vtk-m/vtkmstd/void_t.h

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//============================================================================
// Copyright (c) Kitware, Inc.
// All rights reserved.
// See LICENSE.txt for details.
//
// This software is distributed WITHOUT ANY WARRANTY; without even
// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
// PURPOSE. See the above copyright notice for more information.
//============================================================================
#ifndef vtk_m_std_void_t_h
#define vtk_m_std_void_t_h
#include <vtkm/internal/Configure.h>
namespace vtkmstd
{
/// Implementation of std::void_t (C++17):
/// Allows for specialization of class templates based on members of template
/// parameters.
#if defined(VTKM_GCC) && (__GNUC__ < 5)
// Due to a defect in the wording (CWG 1558) unused parameters in alias templates
// were not guaranteed to ensure SFINAE, and therefore would consider everything
// to match the 'true' side. For VTK-m the only known compiler that implemented
// this defect is GCC < 5.
template <class... T>
struct void_pack
{
using type = void;
};
template <class... T>
using void_t = typename void_pack<T...>::type;
#else
template <typename...>
using void_t = void;
#endif
} // end namespace vtkmstd
#endif //vtk_m_std_void_t_h