VERT: Polyglot Verified Equivalent Rust Transpilation with Large Language Models

Rust is a programming language that combines memory safety and low-level control, providing C-like performance while guaranteeing the absence of undefined behaviors by default. Rust’s growing popularity has prompted research on correct and idiomatic transpiling of existing code-bases to Rust. Existing work falls into two categories: rule-based and large language model (LLM)-based. While rule-based approaches are theoretically sound, they often yield unidiomatic and unsafe Rust code, and are limited to few source languages, which hinders maintainability and industrial application. By contrast, LLM-based approaches, while providing no guarantees, are polyglot and typically produce more idiomatic and safe Rust code. In this work, we present VERT, a formally correct, polyglot Rust translator with more idiomatic outputs. VERT supports any language that compiles to Web Assembly. Using the Web Assembly compiler, VERT obtains an oracle Rust program. Leveraging the LLM, VERT generates an idiomatic candidate Rust program. This candidate is verified against the oracle with model-checking to ensure equivalence.