Worked on the facebook/pyrefly repository to deliver a Redundant Type Casting Warning feature aimed at improving type correctness. The solution detects and warns when a value is cast to its existing type, reducing silent casting issues and enhancing code clarity. This involved introducing a new redundant cast error kind, implementing comprehensive tests to validate the feature’s behavior, and updating documentation to guide developers on the new warning. The work was carried out using Python and Rust, with a focus on robust type checking and thorough testing practices. These changes contribute to higher code quality and clearer developer guidance within the project.