A completion handler object of type CompletionHandler has an associated executor satisfying the Executor requirements ([async.reqmts.executor]). The type of this associated executor is associated_executor_t<CompletionHandler, Executor1>. Let Executor2 be the type associated_executor_t<CompletionHandler, Executor1>. Let ex2 be a value of type Executor2 obtained by performing get_associated_executor(completion_handler, ex1).