34 Execution control library [exec]

34.9 Senders [exec.snd]

34.9.7 execution​::​transform_env [exec.snd.transform.env]

namespace std::execution { template<class Domain, sender Sndr, queryable Env> constexpr queryable decltype(auto) transform_env(Domain dom, Sndr&& sndr, Env&& env) noexcept; }
Let e be the expression dom.transform_env(std::forward<Sndr>(sndr), std::forward<Env>(env)) if that expression is well-formed; otherwise, default_domain().transform_env(std::forward<Sndr>(sndr), std::forward<Env>(env))
Mandates: noexcept(e) is true.
Returns: e.