1 files changed, 50 insertions, 0 deletions
diff --git a/src/boost/libs/hana/test/integral_constant/constexpr_init.cpp b/src/boost/libs/hana/test/integral_constant/constexpr_init.cpp
new file mode 100644
index 000000000..0656eb6d0
--- /dev/null
+++ b/src/boost/libs/hana/test/integral_constant/constexpr_init.cpp
@@ -0,0 +1,50 @@
+// 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)
+
+#include <boost/hana/bool.hpp>
+#include <boost/hana/integral_constant.hpp>
+namespace hana = boost::hana;
+
+
+/*
+When we use `int_<...>` in a template, Clang 3.5 says:
+
+--------------------------------
+include/boost/hana/integral_constant.hpp:80:20: error: constexpr variable 'int_<1>' must be initialized by a constant expression
+    constexpr auto int_ = integral<int, i>;
+                   ^      ~~~~~~~~~~~~~~~~
+test/integral/constexpr_bug.cpp:41:37: note: in instantiation of variable template specialization 'boost::hana::int_' requested here
+constexpr auto check_int() { return int_<1>; }
+                                    ^
+include/boost/hana/integral_constant.hpp:80:27: note: subexpression not valid in a constant expression
+    constexpr auto int_ = integral<int, i>;
+                          ^
+include/boost/hana/integral_constant.hpp:80:27: note: in call to 'integral_type(integral)'
+--------------------------------
+
+if we define int_ & friends like
+
+    template <int i>
+    constexpr auto int_ = integral<int, i>;
+
+Instead, we do
+
+    template <int i>
+    constexpr decltype(integral<int, i>) int_{};
+
+which is equivalent but uglier. Note that everything works just fine when
+we're not in a template.
+*/
+
+template <typename T>
+constexpr auto check_int() { return hana::int_c<1>; }
+
+template <typename T>
+constexpr auto check_true() { return hana::true_c; }
+
+template <typename T>
+constexpr auto check_size_t() { return hana::size_c<0>; }
+
+
+int main() { }