151 lines
5.0 KiB
C++
151 lines
5.0 KiB
C++
/*!
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@file
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@Copyright Barrett Adair 2015-2017
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_CLBL_TRTS_IS_INVOCABLE_IMPL_HPP
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#define BOOST_CLBL_TRTS_IS_INVOCABLE_IMPL_HPP
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#include <boost/callable_traits/detail/config.hpp>
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#include <boost/callable_traits/detail/forward_declarations.hpp>
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#include <boost/callable_traits/detail/utility.hpp>
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#include <type_traits>
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#include <utility>
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namespace boost { namespace callable_traits { namespace detail {
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template<typename T>
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struct can_dereference_t
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{
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template<typename>
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struct check {};
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template<typename U>
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static std::int8_t test(
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check<typename std::remove_reference<decltype(*std::declval<U>())>::type>*
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);
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template<typename>
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static std::int16_t test(...);
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static constexpr const bool value =
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sizeof(test<T>(nullptr)) == sizeof(std::int8_t);
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};
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//returns std::true_type for pointers and smart pointers
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template<typename T>
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using can_dereference = std::integral_constant<bool,
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can_dereference_t<T>::value>;
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template<typename T, typename = std::true_type>
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struct generalize_t {
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using type = T;
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};
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template<typename T>
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struct generalize_t<T, std::integral_constant<bool,
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can_dereference<T>::value && !is_reference_wrapper<T>::value
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>>{
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using type = decltype(*std::declval<T>());
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};
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template<typename T>
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struct generalize_t<T, is_reference_wrapper<T>> {
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using type = decltype(std::declval<T>().get());
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};
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// When T is a pointer, generalize<T> is the resulting type of the
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// pointer dereferenced. When T is an std::reference_wrapper, generalize<T>
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// is the underlying reference type. Otherwise, generalize<T> is T.
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template<typename T>
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using generalize = typename generalize_t<T>::type;
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// handles the member pointer rules of INVOKE
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template<typename Base, typename T,
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typename IsBaseOf = std::is_base_of<Base, shallow_decay<T>>,
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typename IsSame = std::is_same<Base, shallow_decay<T>>>
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using generalize_if_dissimilar = typename std::conditional<
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IsBaseOf::value || IsSame::value, T, generalize<T>>::type;
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template<typename Traits, bool = Traits::is_const_member::value
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|| Traits::is_volatile_member::value
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|| Traits::is_lvalue_reference_member::value
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|| Traits::is_rvalue_reference_member::value>
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struct test_invoke {
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template<typename... Rgs,
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typename U = typename Traits::type>
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auto operator()(int, Rgs&&... rgs) const ->
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success<decltype(std::declval<U>()(static_cast<Rgs&&>(rgs)...))>;
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auto operator()(long, ...) const -> substitution_failure;
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};
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template<typename F>
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struct test_invoke<function<F>, true /*abominable*/> {
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auto operator()(...) const -> substitution_failure;
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};
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template<typename Pmf, bool Ignored>
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struct test_invoke<pmf<Pmf>, Ignored> {
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using class_t = typename pmf<Pmf>::class_type;
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template<typename U, typename... Rgs,
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typename Obj = generalize_if_dissimilar<class_t, U&&>>
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auto operator()(int, U&& u, Rgs&&... rgs) const ->
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success<decltype((std::declval<Obj>().*std::declval<Pmf>())(static_cast<Rgs&&>(rgs)...))>;
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auto operator()(long, ...) const -> substitution_failure;
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};
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template<typename Pmd, bool Ignored>
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struct test_invoke<pmd<Pmd>, Ignored> {
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using class_t = typename pmd<Pmd>::class_type;
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template<typename U,
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typename Obj = generalize_if_dissimilar<class_t, U&&>>
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auto operator()(int, U&& u) const ->
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success<decltype(std::declval<Obj>().*std::declval<Pmd>())>;
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auto operator()(long, ...) const -> substitution_failure;
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};
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template<typename T, typename... Args>
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struct is_invocable_impl {
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using traits = detail::traits<T>;
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using test = detail::test_invoke<traits>;
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using result = decltype(test{}(0, ::std::declval<Args>()...));
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using type = std::integral_constant<bool, result::value>;
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};
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template<typename... Args>
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struct is_invocable_impl<void, Args...> {
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using type = std::false_type;
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};
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template<typename IsInvocable, typename Ret, typename T, typename... Args>
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struct is_invocable_r_impl {
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using traits = detail::traits<T>;
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using test = detail::test_invoke<traits>;
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using result = decltype(test{}(0, ::std::declval<Args>()...));
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using type = std::integral_constant<bool,
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std::is_convertible<typename result::_::type, Ret>::value
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|| std::is_same<Ret, void>::value>;
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};
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template<typename Ret, typename T, typename... Args>
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struct is_invocable_r_impl<std::false_type, Ret, T, Args...> {
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using type = std::false_type;
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};
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}}} // namespace boost::callable_traits::detail
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#endif // #ifndef BOOST_CLBL_TRTS_IS_INVOCABLE_IMPL_HPP
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