boost::hana::detail::wrong<... > Struct Template Reference

Description

template<typename ...>
struct boost::hana::detail::wrong<... >

Equivalent to a type-dependent std::false_type.

This is useful for making a static assertion that would otherwise always fire up dependent on some template parameters.

Example

// 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/detail/wrong.hpp>
namespace hana = boost::hana;
 
 
template <typename T, typename U>
struct base_template {
    // Can't write this because the assertion would always fire up:
    // static_assert(false, "...");
 
    // So instead we write this:
    static_assert(hana::detail::wrong<base_template<T, U>>::value,
    "base_template does not have a valid default definition");
};
 
template <>
struct base_template<int, int> {
    // something useful
};
 
int main() { }

Inherits std::false_type.