Recency Types for Analyzing Scripting Languages

Abstract. With the current surge of scripting technologies, large programs are being built with dynamically typed languages. As these programs grow in size, semantics-based tools gain importance for detecting programming errors as well as for program understanding. As a basis for such tools, we propose a descriptive type system for an imperative call-by-value lambda calculus with objects. The calculus models essential features of JavaScript, a widely used dynamically-typed language: first-class functions, objects as property maps, and prototypes. Our type system infers precise singleton object types for recently allocated objects. These object types are handled flow-sensitively and change during the objects’ initialization phase. The notion of recency provides an automatic criterion to subsume these precise object types to summary object types, which are handled flow-insensitively. The criterion applies on a per-object basis. Thus, the type system identifies a generalized initial...

• Type: Conference
• Year: 2010
• Where: ECOOP
• Authors: Phillip Heidegger, Peter Thiemann
• Keywords: ECOOP 2010, Initialization Phase, Object Types, Programming Languages, Singleton Object Types