Multiparty GV: functional multiparty session types with certified deadlock freedom

Session types have recently been integrated with functional languages, bringing message-passing concurrency to programming. Channel endpoints then become first-class and can be stored in data structures, captured closures, sent along channels. Representatives of the GV (Wadler's "Good Variation") session type family are particular appeal because they not only assert fidelity but also deadlock freedom, inspired by a Curry-Howard correspondence linear logic. A restriction current versions GV, however, is focus on binary sessions, limiting concurrent interactions within two participants. This paper introduces Multiparty (MPGV), language multiparty types, allowing among several MPGV upholds strong guarantees its ancestor including despite interleaving delegation. has novel redirecting construct for modular programming endpoints, thanks which we give type-preserving translation from show that strictly more general than GV. All results this mechanized using Coq proof assistant.