From 1e1aa33b75a6a36375b3c39de1a7326c7866edb4 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 29 Aug 2019 14:05:39 +1000
Subject: [PATCH] parse/enum: detect types with underlying_type members

---
 parse/enum.hpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/parse/enum.hpp b/parse/enum.hpp
index bc969db1..a9bedf7f 100644
--- a/parse/enum.hpp
+++ b/parse/enum.hpp
@@ -33,6 +33,13 @@ namespace cruft::parse::enumeration {
         > { using type = std::underlying_type_t<EnumT>; };
 
 
+        template <typename EnumT>
+        struct underlying_else_identity<
+            EnumT,
+            std::void_t<typename EnumT::underlying_type>
+        > { using type = typename underlying_else_identity<typename EnumT::underlying_type>::type; };
+
+
         template <typename EnumT>
         using underlying_else_identity_t = typename underlying_else_identity<EnumT>::type;