Archivo de encabezado de la biblioteca estándar <coroutine>

#include <compare>
 
namespace std {
  // rasgos de corrutinas
  template<class R, class... ArgTypes>
    struct coroutine_traits;
 
  // identificador de corrutina
  template<class Promise = void>
    struct coroutine_handle;
 
  // operadores de comparación
  constexpr bool operator==(coroutine_handle<> x, coroutine_handle<> y) noexcept;
  constexpr strong_ordering operator<=>(coroutine_handle<> x, coroutine_handle<> y) noexcept;
 
  // soporte para hash (resumen)
  template<class T> struct hash;
  template<class P> struct hash<coroutine_handle<P>>;
 
  // corrutinas no operativas
  struct noop_coroutine_promise;
 
  template<> struct coroutine_handle<noop_coroutine_promise>;
  using noop_coroutine_handle = coroutine_handle<noop_coroutine_promise>;
 
  noop_coroutine_handle noop_coroutine() noexcept;
 
  // en espera triviales
  struct suspend_never;
  struct suspend_always;
}

namespace std {
  template<>
  struct coroutine_handle<void>
  {
    // construir/restablecer
    constexpr coroutine_handle() noexcept;
    constexpr coroutine_handle(nullptr_t) noexcept;
    coroutine_handle& operator=(nullptr_t) noexcept;
 
    // exportar/importar
    constexpr void* address() const noexcept;
    static constexpr coroutine_handle from_address(void* addr);
 
    // observadores
    constexpr explicit operator bool() const noexcept;
    bool done() const;
 
    // reanudación
    void operator()() const;
    void resume() const;
    void destroy() const;
 
  private:
    void* ptr;  // solo exposición
  };
 
  template<class Promise>
  struct coroutine_handle : coroutine_handle<>
  {
    // construir/restablecer
    using coroutine_handle<>::coroutine_handle;
    static coroutine_handle from_promise(Promise&);
    coroutine_handle& operator=(nullptr_t) noexcept;
 
    // exportar/importar
    static constexpr coroutine_handle from_address(void* addr);
 
    // accesso a promesa
    Promise& promise() const;
  };
}

namespace std {
  struct noop_coroutine_promise {};
}

namespace std {
  template<>
  struct coroutine_handle<noop_coroutine_promise> : coroutine_handle<>
  {
    // observadores
    constexpr explicit operator bool() const noexcept;
    constexpr bool done() const noexcept;
 
    // reanudación
    constexpr void operator()() const noexcept;
    constexpr void resume() const noexcept;
    constexpr void destroy() const noexcept;
 
    // acceso a promesa
    noop_coroutine_promise& promise() const noexcept;
 
    // dirección
    constexpr void* address() const noexcept;
  private:
    coroutine_handle(/* sin especificar */);
  };
}

namespace std {
  struct suspend_never {
    constexpr bool await_ready() const noexcept { return true; }
    constexpr void await_suspend(coroutine_handle<>) const noexcept {}
    constexpr void await_resume() const noexcept {}
  };
}

namespace std {
  struct suspend_always {
    constexpr bool await_ready() const noexcept { return false; }
    constexpr void await_suspend(coroutine_handle<>) const noexcept {}
    constexpr void await_resume() const noexcept {}
  };
}