Deriving overloaded success type schemes in Erlang

Erlang is a programming language which brings together the features of functional programming and actor-based concurrency. Although it is a dynamically-typed language, there exists a tool (Dialyzer) that analyses Erlang programs in order to detect type discrepancies at compile-time. This tool is based on the notion of success types, which are overapproximations to the actual semantics of expressions, so that the evaluation of an ‘ill-typed’ expression will eventually fail at runtime. Dialyzer allows programmers to provide their own type specifications. Although such specifications can be polymorphic and overloaded (i.e., reflecting different executing branches) for documentation purposes, the type analysis disregards the information provided by polymorphic type schemes and so does, in some cases, with overloaded types. In this paper we introduce: (1) a type system that allows us to obtain polymorphic overloaded success type schemes for programs, (2) a semantic definition of this kind of types, and (3) correctness results that prove that the adequacy of the obtained types w.r.t. the semantics of expressions

Improving Precision of Type Analysis Using Non-Discriminative Union

This paper presents a new type analysis for logic programs. The analysis is performed with a priori type definitions; and type expressions are formed from a fixed alphabet of type constructors. Non-discriminative union is used to join type information from different sources without loss of precision. An operation that is performed repeatedly during an analysis is to detect if a fixpoint has been reached. This is reduced to checking the emptiness of types. Due to the use of non-discriminative union, the fundamental problem of checking the emptiness of types is more complex in the proposed type analysis than in other type analyses with a priori type definitions. The experimental results, however, show that use of tabling reduces the effect to a small fraction of analysis time on a set of benchmarks