Session types describe and constrain the input/output behaviour of systems. Existing session typing systems have limited support for polymorphism. For example, existing systems cannot provide the most general type for a generic proxy process that forwards messages between two channels. We provide a polymorphic session typing system for the π calculus, and demonstrate the utility of session-type-level functions in combination with polymorphic session typing. The type system guarantees subject reduction and safety properties, but not deadlock freedom. We describe a formalization of the type system in Coq. The proofs of subject reduction and safety properties, as well as typing of example processes, have been mechanically verified.

Multicore computers implementing weak memory models are mainstream, yet type-based analyses of these models remain rare. We help fill this gap. We not only prove the soundness of a type system for a weak execution model, but we also show that interesting properties of that model can be embedded in the types themselves.We argue that correspondence assertions can be used in a programming discipline that captures happens-before relationships, which are the basis for reasoning about weak memory in Java. This programming discipline is flexible and can be statically enforced. We present several examples from java.util.concurrent and prove the static semantics sound with respect to an execution model based on Java's memory model.

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