refactor: some TODO comments resolved

src/core/include/mp-units/bits/hacks.h

@@ -87,14 +87,9 @@
 
 #endif
 
-// TODO revise the below when clang-18 is released
-#if MP_UNITS_COMP_CLANG >= 18 && __cplusplus >= 202300L && !defined __cpp_explicit_this_parameter
-
-#define __cpp_explicit_this_parameter 202110L
 
 #endif
 
-
 #if !defined __cpp_lib_ranges_to_container
 
 namespace std {

src/core/include/mp-units/ext/type_traits.h

@@ -88,9 +88,8 @@ void to_base_specialization_of(const volatile Type<Params...>*);
 }  // namespace detail
 
 template<typename T, template<typename...> typename Type>
-// inline constexpr bool // TODO: Replace with concept when it works with MSVC
-concept is_derived_from_specialization_of = requires(T* t) { detail::to_base_specialization_of<Type>(t); };
-
+inline constexpr bool is_derived_from_specialization_of =
+  requires(T* t) { detail::to_base_specialization_of<Type>(t); };
 
 namespace detail {