POPL 2024
Sun 14 - Sat 20 January 2024 London, United Kingdom
Tue 16 Jan 2024 16:23 - 16:45 at Mountbatten Exhibition - Types Chair(s): Azalea Raad

We introduce two-sided type systems, which are sequent calculi for typing formulas. Two-sided type systems allow for hypothetical reasoning over the typing of compound program expressions, and the refutation of typing formulas. By incorporating a type of all values, these type systems support more refined notions of well-typing and ill-typing, guaranteeing both that well-typed programs don’t go wrong and that ill-typed programs don’t evaluate - that is, reach a value. This makes two-sided type systems suitable for incorrectness reasoning in higher-order program verification, which we illustrate through an application to precise data-flow typing in a language with constructors and pattern matching. Finally, we investigate the internalisation of the meta-level negation in the system as a complement operator on types. This motivates an alternative semantics for the typing judgement, which guarantees that ill-typed programs don’t evaluate, but in which well-typed programs may yet go wrong.

Tue 16 Jan

Displayed time zone: London change

16:00 - 17:30
TypesIncorrectness at Mountbatten Exhibition
Chair(s): Azalea Raad Imperial College London
Type-Based Incorrectness Reasoning
Zhe Zhou Purdue University, Benjamin Delaware Purdue University, Suresh Jagannathan Purdue University
Ill-Typed Programs Don't Evaluate
Steven Ramsay University of Bristol, Charlie Walpole University of Bristol