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https://github.com/TartanLlama/expected.git
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Add SFINAE
This commit is contained in:
Simon Brand
168
expected.hpp
168
expected.hpp
@@ -69,62 +69,6 @@
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namespace tl {
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template <class T, class E> class expected;
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/// \exclude
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namespace detail {
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template <bool E, class T = void>
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using enable_if_t = typename std::enable_if<E, T>::type;
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template <class T> using decay_t = typename std::decay<T>::type;
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// std::conjunction from C++17
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template <class...> struct conjunction : std::true_type {};
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template <class B> struct conjunction<B> : B {};
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template <class B, class... Bs>
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struct conjunction<B, Bs...>
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: std::conditional<bool(B::value), conjunction<Bs...>, B>::type {};
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// Trait for checking if a type is a tl::expected
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template <class T> struct is_expected_impl : std::false_type {};
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template <class T, class E>
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struct is_expected_impl<expected<T, E>> : std::true_type {};
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template <class T> using is_expected = is_expected_impl<decay_t<T>>;
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// std::invoke from C++17
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// https://stackoverflow.com/questions/38288042/c11-14-invoke-workaround
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template <typename Fn, typename... Args,
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typename = enable_if_t<std::is_member_pointer<decay_t<Fn>>{}>,
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int = 0>
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constexpr auto invoke(Fn &&f, Args &&... args) noexcept(
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noexcept(std::mem_fn(f)(std::forward<Args>(args)...)))
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-> decltype(std::mem_fn(f)(std::forward<Args>(args)...)) {
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return std::mem_fn(f)(std::forward<Args>(args)...);
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}
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template <typename Fn, typename... Args,
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typename = enable_if_t<!std::is_member_pointer<decay_t<Fn>>{}>>
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constexpr auto invoke(Fn &&f, Args &&... args) noexcept(
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noexcept(std::forward<Fn>(f)(std::forward<Args>(args)...)))
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-> decltype(std::forward<Fn>(f)(std::forward<Args>(args)...)) {
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return std::forward<Fn>(f)(std::forward<Args>(args)...);
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}
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// std::invoke_result from C++17
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template <class F, class, class... Us> struct invoke_result_impl;
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template <class F, class... Us>
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struct invoke_result_impl<
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F, decltype(invoke(std::declval<F>(), std::declval<Us>()...), void()),
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Us...> {
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using type = decltype(invoke(std::declval<F>(), std::declval<Us>()...));
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};
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template <class F, class... Us>
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using invoke_result = invoke_result_impl<F, void, Us...>;
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template <class F, class... Us>
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using invoke_result_t = typename invoke_result<F, Us...>::type;
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} // namespace detail
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#ifndef TL_IN_PLACE_MONOSTATE_DEFINED
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#define TL_IN_PLACE_MONOSTATE_DEFINED
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/// \brief Used to represent an expected with no data
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@@ -211,6 +155,82 @@ struct unexpect_t {
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/// \brief A tag to tell expected to construct the unexpected value
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static constexpr unexpect_t unexpect{};
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/// \exclude
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namespace detail {
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template <bool E, class T = void>
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using enable_if_t = typename std::enable_if<E, T>::type;
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template <class T> using decay_t = typename std::decay<T>::type;
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// std::conjunction from C++17
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template <class...> struct conjunction : std::true_type {};
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template <class B> struct conjunction<B> : B {};
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template <class B, class... Bs>
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struct conjunction<B, Bs...>
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: std::conditional<bool(B::value), conjunction<Bs...>, B>::type {};
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// Trait for checking if a type is a tl::expected
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template <class T> struct is_expected_impl : std::false_type {};
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template <class T, class E>
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struct is_expected_impl<expected<T, E>> : std::true_type {};
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template <class T> using is_expected = is_expected_impl<decay_t<T>>;
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// std::invoke from C++17
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// https://stackoverflow.com/questions/38288042/c11-14-invoke-workaround
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template <typename Fn, typename... Args,
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typename = enable_if_t<std::is_member_pointer<decay_t<Fn>>{}>,
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int = 0>
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constexpr auto invoke(Fn &&f, Args &&... args) noexcept(
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noexcept(std::mem_fn(f)(std::forward<Args>(args)...)))
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-> decltype(std::mem_fn(f)(std::forward<Args>(args)...)) {
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return std::mem_fn(f)(std::forward<Args>(args)...);
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}
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template <typename Fn, typename... Args,
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typename = enable_if_t<!std::is_member_pointer<decay_t<Fn>>{}>>
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constexpr auto invoke(Fn &&f, Args &&... args) noexcept(
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noexcept(std::forward<Fn>(f)(std::forward<Args>(args)...)))
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-> decltype(std::forward<Fn>(f)(std::forward<Args>(args)...)) {
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return std::forward<Fn>(f)(std::forward<Args>(args)...);
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}
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// std::invoke_result from C++17
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template <class F, class, class... Us> struct invoke_result_impl;
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template <class F, class... Us>
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struct invoke_result_impl<
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F, decltype(invoke(std::declval<F>(), std::declval<Us>()...), void()),
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Us...> {
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using type = decltype(invoke(std::declval<F>(), std::declval<Us>()...));
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};
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template <class F, class... Us>
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using invoke_result = invoke_result_impl<F, void, Us...>;
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template <class F, class... Us>
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using invoke_result_t = typename invoke_result<F, Us...>::type;
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template <class T, class E, class U>
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using enable_forward_value = detail::enable_if_t<
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std::is_constructible<T, U &&>::value &&
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!std::is_same<detail::decay_t<U>, in_place_t>::value &&
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!std::is_same<expected<T, E>, detail::decay_t<U>>::value &&
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!std::is_same<unexpected<E>, detail::decay_t<U>>::value>;
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template <class T, class E, class U, class G, class UR, class GR>
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using enable_from_other = detail::enable_if_t<
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std::is_constructible<T, UR>::value &&
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std::is_constructible<T, GR>::value &&
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!std::is_constructible<T, expected<U, G> &>::value &&
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!std::is_constructible<T, expected<U, G> &&>::value &&
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!std::is_constructible<T, const expected<U, G> &>::value &&
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!std::is_constructible<T, const expected<U, G> &&>::value &&
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!std::is_convertible<expected<U, G> &, T>::value &&
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!std::is_convertible<expected<U, G> &&, T>::value &&
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!std::is_convertible<const expected<U, G> &, T>::value &&
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!std::is_convertible<const expected<U, G> &&, T>::value>;
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} // namespace detail
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/// \exclude
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namespace detail {
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// Implements the storage of the values, and ensures that the destructor is
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@@ -1240,11 +1260,12 @@ public:
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: impl_base(unexpect, il, std::forward<Args>(args)...),
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ctor_base(detail::default_constructor_tag{}) {}
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// TODO SFINAE
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template <class U, class G,
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template <
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class U, class G,
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detail::enable_if_t<!(std::is_convertible<U const &, T>::value &&
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std::is_convertible<G const &, E>::value)> * =
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nullptr>
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nullptr,
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detail::enable_from_other<T, E, U, G, const U &, const G &> * = nullptr>
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explicit TL_EXPECTED_11_CONSTEXPR expected(const expected<U, G> &rhs)
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: ctor_base(detail::default_constructor_tag{}) {
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if (rhs.has_value()) {
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@@ -1254,12 +1275,13 @@ public:
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}
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}
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// TODO SFINAE
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/// \exclude
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template <class U, class G,
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template <
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class U, class G,
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detail::enable_if_t<(std::is_convertible<U const &, T>::value &&
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std::is_convertible<G const &, E>::value)> * =
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nullptr>
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nullptr,
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detail::enable_from_other<T, E, U, G, const U &, const G &> * = nullptr>
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TL_EXPECTED_11_CONSTEXPR expected(const expected<U, G> &rhs)
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: ctor_base(detail::default_constructor_tag{}) {
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if (rhs.has_value()) {
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@@ -1269,11 +1291,11 @@ public:
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}
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}
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// TODO SFINAE
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template <
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class U, class G,
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detail::enable_if_t<!(std::is_convertible<U &&, T>::value &&
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std::is_convertible<G &&, E>::value)> * = nullptr>
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std::is_convertible<G &&, E>::value)> * = nullptr,
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detail::enable_from_other<T, E, U, G, U &&, G &&> * = nullptr>
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explicit TL_EXPECTED_11_CONSTEXPR expected(expected<U, G> &&rhs)
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: ctor_base(detail::default_constructor_tag{}) {
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if (rhs.has_value()) {
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@@ -1283,12 +1305,12 @@ public:
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}
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}
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// TODO SFINAE
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/// \exclude
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template <
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class U, class G,
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detail::enable_if_t<(std::is_convertible<U &&, T>::value &&
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std::is_convertible<G &&, E>::value)> * = nullptr>
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std::is_convertible<G &&, E>::value)> * = nullptr,
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detail::enable_from_other<T, E, U, G, U &&, G &&> * = nullptr>
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TL_EXPECTED_11_CONSTEXPR expected(expected<U, G> &&rhs)
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: ctor_base(detail::default_constructor_tag{}) {
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if (rhs.has_value()) {
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@@ -1298,15 +1320,17 @@ public:
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}
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}
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// TODO SFINAE
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template <class U = T, detail::enable_if_t<
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!std::is_convertible<U &&, T>::value> * = nullptr>
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template <
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class U = T,
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detail::enable_if_t<!std::is_convertible<U &&, T>::value> * = nullptr,
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detail::enable_forward_value<T, E, U> * = nullptr>
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explicit constexpr expected(U &&v) : expected(in_place, std::forward<U>(v)) {}
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// TODO SFINAE
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/// \exclude
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template <class U = T, detail::enable_if_t<
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std::is_convertible<U &&, T>::value> * = nullptr>
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template <
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class U = T,
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detail::enable_if_t<std::is_convertible<U &&, T>::value> * = nullptr,
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detail::enable_forward_value<T, E, U> * = nullptr>
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constexpr expected(U &&v) : expected(in_place, std::forward<U>(v)) {}
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template <
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