WITS 2022 is the first Workshop on the Implementation of Type Systems. The workshop will be held on January 22, 2022, in Philadelphia, PA, United States, co-located with POPL. The goal of this workshop is to bring together the implementors of a variety of languages with advanced type systems. The main focus is on the practical issues that come up in the implementation of these systems, rather than the theoretical frameworks that underlie them. In particular, we want to encourage exchanging ideas between the communities around specific systems that would otherwise be accessible to only a very select group.

Given the importance of collaboration among the attendees at WITS, if circumstances around covid-19 force POPL (and its co-located events) to go virtual, WITS will be deferred until a time when we can come together safely in person.

The workshop will have a mix of invited and contributed talks, organized discussion times, and informal collaboration time.


We invite participants to share their experiences, study differences among the implementations, and generalize lessons from those. We also want to promote the creation of a shared vocabulary and set of best practices for implementing type systems.

Here are a few examples of topics we are interested to discuss:

  • syntax with binders and substitution
  • conversion modulo beta and eta
  • implicit arguments and metavariables
  • unification and constraint solving
  • metaprogramming and tactic languages
  • editor integration and automation
  • discoverability of language features
  • pretty printing and error messages

This list is not exhaustive, so please contact the PC chairs in case you are unsure if a topic falls within the scope of the workshop.

Important Dates

  • Abstract submission deadline: 16 November, 2021 (AoE)
  • Notification: 1 December, 2021 (AoE)
  • Workshop in Philadelphia: 22 January, 2022

Attendance and registration

WITS 2022 is colocated with POPL 2022 in Philadelphia, USA. More information on registration and attendance will be announced later.

Call for Contributions

WITS solicits two kinds of submissions:

  • Contributed talks on the basis of an abstract. This can be on recently published or submitted work, work in progress, or even a project that is still in the idea phase.

  • Proposals for roundtable discussions. This can be on any topic within the scope of the workshop, but should have a broader scope than a contributed talk. If accepted, you will be in charge of leading a discussion of 45 minutes around the proposed topic together with other interested attendees.

Both kinds of proposals should be accompanied by an abstract of max. 1 page (exclusive of references), formatted according to the guidelines for SIGPLAN conferences: use the sigplan option to the acmart LaTeX document class. WITS will have no published proceedings, so submitting to WITS does not interfere with submission (before, after, or simultaneously) with other venues.

Questions? Use the WITS contact form.