Featherweight generic confinement

Abstract

Existing approaches to object encapsulation either rely on ad hoc syntactic restrictions or require the use of specialised type systems. Syntactic restrictions are difficult to scale and to prove correct, while specialised type systems require extensive changes to programming languages. We demonstrate that confinement can be enforced cheaply in Featherweight Generic Java, with no essential change to the underlying language or type system. This result demonstrates that polymorphic type parameters can simultaneously act as ownership parameters and should facilitate the adoption of confinement and ownership type systems in general-purpose programming languages.

Universes: Lightweight Ownership for JML.

“…In recent work, Noble et al [PNCB03,PNCR04] combined ownership and type parameterization by introducing generic ownership. This proposal reduces the annotation overhead for generic classes, but does not address the other shortcomings of ownership types.…”

JavaD: Bringing Ownership Domains to Mainstream Java

“…A promising alternative approach is to combine ownership and generic types, as is being proposed by Potanin et al [16]. This is an area that we will be watching closely.…”

Scoped Types for Real-Time Java

“…In contrast, the explicit approach, pioneered by Ownership Types [13], explicitly annotates types with extra information denoting objects' ownership: these annotations impose a significant syntactic burden on the programmer. While the earliest Ownership Types proposals supported nested objects as the unit of encapsulation ("deep ownership" [12,10]), more recent work has supported individual un-nested objects ("shallow ownership" [1,6]) and also per-package ownership [38,30]. Cyclone [19] is a type-safe language derived from C and it supports region-based memory management.…”