template_inspection.hpp

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// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2019, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2019, Knut Reinert & MPI für molekulare Genetik
// This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
// shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
// -----------------------------------------------------------------------------------------------------

#pragma once

#include <meta/meta.hpp>

#include <seqan3/core/type_traits/transformation_trait_or.hpp>

#include <seqan3/std/concepts>

namespace seqan3::detail
{

// ----------------------------------------------------------------------------
// transfer_template_args_onto
// ----------------------------------------------------------------------------

template <typename source_type, template <typename ...> typename target_template>
struct transfer_template_args_onto
{};

template <template <typename ...> typename source_template,
          template <typename ...> typename target_template,
          typename ... source_arg_types>
    requires requires ()
    {
        std::declval<target_template<source_arg_types...>>();
    }
struct transfer_template_args_onto<source_template<source_arg_types...>, target_template>
{
    using type = target_template<source_arg_types...>;
};

template <typename source_type, template <typename ...> typename target_template>
using transfer_template_args_onto_t = typename transfer_template_args_onto<source_type, target_template>::type;

// ----------------------------------------------------------------------------
// transfer_template_vargs_onto
// ----------------------------------------------------------------------------

template <typename source_type, template <auto ...> typename target_template>
struct transfer_template_vargs_onto
{};

template <template <auto ...> typename source_template,
          template <auto ...> typename target_template,
          auto ... source_varg_types>
    requires requires ()
    {
        std::declval<target_template<source_varg_types...>>();
    }
struct transfer_template_vargs_onto<source_template<source_varg_types...>, target_template>
{
    using type = target_template<source_varg_types...>;
};

template <typename source_type, template <auto ...> typename target_template>
using transfer_template_vargs_onto_t = typename transfer_template_vargs_onto<source_type, target_template>::type;

// ----------------------------------------------------------------------------
// is_type_specialisation_of_v
// ----------------------------------------------------------------------------

template <typename source_t, template <typename ...> typename target_template>
struct is_type_specialisation_of : public std::false_type
{};

template <typename source_t, template <typename ...> typename target_template>
    requires !std::Same<transformation_trait_or_t<transfer_template_args_onto<source_t, target_template>, void>,
                        void>
struct is_type_specialisation_of<source_t, target_template> :
        std::is_same<source_t, transfer_template_args_onto_t<source_t, target_template>>
{};

template <typename source_t, template <typename ...> typename target_template>
inline constexpr bool is_type_specialisation_of_v = is_type_specialisation_of<source_t, target_template>::value;

// ----------------------------------------------------------------------------
// is_value_specialisation_of_v
// ----------------------------------------------------------------------------

template <typename source_t, template <auto ...> typename target_template>
struct is_value_specialisation_of : std::false_type
{};

template <typename source_t, template <auto ...> typename target_template>
    requires !std::Same<transformation_trait_or_t<transfer_template_vargs_onto<source_t, target_template>, void>,
                        void>
struct is_value_specialisation_of<source_t, target_template> :
    std::is_same<source_t, transfer_template_vargs_onto_t<source_t, target_template>>
{};

template <typename source_t, template <auto ...> typename target_template>
inline constexpr bool is_value_specialisation_of_v = is_value_specialisation_of<source_t, target_template>::value;

template <typename fallback_t, template <typename...> typename templ_t, typename ...spec_t>
struct valid_template_spec_or
{
    using type = fallback_t;
};

template <typename fallback_t, template <typename...> typename templ_t, typename ...spec_t>
    requires requires { typename templ_t<spec_t...>; }
struct valid_template_spec_or<fallback_t, templ_t, spec_t...>
{
    using type = templ_t<spec_t...>;
};

template <typename fallback_t, template <typename...> typename templ_t, typename ...spec_t>
using valid_template_spec_or_t = typename valid_template_spec_or<fallback_t, templ_t, spec_t...>::type;

} // namespace seqan3::detail