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The sender attributes of then and upon_xxx incorrectly answer queries for get_completion_scheduler and get_completion_domain #2415
Description
The sender attributes of then, upon_error, and upon_stopped incorrectly answer queries for get_completion_scheduler and get_completion_domain.
For example, in the current implementation, the set_value completion scheduler and completion domain of sndr | ex::upon_error([](...) noexcept { ... }) are reported as sndr's set_value completion scheduler and completion domain. However, this is incorrect; it should instead consider sndr's set_error completion scheduler and completion domain, because the receiver's set_value may complete on an execution agent of sndr's set_error completion scheduler.
Activity
[-]The sender attributes of `then`, `upon_error`, and `upon_stopped` incorrectly answer queries for `get_completion_scheduler` and `get_completion_domai`n[/-][+]The sender attributes of `then` and `upon_xxx` incorrectly answer queries for `get_completion_scheduler` and `get_completion_domain`[/+]Cra3z commentedon Nov 6, 2026
stopped_as_optionalandstopped_as_erroralso have similar problems.Cra3z commentedon Nov 6, 2026
In the current implementation, the following program cannot be compiled:
ex::run_loop loop; ex::prop env{ ex::get_start_scheduler, loop.get_scheduler() }; auto sndr1 = ex::just_stopped() | ex::stopped_as_error(-1); auto sch1 = ex::get_completion_scheduler<ex::set_error_t>(ex::get_env(sndr1), env); assert(sch1 == loop.get_scheduler()); auto sndr2 = ex::just_error(-1) | ex::upon_error([](int i) noexcept { return i; }); auto sch2 = ex::get_completion_scheduler<ex::set_value_t>(ex::get_env(sndr2), env); assert(sch2 == loop.get_scheduler());