Global Type Inference for Featherweight Generic Java

TL;DR

This paper presents a constraint-based global type inference algorithm for Featherweight Generic Java, capable of inferring all method types under certain conditions, and discusses its computational complexity.

Contribution

It introduces a novel global type inference algorithm for FGJ that improves upon previous methods and analyzes its NP-completeness.

Findings

The algorithm infers all method types given class headers and fields.

Global type inference for FGJ is NP-complete.

The algorithm works when classes do not use polymorphic recursion.

Abstract

Java's type system mostly relies on type checking augmented with local type inference to improve programmer convenience. We study global type inference for Featherweight Generic Java (FGJ), a functional Java core language. Given generic class headers and field specifications, our inference algorithm infers all method types if classes do not make use of polymorphic recursion. The algorithm is constraint-based and improves on prior work in several respects. Despite the restricted setting, global type inference for FGJ is NP-complete.