Worked on the rust-lang/rust-analyzer repository to improve C interop reliability by addressing a bug in variadic function-pointer lowering. Focused on Rust and systems programming, the developer ensured that C-variadic parameters, represented by '...', were no longer counted as real inputs during the lowering process. This change prevented spurious argument-count errors and brought function-pointer lowering in line with the function-declaration path. A regression test was added to verify correct behavior, reducing false positives in FFI-heavy codebases. The work demonstrated careful debugging, test-driven development, and a strong understanding of Rust’s lowering mechanisms for cross-language scenarios involving C and Rust.