From 782d7387d5ac0f965b2e61d6142f55ab2ce31411 Mon Sep 17 00:00:00 2001
From: Sumit Bhardwaj <bhardwajs@outlook.com>
Date: Thu, 2 Jul 2020 23:36:10 -0700
Subject: Implement cm::static_reference_cast by declval

Previously, cm::static_reference_cast used invoke_result_t and took the
address of O::get. This is not in complete conformance with standard.

This MR changes the implementation to use std::declval<O>.get() which is
always well-defined.
---
 Utilities/std/cmext/memory | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/Utilities/std/cmext/memory b/Utilities/std/cmext/memory
index 50e79df..fa326f0 100644
--- a/Utilities/std/cmext/memory
+++ b/Utilities/std/cmext/memory
@@ -12,18 +12,19 @@
 
 namespace cm {
 
-template <typename T, typename O,
-          cm::enable_if_t<
-            std::is_pointer<cm::invoke_result_t<decltype(&O::get), O>>::value,
-            int> = 0>
+template <
+  typename T, typename O,
+  cm::enable_if_t<std::is_pointer<decltype(std::declval<O>().get())>::value,
+                  int> = 0>
 T& static_reference_cast(O& item)
 {
   return *(static_cast<T*>(item.get()));
 }
-template <typename T, typename O,
-          cm::enable_if_t<
-            std::is_pointer<cm::invoke_result_t<decltype(&O::get), O>>::value,
-            int> = 0>
+
+template <
+  typename T, typename O,
+  cm::enable_if_t<std::is_pointer<decltype(std::declval<O>().get())>::value,
+                  int> = 0>
 T& dynamic_reference_cast(O& item)
 {
   auto p = dynamic_cast<T*>(item.get());
-- 
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