The new thread of execution executes
invoke(auto(std::forward<F>(f)), get_stop_token(),
auto(std::forward<Args>(args))...)
if that expression is well-formed,
otherwise
invoke(auto(std::forward<F>(f)), auto(std::forward<Args>(args))...)
with the values produced by auto
being materialized ([conv.rval]) in the constructing thread.
resource_unavailable_try_again — the system lacked
the necessary resources to create another thread,
or the system-imposed limit on the number of threads in a process
would be exceeded.