From d57a4dddc20b6ebabe0922a775545fee7b06dce0 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 5 Feb 2019 18:16:36 +1100
Subject: [PATCH] debug: pretend to return the same type in `unhandled`

---
 debug.hpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/debug.hpp b/debug.hpp
index 03ef4372..bc9dbeb0 100644
--- a/debug.hpp
+++ b/debug.hpp
@@ -524,9 +524,13 @@ unreachable [[noreturn]] (void)
 /// statements. will almost invariably abort the application.
 namespace cruft::debug::detail {
     template <typename T>
-    void
+    T
     unhandled [[noreturn]] (T &&t) noexcept
     {
+        // If we've been given an enum we should handle it like its underlying
+        // type so that when we end up logging it we don't accidentally
+        // trigger an infinite loop of calls to `unhandled` within the
+        // ostream operator. It doesn't have to be pretty, just functional.
         using base_type = std::remove_reference_t<std::decay_t<T>>;
         if constexpr (std::is_enum_v<base_type>) {
             unhandled (static_cast<std::underlying_type_t<base_type>> (t));
@@ -540,7 +544,7 @@ namespace cruft::debug::detail {
 
 
 template <typename T>
-constexpr void
+constexpr T
 unhandled [[noreturn]] (T &&t) noexcept
 {
     cruft::debug::detail::unhandled (std::forward<T> (t));