test/std/language.support/support.coroutines/coroutine.traits/promise_type.pass.cpp

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14, c++17
// UNSUPPORTED: libcpp-no-coroutines

#include <coroutine>
#include <type_traits>

#include "test_macros.h"

template <class T, class = typename T::promise_type>
constexpr bool has_promise_type(int) { return true; }
template <class>
constexpr bool has_promise_type(long) { return false; }
template <class T>
constexpr bool has_promise_type() { return has_promise_type<T>(0); }

struct A {
  using promise_type = A*;
};

struct B {};
struct C {};
struct D {
private:
  using promise_type = void;
};
struct E {};

template <>
struct std::coroutine_traits<A, int> {
  using promise_type = int*;
};
template <class ...Args>
struct std::coroutine_traits<B, Args...> {
  using promise_type = B*;
};
template <>
struct std::coroutine_traits<C> {
  using promise_type = void;
};

template <class Expect, class T, class ...Args>
void check_type() {
  using Traits = std::coroutine_traits<T, Args...>;
  static_assert(has_promise_type<Traits>(), "");
  static_assert(std::is_same<typename Traits::promise_type, Expect>::value, "");
}

template <class T, class ...Args>
void check_no_type() {
  using Traits = std::coroutine_traits<T, Args...>;
  static_assert(!has_promise_type<Traits>(), "");
}

int main(int, char**)
{
  {
    check_type<A*, A>();
    check_type<int*, A, int>();
    check_type<B*, B>();
    check_type<void, C>();
  }
  {
    check_no_type<D>();
    check_no_type<E>();
    check_no_type<C, int>();
  }

  return 0;
}