Type Inference with Selftype

The metavariable self is fundamental in object-oriented languages.Typing self in the presence of inheritance has been studied by Abadiand Cardelli, Bruce, and others. A key concept in these developmentsis the notion of selftype, which enables flexible type annotations thatare impossible with recursive types and subtyping. Bruce et al. demonstratedthat, for the language TOOPLE, type checking is decidable.Open until now is the problem of type inference with selftype.In this paper we present a type inference algorithm for a typesystem with selftype, recursive types, and subtyping. The examplelanguage is the object calculus of Abadi and Cardelli, and the typeinference algorithm runs in nondeterministic polynomial time