1 // Copyright 2021 The Fuchsia Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef LIB_STDCOMPAT_INTERNAL_TYPE_TRAITS_H_ 6 #define LIB_STDCOMPAT_INTERNAL_TYPE_TRAITS_H_ 7 8 #include <functional> 9 #include <type_traits> 10 #include <utility> 11 12 namespace cpp17 { 13 namespace internal { 14 15 template <typename T> 16 static constexpr bool is_reference_wrapper = false; 17 template <typename T> 18 static constexpr bool is_reference_wrapper<std::reference_wrapper<T>> = true; 19 20 // These are from [func.require] ¶ 1.1-7 21 template <typename MemFn, typename Class, typename T> 22 static constexpr bool invoke_pmf_base = std::is_member_function_pointer<MemFn Class::*>::value && 23 std::is_base_of<Class, std::remove_reference_t<T>>::value; 24 25 template <typename MemFn, typename Class, typename T> 26 static constexpr bool invoke_pmf_refwrap = 27 std::is_member_function_pointer<MemFn Class::*>::value && 28 is_reference_wrapper<std::remove_cv_t<std::remove_reference_t<T>>>; 29 30 template <typename MemFn, typename Class, typename T> 31 static constexpr bool invoke_pmf_other = 32 std::is_member_function_pointer<MemFn Class::*>::value && !invoke_pmf_base<MemFn, Class, T> && 33 !invoke_pmf_refwrap<MemFn, Class, T>; 34 35 template <typename MemObj, typename Class, typename T> 36 static constexpr bool invoke_pmd_base = std::is_member_object_pointer<MemObj Class::*>::value && 37 std::is_base_of<Class, std::remove_reference_t<T>>::value; 38 39 template <typename MemObj, typename Class, typename T> 40 static constexpr bool invoke_pmd_refwrap = 41 std::is_member_object_pointer<MemObj Class::*>::value && 42 is_reference_wrapper<std::remove_cv_t<std::remove_reference_t<T>>>; 43 44 template <typename MemObj, typename Class, typename T> 45 static constexpr bool invoke_pmd_other = 46 std::is_member_object_pointer<MemObj Class::*>::value && !invoke_pmd_base<MemObj, Class, T> && 47 !invoke_pmd_refwrap<MemObj, Class, T>; 48 49 // ¶ 1.7 says to just return f(t1, t2, ..., tn) in all other cases 50 51 // Just internal forward declarations for SFINAE; cpp20::invoke is defined in 52 // lib/stdcompat/functional.h 53 template <typename MemFn, typename Class, typename T, typename... Args> 54 constexpr auto invoke(MemFn Class::*f, T&& obj, Args&&... args) 55 -> std::enable_if_t<invoke_pmf_base<MemFn, Class, T>, 56 decltype((std::forward<T>(obj).*f)(std::forward<Args>(args)...))>; 57 58 template <typename MemFn, typename Class, typename T, typename... Args> 59 constexpr auto invoke(MemFn Class::*f, T&& obj, Args&&... args) 60 -> std::enable_if_t<invoke_pmf_refwrap<MemFn, Class, T>, 61 decltype((obj.get().*f)(std::forward<Args>(args)...))>; 62 63 template <typename MemFn, typename Class, typename T, typename... Args> 64 constexpr auto invoke(MemFn Class::*f, T&& obj, Args&&... args) 65 -> std::enable_if_t<invoke_pmf_other<MemFn, Class, T>, 66 decltype(((*std::forward<T>(obj)).*f)(std::forward<Args>(args)...))>; 67 68 template <typename MemObj, typename Class, typename T> 69 constexpr auto invoke(MemObj Class::*f, T&& obj) 70 -> std::enable_if_t<invoke_pmd_base<MemObj, Class, T>, decltype(std::forward<T>(obj).*f)>; 71 72 template <typename MemObj, typename Class, typename T> 73 constexpr auto invoke(MemObj Class::*f, T&& obj) 74 -> std::enable_if_t<invoke_pmd_refwrap<MemObj, Class, T>, decltype(obj.get().*f)>; 75 76 template <typename MemObj, typename Class, typename T> 77 constexpr auto invoke(MemObj Class::*f, T&& obj) 78 -> std::enable_if_t<invoke_pmd_other<MemObj, Class, T>, decltype((*std::forward<T>(obj)).*f)>; 79 80 template <typename F, typename... Args> 81 constexpr auto invoke(F&& f, Args&&... args) 82 -> decltype(std::forward<F>(f)(std::forward<Args>(args)...)); 83 84 template <typename R, typename F, typename... Args, 85 typename = std::enable_if_t<std::is_void<R>::value>> 86 constexpr auto invoke_r(F&& f, Args&&... args) 87 -> decltype(static_cast<void>(::cpp17::internal::invoke(std::forward<F>(f), 88 std::forward<Args>(args)...))); 89 90 template <typename R, typename F, typename... Args, 91 typename = std::enable_if_t<!std::is_void<R>::value>> 92 constexpr auto invoke_r(F&& f, Args&&... args) 93 -> std::enable_if_t<std::is_convertible<decltype(::cpp17::internal::invoke( 94 std::forward<F>(f), std::forward<Args>(args)...)), 95 R>::value, 96 R>; 97 98 template <typename R, typename F, typename... Args> 99 constexpr auto is_valid_invoke(std::nullptr_t) 100 -> decltype(invoke_r<R>(std::declval<F>(), std::declval<Args>()...), std::true_type()); 101 102 template <typename R, typename F, typename... Args> 103 constexpr std::false_type is_valid_invoke(...); 104 105 template <bool Enable, typename F, typename... Args> 106 struct invoke_result {}; 107 108 template <typename F, typename... Args> 109 struct invoke_result<true, F, Args...> { 110 using type = decltype(::cpp17::internal::invoke(std::declval<F>(), std::declval<Args>()...)); 111 }; 112 113 } // namespace internal 114 } // namespace cpp17 115 116 #endif // LIB_STDCOMPAT_INTERNAL_TYPE_TRAITS_H_ 117