✨ Add is_scoped_enum

Problem:
- `is_scoped_enum_v` is fine, but a type is also needed for use in the
  `has_trait` concept.

Solution:
- Add `is_scoped_enum`.

Author: elbeno

include/stdx/type_traits.hpp

@@ -114,8 +114,9 @@ constexpr auto is_specialization_of()
 
 template <typename E>
 constexpr bool is_scoped_enum_v =
-    std::is_enum_v<E> and
-    not std::is_convertible_v<E, std::underlying_type_t<E>>;
+    std::is_enum_v<E> and not std::is_convertible_v<E, underlying_type_t<E>>;
+template <typename E>
+using is_scoped_enum = std::bool_constant<is_scoped_enum_v<E>>;
 
 template <typename...> struct type_list {};
 template <auto...> struct value_list {};

test/type_traits.cpp

@@ -77,8 +77,13 @@ enum struct E2 {};
 } // namespace
 
 TEST_CASE("is_scoped_enum", "[type_traits]") {
+    static_assert(not stdx::is_scoped_enum_v<int>);
     static_assert(not stdx::is_scoped_enum_v<E1>);
     static_assert(stdx::is_scoped_enum_v<E2>);
+
+    static_assert(not stdx::is_scoped_enum<int>::value);
+    static_assert(not stdx::is_scoped_enum<E1>::value);
+    static_assert(stdx::is_scoped_enum<E2>::value);
 }
 
 TEST_CASE("type_identity", "[type_traits]") {