Ready, Set, Verify! Applying hs-to-coq to real-world haskell code (experience report)

Abstract

Good tools can bring mechanical verification to programs written in mainstream functional languages.We use hs-to-coq to translate significant portions of Haskell's containers library into Coq, and verify it against specifications that we derive from a variety of sources including type class laws, the library's test suite, and interfaces from Coq's standard library. Our work shows that it is feasible to verify mature, widely-used, highly optimized, and unmodified Haskell code.We also learn more about the theory of weight-balanced trees, extend hs-to-coq to handle partiality, and œ since we found no bugs œ attest to the superb quality of well-tested functional code.