Kind inference for the FreeST programming language

Abstract

FreeST is a message-passing concurrent functional programming language where messages are exchanged on channels governed by context-free session types. Thus far, FreeST only distinguishes two kinds of types: arbitrary types and session types. We introduce explicit channel closing operators — close and wait — together with their corresponding types — Close and Wait — which call for a third kind of types, that of channel types. Type variable declaration is usually annotated with its kind. We provide a sound and complete algorithm for kind inference and prove that it terminates yielding the most general kind.