Rewriting for sound and complete union, intersection and negation types

Abstract

Implementing the type system of a programming language is a critical task that is often done in an ad-hoc fashion. Whilst this makes it hard to ensure the system is sound, it also makes it difficult to extend as the language evolves. We are interested in describing type systems using declarative rewrite rules from which an implementation can be automatically generated. Whilst not all type systems are easily expressed in this manner, those involving unions, intersections and negations are well-suited for this.