text: //===----------------------------------------------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is dual licensed under the MIT and the University of Illinois Open
  // Source Licenses. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  
  // <functional>
  
  // template <class T>
  // struct hash
  //     : public unary_function<T, size_t>
  // {
  //     size_t operator()(T val) const;
  // };
  
  #include <system_error>
  #include <cassert>
  #include <type_traits>
  
  #include "test_macros.h"
  
  void
  test(int i)
  {
      typedef std::error_condition T;
      typedef std::hash<T> H;
      static_assert((std::is_same<H::argument_type, T>::value), "" );
      static_assert((std::is_same<H::result_type, std::size_t>::value), "" );
      H h;
      T ec(i, std::system_category());
      const std::size_t result = h(ec);
      LIBCPP_ASSERT(result == static_cast<std::size_t>(i));
      ((void)result); // Prevent unused warning
  }
  
  int main()
  {
      test(0);
      test(2);
      test(10);
  }
  