We present a type system that combines, in a controlled way, first-order polymorphism with
intersection types, union types, and subty**, and prove its safety. We then define a type …

Many programming languages need to check whether two recursive types are in a subty**
relation. Traditionally recursive types are modelled in two different ways: equi-or iso …

Creating good type error messages for constraint-based type inference systems is difficult.
Typical type error messages reflect implementation details of the underlying constraint …

Type inference in the presence of first-class or “impredicative” second-order polymorphism à
la System F has been an active research area for several decades, with original works …

A pluggable type system extends a host programming language with type qualifiers. It lets
programmers write types like unsigned int, secret string, and nonnull object. Typechecking …

Erlang is a functional programming language with dynamic ty**. The language offers
great flexibility for destructing values through pattern matching and dynamic type tests …

Structural subty** and parametric polymorphism provide similar flexibility and reusability
to programmers. For example, both features enable the programmer to provide a wider …

We introduce two-sided type systems, which are sequent calculi for ty** formulas. Two-
sided type systems allow for hypothetical reasoning over the ty** of compound program …

We study the proof theory and algorithms for orthologic, a logical system based on
ortholattices, which have shown practical relevance in simplification and normalization of …

We present a new variation of object-oriented programming built around three simple and
orthogonal constructs: classes for storing object state, interfaces for expressing object types …