If does not have name return empty string

example/example.cpp

@@ -77,7 +77,7 @@ struct Long {
   LL ll;
 };
 
-enum class Color { RED = -10, GREEN, BLUE };
+enum class Color { RED, GREEN, BLUE };
 
 SomeStruct structvar;
 Long othervar;

include/nameof.hpp

@@ -136,7 +136,7 @@ template <typename T>
   constexpr auto prefix = sizeof("class std::basic_string_view<char,struct std::char_traits<char> > __cdecl nameof::detail::nameof_type_impl<struct nameof::detail::identity<") - 1;
   constexpr auto suffix = sizeof(">>(void) noexcept") - 1;
 #else
-  return "nameof_type::unsupported_compiler";
+  return {}; // Unsupported compiler.
 #endif
 
 #if defined(__clang__) || defined(__GNUC__) || defined(_MSC_VER)
@@ -156,6 +156,7 @@ template <typename T>
   while (name.back() == ' ') {
     name.remove_suffix(1);
   }
+
   return name;
 #endif
 }
@@ -173,7 +174,7 @@ template <auto V>
   std::string_view name{__FUNCSIG__};
   constexpr auto suffix = sizeof(">(void) noexcept") - 1;
 #else
-  return "nameof_enum::unsupported_compiler";
+  return {}; // Unsupported compiler.
 #endif
 
 #if defined(__clang__) || (defined(__GNUC__) && __GNUC__ >= 9) || defined(_MSC_VER)
@@ -184,7 +185,12 @@ template <auto V>
       break;
     }
   }
-  return name;
+
+  if (name.front() >= '0' && name.front() <= '9') {
+    return {}; // Enum variable does not have name.
+  } else {
+    return name;
+  }
 #endif
 }
 
@@ -193,7 +199,7 @@ struct nameof_enum_impl_t final {
   [[nodiscard]] constexpr std::string_view operator()(int value) const noexcept {
     static_assert(std::is_enum_v<E>);
     if constexpr (V > std::numeric_limits<std::underlying_type_t<E>>::max()) {
-      return "nameof_enum::out_of_range";
+      return {}; // Enum variable out of range.
     }
 
     switch (value - V) {
@@ -223,7 +229,7 @@ template <typename E>
 struct nameof_enum_impl_t<E, NAMEOF_ENUM_MAX_SEARCH_DEPTH> final {
   [[nodiscard]] constexpr std::string_view operator()(int) const noexcept {
     static_assert(std::is_enum_v<E>);
-    return "nameof_enum::out_of_range";
+    return {}; // Enum variable out of range NAMEOF_ENUM_MAX_SEARCH_DEPTH.
   }
 };
 

test/test.cpp

@@ -23,6 +23,7 @@
 #define CATCH_CONFIG_MAIN
 #include <catch.hpp>
 
+#define NAMEOF_ENUM_MAX_SEARCH_DEPTH 120
 #include <nameof.hpp>
 
 #include <string>
@@ -67,9 +68,9 @@ struct Long {
   LL ll;
 };
 
-enum class Color { RED = -1, GREEN, BLUE };
+enum class Color : int { RED = -10, GREEN = 0, BLUE = 10 };
 
-enum Directions { Up, Down, Right, Left };
+enum Directions : unsigned int { Up, Down, Right, Left };
 
 SomeStruct struct_var;
 Long othervar;
@@ -223,6 +224,13 @@ TEST_CASE("NAMEOF_ENUM") {
 
   REQUIRE(NAMEOF_ENUM(Directions::Right) == "Right");
   REQUIRE(NAMEOF_ENUM(directions) == "Right");
+
+  REQUIRE(NAMEOF_ENUM((Color)NAMEOF_ENUM_MAX_SEARCH_DEPTH).empty());
+  REQUIRE(NAMEOF_ENUM((Color)-100).empty());
+  REQUIRE(NAMEOF_ENUM((Color)100).empty());
+  REQUIRE(NAMEOF_ENUM((Directions)NAMEOF_ENUM_MAX_SEARCH_DEPTH).empty());
+  REQUIRE(NAMEOF_ENUM((Directions)100).empty());
+  REQUIRE(NAMEOF_ENUM((Directions)100).empty());
 #endif
 }
 
@@ -240,6 +248,13 @@ TEST_CASE("nameof::nameof_enum<T>(value)") {
 
   REQUIRE(nameof::nameof_enum(Directions::Right) == "Right");
   REQUIRE(nameof::nameof_enum(directions) == "Right");
+
+  REQUIRE(nameof::nameof_enum((Color)NAMEOF_ENUM_MAX_SEARCH_DEPTH).empty());
+  REQUIRE(nameof::nameof_enum((Color)-100).empty());
+  REQUIRE(nameof::nameof_enum((Color)100).empty());
+  REQUIRE(nameof::nameof_enum((Directions)NAMEOF_ENUM_MAX_SEARCH_DEPTH).empty());
+  REQUIRE(nameof::nameof_enum((Directions)100).empty());
+  REQUIRE(nameof::nameof_enum((Directions)100).empty());
 #endif
 }
 
@@ -257,6 +272,13 @@ TEST_CASE("nameof::nameof_enum<value>()") {
 
   REQUIRE(nameof::nameof_enum<Directions::Right>() == "Right");
   REQUIRE(nameof::nameof_enum<directions>() == "Right");
+
+  REQUIRE(nameof::nameof_enum<(Color)NAMEOF_ENUM_MAX_SEARCH_DEPTH>().empty());
+  REQUIRE(nameof::nameof_enum<(Color)-100>().empty());
+  REQUIRE(nameof::nameof_enum<(Color)100>().empty());
+  REQUIRE(nameof::nameof_enum<(Directions)NAMEOF_ENUM_MAX_SEARCH_DEPTH>().empty());
+  REQUIRE(nameof::nameof_enum<(Directions)100>().empty());
+  REQUIRE(nameof::nameof_enum<(Directions)100>().empty());
 #endif
 }