33 Execution control library [exec]

33.9 Senders [exec.snd]

33.9.9 execution​::​get_completion_signatures [exec.getcomplsigs]

🔗
template<class Sndr, class... Env> consteval auto get_completion_signatures() -> valid-completion-signatures auto;
1
#
Let except be an rvalue subexpression of an unspecified class type Except such that move_constructible<Except> && derived_from<Except, exception> is true.
Let CHECKED-COMPLSIGS(e) be e if e is a core constant expression whose type satisfies valid-completion-signatures; otherwise, it is the following expression: (e, throw except, completion_signatures())
Let get-complsigs<Sndr, Env...>() be expression-equivalent to remove_reference_t<Sndr>​::​template get_completion_signatures<Sndr, Env...>().
Let NewSndr be Sndr if sizeof...(Env) == 0 is true; otherwise, decltype(s) where s is the following expression: transform_sender( get-domain-late(declval<Sndr>(), declval<Env>()...), declval<Sndr>(), declval<Env>()...)
2
#
Constraints: sizeof...(Env) <= 1 is true.
3
#
Effects: Equivalent to: return e; where e is expression-equivalent to the following:
  • (3.1)
    CHECKED-COMPLSIGS(get-complsigs<NewSndr, Env...>()) if get-complsigs<NewSndr, Env
    ...>()     is a well-formed expression.
  • (3.2)
    Otherwise, CHECKED-COMPLSIGS(get-complsigs<NewSndr>()) if get-complsigs<NewSndr>() is a well-formed expression.
  • (3.3)
    Otherwise, completion_signatures< SET-VALUE-SIG(await-result-type<NewSndr, env-promise<Env>...>), // [exec.snd.concepts] set_error_t(exception_ptr), set_stopped_t()> if is-awaitable<NewSndr, env-promise<Env>...> is true.
  • (3.4)
    Otherwise, (throw dependent-sender-error(), completion_signatures()) if sizeof...(
    Env) == 0     is true, where dependent-sender-error is dependent_sender_error or an unspecified type derived publicly and unambiguously from dependent_sender_error.
  • (3.5)
    Otherwise, (throw except, completion_signatures()).
4
#
Given a type Env, if completion_signatures_of_t<Sndr> and completion_signatures_of_t<Sndr, Env> are both well-formed, they shall denote the same type.
5
#
Let rcvr be an rvalue whose type Rcvr models receiver, and let Sndr be the type of a sender such that sender_in<Sndr, env_of_t<Rcvr>> is true.
Let Sigs... be the template arguments of the completion_signatures specialization named by completion_signatures_of_t<Sndr, env_of_t<Rcvr>>.
Let CSO be a completion function.
If sender Sndr or its operation state cause the expression CSO(rcvr, args...) to be potentially evaluated ([basic.def.odr]) then there shall be a signature Sig in Sigs... such that MATCHING-SIG(decayed-typeof<CSO>(decltype(args)...), Sig) is true ([exec.general]).