optional_value<Attr>::type val{}; // value-initialize
 
-        static_assert(Parsable<Subject, It, Se, Context, value_type>);
         if (this->subject.parse(first, last, ctx, val)) {
             // assign the parsed value into our attribute
             x4::move_to(std::move(val), attr);
diff --git a/include/iris/x4/operator/plus.hpp b/include/iris/x4/operator/plus.hpp
index 45f1ce0e9..4b16ca713 100644
--- a/include/iris/x4/operator/plus.hpp
+++ b/include/iris/x4/operator/plus.hpp
@@ -28,7 +28,7 @@ namespace iris::x4 {
 template<class Subject>
 struct plus : unary_parser<Subject, plus<Subject>>
 {
-    using attribute_type = traits::build_container_t<typename parser_traits<Subject>::attribute_type>;
+    using attribute_type = traits::build_container<typename parser_traits<Subject>::attribute_type>::type;
 
     static constexpr bool handles_container = true;
 
diff --git a/include/iris/x4/operator/sequence.hpp b/include/iris/x4/operator/sequence.hpp
index 3b9b91b90..67109b1a9 100644
--- a/include/iris/x4/operator/sequence.hpp
+++ b/include/iris/x4/operator/sequence.hpp
@@ -31,7 +31,7 @@ namespace iris::x4 {
 template<class Left, class Right>
 struct sequence : binary_parser<Left, Right, sequence<Left, Right>>
 {
-    using attribute_type = traits::attribute_of_binary<alloy::tuple, Left, Right>::type;
+    using attribute_type = traits::detail::attribute_of_sequence<Left, Right>::type;
 
     static constexpr std::size_t sequence_size =
         parser_traits<Left>::sequence_size + parser_traits<Right>::sequence_size;
diff --git a/include/iris/x4/string/detail/string_parse.hpp b/include/iris/x4/string/detail/string_parse.hpp
index c027248d0..945a6a732 100644
--- a/include/iris/x4/string/detail/string_parse.hpp
+++ b/include/iris/x4/string/detail/string_parse.hpp
@@ -32,7 +32,7 @@ string_parse(
 {
     using synthesized_value_type = traits::synthesized_value_t<Attr>;
     static_assert(std::same_as<traits::attribute_category_t<synthesized_value_type>, traits::container_attr>);
-    using value_type = traits::container_value_t<synthesized_value_type>;
+    using value_type = traits::container_value<synthesized_value_type>::type;
     static_assert(!traits::CharLike<value_type> || std::same_as<value_type, CharT>, "Mixing incompatible char types is not allowed");
 
     It it = first;
@@ -79,7 +79,7 @@ string_parse(
 {
     using synthesized_value_type = traits::synthesized_value_t<Attr>;
     static_assert(std::same_as<traits::attribute_category_t<synthesized_value_type>, traits::container_attr>);
-    using value_type = traits::container_value_t<synthesized_value_type>;
+    using value_type = traits::container_value<synthesized_value_type>::type;
     static_assert(!traits::CharLike<value_type> || std::same_as<value_type, CharT>, "Mixing incompatible char types is not allowed");
 
     auto uc_it = ucstr.begin();
diff --git a/include/iris/x4/traits/attribute_of_binary.hpp b/include/iris/x4/traits/attribute_of_binary.hpp
index ffd60eb94..87fd59bae 100644
--- a/include/iris/x4/traits/attribute_of_binary.hpp
+++ b/include/iris/x4/traits/attribute_of_binary.hpp
@@ -12,108 +12,113 @@
     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 =============================================================================*/
 
-#include <iris/x4/core/attribute.hpp>
 #include <iris/x4/core/unused.hpp>
 #include <iris/x4/core/parser_traits.hpp>
 
 #include <iris/type_traits.hpp>  // TODO: move iris::type_list to separate header
 
-#include <type_traits>
-
 namespace iris::x4::traits {
 
 namespace detail {
 
-template<class TypeList, class... Us>
-struct append_to_type_list {};
-
-template<class TypeList, class... Us>
-using append_to_type_list_t = append_to_type_list<TypeList, Us...>::type;
-
-template<class... Ts>
-struct append_to_type_list<type_list<Ts...>>
-{
-    using type = type_list<Ts...>;
-};
+template<class TTypeList, class UTypeList>
+struct concat_type_list;
 
 template<class... Ts, class... Us>
-struct append_to_type_list<type_list<Ts...>, unused_type, Us...>
-    : append_to_type_list<type_list<Ts...>, Us...>
-{};
-
-template<class... Ts, class U, class... Us>
-struct append_to_type_list<type_list<Ts...>, U, Us...>
-    : append_to_type_list<type_list<Ts..., U>, Us...>
-{};
-
-template<class... Ts, class... Us, class... Vs>
-struct append_to_type_list<type_list<Ts...>, type_list<Us...>, Vs...>
-    : append_to_type_list<append_to_type_list_t<type_list<Ts...>, Us...>, Vs...>
-{};
-
-template<template<class...> class TupleTT, class T>
-struct tuple_to_type_list;
-
-template<template<class...> class TupleTT, class T>
-using tuple_to_type_list_t = tuple_to_type_list<TupleTT, T>::type;
-
-template<template<class...> class TupleTT, class T>
-struct tuple_to_type_list
-{
-    using type = T;
-};
-
-template<template<class...> class TupleTT, class... Ts>
-struct tuple_to_type_list<TupleTT, TupleTT<Ts...>>
+struct concat_type_list<type_list<Ts...>, type_list<Us...>>
 {
-    using type = type_list<tuple_to_type_list_t<TupleTT, Ts>...>;
+    using type = type_list<Ts..., Us...>;
 };
 
-template<template<class...> class TupleTT, class T>
-using tuple_to_type_list_t = tuple_to_type_list<TupleTT, T>::type;
-
-template<template<class...> class TupleTT, class TypeList>
-struct type_list_to_tuple {};
+#if 0
+#define IRIS_X4_TRAITS_DETAIL_DEFINE_TYPE_LIST_CONV(postfix, tmpl) \
+    template<class T> \
+    struct to_type_list_##postfix \
+    { \
+        using type = type_list<T>; \
+    }; \
+    template<> \
+    struct to_type_list_##postfix<unused_type> \
+    { \
+        using type = type_list<>; \
+    }; \
+    template<class... Ts> \
+    struct to_type_list_##postfix<tmpl<Ts...>> \
+    { \
+        using type = type_list<Ts...>; \
+    }; \
+    \
+    template<class TypeList> \
+    struct from_type_list_##postfix {}; \
+    template<> \
+    struct from_type_list_##postfix<type_list<>> \
+    { \
+        using type = unused_type; \
+    }; \
+    template<class T> \
+    struct from_type_list_##postfix<type_list<T>> \
+    { \
+        using type = T; \
+    }; \
+    template<class T0, class T1, class... Ts> \
+    struct from_type_list_##postfix<type_list<T0, T1, Ts...>> \
+    { \
+        using type = tmpl<T0, T1, Ts...>; \
+    }; \
+    \
+    template<class LeftParser, class RightParser> \
+    struct attribute_of_##postfix { \
+        using type = detail::from_type_list_##postfix< \
+            typename detail::concat_type_list< \
+                typename detail::to_type_list_##postfix<typename parser_traits<LeftParser>::attribute_type>::type, \
+                typename detail::to_type_list_##postfix<typename parser_traits<RightParser>::attribute_type>::type \
+            >::type \
+        >::type; \
+    };
+#endif
 
-template<template<class...> class TupleTT>
-struct type_list_to_tuple<TupleTT, type_list<>>
-{
+//
+// AUTOGENERATED CODE; DO NOT EDIT.
+// Expanded using Visual Studio's "Expand Inline" feature.
+// Code style is kept as-is.
+//
+
+// IRIS_X4_TRAITS_DETAIL_DEFINE_TYPE_LIST_CONV(sequence, alloy::tuple)
+template<class T> struct to_type_list_sequence {
+    using type = type_list<T>;
+}; template<> struct to_type_list_sequence<unused_type> {
+    using type = type_list<>;
+}; template<class... Ts> struct to_type_list_sequence<alloy::tuple<Ts...>> {
+    using type = type_list<Ts...>;
+}; template<class TypeList> struct from_type_list_sequence {}; template<> struct from_type_list_sequence<type_list<>> {
     using type = unused_type;
-};
-
-template<template<class...> class TupleTT, class T>
-struct type_list_to_tuple<TupleTT, type_list<T>>
-{
+}; template<class T> struct from_type_list_sequence<type_list<T>> {
     using type = T;
+}; template<class T0, class T1, class... Ts> struct from_type_list_sequence<type_list<T0, T1, Ts...>> {
+    using type = alloy::tuple<T0, T1, Ts...>;
+}; template<class LeftParser, class RightParser> struct attribute_of_sequence {
+    using type = detail::from_type_list_sequence< typename detail::concat_type_list< typename detail::to_type_list_sequence<typename parser_traits<LeftParser>::attribute_type>::type, typename detail::to_type_list_sequence<typename parser_traits<RightParser>::attribute_type>::type >::type >::type;
 };
 
-template<template<class...> class TupleTT, class T0, class T1, class... Ts>
-struct type_list_to_tuple<TupleTT, type_list<T0, T1, Ts...>>
-{
-    using type = TupleTT<T0, T1, Ts...>;
+// IRIS_X4_TRAITS_DETAIL_DEFINE_TYPE_LIST_CONV(alternative, rvariant)
+template<class T> struct to_type_list_alternative {
+    using type = type_list<T>;
+}; template<> struct to_type_list_alternative<unused_type> {
+    using type = type_list<>;
+}; template<class... Ts> struct to_type_list_alternative<rvariant<Ts...>> {
+    using type = type_list<Ts...>;
+}; template<class TypeList> struct from_type_list_alternative {}; template<> struct from_type_list_alternative<type_list<>> {
+    using type = unused_type;
+}; template<class T> struct from_type_list_alternative<type_list<T>> {
+    using type = T;
+}; template<class T0, class T1, class... Ts> struct from_type_list_alternative<type_list<T0, T1, Ts...>> {
+    using type = rvariant<T0, T1, Ts...>;
+}; template<class LeftParser, class RightParser> struct attribute_of_alternative {
+    using type = detail::from_type_list_alternative< typename detail::concat_type_list< typename detail::to_type_list_alternative<typename parser_traits<LeftParser>::attribute_type>::type, typename detail::to_type_list_alternative<typename parser_traits<RightParser>::attribute_type>::type >::type >::type;
 };
 
-template<template<class...> class TupleTT, class TypeList>
-using type_list_to_tuple_t = type_list_to_tuple<TupleTT, TypeList>::type;
-
 } // detail
 
-template<
-    template<class...> class TupleTT,
-    class LeftParser, class RightParser
->
-struct attribute_of_binary
-{
-    using type = detail::type_list_to_tuple_t<
-        TupleTT,
-        detail::append_to_type_list_t<
-            type_list<>,
-            detail::tuple_to_type_list_t<TupleTT, typename parser_traits<LeftParser>::attribute_type>,
-            detail::tuple_to_type_list_t<TupleTT, typename parser_traits<RightParser>::attribute_type>
-        >
-    >;
-};
-
 } // iris::x4::traits
 
 #endif
diff --git a/include/iris/x4/traits/container_traits.hpp b/include/iris/x4/traits/container_traits.hpp
index b768b1fc5..b48db67e7 100644
--- a/include/iris/x4/traits/container_traits.hpp
+++ b/include/iris/x4/traits/container_traits.hpp
@@ -84,9 +84,6 @@ struct container_value
     : detail::remove_value_const<typename Container::value_type>
 {};
 
-template<class Container>
-using container_value_t = typename container_value<Container>::type;
-
 template<class Container>
 struct container_value<Container const> : container_value<Container> {};
 
@@ -476,9 +473,6 @@ struct build_container
     using type = std::vector<T>;
 };
 
-template<class T>
-using build_container_t = typename build_container<T>::type;
-
 template<class T>
 struct build_container<alloy::tuple<T>> : build_container<T> {};
 
diff --git a/include/iris/x4/traits/optional_traits.hpp b/include/iris/x4/traits/optional_traits.hpp
index 036798150..ab7b4d803 100644
--- a/include/iris/x4/traits/optional_traits.hpp
+++ b/include/iris/x4/traits/optional_traits.hpp
@@ -41,9 +41,6 @@ struct build_optional
     using type = std::optional<T>;
 };
 
-template<class T>
-using build_optional_t = typename build_optional<T>::type;
-
 template<class T>
 struct build_optional<std::optional<T>>
 {
@@ -69,9 +66,6 @@ struct optional_value
     using type = typename T::value_type;
 };
 
-template<class T>
-using optional_value_t = typename optional_value<T>::type;
-
 template<>
 struct optional_value<unused_type>
 {
diff --git a/include/iris/x4/traits/substitution.hpp b/include/iris/x4/traits/substitution.hpp
index d8c04a51d..f675231ea 100644
--- a/include/iris/x4/traits/substitution.hpp
+++ b/include/iris/x4/traits/substitution.hpp
@@ -52,7 +52,7 @@ struct is_all_substitute_for_tuple<TTuple, UTuple> : is_all_substitute_for_tuple
 
 template<class T, X4Attribute Attr>
 struct value_type_is_substitute
-    : is_substitute<container_value_t<T>, container_value_t<Attr>>
+    : is_substitute<typename container_value<T>::type, typename container_value<Attr>::type>
 {};
 
 template<class T, X4Attribute Attr>
diff --git a/modules/iris b/modules/iris
index 32d9fd929..cec583eed 160000
--- a/modules/iris
+++ b/modules/iris
@@ -1 +1 @@
-Subproject commit 32d9fd9299bff648b9852b1bb822f2c53cbd62f2
+Subproject commit cec583eed7ab2fb70e7ef6aa52ab840bc03e92ca