Do Developers Read Type Information? An Eye-Tracking Study on TypeScript

TL;DR

This study investigates whether developers actively read TypeScript type annotations during code comprehension tasks, revealing that they do not focus on type annotations more often, which impacts tool design and educational practices.

Contribution

It provides empirical evidence that developers do not frequently read type annotations, challenging assumptions about their role as in-code documentation during comprehension tasks.

Findings

Developers do not look more at type annotations when present.

Type annotations are not heavily used during bug localization.

Implications for tool design and educational strategies.

Abstract

Statically-annotated types have been shown to aid developers in a number of programming tasks, and this benefit holds true even when static type checking is not used. It is hypothesized that this is because developers use type annotations as in-code documentation. In this study, we aim to provide evidence that developers use type annotations as in-code documentation. Understanding this hypothesized use will help to understand how, and in what contexts, developers use type information; additionally, it may help to design better development tools and inform educational decisions. To provide this evidence, we conduct an eye tracking study with 26 undergraduate students to determine if they read type annotations during code comprehension and bug localization in the TypeScript language. We found that developers do not look directly at lines containing type annotations or type declarations more often when they are present, in either code summarization or bug localization tasks. The results have implications for tool builders to improve the availability of type information, the development community to build good standards for use of type annotations, and education to enforce deliberate teaching of reading patterns.