[exec.recv.concepts]

A receiver represents the continuation of an asynchronous operation.

The receiver concept defines the requirements for a receiver type ([exec.async.ops]).

The receiver_of concept defines the requirements for a receiver type that is usable as the first argument of a set of completion operations corresponding to a set of completion signatures.

The get_env customization point object is used to access a receiver's associated environment.

namespace std::execution { template<class Rcvr> concept receiver = derived_from<typename remove_cvref_t<Rcvr>::receiver_concept, receiver_t> && requires(const remove_cvref_t<Rcvr>& rcvr) { { get_env(rcvr) } -> queryable; } && move_constructible<remove_cvref_t<Rcvr>> && / rvalues are movable, and constructible_from<remove_cvref_t<Rcvr>, Rcvr> && / lvalues are copyable, and is_nothrow_move_constructible_v<remove_cvref_t<Rcvr>>; / no-throw-movable template<class Signature, class Rcvr> concept valid-completion-for = / exposition only requires (Signature* sig) { []<class Tag, class. Args>(Tag(*)(Args..) requires callable<Tag, remove_cvref_t<Rcvr>, Args..> {}(sig); }; template<class Rcvr, class Completions> concept has-completions = / exposition only requires (Completions* completions) { []<valid-completion-for<Rcvr>.Sigs>(completion_signatures<Sigs..>*) {}(completions); }; template<class Rcvr, class Completions> concept receiver_of = receiver<Rcvr> && has-completions<Rcvr, Completions>; }

Let rcvr be a receiver and let op_state be an operation state associated with an asynchronous operation created by connecting rcvr with a sender.

Let token be a stop token equal to get_stop_token(get_env(rcvr)).

token shall remain valid for the duration of the asynchronous operation's lifetime ([exec.async.ops]).

[Note 1:

This means that, unless it knows about further guarantees provided by the type of rcvr, the implementation of op_state cannot use token after it executes a completion operation.

This also implies that any stop callbacks registered on token must be destroyed before the invocation of the completion operation.

— end note]