refactor: 💥 ! U::is_named removed from the unit types and replaced with NamedUnit concept

src/core/include/units/base_dimension.h

@@ -50,8 +50,7 @@ namespace units {
  * @tparam Symbol an unique identifier of the base dimension used to provide dimensional analysis support
  * @tparam U a base unit to be used for this base dimension
  */
-template<basic_fixed_string Symbol, Unit U>
-  requires U::is_named
+template<basic_fixed_string Symbol, NamedUnit U>
 struct base_dimension {
   static constexpr auto symbol = Symbol;  ///< Unique base dimension identifier
   using base_unit = U;                    ///< Base unit adopted for this dimension

src/core/include/units/bits/basic_concepts.h

@@ -96,9 +96,18 @@ void to_base_scaled_unit(const volatile scaled_unit<R, U>*);
 template<typename T>
 concept Unit = requires(T* t) { detail::to_base_scaled_unit(t); };
 
+namespace detail {
+
+template<typename>
+inline constexpr bool is_named = false;
+
+}
+
+template<typename T>
+concept NamedUnit = Unit<T> && detail::is_named<T>;
+
 // BaseDimension
-template<basic_fixed_string Symbol, Unit U>
-  requires U::is_named
+template<basic_fixed_string Symbol, NamedUnit U>
 struct base_dimension;
 
 namespace detail {

src/core/include/units/bits/unit_text.h

@@ -110,7 +110,7 @@ template<Exponent Exp>
 constexpr auto exponent_list_with_named_units(Exp)
 {
   using dim = TYPENAME Exp::dimension;
-  if constexpr (dimension_unit<dim>::is_named) {
+  if constexpr (NamedUnit<dimension_unit<dim>>) {
     return exponent_list<Exp>();
   } else {
     using recipe = TYPENAME dim::recipe;

src/core/include/units/unit.h

@@ -79,7 +79,6 @@ struct same_unit_reference : is_same<typename U1::reference, typename U2::refere
  */
 template<typename Child, basic_symbol_text Symbol, PrefixFamily PF>
 struct named_unit : downcast_dispatch<Child, scaled_unit<ratio(1), Child>> {
-  static constexpr bool is_named = true;
   static constexpr auto symbol = Symbol;
   using prefix_family = PF;
 };
@@ -101,7 +100,6 @@ struct named_unit : downcast_dispatch<Child, scaled_unit<ratio(1), Child>> {
 template<typename Child, basic_symbol_text Symbol, PrefixFamily PF, ratio R, Unit U>
   requires UnitRatio<R>
 struct named_scaled_unit : downcast_dispatch<Child, scaled_unit<R * U::ratio, typename U::reference>> {
-  static constexpr bool is_named = true;
   static constexpr auto symbol = Symbol;
   using prefix_family = PF;
 };
@@ -117,10 +115,9 @@ struct named_scaled_unit : downcast_dispatch<Child, scaled_unit<R * U::ratio, ty
  * @tparam P prefix to be appied to the reference unit
  * @tparam U reference unit
  */
-template<typename Child, Prefix P, Unit U>
-  requires U::is_named && std::same_as<typename P::prefix_family, typename U::prefix_family>
+template<typename Child, Prefix P, NamedUnit U>
+  requires std::same_as<typename P::prefix_family, typename U::prefix_family>
 struct prefixed_unit : downcast_dispatch<Child, scaled_unit<P::ratio * U::ratio, typename U::reference>> {
-  static constexpr bool is_named = true;
   static constexpr auto symbol = P::symbol + U::symbol;
   using prefix_family = no_prefix;
 };
@@ -135,7 +132,6 @@ struct prefixed_unit : downcast_dispatch<Child, scaled_unit<P::ratio * U::ratio,
  */
 template<typename Child>
 struct derived_unit : downcast_dispatch<Child, scaled_unit<ratio(1), Child>> {
-  static constexpr bool is_named = false;
   using prefix_family = no_prefix;
 };
 
@@ -152,11 +148,9 @@ struct derived_unit : downcast_dispatch<Child, scaled_unit<ratio(1), Child>> {
  * @tparam U the unit of the first composite dimension from provided derived dimension's recipe
  * @tparam URest the units for the rest of dimensions from the recipe
  */
-template<typename Child, DerivedDimension Dim, Unit U, Unit... URest>
-  requires detail::same_scaled_units<typename Dim::recipe, U, URest...> &&
-           (U::is_named && (URest::is_named && ... && true))
+template<typename Child, DerivedDimension Dim, NamedUnit U, NamedUnit... URest>
+  requires detail::same_scaled_units<typename Dim::recipe, U, URest...>
 struct derived_deduced_unit : downcast_dispatch<Child, detail::derived_deduced_unit<Dim, U, URest...>> {
-  static constexpr bool is_named = false;
   static constexpr auto symbol = detail::derived_symbol_text<Dim, U, URest...>();
   using prefix_family = no_prefix;
 };
@@ -176,7 +170,6 @@ struct derived_deduced_unit : downcast_dispatch<Child, detail::derived_deduced_u
  */
 template<Unit U, basic_symbol_text Symbol, PrefixFamily PF>
 struct alias_unit : U {
-  static constexpr bool is_named = true;
   static constexpr auto symbol = Symbol;
   using prefix_family = PF;
 };
@@ -196,10 +189,9 @@ struct alias_unit : U {
 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95015
 // template<Unit U, Prefix P, AliasUnit AU>
 //   requires (!AliasUnit<U>) && std::same_as<typename P::prefix_family, typename AU::prefix_family>
-template<Unit U, Prefix P, Unit AU>
-  requires AU::is_named && std::same_as<typename P::prefix_family, typename AU::prefix_family>
+template<Unit U, Prefix P, NamedUnit AU>
+  requires std::same_as<typename P::prefix_family, typename AU::prefix_family>
 struct prefixed_alias_unit : U {
-  static constexpr bool is_named = true;
   static constexpr auto symbol = P::symbol + AU::symbol;
   using prefix_family = no_prefix;
 };
@@ -211,4 +203,26 @@ struct prefixed_alias_unit : U {
  */
 struct unknown_coherent_unit : derived_unit<unknown_coherent_unit> {};
 
+namespace detail {
+
+template<typename Child, basic_symbol_text Symbol, PrefixFamily PF>
+void is_named_impl(const volatile named_unit<Child, Symbol, PF>*);
+
+template<typename Child, basic_symbol_text Symbol, PrefixFamily PF, ratio R, Unit U>
+void is_named_impl(const volatile named_scaled_unit<Child, Symbol, PF, R, U>*);
+
+template<typename Child, typename P, typename U>
+void is_named_impl(const volatile prefixed_unit<Child, P, U>*);
+
+template<Unit U, basic_symbol_text Symbol, PrefixFamily PF>
+void is_named_impl(const volatile alias_unit<U, Symbol, PF>*);
+
+template<typename U, typename P, typename AU>
+void is_named_impl(const volatile prefixed_alias_unit<U, P, AU>*);
+
+template<Unit U>
+inline constexpr bool is_named<U> = requires(U * u) { is_named_impl(u); };
+
+}  // namespace detail
+
 }  // namespace units