libcxx/test/std/utilities/expected/expected.void/monadic/transform.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
  10
  11 // <expected>
  12
  13 // template<class F> constexpr auto transform_error(F&& f) &;
  14 // template<class F> constexpr auto transform_error(F&& f) const &;
  15 // template<class F> constexpr auto transform_error(F&& f) &&;
  16 // template<class F> constexpr auto transform_error(F&& f) const &&;
  17
  18 #include <expected>
  19 #include <concepts>
  20 #include <cassert>
  21 #include <memory>
  22 #include <type_traits>
  23 #include <utility>
  24
  25 template <class E, class F>
  26 concept has_transform =
  27     requires(E&& e, F&& f) {
  28       { std::forward<E>(e).transform(std::forward<F>(f)) };
  29     };
  30
  31 // [LWG 3877] https://cplusplus.github.io/LWG/issue3877, check constraint failing but not compile error inside the function body.
  32 static_assert(!has_transform<const std::expected<int, std::unique_ptr<int>>&, int()>);
  33 static_assert(!has_transform<const std::expected<int, std::unique_ptr<int>>&&, int()>);
  34
  35 constexpr void test_val_types() {
  36   // Test & overload
  37   {
  38     auto l = []() -> int { return 1; };
  39     std::expected<void, int> v;
  40     std::same_as<std::expected<int, int>> decltype(auto) val = v.transform(l);
  41     assert(val == 1);
  42   }
  43
  44   // Test const& overload
  45   {
  46     auto l = []() -> int { return 1; };
  47     const std::expected<void, int> v;
  48     std::same_as<std::expected<int, int>> decltype(auto) val = v.transform(l);
  49     assert(val == 1);
  50   }
  51
  52   // Test && overload
  53   {
  54     auto l = []() -> int { return 1; };
  55     std::expected<void, int> v;
  56     std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).transform(l);
  57     assert(val == 1);
  58   }
  59
  60   // Test const&& overload
  61   {
  62     auto l = []() -> int { return 1; };
  63     const std::expected<void, int> v;
  64     std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).transform(l);
  65     assert(val == 1);
  66   }
  67 }
  68
  69 constexpr void test_fail() {
  70   // Test & overload
  71   {
  72     auto l = []() -> int {
  73       assert(false);
  74       return 0;
  75     };
  76     std::expected<void, int> v(std::unexpected<int>(5));
  77     std::same_as<std::expected<int, int>> decltype(auto) val = v.transform(l);
  78     assert(val.error() == 5);
  79   }
  80
  81   // Test const& overload
  82   {
  83     auto l = []() -> int {
  84       assert(false);
  85       return 0;
  86     };
  87     const std::expected<void, int> v(std::unexpected<int>(5));
  88     std::same_as<std::expected<int, int>> decltype(auto) val = v.transform(l);
  89     assert(val.error() == 5);
  90   }
  91
  92   // Test && overload
  93   {
  94     auto l = []() -> int {
  95       assert(false);
  96       return 0;
  97     };
  98     std::expected<void, int> v(std::unexpected<int>(5));
  99     std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).transform(l);
 100     assert(val.error() == 5);
 101   }
 102
 103   // Test const&& overload
 104   {
 105     auto l = []() -> int {
 106       assert(false);
 107       return 0;
 108     };
 109     const std::expected<void, int> v(std::unexpected<int>(5));
 110     std::same_as<std::expected<int, int>> decltype(auto) val = std::move(v).transform(l);
 111     assert(val.error() == 5);
 112   }
 113 }
 114
 115 constexpr bool test() {
 116   test_fail();
 117   test_val_types();
 118   return true;
 119 }
 120
 121 int main(int, char**) {
 122   test();
 123   static_assert(test());
 124
 125   return 0;
 126 }