check_cxx_source_runs( "
#include <concepts>
#include <coroutine>
#include <exception>

struct ReturnObject {
  struct promise_type {
    ReturnObject get_return_object() { return {}; }
    std::suspend_never initial_suspend() { return {}; }
    std::suspend_never final_suspend() noexcept { return {}; }
    void unhandled_exception() {}
  };
};

struct Awaiter {
  std::coroutine_handle<> *hp_;
  constexpr bool await_ready() const noexcept { return false; }
  void await_suspend(std::coroutine_handle<> h) { *hp_ = h; }
  constexpr void await_resume() const noexcept {}
};

ReturnObject
counter(std::coroutine_handle<> *continuation_out)
{
  Awaiter a{continuation_out};
  for (unsigned i = 0;; ++i) {
    co_await a;
  }
}

int
main()
{
  std::coroutine_handle<> h;
  counter(&h);
  for (int i = 0; i < 3; ++i) {
    h();
  }
  h.destroy();
}
" STLAB_HAVE_FUNCTIONAL_COROUTINES )