From 0691018321f03aad662d7d2ae5b3e060c7109e3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ion=20Gazta=C3=B1aga?= <igaztanaga@gmail.com>
Date: Tue, 26 Mar 2019 22:42:10 +0100
Subject: [PATCH] Avoid using is_convertible during allocator version detection
 to avoid incomplete type problems in clang compilers. has_version, has
 already checked the existence of the "version" typedef.

---
 include/boost/container/detail/version_type.hpp | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/include/boost/container/detail/version_type.hpp b/include/boost/container/detail/version_type.hpp
index c2531cc..58e9da6 100644
--- a/include/boost/container/detail/version_type.hpp
+++ b/include/boost/container/detail/version_type.hpp
@@ -39,24 +39,14 @@ struct version_type
     : public dtl::integral_constant<unsigned, V>
 {
     typedef T type;
-
-    version_type(const version_type<T, 0>&);
 };
 
 namespace impl{
 
-template <class T,
-          bool = dtl::is_convertible<version_type<T, 0>, typename T::version>::value>
-struct extract_version
-{
-   static const unsigned value = 1;
-};
-
 template <class T>
-struct extract_version<T, true>
-{
-   static const unsigned value = T::version::value;
-};
+struct extract_version
+   : T::version
+{};
 
 template <class T>
 struct has_version