Abstract compilation of object-oriented languages into coinductive CLP(X): when type inference meets verification

We propose a novel general approach for defining expressive type systems for object-oriented languages, based on abstract compilation of programs into coinductive constraint logic programs defined on a specific constraint domain X called type domain. In this way, type checking and type inference amount to resolving a certain goal w.r.t. the coinductive (that is, the greatest) Herbrand model of a logic program (that is, a Horn formula) with constraints over a fixed type domain X. In particular, we show an interesting instantiation where the constraint predicates of X are syntactic equality and subtyping over coinductive object and union types. The corresponding type system is so expressive to allow verification of simple properties like data structure invariants. Finally, we show a prototype implementation, written in Prolog, of the inference engine for coinductive CLP(X), which is parametric in the solver for the type domain X.