A do expression allows all the normal control flow, e.g. return, break, continue (or in same cases even goto). That is not possible with a lambda (e.g. an immediately invoked one in this case). -----Ursprüngliche Nachricht----- Von:Tymi via Std-Proposals <std-proposals_at_[hidden]> I don't understand the difference between that and a lambda tbh I might be misunderstanding something though, or maybe missing the point of possible optimisations here