A Subtyping for Extensible, Incomplete Objects

http://dl.acm.org/citation.cfm?id=2378060.2378061International audienceWe extend the type system for the Lambda Calculus of Objects [16] with a mechanism of width subtyping and a treatment of incomplete objects. The main novelties over previous work are the use of subtype-bounded quantification to capture a new and more direct rendering of MyType polymorphism, and a uniform treatment for other features that were accounted for via different systems in subsequent extensions [7, 6] of [16]. The new system provides for (i) appropriate type specialization of inherited methods, (ii) static detection of errors, (iii) width subtyp-ing compatible with object extension, and (iv) sound typing for partially specified objects