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Programmers learning Rust struggle to understand ownership types, Rust’s core mechanism for ensuring memory safety without garbage collection. This paper describes our attempt to systematically design a pedagogy for ownership types. First, we studied Rust developers’ misconceptions of ownership to create the Ownership Inventory, a new instrument for measuring a person’s knowledge of ownership. We found that Rust learners could not connect Rust’s static and dynamic semantics, such as determining why an ill-typed program would (or would not) exhibit undefined behavior. Second, we created a conceptual model of Rust’s semantics that explains borrow checking in terms of flow-sensitive permissions on paths into memory. Third, we implemented a Rust compiler plugin that visualizes programs under the model. Fourth, we integrated the permissions model and visualizations into a broader pedagogy of ownership by writing a new ownership chapter forThe Rust Programming Language, a popular Rust textbook. Fifth, we evaluated an initial deployment of our pedagogy against the original version, using reader responses to the Ownership Inventory as a point of comparison. Thus far, the new pedagogy has improved learner scores on the Ownership Inventory by an average of 9
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Learning and Programming Challenges of Rust: A Mixed-Methods Study
Rust is a young systems programming language designed to provide both the safety guarantees of high-level languages and the execution performance of low-level languages. To achieve this design goal, Rust provides a suite of safety rules and checks against those rules at the compile time to eliminate many memory-safety and thread-safety issues. Due to its safety and performance, Rust’s popularity has increased significantly in recent years, and it has already been adopted to build many safety-critical software systems. It is critical to understand the learning and programming challenges imposed by Rust’s safety rules. For this purpose, we first conducted an empirical study through close, manual inspection of 100 Rust-related Stack Overflow questions. We sought to understand (1) what safety rules are challenging to learn and program with, (2) under which contexts a safety rule becomes more difficult to apply, and (3) whether the Rust compiler is sufficiently helpful in debugging safety-rule violations. We then performed an online survey with 101 Rust programmers to validate the findings of the empirical study. We invited participants to evaluate program variants that differ from each other, either in terms of violated safety rules or the code constructs involved in the violation, and compared the participants’ performance on the variants. Our mixed-methods investigation revealed a range of consistent findings that can benefit Rust learners, practitioners, and language designers.
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- Award ID(s):
- 1955965
- PAR ID:
- 10321050
- Date Published:
- Journal Name:
- Proceedings of the 44th International Conference on Software Engineering
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1145/3510003.3510164
