commit 4d626e1a931f73f1f0f721e3a910c57911bffa6f
author William A. Kennington III <wak@google.com> Thu Jul 06 16:13:54 2023 -0700
committer William A. Kennington III <wak@google.com> Thu Jul 06 16:13:59 2023 -0700
tree 583ab7dc0b9d780ac3208cafd76e1a3f764b7b96
parent cf11a4a68e62809943f0025c9c1f08768c0b4d45

variant: Use concepts

This makes the code a little more concise and removes the need for extra
template parameters.

Change-Id: Ie990ec27eb99e15a2b7d12175f4afab473fa049b
Signed-off-by: William A. Kennington III <wak@google.com>

include/stdplus/variant.hpp

diff --git a/include/stdplus/variant.hpp b/include/stdplus/variant.hpp
index 61d2e27..fe849da 100644
--- a/include/stdplus/variant.hpp
+++ b/include/stdplus/variant.hpp
@@ -1,3 +1,6 @@
+#include <stdplus/concepts.hpp>
+
+#include <concepts>
 #include <type_traits>
 #include <utility>
 #include <variant>
@@ -7,19 +10,17 @@
 namespace detail
 {
 
-template <template <typename, typename, typename = void> typename Veq,
-          typename...>
+template <template <typename, typename> typename Veq, typename...>
 struct CanVeq;
 
-template <template <typename, typename, typename = void> typename Veq,
-          typename T>
+template <template <typename, typename> typename Veq, typename T>
 struct CanVeq<Veq, T>
 {
     static constexpr inline bool value = false;
 };
 
-template <template <typename, typename, typename = void> typename Veq,
-          typename T, typename V, typename... Vs>
+template <template <typename, typename> typename Veq, typename T, typename V,
+          typename... Vs>
 struct CanVeq<Veq, T, V, Vs...>
 {
     static constexpr inline bool value = Veq<T, V>::value ||
@@ -37,14 +38,12 @@
     }
 };
 
-template <typename T1, typename T2, typename = void>
+template <typename T1, typename T2>
 struct VeqFuzzy : VeqBase<T1, T2>
 {};
 
-template <typename T1, typename T2>
-struct VeqFuzzy<T1, T2,
-                std::enable_if_t<std::is_same_v<
-                    decltype(std::declval<T1>() == std::declval<T2>()), bool>>>
+template <typename T1, WeaklyEqualityComparableWith<T1> T2>
+struct VeqFuzzy<T1, T2>
 {
     static constexpr inline bool value = true;
 
@@ -54,12 +53,12 @@
     }
 };
 
-template <typename T1, typename T2, typename = void>
+template <typename T1, typename T2>
 struct VeqStrict : VeqBase<T1, T2>
 {};
 
-template <typename T1, typename T2>
-struct VeqStrict<T1, T2, std::enable_if_t<std::is_same_v<T1, T2>>>
+template <typename T1, std::same_as<T1> T2>
+struct VeqStrict<T1, T2>
 {
     static constexpr inline bool value = true;
 
@@ -71,8 +70,8 @@
 
 } // namespace detail
 
-template <template <typename, typename, typename = void> typename Veq,
-          typename... Vs, typename T,
+template <template <typename, typename> typename Veq, typename... Vs,
+          typename T,
           std::enable_if_t<detail::CanVeq<Veq, T, Vs...>::value, bool> = true>
 constexpr bool variantEq(const std::variant<Vs...>& vs, const T& t) noexcept
 {
@@ -83,8 +82,8 @@
         vs);
 }
 
-template <template <typename, typename, typename = void> typename Veq,
-          typename... Vs, typename... Vs2>
+template <template <typename, typename> typename Veq, typename... Vs,
+          typename... Vs2>
 constexpr bool variantEq(const std::variant<Vs...>& vs,
                          const std::variant<Vs2...>& vs2) noexcept
 {