A framework for implementing pluggable type systems

Abstract

Pluggable types have been proposed to support multiple type systems in the same programming language. We have designed and implemented J ava COP, a program constraint system for implementing practical pluggable type systems for Java. J ava COP enforces user-defined typing constraints written in a declarative and expressive rule language. We have validated our design by (re)implementing a range of type systems and program checkers. By using a program constraint system to implement pluggable types, programmers are able to check that their programs will operate correctly in restricted environments, adhere to strict programming rules, avoid null pointer errors or scoped memory exceptions, and meet style guidelines, while programming language researchers can easily experiment with novel type systems.