GADT meet subtyping

Gabriel Scherer (1) , Didier Rémy (1)

1 GALLIUM - Programming languages, types, compilation and proofs

While generalized abstract datatypes 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 and involves new semantic properties of types that raise interesting design questions. We allow variance annotations in GADT definitions, present a sound and effective algorithm to check such declarations, and describe its application in a real-world language.

Domaines: Langage de programmation [cs.PL]

Gabriel Scherer, Didier Rémy. GADT meet subtyping. ACM SIGPLAN Workshop on ML, Aug 2012, Copenhague, Denmark. ⟨hal-01093940⟩