Untangling Typechecking of Intersections and Unions

Dunfield, Joshua

doi:10.4204/eptcs.45.5

Cited by 5 publications

(4 citation statements)

References 25 publications

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“…For further discussion of this rule, see Dunfield and Pfenning (2003). Finally, note that the evaluation context E need not be unique, which creates some difficulties for practical typechecking (Dunfield, 2011).…”

Section: Union Typesmentioning

confidence: 99%

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Elaborating intersection and union types

Dunfield¹

2014

J. Funct. Prog.

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Designing and implementing typed programming languages is hard. Every new type system feature requires extending the metatheory and implementation, which are often complicated and fragile. To ease this process, we would like to provide general mechanisms that subsume many different features.In modern type systems, parametric polymorphism is fundamental, but intersection polymorphism has gained little traction in programming languages. Most practical intersection type systems have supported only refinement intersections, which increase the expressiveness of types (more precise properties can be checked) without altering the expressiveness of terms; refinement intersections can simply be erased during compilation. In contrast, unrestricted intersections increase the expressiveness of terms, and can be used to encode diverse language features, promising an economy of both theory and implementation.We describe a foundation for compiling unrestricted intersection and union types: an elaboration type system that generates ordinary λ-calculus terms. The key feature is a Forsythe-like merge construct. With this construct, not all reductions of the source program preserve types; however, we prove that ordinary call-byvalue evaluation of the elaborated program corresponds to a typepreserving evaluation of the source program.We also describe a prototype implementation and applications of unrestricted intersections and unions: records, operator overloading, and simulating dynamic typing.

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Section: Union Typesmentioning

confidence: 99%

“…The evaluation context E need not be unique, which creates some difficulties for practical typechecking (Dunfield 2011). For further discussion of this rule, see Dunfield and Pfenning (2003).…”

Section: Union Typesmentioning

confidence: 99%

Elaborating intersection and union types

Dunfield¹

2014

J. Funct. Prog.

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“…They propose an evaluation context restriction that recovers soundness, but this is not enough to make type-checking efficient. In recent work, Dunfield [72], shows that carefully transforming programs into let-normal form improves efficiency. This is encouraging, since our expressions are already in let-normal form, so we can hope to replace the case construct by a normal let in the future, and still preserve efficient type-checking.…”

Section: Related Work On Unions and Intersectionsmentioning

confidence: 99%

Union, intersection and refinement types and reasoning about type disjointness for secure protocol implementations

Backes

Hriţcu

Maffei

2014

JCS

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We present a new type system for verifying the security of reference implementations of cryptographic protocols written in a core functional programming language.The type system combines prior work on refinement types, with union, intersection, and polymorphic types, and with the novel ability to reason statically about the disjointness of types. The increased expressivity enables the analysis of important protocol classes that were previously out of scope for the type-based analyses of reference protocol implementations. In particular, our types can statically characterize:(i) more usages of asymmetric cryptography, such as signatures of private data and encryptions of authenticated data; (ii) authenticity and integrity properties achieved by showing knowledge of secret data; (iii) applications based on zero-knowledge proofs. The type system comes with a mechanized proof of correctness and an efficient type-checker.

show abstract

“…They propose an evaluation context restriction that recovers soundness, but this is not enough to make type-checking efficient. In recent work, Dunfield [27], shows that carefully transforming programs into let-normal form improves efficiency. This is encouraging, since our expressions are already in let normal form, so we can hope to replace the case construct by a normal let in the future, and still preserve efficient type-checking.…”

Section: Related Work On Unions and Intersectionsmentioning

confidence: 99%

Union and Intersection Types for Secure Protocol Implementations

Backes

Hriţcu

Maffei

2012

Theory of Security and Applications

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Abstract.We present a new type system for verifying the security of cryptographic protocol implementations. The type system combines prior work on refinement types, with union, intersection, and polymorphic types, and with the novel ability to reason statically about the disjointness of types. The increased expressivity enables the analysis of important protocol classes that were previously out of scope for the type-based analyses of protocol implementations. In particular, our types can statically characterize: (i) more usages of asymmetric cryptography, such as signatures of private data and encryptions of authenticated data; (ii) authenticity and integrity properties achieved by showing knowledge of secret data; (iii) applications based on zero-knowledge proofs. The type system comes with a mechanized proof of correctness and an efficient type-checker.

show abstract

Untangling Typechecking of Intersections and Unions

Cited by 5 publications

References 25 publications

Elaborating intersection and union types

Elaborating intersection and union types

Union, intersection and refinement types and reasoning about type disjointness for secure protocol implementations

Union and Intersection Types for Secure Protocol Implementations

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