NEW How Developers Use Type-System Related Programming Language Features

Background: 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.

Objective: 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.

Methods: To provide this evidence, we use eye-tracking to determine if developers read type annotations during code comprehension and bug localization in the TypeScript language.

Results: We found that developers do not appear to refer to lines containing type annotations or declarations more or less often when they are present, in either code summarization or bug localization tasks.

Implications: Finally, we note implications for tool builders (improving availability of type information is important), the development community (building good standards for use of type annotations), and education (deliberate teaching of reading patterns may be wise).