We study HMG(X), an extension of the constraint-based type system HM(X) with deep pattern matching, polymorphic recursion, andguarded algebraic data types. Guarded algebraic data types subsume the concepts known in the literature asindexed types,guarded recursive datatype constructors,(first-class) phantom types, andequality qualified types, and are closely related toinductive types. Their characteristic property is to allow every branch of a case construct to be typechecked under different assumptions about the type variables in scope. We prove that HMG(X) is sound and that, provided recursive definitions carry a type annotation, type inference can be reduced to constraint solving. Constraint solving is decidable, at least for some instances ofX, but prohibitively expensive. Effective type inference for guarded algebraic data types is left as an issue for future research.

We propose a conservative extension of HM(X), a generic constraint-based type inference framework, with bounded existential (a.k.a. abstract) and universal (a.k.a. polymorphic) data-types. In the first part of the article, which remains abstract of the type and constraint language (i.e. the logic X), we introduce the type system, prove its safety and define a type inference algorithm which computes principal typing judgments. In the second part, we propose a realistic constraint solving algorithm for the case of structural sub-typing, which handles the non-standard construct of the constraint language generated by type inference: a form of bounded universal quantification.

This paper presents a type-based information flow analysis for a call-by-value λ-calculus equipped with references, exceptions and let-polymorphism, which we refer to as ML. The type system is constraint-based and has decidable type inference. Its noninterference proof is reasonably light-weight, thanks to the use of a number of orthogonal techniques. First, a syntactic segregation between values and expressions allows a lighter formulation of the type system. Second, noninterference is reduced to subject reduction for a nonstandard language extension. Lastly, a semi-syntactic approach to type soundness allows dealing with constraint-based polymorphism separately.

This paper presents a new type system tracing information flow for a λ-calculus equipped with polymorphic “let ” and with sums (a.k.a. union types or polymorphic variants). The type system allows establishing (weak) noninterference properties. Thanks to original forms of security annotations and constraints, it is more accurate than existing analyses. Through a straightforward encoding into sums, this work also provides a new type-based information flow analysis for programming languages featuring exceptions. From these systems, one may derive constraint-based formulations, in the style of HM(X), which have decidable type inference. 1

This paper presents a type-based information flow analysis for a call-by-value λ-calculus equipped with references, exceptions and let-polymorphism, which we refer to as Core ML. The type system is constraint-based and has decidable type inference. Its non-interference proof is reasonably lightweight, thanks to the use of a number of orthogonal techniques. First, a syntactic segregation between values and expressions allows a lighter formulation of the type system. Second, non-interference is reduced to subject reduction for a non-standard language extension. Lastly, a semi-syntactic approach to type soundness allows dealing with constraint-based polymorphism separately.