From 5ed58ee20fd7f362839086ea409a24b77f874206 Mon Sep 17 00:00:00 2001
From: Glen Fernandes <glen.fernandes@gmail.com>
Date: Mon, 1 Oct 2018 00:26:08 -0400
Subject: [PATCH] Add ADL guard for empty_value and new member typedef

---
 doc/empty_value.qbk                |  8 ++++++++
 include/boost/core/empty_value.hpp | 10 ++++++++++
 2 files changed, 18 insertions(+)

diff --git a/doc/empty_value.qbk b/doc/empty_value.qbk
index 60149e9..ce0d906 100644
--- a/doc/empty_value.qbk
+++ b/doc/empty_value.qbk
@@ -85,6 +85,8 @@ struct empty_init_t { };
 template<class T, unsigned Index = 0, bool Empty = ``/see below/``>
 class empty_value {
 public:
+    typedef T type;
+
     empty_value() = default;
 
     template<class... Args>
@@ -107,6 +109,12 @@ public:
 
 [endsect]
 
+[section Member types]
+
+[variablelist [[`type`][The template parameter `T`]]]
+
+[endsect]
+
 [section Constructors]
 
 [variablelist
diff --git a/include/boost/core/empty_value.hpp b/include/boost/core/empty_value.hpp
index 0902e00..60ca36f 100644
--- a/include/boost/core/empty_value.hpp
+++ b/include/boost/core/empty_value.hpp
@@ -40,9 +40,13 @@ struct use_empty_value_base {
 
 struct empty_init_t { };
 
+namespace empty_ {
+
 template<class T, unsigned N = 0, bool E = use_empty_value_base<T>::value>
 class empty_value {
 public:
+    typedef T type;
+
 #if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
     empty_value() = default;
 #else
@@ -85,6 +89,8 @@ template<class T, unsigned N>
 class empty_value<T, N, true>
     : T {
 public:
+    typedef T type;
+
 #if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
     empty_value() = default;
 #else
@@ -120,6 +126,10 @@ public:
 };
 #endif
 
+} /* empty_ */
+
+using empty_::empty_value;
+
 } /* boost */
 
 #endif