A practical type system and language for reference immutability

This paper describes a type system that is capable of expressing and enforcing immutability constraints. The specific constraint exis that the abstract state of the object to which an immutable reference refers cannot be modified using that reference. The abstract state is (part of) the transitively reachable state: that is, the state of the object and all state reachable from it by following references. The type system permits explicitly excluding fields or obom the abstract state of an object. For a statically type-safe language, the type system guarantees reference immutability. If the language is extended with immutability downcasts, then run-time checks enforce the reference immutability constraints. In order to better understand the usability and efficacy of the type system, we have implemented an extension to Java, called Javari, that includes all the features of our type system. Javari is interoperable with Java and existing JVMs. It can be viewed as a proposal for the sem...

• Type: Conference
• Year: 2004
• Where: OOPSLA
• Authors: Adrian Birka, Michael D. Ernst
• Keywords: Abstract State, Immutability Constraints, OOPSLA 2004, Type System