From 754eaae8e5fae4c0fb00265180b832aab1fdf736 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ion=20Gazta=C3=B1aga?= <igaztanaga@gmail.com>
Date: Thu, 3 Jan 2019 00:07:21 +0100
Subject: [PATCH] Default disable/enable_if to a nat type instead of void, as
 many SFINAE expressions in funcions default to void *values that are valid
 parameters.

---
 doc/move.qbk                                  |  8 ++++++++
 include/boost/move/detail/meta_utils_core.hpp | 17 +++++++++++------
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/doc/move.qbk b/doc/move.qbk
index e75722d..eaa3c22 100644
--- a/doc/move.qbk
+++ b/doc/move.qbk
@@ -802,6 +802,14 @@ Special thanks to:
 
 [section:release_notes Release Notes]
 
+[section:release_notes_boost_1_70 Boost 1.70 Release]
+
+*  Removed support for deprecated GCC compilers.
+*  Fixed bugs:
+   *  [@https://github.com/boostorg/move/pull/23 Git Pull #23: ['"Add minimal cmake file "]].
+
+[endsect]
+
 [section:release_notes_boost_1_69 Boost 1.69 Release]
 
 *  Deprecated GCC < 4.3 and MSVC < 9.0 (Visual 2008) compilers.
diff --git a/include/boost/move/detail/meta_utils_core.hpp b/include/boost/move/detail/meta_utils_core.hpp
index 40dbb6e..4e11673 100644
--- a/include/boost/move/detail/meta_utils_core.hpp
+++ b/include/boost/move/detail/meta_utils_core.hpp
@@ -27,6 +27,9 @@
 namespace boost {
 namespace move_detail {
 
+template<typename T>
+struct voider { typedef void type; };
+
 //////////////////////////////////////
 //             if_c
 //////////////////////////////////////
@@ -52,7 +55,9 @@ struct if_ : if_c<0 != T1::value, T2, T3>
 //////////////////////////////////////
 //          enable_if_c
 //////////////////////////////////////
-template <bool B, class T = void>
+struct enable_if_nat{};
+
+template <bool B, class T = enable_if_nat>
 struct enable_if_c
 {
    typedef T type;
@@ -64,13 +69,13 @@ struct enable_if_c<false, T> {};
 //////////////////////////////////////
 //           enable_if
 //////////////////////////////////////
-template <class Cond, class T = void>
+template <class Cond, class T = enable_if_nat>
 struct enable_if : enable_if_c<Cond::value, T> {};
 
 //////////////////////////////////////
 //          disable_if_c
 //////////////////////////////////////
-template <bool B, class T = void>
+template <bool B, class T = enable_if_nat>
 struct disable_if_c
    : enable_if_c<!B, T>
 {};
@@ -78,7 +83,7 @@ struct disable_if_c
 //////////////////////////////////////
 //          disable_if
 //////////////////////////////////////
-template <class Cond, class T = void>
+template <class Cond, class T = enable_if_nat>
 struct disable_if : enable_if_c<!Cond::value, T> {};
 
 //////////////////////////////////////
@@ -117,13 +122,13 @@ struct is_same<T, T>
 //////////////////////////////////////
 //        enable_if_same
 //////////////////////////////////////
-template <class T, class U, class R = void>
+template <class T, class U, class R = enable_if_nat>
 struct enable_if_same : enable_if<is_same<T, U>, R> {};
 
 //////////////////////////////////////
 //        disable_if_same
 //////////////////////////////////////
-template <class T, class U, class R = void>
+template <class T, class U, class R = enable_if_nat>
 struct disable_if_same : disable_if<is_same<T, U>, R> {};
 
 }  //namespace move_detail {