entity: make constantly() even more evil

2 files changed, 14 insertions, 12 deletions

diff --git a/entity/metadata.hpp b/entity/metadata.hpp
index 1067a006..935f1792 100644
--- a/entity/metadata.hpp
+++ b/entity/metadata.hpp
@@ -70,17 +70,19 @@ struct find_reader<Obj, Type, Default, I, F, Fs...> { using type = F; static con
 
 namespace floormat::entities {
 
-template<typename... Ts> constexpr auto constantly(const auto& x) noexcept { return [x](const Ts&...) constexpr { return x; }; }
+constexpr auto constantly(const auto& x) noexcept {
+    return [x]<typename... Ts> (const Ts&...) constexpr -> const auto& { 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::max_length{std::size_t(-1)});
-    static constexpr auto default_c_group   = constantly<Obj>(StringView{});
+    static constexpr auto default_predicate = constantly(field_status::enabled);
+    static constexpr auto default_c_range   = constantly(constraints::range<Type>{});
+    static constexpr auto default_c_length  = constantly(constraints::max_length{std::size_t(-1)});
+    static constexpr auto default_c_group   = constantly(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 188b3b19..a10cbb98 100644
--- a/test/entity.cpp
+++ b/test/entity.cpp
@@ -191,9 +191,9 @@ constexpr void test_constraints()
     constexpr auto x = TestAccessors{};
     constexpr auto foo = entity::type<int>::field{
         "foo"_s, &TestAccessors::foo, &TestAccessors::foo,
-        constantly<TestAccessors>(constraints::max_length{42}),
-        constantly<TestAccessors>(constraints::range<int>{37, 42}),
-        constantly<TestAccessors>(constraints::group{"foo"_s})
+        constantly(constraints::max_length{42}),
+        constantly(constraints::range<int>{37, 42}),
+        constantly(constraints::group{"foo"_s})
     };
 
     static_assert(foo.get_range(x) == constraints::range<int>{37, 42});
@@ -206,7 +206,7 @@ constexpr void test_constraints()
 
     constexpr auto foo2 = entity::type<int>::field {
         "foo"_s, &TestAccessors::foo, &TestAccessors::foo,
-        constantly<TestAccessors>(constraints::max_length {123}),
+        constantly(constraints::max_length {123}),
     };
     static_assert(foo2.get_range(x) == constraints::range<int>{});
     static_assert(foo2.get_max_length(x) == 123);
@@ -217,9 +217,9 @@ void test_erased_constraints()
 {
     static constexpr auto foo = entity::type<int>::field{
         "foo"_s, &TestAccessors::foo, &TestAccessors::foo,
-        constantly<TestAccessors>(constraints::max_length{42}),
-        constantly<TestAccessors>(constraints::range<int>{37, 42}),
-        constantly<TestAccessors>(constraints::group{"foo"_s})
+        constantly(constraints::max_length{42}),
+        constantly(constraints::range<int>{37, 42}),
+        constantly(constraints::group{"foo"_s})
     };
     const auto x = TestAccessors{};
     const auto erased = foo.erased();