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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)
- #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() { }
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