Speaker

Tom Schrijvers (KU, Leuven, Be)

j.w.w. Simon Peyton Jones, (Microsoft Research Cambridge, UK), Martin Sulzmann (Intaris Software GmbH, Germany) and Dimitrios Vytiniotis (Microsoft Research Cambrige, UK).

Abstract

Generalized Algebraic Data Types (GADTs) have proven to be an invaluable language extension, a.o. for ensuring data invariants and program correctness. Unfortunately, they pose a tough problem for type inference: we lose the principal-type property, which is necessary for modular type inference.

We present a novel and simplified type inference approach for local type assumptions from GADT pattern matches. Our approach is complete and decidable, while more liberal than previous such approaches.