Affiliation:
1. Indiana University, USA
Abstract
We present a new type system combining occurrence typing---a technique previously used to type check programs in dynamically-typed languages such as Racket, Clojure, and JavaScript---with dependent refinement types. We demonstrate that the addition of refinement types allows the integration of arbitrary solver-backed reasoning about logical propositions from external theories. By building on occurrence typing, we can add our enriched type system as a natural extension of Typed Racket, reusing its core while increasing its expressiveness. The result is a well-tested type system with a conservative, decidable core in which types may depend on a small but extensible set of program terms. In addition to describing our design, we present the following: a formal model and proof of correctness; a strategy for integrating new theories, with specific examples including linear arithmetic and bitvectors; and an evaluation in the context of the full Typed Racket implementation. Specifically, we take safe vector operations as a case study, examining all vector accesses in a 56,000 line corpus of Typed Racket programs. Our system is able to prove that 50% of these are safe with no new annotations, and with a few annotations and modifications we capture more than 70%.
Publisher
Association for Computing Machinery (ACM)
Subject
Computer Graphics and Computer-Aided Design,Software
Cited by
3 articles.
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1. Correctness-by-Construction Meets Refinement Types;Proceedings of the 25th ACM International Workshop on Formal Techniques for Java-like Programs;2023-07-18
2. What Types Are Needed for Typing Dynamic Objects? A Python-Based Empirical Study;Programming Languages and Systems;2023
3. Verifiable Certificates for Predicate Subtyping;Programming Languages and Systems;2019