From c23d2e38f3d60ab7e0a619523f804befc027e69d Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Fri, 11 Sep 2020 13:36:17 +1000
Subject: [PATCH] types/traits: add `try_underlying`

---
 types/traits.hpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/types/traits.hpp b/types/traits.hpp
index 45e48c2a..b64f875f 100644
--- a/types/traits.hpp
+++ b/types/traits.hpp
@@ -120,6 +120,20 @@ template <typename ValueT>
 using try_signed_t = typename try_signed<ValueT>::type;
 
 
+///////////////////////////////////////////////////////////////////////////////
+namespace cruft {
+    template <typename ValueT, typename = void>
+    struct try_underlying { using type = ValueT; };
+
+
+    template <typename ValueT>
+    struct try_underlying<
+        ValueT,
+        std::void_t<std::underlying_type_t<ValueT>>
+    > { using type = std::underlying_type<ValueT>; };
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 /// checks if a type can be converted in all cases without modification
 template <typename T, typename U> struct is_lossless_cast : std::enable_if<