Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

libs/function/test/function_test_fail2.cpp

// Boost.Function library

//  Copyright (C) Douglas Gregor 2001-2005. Use, modification and
//  distribution is subject to the Boost Software License, Version
//  1.0. (See accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)

// For more information, see http://www.boost.org

#include <boost/function.hpp>

static int bad_fn(float f) { return static_cast<int>(f); }

void test()
{
    boost::function0<int> f1;
    f1 = bad_fn;
}