On understanding types, data abstraction, and polymorphism
ACM Computing Surveys (CSUR) - The MIT Press scientific computation series
Abstract types have existential type
ACM Transactions on Programming Languages and Systems (TOPLAS)
How to make ad-hoc polymorphism less ad hoc
POPL '89 Proceedings of the 16th ACM SIGPLAN-SIGACT symposium on Principles of programming languages
Bounded quantification is undecidable
Information and Computation
Bounded existentials and minimal typing
Theoretical Computer Science
Information and Computation
A Theory of Objects
Parametric Overloading in Polymorphic Programming Languages
ESOP '88 Proceedings of the 2nd European Symposium on Programming
Advanced Topics in Types and Programming Languages
Advanced Topics in Types and Programming Languages
Introduction to Automata Theory, Languages, and Computation (3rd Edition)
Introduction to Automata Theory, Languages, and Computation (3rd Edition)
Typeless programming in Java 5.0 with wildcards
Proceedings of the 5th international symposium on Principles and practice of programming in Java
A Model for Java with Wildcards
ECOOP '08 Proceedings of the 22nd European conference on Object-Oriented Programming
Java Type Unification with Wildcards
Applications of Declarative Programming and Knowledge Management
JavaGI in the battlefield: practical experience with generalized interfaces
GPCE '09 Proceedings of the eighth international conference on Generative programming and component engineering
JavaGI: generalized interfaces for java
ECOOP'07 Proceedings of the 21st European conference on Object-Oriented Programming
Towards a semantic model for Java wildcards
Proceedings of the 12th Workshop on Formal Techniques for Java-Like Programs
JavaGI: The Interaction of Type Classes with Interfaces and Inheritance
ACM Transactions on Programming Languages and Systems (TOPLAS)
Taming wildcards in Java's type system
Proceedings of the 32nd ACM SIGPLAN conference on Programming language design and implementation
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Bounded existential types are a powerful language feature for modeling partial data abstraction and information hiding. However, existentials do not mingle well with subtyping as found in current object-oriented languages: the subtyping relation is already undecidable for very restrictive settings. This paper considers two subtyping relations defined by extracting the features specific to existentials from current language proposals (JavaGI, WildFJ, and Scala) and shows that both subtyping relations are undecidable. One of the two subtyping relations remains undecidable even if bounded existential types are removed. With the goal of regaining decidable type checking for the JavaGI language, the paper also discusses various restrictions including the elimination of bounded existentials from the language as well as possible amendments to regain some of their features.