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diff --git a/src/boost/libs/hana/test/concept/constant/minimal.hpp b/src/boost/libs/hana/test/concept/constant/minimal.hpp
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+++ b/src/boost/libs/hana/test/concept/constant/minimal.hpp
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+// Copyright Louis Dionne 2013-2017
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+
+#ifndef TEST_CONCEPT_CONSTANT_MINIMAL_HPP
+#define TEST_CONCEPT_CONSTANT_MINIMAL_HPP
+
+#include <boost/hana/concept/constant.hpp>
+#include <boost/hana/core/when.hpp>
+#include <boost/hana/fwd/core/to.hpp>
+#include <boost/hana/value.hpp>
+
+
+template <typename T>
+struct minimal_constant_tag {
+    using value_type = T;
+};
+
+template <typename T, T v>
+struct minimal_constant {
+    using hana_tag = minimal_constant_tag<T>;
+    static constexpr T value_ = v;
+};
+
+namespace boost { namespace hana {
+    template <typename T>
+    struct value_impl<minimal_constant_tag<T>> {
+        template <typename N>
+        static constexpr T apply() { return N::value_; }
+    };
+
+    template <typename T, typename C>
+    struct to_impl<minimal_constant_tag<T>, C, hana::when<
+        hana::Constant<C>::value &&
+        hana::is_convertible<typename C::value_type, T>::value
+    >>
+        : hana::embedding<hana::is_embedded<typename C::value_type, T>::value>
+    {
+        template <typename N>
+        static constexpr auto apply(N const&)
+        { return minimal_constant<T, hana::value<N>()>{}; }
+    };
+}} // end namespace boost::hana
+
+#endif // !TEST_CONCEPT_CONSTANT_MINIMAL_HPP