From d2472e229c9742998452c7187c1e07220a383b21 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Thu, 7 Sep 2017 12:48:47 +1000
Subject: [PATCH] except: allow void functions in try_func

---
 except.hpp | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/except.hpp b/except.hpp
index f8c4c48..3b8769e 100644
--- a/except.hpp
+++ b/except.hpp
@@ -36,20 +36,31 @@ namespace cruft::vk {
 
 
         /// invokes a supplied function with the given arguments and tests
-        /// that it returns indicating success using try_code.
+        /// that it indicates success using try_code iff it returns a VkResult,
+        /// else it returns the result of the function.
+        ///
+        /// while it would simplify writing this function to avoid
+        /// non-VkResult functions it simplifies some of the upper layers of
+        /// try_foo functions to allow them anyway (eg,
+        /// vkGetBufferMemoryRequirements is otherwise usable with try_query
+        /// if we ignore the VkResult requirement)
         template <
             typename FuncT,
             typename ...Args
         >
-        static void
+        static auto
         try_func (FuncT &&func, Args &&...args)
         {
-            static_assert(std::is_same_v<
-                typename func_traits<FuncT>::return_type,
-                VkResult
-            >);
-
-            try_code (func (std::forward<Args> (args)...));
+            if constexpr (std::is_same_v<
+                              typename func_traits<FuncT>::return_type,
+                              VkResult
+                          >)
+            {
+                try_code (func (std::forward<Args> (args)...));
+                return;
+            }
+            else
+                return func (std::forward<Args> (args)...);
         }