add enum_reflected

Author: Neargye

doc/reference.md

@@ -10,6 +10,7 @@
 * [`enum_entries` obtains pair (value enum, string enum name) sequence.](#enum_entries)
 * [`enum_index` obtains index in enum value sequence from enum value.](#enum_index)
 * [`enum_contains` checks whether enum contains enumerator with such value.](#enum_contains)
+* [`enum_reflected` returns true if the enum value is in the range of values that can be reflected..](#enum_reflected)
 * [`enum_type_name` returns type name of enum.](#enum_type_name)
 * [`enum_fuse` returns a bijective mix of enum values.](#enum_fuse)
 * [`enum_switch` allows runtime enum value transformation to constexpr context.](#enum_switch)
@@ -316,6 +317,21 @@ constexpr bool enum_contains(string_view value, BinaryPredicate p) noexcept(is_n
   magic_enum::enum_contains<Color>("fda"); // -> false
   ```
 
+## `enum_reflected`
+
+```cpp
+template <typename E>
+constexpr bool enum_contains(E value) noexcept;
+
+template <typename E>
+constexpr bool enum_contains(underlying_type_t<E> value) noexcept;
+
+template <typename E>
+constexpr bool enum_contains(string_view value) noexcept;
+```
+
+* Returns true if the enum value is in the range of values that can be reflected.
+
 ## `enum_type_name`
 
 ```cpp

include/magic_enum/magic_enum.hpp

@@ -1414,6 +1414,35 @@ template <typename E, detail::enum_subtype S = detail::subtype_v<E>, typename Bi
   return static_cast<bool>(enum_cast<D, S>(value, std::move(p)));
 }
 
+// Returns true if the enum value is in the range of values that can be reflected.
+template <typename E, detail::enum_subtype S = detail::subtype_v<E>>
+[[nodiscard]] constexpr auto enum_reflected(E value) noexcept -> detail::enable_if_t<E, bool> {
+  using D = std::decay_t<E>;
+
+  if constexpr (detail::is_reflected_v<D, S>) {
+    constexpr auto min = detail::reflected_min<E, S>();
+    constexpr auto max = detail::reflected_max<E, S>();
+    return value >= min && value <= max;
+  }
+  return false;
+}
+
+// Returns true if the enum value is in the range of values that can be reflected.
+template <detail::enum_subtype S, typename E>
+[[nodiscard]] constexpr auto enum_reflected(E value) noexcept -> detail::enable_if_t<E, bool> {
+  using D = std::decay_t<E>;
+
+  return enum_cast<D, S>(value);
+}
+
+// Returns true if the enum integer value is in the range of values that can be reflected.
+template <typename E, detail::enum_subtype S = detail::subtype_v<E>>
+[[nodiscard]] constexpr auto enum_reflected(underlying_type_t<E> value) noexcept -> detail::enable_if_t<E, bool> {
+  using D = std::decay_t<E>;
+
+  return enum_cast<D, S>(value);
+}
+
 template <bool AsFlags = true>
 inline constexpr auto as_flags = AsFlags ? detail::enum_subtype::flags : detail::enum_subtype::common;
 

test/test.cpp

@@ -1274,3 +1274,13 @@ TEST_CASE("valid_enum") {
   REQUIRE(magic_enum::detail::is_reflected_v<Empty4, as_flags<true>>);
   REQUIRE(magic_enum::detail::is_reflected_v<Empty4, as_flags<false>>);
 }
+
+TEST_CASE("enum_reflected") {
+  REQUIRE(enum_reflected<number>(number::one));
+  REQUIRE(enum_reflected<number>(number::three));
+  REQUIRE_FALSE(enum_reflected<number>(number::four));
+  REQUIRE(enum_reflected<number>(1));
+  REQUIRE(enum_reflected<number>(234));
+  REQUIRE_FALSE(enum_reflected<number>(400));
+  REQUIRE_FALSE(enum_reflected<number>(500));
+}