entity: make `constantly` more generic

2 files changed, 11 insertions, 10 deletions

diff --git a/entity/metadata.hpp b/entity/metadata.hpp
index 60e9c458..c9b9a1d5 100644
--- a/entity/metadata.hpp
+++ b/entity/metadata.hpp
@@ -70,18 +70,17 @@ struct find_reader<Obj, Type, Default, I, F, Fs...> { using type = F; static con
 
 namespace floormat::entities {
 
-template<typename Obj, auto constant>
-constexpr auto constantly = [](const Obj&) constexpr { return constant; };
+template<typename... Ts> constexpr auto constantly(const auto& x) noexcept { return [x](const Ts&...) constexpr { return x; }; }
 
 template<typename Obj, typename Type> struct entity_field_base {};
 
 template<typename Obj, typename Type, FieldReader<Obj, Type> R, FieldWriter<Obj, Type> W, typename... Ts>
 struct entity_field : entity_field_base<Obj, Type> {
 private:
-    static constexpr auto default_predicate = constantly<Obj, field_status::enabled>;
-    static constexpr auto default_c_range   = constantly<Obj, constraints::range<Type>{}>;
-    static constexpr auto default_c_length  = constantly<Obj, constraints::length{std::size_t(-1)}>;
-    static constexpr auto default_c_group   = [](const Obj&) constexpr { return StringView{}; };
+    static constexpr auto default_predicate = constantly<Obj>(field_status::enabled);
+    static constexpr auto default_c_range   = constantly<Obj>(constraints::range<Type>{});
+    static constexpr auto default_c_length  = constantly<Obj>(constraints::length{std::size_t(-1)});
+    static constexpr auto default_c_group   = constantly<Obj>(StringView{});
     using default_predicate_t = std::decay_t<decltype(default_predicate)>;
     using default_c_range_t   = std::decay_t<decltype(default_c_range)>;
     using default_c_length_t  = std::decay_t<decltype(default_c_length)>;
diff --git a/test/entity.cpp b/test/entity.cpp
index d09c94ba..4e0935f2 100644
--- a/test/entity.cpp
+++ b/test/entity.cpp
@@ -189,10 +189,12 @@ constexpr bool test_names()
 constexpr void test_range()
 {
     constexpr auto x = TestAccessors{};
-    constexpr auto foo = entity::type<int>::field{"foo"_s, &TestAccessors::foo, &TestAccessors::foo,
-                                                  constantly<TestAccessors, constraints::length{42}>,
-                                                  constantly<TestAccessors, constraints::range<int>{37, 42}>,
-                                                  [](const TestAccessors&) constexpr -> constraints::group { return "foo"_s; }};
+    constexpr auto foo = entity::type<int>::field{
+        "foo"_s, &TestAccessors::foo, &TestAccessors::foo,
+        constantly<TestAccessors>(constraints::length{42}),
+        constantly<TestAccessors>(constraints::range<int>{37, 42}),
+        constantly<TestAccessors>(constraints::group{"foo"_s})
+    };
 
     using limits = std::numeric_limits<int>;