refactor: simplify unit type detection using C++20 concepts

Author: SticksDev

docs/core/units.md

@@ -148,17 +148,25 @@ TelemetryKit works with any WPILib unit type. See the [WPILib Units Documentatio
 
 ## How It Works
 
-TelemetryKit uses C++ type traits to detect WPILib unit types at compile time via SFINAE. When a unit type is detected:
+TelemetryKit uses a C++20 concept to detect WPILib unit types at compile time:
+
+```cpp
+template<typename T>
+concept UnitType = requires(T t) {
+    { t.value() } -> std::convertible_to<double>;
+    typename T::unit_type;
+};
+```
+
+When a unit type is detected:
 
 1. `value.value()` extracts the numeric value
-2. `units::abbreviation(UnitType{})` gets the unit string
+2. `units::abbreviation(T{})` gets the unit string
 3. Both are passed to the standard logging functions
 
 ```cpp
-template<typename T>
-inline auto RecordOutput(std::string_view key, const T& value)
-    -> std::enable_if_t<detail::is_unit_type_v<T>, void>
-{
+template<UnitType T>
+inline void RecordOutput(std::string_view key, const T& value) {
     std::string unit = detail::GetUnitAbbreviation<T>();
     Logger::GetInstance().RecordOutput(key, value.value(), unit);
 }

src/main/native/include/telemetrykit/core/Units.h

@@ -1,8 +1,8 @@
 #pragma once
 
+#include <concepts>
 #include <string>
 #include <string_view>
-#include <type_traits>
 
 #include <units/base.h>
 
@@ -22,25 +22,19 @@ namespace tkit {
  *   tkit::RecordOutput("/Speed", units::meters_per_second_t{2.5});
  */
 
-namespace detail {
-
-// Detects whether a type is a WPILib units::unit_t
-template<typename T, typename = void>
-struct is_unit_type : std::false_type {};
-
+// Concept for WPILib unit types
 template<typename T>
-struct is_unit_type<T, std::void_t<
-    decltype(std::declval<T>().value()),
-    typename T::unit_type
->> : std::true_type {};
+concept UnitType = requires(T t) {
+    { t.value() } -> std::convertible_to<double>;
+    typename T::unit_type;
+};
 
-template<typename T>
-inline constexpr bool is_unit_type_v = is_unit_type<T>::value;
+namespace detail {
 
 // Returns the abbreviation string for a unit type
-template<typename UnitType>
+template<UnitType T>
 std::string GetUnitAbbreviation() {
-    return std::string(units::abbreviation(UnitType{}));
+    return std::string(units::abbreviation(T{}));
 }
 
 }  // namespace detail
@@ -54,21 +48,17 @@ std::string GetUnitAbbreviation() {
  *   tkit::RecordOutput("/Distance", units::meter_t{3.5}); // 3.5, "m"
  *   tkit::RecordOutput("/Angle", units::degree_t{90.0});  // 90.0, "deg"
  */
-template<typename T>
-inline auto RecordOutput(std::string_view key, const T& value)
-    -> std::enable_if_t<detail::is_unit_type_v<T>, void>
-{
+template<UnitType T>
+inline void RecordOutput(std::string_view key, const T& value) {
     std::string unit = detail::GetUnitAbbreviation<T>();
     Logger::GetInstance().RecordOutput(key, value.value(), unit);
 }
 
 /**
  * LogTable::Put overload for WPILib unit types.
  */
-template<typename T>
-inline auto Put(LogTable& table, std::string_view key, const T& value)
-    -> std::enable_if_t<detail::is_unit_type_v<T>, void>
-{
+template<UnitType T>
+inline void Put(LogTable& table, std::string_view key, const T& value) {
     std::string unit = detail::GetUnitAbbreviation<T>();
     table.Put(key, value.value(), unit);
 }