Olek Gierczak

Headshot of Olek Gierczak

Olek Gierczak is a PhD Student at NEU studying PL


Hi! My name is Olek and I’m a third year PhD student studying under Amal Ahmed at the Secure Interoperability, Languages, and Compilers group, which is part of the Programming Research Laboratory at Northeastern University. Before coming to Northeastern, I worked under Steve Zdancewic and Benjamin C. Pierce at the University of Pennsylvania.

Research Interests

I’m interested in creating formal models and properties that help researchers understand, compare, and expand programming languages. In particular, I’ve been interested in gradually typed languages, and the distinctions between type soundness and other correctness properties, as well as Rust and more generally alias management type systems.


I’ve also developed a semantic property of gradually typed languages called Type Vigilance that determines when a language’s type system matches its semantics, meaning that the static reasoning provided by types and the dynamic type based reasoning programmers can perform based on those types correspond. I proved that as expected the Natural semantics is Vigilant with the standard type system. But I also examined what type systems the Transient semantics is Vigilant for, and developed a type system, dubbed Truer Transient Typing, that provides stronger types than the first order tags seen in previous work. I proved that Transient is vigilant with Truer Transient Typing, showing that these types are a match with the semantics. I also found that with these types came type based optimizations, which means that type systems like Truer Transient Typing could provide more efficient gradual typing with semantically honest types. In the future, I plan to explore this by extending, implementing, and evaluating Truer Transient Typing.

I’ve also been working on Oxide, a type safe formalized semantics for surface level safe Rust which includes features like non lexical lifetimes, reborrowing, and closures. The crucial realizations are that lifetimes can be modelled by information from a form of points to analysis, and that this information can be used to give a formal model of the borrowchecker. Using this realization we were able to prove Progress and Preservation style soundness, and demonstrated our type system worked for the portion of the Rust test suite we supported.

I’ve additionally been working on a type preserving compilation of Oxide down to a lower level intermediate language based on Paul Levy’s Call By Push Value. With such a type preserving compilation in hand, we could model safe interoperation at the low level language, and apply this to contexts where we have a core safety sensitive component interacting with unsafe code. The goal is to preserve Oxide types by mapping them to a range of capabilities, some already well understood in the field, and some new but fundamental, that are sufficient to model the interactions between the features in Oxide.


Type Vigilance And The Truth About Transient Gradual Typing, Olek Gierczak, Lucy Menon, Christos Dimoulas, Amal Ahmed. In Submission PoPL 2024, July 2023. Technical Appendix

Oxide: The Essence of Rust, Aaron Weiss, Olek Gierczak, Daniel Patterson, Amal Ahmed. On arXiv, October 2021.