GADTs meet subtyping [article]

Gabriel Scherer, Didier Rémy (INRIA Rocquencourt)
2013 arXiv   pre-print
While generalized algebraic datatypes (\GADTs) are now considered well-understood, adding them to a language with a notion of subtyping comes with a few surprises. What does it mean for a \GADT parameter to be covariant? The answer turns out to be quite subtle. It involves fine-grained properties of the subtyping relation that raise interesting design questions. We allow variance annotations in \GADT definitions, study their soundness, and present a sound and complete algorithm to check them.
more » ... r work may be applied to real-world ML-like languages with explicit subtyping such as OCaml, or to languages with general subtyping constraints.
arXiv:1301.2903v1 fatcat:fytxjm473fhdlc34dzkr7zoej4