Deconfined Intersection Types in Java

Authors Mariangiola Dezani-Ciancaglini , Paola Giannini , Betti Venneri

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Mariangiola Dezani-Ciancaglini
  • Computer Science Department, University of Torino, Italy
Paola Giannini
  • Department of Advanced Science and Technology, University of Eastern Piedmont, Alessandria, Italy
Betti Venneri
  • Department of Statistics, Computer Science, Applications, University of Firenze, Italy


We are very pleased to dedicate this work to Maurizio, whose notable contributions to the theory of programming languages are well known and appreciated by the scientific community. We would like to thank the anonymous referees for their helpful comments.

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Mariangiola Dezani-Ciancaglini, Paola Giannini, and Betti Venneri. Deconfined Intersection Types in Java. In Recent Developments in the Design and Implementation of Programming Languages. Open Access Series in Informatics (OASIcs), Volume 86, pp. 3:1-3:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


We show how Java intersection types can be freed from their confinement in type casts, in such a way that the proposed Java extension is safe and fully compatible with the current language. To this aim, we exploit two calculi which formalise the simple Java core and the extended language, respectively. Namely, the second calculus extends the first one by allowing an intersection type to be used anywhere in place of a nominal type. We define a translation algorithm, compiling programs of the extended language into programs of the former calculus. The key point is the interaction between λ-expressions and intersection types, that adds safe expressiveness while being the crucial matter in the translation. We prove that the translation preserves typing and semantics. Thus, typed programs in the proposed extension are translated to typed Java programs. Moreover, semantics of translated programs coincides with the one of the source programs.

Subject Classification

ACM Subject Classification
  • Theory of computation → Type structures
  • Theory of computation → Semantics and reasoning
  • Intersection Types
  • Featherweight Java
  • Lambda Expressions


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